ALBERT

Beschreibung: Most soils in Nigeria are known to be slightly acidic and very low in plant-available P. These soils need to be fertilized for optimal crop production but cost and scarcity of mineral P fertilizers shifted attention to making direct application of indigenous phosphate rock viable alternative. Laboratory and greenhouse studies were carried out to monitor the effect of the decomposition of legume biomass on the solubilization of Ogun phosphate rock (OPR) on slightly acidic soils. Surface soil samples collected from three experimental sites in SW Nigeria were used. The fertilizer treatments were four rates of P as OPR (0, 30, 60, and 90 kg ha –1 ) and one rate of triple superphosphate (TSP, 40 kg P ha –1 ). The legume treatments were cowpea ( Vigna unguiculata L Walp) and mucuna ( Mucuna puriens L). Rice ( Oryza sativa ) was used in the greenhouse study as the test crop. Soil samples were analyzed for soluble P and pH after 2, 4, 6, and 10 months of incubation in the laboratory while plant tissues collected from greenhouse study were analyzed for P. In the incubation study, significant increase in water-soluble P was observed when legume biomass was incorporated with phosphate rock at p 〈 0.05. Highest value in rice dry-matter yield was recorded with pots treated with mucuna and TSP, also treatment combination of cowpea and OPR significantly increased rice dry-matter yield by 16% over pots treated with cowpea biomass alone and 42% over control pot (no legume biomass and OPR in the green house ( p 〈 0.05). Thus incorporation of legume biomass significantly increased rate of OPR solubilization.

Beschreibung: We applied digestate generated from the anaerobic digestion of slurry, undigested slurry, or inorganic N (ammonium nitrate) or NPK compound fertilizer to pots of grass and a grass–clover mix grown in two soils. Crop yields were equal or enhanced with digestate, and analysis of soil water showed that there was less potential for loss of nutrients via leaching. Replacing inorganic fertilizer with digestate may therefore maintain grassland productivity but with less impact on the environment.

Beschreibung: Nitrous oxide (N 2 O) is a high-impact greenhouse gas. Due to the scarcity of unmanaged forests in Central Europe, its long-term natural background emission level is not entirely clear. We measured soil N 2 O emissions in an unmanaged, old-growth beech forest in the Hainich National Park, Germany, at 15 plots over a 1-year period. The average annual measured N 2 O flux rate was (0.49 ± 0.44) kg N ha –1  y –1 . The N 2 O emissions showed background-emission patterns with two N 2 O peaks. A correlation analysis shows that the distance between plots (up to 380 m) does not control flux correlations. Comparison of measured data with annual N 2 O flux rates obtained from a standard model (Forest-DNDC) without site-specific recalibration reveals that the model overestimates the actual measured N 2 O flux rates mainly in spring. Temporal variability of measured N 2 O flux was better depicted by the model at plots with high soil organic C (SOC) content. Modeled N 2 O flux rates were increased during freezing only when SOC was 〉 0.06 kg C kg –1 . The results indicate that the natural background of N 2 O emissions may be lower than assumed by most approaches.

Beschreibung: A greenhouse rhizobox experiment was carried out to investigate the fate and turnover of 13 C- and 15 N-labeled rhizodeposits within a rhizosphere gradient from 0–8 mm distance to the roots of wheat. Rhizosphere soil layers from 0–1, 1–2, 2–3, 3–4, 4–6, and 6–8 mm distance to separated roots were investigated in an incubation experiment (42 d, 15°C) for changes in total C and N and that derived from rhizodeposition in total soil, in soil microbial biomass, and in the 0.05 M K 2 SO 4 –extractable soil fraction. CO 2 -C respiration in total and that derived from rhizodeposition were measured from the incubated rhizosphere soil samples. Rhizodeposition C was detected in rhizosphere soil up to 4–6 mm distance from the separated roots. Rhizodeposition N was only detected in the rhizosphere soils up to 3–4 mm distance from the roots. Microbial biomass C and N was increased with increasing proximity to the separated roots. Beside 13 C and 15 N derived from rhizodeposits, unlabeled soil C and N (native SOM) were incorporated into the growing microbial biomass towards the roots, indicating a distinct acceleration of soil organic matter (SOM) decomposition and N immobilization into the growing microbial biomass, even under the competition of plant growth. During the soil incubation, microbial biomass C and N decreased in all samples. Any decrease in microbial biomass C and N in the incubated rhizosphere soil layers is attributed mainly to a decrease of unlabeled (native) C and N, whereas the main portion of previously incorporated rhizodeposition C and N during the plant growth period remained immobilized in the microbial biomass during the incubation. Mineralization of native SOM C and N was enhanced within the entire investigated rhizosphere gradient. The results indicate complex interactions between substrate input derived from rhizodeposition, microbial growth, and accelerated C and N turnover, including the decomposition of native SOM ( i.e., rhizosphere priming effects) at a high spatial resolution from the roots.

Beschreibung: Interest in developing crop varieties with low grain phosphorus (P) in order to minimize the removal of P from fields in harvested grain has been limited due to the view that a low-P grain trait may impair subsequent seedling vigor. This perception is based on relatively few studies, which typically investigated seedling growth on infertile soils, and used seed that may have differed in attributes other than P concentration. To investigate whether these anomalies cast sufficient doubt to warrant renewed research in this field, we compared the growth of rice seedlings from seed low in P obtained from P-starved plants (P-starved seed) vs. high-P seeds (obtained from P-fertilized plants) in P-deficient and P-replete soils. While plants from high-P seed were superior in the P-deficient soil, plants grown from P-starved seed overcame an initial lull in early vigor to obtain similar biomass at maturity as plants grown from high-P seed. Subsequent experiments were undertaken using high-P seed vs. seed low in P from a range of rice genotypes that was not obtained from P-stressed plants (low-P seed): There was no reduction in seedling vigor or biomass and grain yields at maturity of plants from low-P seeds in low-P soil compared to plants from high-P seed, though responses were genotype-specific. The results suggest that multiple factors can confound the results of seed P × seedling vigor studies, and that a renewed research effort to define the minimum P levels in seeds required for adequate seedling growth across a range of environments is warranted.

Beschreibung: The assessment of grassland degradation due to overgrazing is a global challenge in semiarid environments. In particular, investigations of beginning steppe degradation after a change or intensification of the land use are needed in order to detect and adjust detrimental land-use management rapidly and thus prevent severe damages in these sensitive ecosystems. A controlled-grazing experiment was established in Inner Mongolia (China) in 2005 that included ungrazed (UG) and heavily grazed plots with grazing intensities of 4.5 (HG4.5) and 7.5 (HG7.5) sheep per hectare. Several soil and vegetation parameters were investigated at all sites before the start of the experiment. Topsoil samples were analyzed for soil organic C (SOC), total N (N tot ), total S (S tot ), and bulk density (BD). As vegetation parameters, aboveground net primary productivity (ANPP), tiller density (TD), and leaf-area index (LAI) were determined. After 3 y of the grazing experiment, BD increased and SOC, N tot , S tot , ANPP, and LAI significantly decreased with increasing grazing intensity. These sensitive parameters can be regarded as early-warning indicators for degradation of semiarid grasslands. Vegetation parameters were, however, more sensitive not only to grazing but also to temporal variation of precipitation between 2006 and 2008. Contrary, soil parameters were primarily affected by grazing and resistant against climatic variations. The assessment of starting conditions in the study area and the application of defined grazing intensities is essential for the investigation of short-term degradation in semiarid environments.

Beschreibung: A survey on the endorhizal status of 39 fruit crops of 25 families, indicated that 22 fruit crops had arbuscular mycorrhizal (AM)–, four had dark septate endophyte (DSE)–fungal association, and 13 had dual colonization of AM and DSE fungi. Fruit crops were capable of forming Arum-, Paris -, or intermediate-types of AM morphologies of which intermediate-type was common. To our knowledge, we report for the first time AM in 10 fruit crops and DSE-fungal association in 17 fruit crops. The extent of AM- and DSE-fungal colonization ranged from 41% to 98% and 〈 1% to 89.9%, respectively, in different fruit crops. Arbuscular mycorrhizal–fungal spore numbers in the rhizosphere ranged from 6 to 61 spores per 25 g of soil. Arbuscular mycorrhizal–fungal spores belonging to Acaulospora, Glomus, and Scutellospora were isolated from the rhizosphere soil.

Beschreibung: Acid phosphomonoesterase (APM) (E.C. 3.1.3.2) in soil is either of plant-root or microbial origin. Each of these sources may be dominant in certain ecosystems. Generally, extracellular APM in soil has been reported. However, the lack of suitable methods limits investigations of APM in soil. Root-derived APM comes from intact plant roots, root exudates, root apoplastic sap, root extracts, or mycorrhizal fungi. The significance of these sources of APM is discussed in this review being the highest in intact roots or root extracts, and within wall- and membrane-bound fraction of mycorrhizal fungi. Evaluation of the location of APM has been based on extraction of fractions of APM with different types of extractants. The suitability of individual extractants and lack of these procedures as well as the need to search for other suitable solutions to increase extraction efficiency, minimalize extraction of inhibitors and solubilization of organic compounds are discussed. As APM derived from roots and soil microorganisms show different kinetic properties, and differ in their response to environmental factors, determination of the significance of root and microbial APM within ecosystems requires further research aimed at evaluating the response of P transformation to climatic and other environmental changes.

Beschreibung: Both earthworms and plant growth–promoting rhizobacteria (PGPR) are ubiquitous and important for promoting circulation of plant macronutrients. Two series of laboratory experiments were conducted to investigate the effects of earthworm casts and activities on the growth of PGPR, and the inoculation of earthworms and PGPR on the availability of N, P, and K in soils, respectively. During a short incubation period (0–34 h), the extracts of earthworm ( Pheretima guillelmi )-worked soil significantly ( p 〈 0.05) increased the abundance of the three species of PGPR, including N-fixing bacteria (NFB) ( Azotobacter chroococcum HKN-5), phosphate-solubilizing bacteria (PSB) ( Bacillus megaterium HKP-1), and K-solubilizing bacteria (KSB) ( B. mucilaginous HKK-1), in Luria-Bertani (LB) broth. There were synergistic effects of dual inoculation of earthworms and PGPR on increasing the concentrations of NH -N, (NO + NO )-N, NaHCO 3 -extractable P, and NH 4 OAc-extractable K in the corresponding soils. Bioavailable N (the sum of NH -N and [NO + NO ]-N) in the dual inoculation was 4 to 24 times those inoculated with earthworms or NFB alone, respectively. The significantly higher concentrations of bioavailable N and P in the dual inoculation of earthworms and NFB or PSB may be due to the higher abundance of PGPR and/or higher activities of urease and acid phosphatase than those of single inoculation of NFB or PSB, respectively. Dual inoculation of earthworms and PGPR would be most effective in reducing the need for chemical fertilizers in agriculture.

Beschreibung: Several methods are used for the extraction of soil solution. The objective of this study was to find out to what extent the different extraction methods yield complementary or equivalent information. Soil solutions were sampled once at 10 different forest sites in Germany, with 4 sampling points per site, using 5 different extraction methods. Concentrations of the major ions in the 1:2 extracts and the equilibrium soil-pore solutions (obtained from percolation of field-fresh soil cores) were generally lower than in desorption solutions, suction-cup solutions, and saturation extracts. Surprisingly, the latter three methods generally yielded equivalent results. However, possible systematic differences between these methods could have been masked by the high small-scale spatial variability within the sites.

Beschreibung: Experiments to assess the rate of absorption and translocation of foliar-applied, isotopically labeled boric acid (BA) were carried out with lychee ( Litchi chinensis Sonn.) and soybean ( Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl 2 and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of 10 B to other leaf parts and no effect of adjuvants in increasing 10 B absorption were recorded. In contrast, 10 B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of 10 B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased 10 B absorption and enhanced acropetal 10 B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl 2 in combination with 500 mM sorbitol decreased the rate of 10 B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal 10 B translocation was very limited. A distinct effect of B-sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.

Beschreibung: Recent studies indicate that soil soluble organic nitrogen (SON) plays an important regulatory role in the soil–plant N cycle. The aims of this study were to identify the vertical distribution of SON and its correlation with N mineralization, nitrification, and amidohydrolase activities, in a soil repeatedly amended with cow manure or chemical fertilizer. For this purpose, soil samples were collected from 0–20, 20–40, 40–60, 60–80, and 80–100 cm depths of a calcareous soil, which has been annually amended for 5 y with cow manure (CM) at two rates of 50 (CM 50 ) and 100 (CM 100 ) Mg CM ha –1 y –1 . Treatments with chemical fertilizer (CF) and a control (CT) were also included. Soluble organic N, N mineralization, nitrification rates, as well as L-glutaminase and L-asparaginase activities were determined. Both CM 50 and CM 100 enhanced SON content throughout the soil profile. Nitrogen-mineralization rate (N m ) was increased at the 0–20 cm depth of the CM 100 treatment and remained unaffected at the deeper depths. Nitrification rate (N n ) was significantly higher at the 0–60 cm depth of CM 100 compared to CF and CT. L-glutaminase and L-asparaginase activities were significantly increased at the 0–40 cm depth in both CM 50 and CM 100 compared to CF and CT. The amidohydrolase activities could not be detected below 40 cm, regardless of the fertilizer treatments. Our results suggest that SON makes a minor contribution to N mineralization in deep soil layers. It was also concluded that changes in the SON throughout the soil profile were not associated with changes in the N-transformation rates (N m and N n ) and amidohydrolase activities. While we conclude that SON is a major N pool in the whole profile of the manure applied soil further investigation is required to characterize SON and to investigate the bioavailability of SON for microbial activity in different soil depths.

Beschreibung: The aim of this study was to improve the fertilizer-nitrogen-use efficiency (NUE) for a sustainable citrus production where yield, fruit quality, and environment are reconciled. A soil pot experiment was conducted using 5-year-old orange trees ( Citrus sinensis cv. Navel Lane Late) to determine the response of NUE to timing of N-fertilizer supply. An equal N rate (50 g tree –1 ) following two seasonal supply distributions was tested: (1) ENS (early supply from March to June of 75% of the N rate, with the remaining 25% administered between July and October) and (2) LNS (late supply of the bulk of the N rate with 25% between March and June and 75% between July and October). Labeled fertilizer (5 atom% 15 N excess) was applied in order to accurately quantify N uptake, its partitioning among plant–soil compartments and NUE at the end of fruit drop and at fruit maturity. LNS resulted in a significant increase in NUE in both stages (up to 19% at the end of fruit drop and 9% at fruit maturity), while also increasing summer/autumn flush development. ENS showed lower fruit abscission, an enhanced final fruit load (up to 45%), and a more profuse development of spring flush. It is worth mentioning that LNS led to higher 15 N content in the majority of the tree storage organs available for next spring growth resumption. The amount of 15 N remaining in the soil of ENS trees at the end of the trial, which represented 16% of the supplied 15 N, was 1.5-fold higher than that of LNS trees as a result of the lower NUE of the former. Irrespective of the seasonal distribution of the fertilizer, mean 15 N recovery in the soil–plant system at the end of the trial was about 71%. The results clearly confirm that the N seasonal distribution curve affects NUE in young citrus trees and NUE increases when the bulk of supply of the N rate is delayed to the summer months.

Beschreibung: There is lack of information available concerning the effect of humic substances (HS) applied via fertigation on plant growth in sandy soils. Therefore, a field experiment was carried out at El-Saff district (20 km southwest of Cairo), Egypt, to investigate the role of HS fertigation on water retention of a sandy soil, yield and quality of broccoli ( Broccoli oleracea L.) as well as on soil nutrient concentration retained after harvest. The experiment consisted of six fertigation treatments (50%, 75%, and 100% of the recommended NPK-fertilizer rate for broccoli combined with and without HS application at 120 L ha –1 ) in a complete randomized block design with three replicates. Humic substances affected spatial water distribution and improved water retention in the root zone. Furthermore, application of HS increased total marketable yield and head diameter of broccoli as well as quality parameters ( i.e., total soluble solids, protein, and vitamin C). Higher nutrient concentrations were found in the broccoli heads and concentrations of plant-available nutrients in soil after harvesting were also higher, indicating an improvement in soil fertility. In conclusion, HS fertigation can be judged as an interesting option to improve soil water and nutrient status leading to better plant growth.

Beschreibung: The hydraulic properties of soils, i.e., their ability to store and conduct water, mainly govern the availability of soil water for plants. Information on the hydraulic properties is needed, e.g., for the quantification of drought risk at a given site. Furthermore, knowledge of the water transport is the precondition for the estimation of element fluxes in the soil, e.g., when predicting element leaching from the root zone to the groundwater. For forest soils, only few systematic investigations of their hydraulic properties exist. Within the 2nd forest-soil survey of Germany, soil samples were taken along a regular 8 km × 8 km grid in the forests of the State of Baden-Württemberg and the hydraulic properties were estimated in the laboratory by multistep outflow experiments. Besides the soil-hydraulic measurements, numerous additional soil chemical and physical analyses were carried out and comprehensive profile descriptions were compiled and integrated in a hydraulic database. Based on this database, multiple-linear-regression techniques were used to develop pedotransfer functions for the water-retention curve and the unsaturated-hydraulic-conductivity curve using the parametric models of Mualem/van-Genuchten. Our work fills a gap since to our knowledge, no pedotransfer functions for the unsaturated hydraulic conductivity for forest soils exist so far. The predictive accuracy of the established pedotransfer functions, both for the water-retention curve and the hydraulic-conductivity curve, is in the range of (and in some cases better than) other published pedotransfer functions that were mostly derived for agricultural soils.

Beschreibung: Our contemporary society is struggling with soil degradation due to overuse and climate change. Pre-Columbian people left behind sustainably fertile soils rich in organic matter and nutrients well known as terra preta (de Indio) by adding charred residues (biochar) together with organic and inorganic wastes such as excrements and household garbage being a model for sustainable agriculture today. This is the reason why new studies on biochar effects on ecosystem services rapidly emerge. Beneficial effects of biochar amendment on plant growth, soil nutrient content, and C storage were repeatedly observed although a number of negative effects were reported, too. In addition, there is no consensus on benefits of biochar when combined with fertilizers. Therefore, the objective of this study was to test whether biochar effects on soil quality and plant growth could be improved by addition of mineral and organic fertilizers. For this purpose, two growth periods of oat ( Avena sativa L.) were studied under tropical conditions (26°C and 2600 mm annual rainfall) on an infertile sandy soil in the greenhouse in fivefold replication. Treatments comprised control (only water), mineral fertilizer (111.5 kg N ha –1 , 111.5 kg P ha –1 , and 82.9 kg K ha –1 ), compost (5% by weight), biochar (5% by weight), and combinations of biochar (5% by weight) plus mineral fertilizer (111.5 kg N ha –1 , 111.5 kg P ha –1 , and 82.9 kg K ha –1 ), and biochar (2.5% by weight) plus compost (2.5% by weight). Pure compost application showed highest yield during the two growth periods, followed by the biochar + compost mixture. biochar addition to mineral fertilizer significantly increased plant growth compared to mineral fertilizer alone. During the second growth period, plant yields were significantly smaller compared to the first growth period. biochar and compost additions significantly increased total organic C content during the two growth periods. Cation-exchange capacity (CEC) could not be increased upon biochar addition while base saturation (BS) was significantly increased due to ash addition with biochar. On the other hand, compost addition significantly increased CEC. Biochar addition significantly increased soil pH but pH value was generally lower during the second growth period probably due to leaching of base cations. Biochar addition did not reduce ammonium, nitrate, and phosphate leaching during the experiment but it reduced nitrification. The overall plant growth and soil fertility decreased in the order compost 〉 biochar + compost 〉 mineral fertilizer + biochar 〉 mineral fertilizer 〉 control. Further experiments should optimize biochar–organic fertilizer systems.

Beschreibung: The Argentine Pampa is one of the major global regions for the production of maize ( Zea mays L.) and soybean ( Glycine max L. [Merr.]), but intense management practices have led to soil degradation and amplified greenhouse-gas (GHG) emissions. This paper presents preliminary data on the effect of maize-soybean intercrops compared with maize and soybean sole crops on the short-term emission rates of CO 2 and N 2 O and its relationship to soil moisture or temperature over two field seasons. Soil organic carbon (SOC) concentrations were significantly greater ( p 〈 0.05) in the maize sole crop and intercrops, whereas soil bulk density was significantly lower in the intercrops. Soil CO 2 emission rates were significantly greater in the maize sole crop but did not differ significantly for N 2 O emissions. Over two field seasons, both trace gases showed a general trend of greater emission rates in the maize sole crop followed by the soybean sole crop and were lowest in the intercrops. Linear regression between soil GHG (CO 2 and N 2 O) emission rates and soil temperature or volumetric soil moisture were not significant except in the 1:2 intercrop where a significant relationship was observed between N 2 O emissions and soil temperature in the first field season and between N 2 O and volumetric soil moisture in the second field season. Our results demonstrated that intercropping in the Argentine Pampa may be a more sustainable agroecosystem land-management practice with respect to GHG emissions.

Beschreibung: Wettability is related to forces or surface tensions (σ) acting at the solid–liquid–vapor interface. Given that surface tensions are difficult to assess directly, contact angles (CA) are used as indicators of the balance of forces acting in the system. In this context, the ES theory was developed as an alternative to assess the σ parameters of the Young's equation. This research evaluates the applicability of a proposed equation of state (ES), which is in theory also able to predict the CA of a sample when two σ parameters of the Young's equation and two fitting parameters (β and α) of the function Φ = (σ SL ) are known (Φ: molecular interaction parameter, σ SL : solid–liquid surface tension). These parameters were determined by different experimental methods assessing the CA, in order to determine which method is more suitable to validate the ES theory: Capillary Rise Method (CRM) and Wilhelmy Plate Method (WPM). For WPM, two modes (advancing and equilibrium CA) were applied. Finally, results of CA between the experimental measurements obtained by WPM and those predicted by the ES were compared. Samples of coarse silt, fine sand, and nonporous glass beads with different levels of water repellency were used as test materials. In line with previous research, all methods showed lower values of σ for samples with increasing hydrophobicity. At the same time, Φ reduces consistently with higher hydrophobicity, up to ≈ 0.5–0.6 based on CRM and WPM-ECA data, and even lower (≈ 0.1–0.2) in WPM-ACA. α increased with higher hydrophobicity, having relatively stable values in samples having σ SV 〉 40 mN m –1 . β showed stable values for samples having σ SV 〉 35–40 mN m –1 . In hydrophobic samples (σ SV 〈 35 mN m –1 ), β decreased in calculations based on WPM-ACA data, and to a minor degree in WPM-ECA. The agreement between the CA directly measured (WPM) and those predicted by the ES was low, although better for the WPM-ECA, suggesting that this last approach can be considered more suitable to evaluate the ES theory.

Beschreibung: Most soils in Nigeria are known to be slightly acidic and very low in plant-available P. These soils need to be fertilized for optimal crop production but cost and scarcity of mineral P fertilizers shifted attention to making direct application of indigenous phosphate rock viable alternative. Laboratory and greenhouse studies were carried out to monitor the effect of the decomposition of legume biomass on the solubilization of Ogun phosphate rock (OPR) on slightly acidic soils. Surface soil samples collected from three experimental sites in SW Nigeria were used. The fertilizer treatments were four rates of P as OPR (0, 30, 60, and 90 kg ha –1 ) and one rate of triple superphosphate (TSP, 40 kg P ha –1 ). The legume treatments were cowpea ( Vigna unguiculata L Walp) and mucuna ( Mucuna puriens L). Rice ( Oryza sativa ) was used in the greenhouse study as the test crop. Soil samples were analyzed for soluble P and pH after 2, 4, 6, and 10 months of incubation in the laboratory while plant tissues collected from greenhouse study were analyzed for P. In the incubation study, significant increase in water-soluble P was observed when legume biomass was incorporated with phosphate rock at p 〈 0.05. Highest value in rice dry-matter yield was recorded with pots treated with mucuna and TSP, also treatment combination of cowpea and OPR significantly increased rice dry-matter yield by 16% over pots treated with cowpea biomass alone and 42% over control pot (no legume biomass and OPR in the green house ( p 〈 0.05). Thus incorporation of legume biomass significantly increased rate of OPR solubilization.

Beschreibung: Abandonment of mountain grassland often changes vegetation composition and litter quantity and quality, but related effects on labile soil organic matter (SOM) are largely unknown. The aim of this study was to investigate the impacts of grassland management and abandonment on soil Carbon distribution in light (〈 1.6 g cm –3 ) particulate organic matter (POM) and aggregation along a gradient of management intensity including hay meadows, pastures, and abandoned grasslands. The reduction of management intensity is an interregional phenomenon throughout the European Alps. We therefore selected sites from two typical climate regions, namely at Stubai Valley, Austria (MAT: 3°C, MAP: 1097 mm) and Matsch Valley, Italy (MAT: 6.6°C, MAP: 527 mm), to evaluate effects of land-use change in relation to climate. Free water-floatable and free POM (wPOM, fPOM), and an occluded POM fraction (oPOM), were isolated from three water-stable aggregate size classes (2–6.3 mm, 0.25–2 mm, 〈 0.25 mm) using density fractionation. Aggregate mean weight diameter slightly decreased with decreasing management intensity. In contrast to absolute POM-C, fPOM-C increased in aggregates at both sites with abandonment. Because the oPOM-C was less affected by abandonment, the ratio of oPOM-C : fPOM-C shifted from 〉 1 to 〈 1 from meadow to abandoned grassland in aggregates at both sites and thus independent of climate. This suggests that in differently managed mountain grasslands free and occluded POM are functionally different SOM fractions. In bulk soil, the oPOM-C : fPOM-C ratio is better suited as an indicator for the response of SOM to management reduction in subalpine grasslands than the total soil C, absolute or relative POM-C content.

Beschreibung: Lower P-input levels in organic than conventional farming can decrease soil total and available P, which can potentially be resupplied from soil organic P. We studied the effect of 30 y of conventional and organic farming on soil P forms, focussing especially on organic P. Soil samples (0–20 cm) were taken in a field experiment with a nonfertilized control, two organic systems receiving P inputs as animal manure, and two conventional systems receiving only mineral P or mineral P and manure. Soils were analyzed for total, inorganic, organic, and microbial P, by sequential P fractionation and by enzyme additions to alkaline soil extracts. Samples taken prior to starting the experiment were also analyzed. Average annual P balances ranged from –20 to +5 kg ha –1 . For systems with a negative balance, labile and moderately labile inorganic P fractions decreased, while organic and stable inorganic P fractions were hardly affected. Similar quantities and proportions of organic P extracted with NaOH-EDTA were hydrolyzed in all soils after addition of an acid phosphatase, a nuclease, and a phytase, and enzyme-stable organic P was also similar among soils. Thus, neither sequential fractionation nor enzyme addition to alkaline soil extracts showed an effect of the type of applied P (manure vs. mineral) on organic P, suggesting that organic P from manure has largely been mineralized. Thus far, we have no indication that the greater microbial activity of the organic systems resulted in a use of stable P forms.

Beschreibung: Apparent electrical conductivity of soil (ECa) is a property frequently used as a diagnostic tool in precision agriculture, and is measured using vehicle-mounted proximal sensors. Crop-yield data, which is measured by harvester-mounted sensors, is usually collected at a higher spatial density compared to ECa. ECa and crop-yield maps frequently exhibit similar spatial patterns because ECa is primarily controlled by the soil clay content and the interrelated soil moisture content, which are often significant contributors to crop-yield potential. By quantifying the spatial relationship between soil ECa and crop yield, it is possible to estimate the value of ECa at the spatial resolution of the crop-yield data. This is achieved through the use of a local regression kriging approach which uses the higher-resolution crop-yield data as a covariate to predict ECa at a higher spatial resolution than would be prudent with the original ECa data alone. The accuracy of the local regression kriging (LRK) method is evaluated against local kriging (LK) and local regression (LR) to predict ECa. The results indicate that the performance of LRK is dependent on the performance of the inherent local regression. Over a range of ECa transect survey densities, LRK provides greater accuracy than LK and LR, except at very low density. Maps of the regression coefficients demonstrated that the relationship between ECa and crop yield varies from year to year, and across a field. The application of LRK to commercial scale ECa survey data, using crop yield as a covariate, should improve the accuracy of the resultant maps. This has implications for employing the maps in crop-management decisions and building more robust calibrations between field-gathered soil ECa and primary soil properties such as clay content.

Beschreibung: Today rapid survey methods of proximal soil sensing (PSS) provide an increasing number of different and highly resolved data. These multidimensional data sets can lead to multilayered and complex maps of parameters which are only indirectly related to soil properties and soil functions. However, in applications usually just one clear elementary map is required. It is of increasing importance to tackle this problem utilizing a cluster algorithm for the synthesis and reduction of multidimensional input variables. The cluster algorithm provides a partitioning of the investigated site whereby the units are characterized by the statistics of the PSS data. Therefore, the question that arises is how suitable is the suggested partitioning in terms of the delineation of different soil units. In this study, we investigate the suitability of cluster partitioning through a case study at a medium-scale test site (≈ 50 000 m 2 ). Two common PSS methods: electromagnetic induction (EMI) and gamma spectrometry (GS) will be employed to create a data set for partitioning by a K-means cluster. The result of the cluster analysis is a delineation of three different parts. In contrast to previous studies, we evaluate the generated partitions by independent soil properties such as grain size, horizon thickness, and color of stratified randomly taken soil samples. The soil analyses show that one of three clusters significantly differs from the others in terms of grain-size distribution and horizon thickness. The partitioning of the other two clusters could not be confirmed by the considered soil parameters. Nevertheless, the case study demonstrates the combination of different PSS data by K-means clustering as a potential approach for site partitioning. An evaluation of the results of the cluster analysis through the collection and analysis of soil samples is highly recommended.

Beschreibung: The use of suitable plants that can accumulate excess phosphorus (P) from contaminated soil may serve as an attractive method for phytoremediation. In this study, pot experiments were conducted to investigate the effects of P incorporation on P accumulation and physiological mechanisms of Polygonum hydropiper in a mining ecotype (ME) and nonmining ecotype (NME) from a phosphorus mining and a noncontaminated agricultural area, respectively. The results demonstrate that the ME of P. hydropiper growing in soil supplied with 0, 100, 200, 400, 800, 1600 mg P (kg soil) –1 showed a significantly higher biomass compared to the NME. Phosphorus accumulation of the ME was positively correlated with the soil P concentration. APase activity in roots of the ME significantly increased at 1600 mg P (kg soil) –1 and phytase activity of the ME increased with increasing P supply. APase activity of the ME was more than twice that of the NME on average. A significant increase of superoxide dismutase (SOD) was observed compared with the NME at all supplied P levels. Peroxidase (POD) activity of the ME was significantly higher at 200 and 400 mg P (kg soil) –1 . No statistical differences in the catalase (CAT) activity of the ME were observed compared with the control. Activity of CAT in the NME was obviously induced after exposure to 100–800 mg P (kg soil) –1 . Malondialdehyde (MDA) concentration in leaves of the ME decreased with increasing P supply to reach a minimum at 400 mg P (kg soil) –1 . In the NME, an increase in MDA concentration compared to the control was observed at higher P levels. The APase and phytase induction and antioxidative defense allowed for the high P accumulation of the ME.

Beschreibung: To investigate the mechanism of cadmium (Cd) detoxification in rice ( Oryza sativa L.), a Cd-tolerant mutant cadH-5 , obtained by an Agrobacterium tumefaciens -based gene-delivery system, was used for a Cd-tolerance and accumulation study. After 15 d of exposure to 0.75 mM CdCl 2 , significant phenotypic differences were observed between the wild type (WT) and cadH-5. When exposed to 0.5 mM CdCl 2 , higher Cd levels were accumulated in cadH-5 root cell wall, root cytosol, and membranes than those in WT. However, Cd concentrations in root tissues varied in both WT and cadH5. No significant difference of hydrogen peroxide (H 2 O 2 ) concentrations was observed between WT and cadH-5 , while contents of cell-wall polysaccharides and phytochelatins (PCs) in the mutant were higher compared to WT. The ratios of reduced glutathione to oxidized glutathione (GSH : GSSG) and ascorbate to dehydroascorbate (ASC : DHA) were lower in WT than in cadH-5 , while the NADPH : NADP + ratio was different to the ratios of GSH : GSSG and ASC : DHA; the ascorbate peroxidase (APX, EC 1.11.1.11), glutathione peroxidase (GR, EC 1.6.4.2), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activities were lower in WT compared to cadH-5. Our results indicate that under long-term Cd stress, cadH-5 plants can accumulate more Cd with more PC. Also, the redox status of ASC-GSH cycle was more inhibited in WT than in cadH-5 plants, rendering WT less able to scavenge reactive oxygen species (ROS). The cadH-5 mutant maintains relatively high ASC, GSH, and NADPH concentrations, ratios of ASC : DHA, GSH : GSSG, and NADPH : NADP + , as well as antioxidative enzymatic activities and PC concentrations. Thus, it is tolerant of relatively high Cd accumulation.

Beschreibung: Red lead (Pb 3 O 4 )- and ZnO-containing anticorrosion paints in the past have been extensively applied to high-voltage steel pylons which has led to heavy metal (HM) soil contaminations in their vicinity. Since pylons are commonly found on agricultural land, there is a potential risk of HM plant uptake. This is promoted by the fact that in contrast to the moderate total Pb contents (several 100 mg kg –1 ) in three nutrient-poor and acidic pylon soils the Pb amounts extractable with NH 4 NO 3 were extremely high, reaching almost 20% of total Pb. A 18-week field pot trial (three harvests in a six-week interval) using Lolium multiflorum was conducted to study the HM plant uptake and the efficiency of the four soil additives, lime (LI), Novaphos (NP), water-treatment sludge (WS), and ilmenite residue (IR) in reducing the plant uptake and NH 4 NO 3 -extractability of Pb and Zn in the soils. Lead concentrations in L. multiflorum shoots grown in the untreated soils reached maximum values of 128 mg (kg dry weight) –1 . Novaphos was most efficient in decreasing shoot Pb (–90%) followed by LI (–78%) and WS (–73%). For Zn, too, LI (–82%), NP, and WS (both –66%) substantially reduced plant uptake. Ilmenite residue was generally only poorly efficient. The dry-matter yield in the NP, LI, and WS treatments was significantly increased. While the relationship between Pb-NH 4 NO 3 and Pb-plant was high when considering the three harvests separately ( R 〉 0.93) a poor relationship ( R = 0.63) exists over all harvests together. This was attributed to different transpiration rates affecting the HM flux into the plants, since the temperature regime changed greatly during the cultivation period. For Zn, no such close relationship between the NH 4 NO 3 -extractable soil fraction and shoot Zn was found, most likely due to antagonistic effects from Mg which greatly varied in the three soils.

Beschreibung: Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil-texture analysis is costly and time-consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot-scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air-dried soil. The soil samples used for this study originated from four different European regions (Hainich-Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air-dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air-dried soil samples ranged from 2.8 g kg –1 to 63.3 g kg –1 and the corresponding clay contents from 60.0 g kg –1 to 815.7 g kg –1 . A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air-dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine-textured than in coarse-textured soils. In this study, organic-C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse-textured soils was more sensitive to the amount of organic C than that of fine-textured soils. The results indicate that in our study the water content of air-dried soil samples was a good quantitative proxy of clay contents, especially useful for fine-textured soils.

Beschreibung: Root active uptake and remobilization of boron (B) have been accepted as mechanisms contributing to nutrient efficiency under low supply of boron. Here, we examined the existence of these mechanisms in eggplant ( Solanum melongena L.) supplied either with luxury (100 μM, B+) or low (7.5 μM, B–) B in the growth medium via semihydroponic cultivation. Boron treatment was marginally not limiting growth thus avoiding side-effects and impairment of acclimation mechanisms of plants. The induction of a B-concentrating mechanism was evident in the roots as B concentration in the xylem sap was only decreased by 23% in B– compared to B+ plants, i.e. , B– roots concentrated B by a factor of 2.7 relative to the external solution. Leaf B concentration in the B– treatment decreased by 33% and 40% in young fully expanded and mature leaves, respectively. Larger differences were observed in the soluble B fraction that decreased by 65% in mature leaves. However, both total and soluble B concentrations in developing leaves were almost equal for both treatments exhibiting a pattern commonly observed in B-remobilizing plants. On the other hand, amounts of B export in the phloem sap were small compared to other species in which B is highly mobile. The B export rate from source leaves was slightly increased under low B supply while that of sucrose was not affected. We conclude that the root concentrating mechanism contributes to the alleviation of B deficiency in eggplant under low B supply while B remobilization may also contribute to a lower degree.

Beschreibung: Due to energy crises and stricter environmental regulations, renewable energy sources like bio-methane produced by anaerobic digestion (biogas) become increasingly important. However, the application of slurries produced by biogas fermentation to agricultural land and subsequent ammonia emission may also create environmental risks to the atmosphere and to N-limited ecosystems. Evaluating ammonia loss from agricultural land by model simulation is an important tool of agricultural-systems analysis. The objective of this study was the systematical comparison of ammonia volatilization after application of two types of biogas slurries containing high amounts of energy crops in comparison with conventional animal slurries and to investigate the relative importance of factors affecting the emission process through an empirical model. A high number of ammonia-loss field measurements were carried out in the years 2007/08 in biogas cropping systems in N Germany. The study consisted of simultaneous measurement of NH 3 losses from animal and biogas slurries in multiple-plot field experiments with different N-fertilization levels. The derived empirical model for the calculation of NH 3 losses based on explanatory variables gave good predictions of ammonia emission for both biogas and pig slurries. The root mean square error ( RMSE ) and mean bias error ( MBE ) of the empirical model for validation data were 2.19 kg N ha –1 ( rRMSE 29%) and –1.19 kg N ha –1 , respectively. Biogas slurries produced highest NH 3 emissions compared to the two animal slurries. In view of the explanatory variables included in the model, total NH application rate, slurry type, temperature, precipitation, crop type, and leaf-area index were important for ammonia-volatilization losses.

Beschreibung: Willows ( Salix spp.) were supposed to be suitable candidates for the phytoremediation of polluted floodplain soils, but it is unknown how willow growth alters concentrations and mobility of pollutants under the conditions of ongoing periodically flooding. Therefore, effects of willow cropping on total concentrations and mobility of As and heavy metals and soil microbial properties were determined after three and four growing seasons under willows in comparison to native grassland in a flood channel of a River Elbe floodplain (Central Germany). After 4 y of willow coppice, the heavy metal concentrations (mg kg –1 ) were increased not only in the grass control plots (final Cu 274, Pb 276, Zn 935) but also under the willows (final Cu 248, Pb 251, Zn 779) compared to the initial concentrations (initial Cu 170, Pb 156, Zn 579). This increase might likely be caused by the ongoing sedimentation by flood events. The smaller increase under willows compared to grass might be related to an initial net effect of phytoextraction. The concentrations of the mobile fractions of Cd, Cu, Ni, and Zn were significantly lower under willows than under grass. Higher β-glucosidase activities under willows than under grass might indicate a starting net decomposition of organic matter. Therefore, the study of long-term and large-scale effects are recommend before an appropriate evaluation of willow short-rotation coppice for phytoremediation of polluted floodplains will be established.

Beschreibung: The aim was to find an adequate, cost-efficient in situ remediation technique for the Mashavera valley, a mining area in SE Georgia heavily contaminated with Cd, Cu, and Zn. A 12-month experiment was conducted to test: iron grit, natural zeolite, biochar, and Divergan® (a scavenger) for soil melioration. The amendments were added in different concentrations to the topsoil of a Kastanozem. Mobile metal concentrations decreased with increasing concentrations of amendments in the sequence Divergan® 〉〉 iron grit ≈ natural zeolite 〉 biochar. In the same order amendments enhanced activities of soil microbial respiration, alkaline phosphatase, and dehydrogenase; microbial C also followed this trend. A sequential extraction confirmed a shift from easily mobilized to heavily bound fractions. The addition of 2% (w/w) of Divergan® was sufficient to lower mobile trace metal concentrations below German thresholds by chemisorption, and soil microbial activity was significantly increased. The effects of all other treatments were at a much lower level and not found suitable due to needed application rates.

Beschreibung: The present study evaluated effects of seed zinc (Zn) priming at concentrations from 0 to 25 mM ZnSO 4 on seedling vigor and viability in rice ( Oryza sativa L.). Zinc priming substantially increased Zn concentration in the husk, but not in brown rice. The movement of primed Zn from the husk into the inner layers of rice seed during germination was suggested by Zn concentration declining in the husk coinciding with the increase in brown rice over time ( r = –0.62; p 〈 1%), which did not happen in unprimed seed. Zinc priming significantly enhanced seedling growth and development up to 5 mM. Germination rate, root number, and dry weight were much higher than in unprimed seed, but higher Zn concentrations (10 and 25 mM) depressed seedling vigor. Priming rice seed with 2.5 mM Zn also improved the germination rate of rice in a Zn-deficient soil, with or without soil Zn application. The results confirm that priming rice seed with Zn can improve germination and seedling vigor and for the first time show how Zn requirement of germinating rice seed and seedlings can be met by the prime Zn accumulated in the husk.

Beschreibung: Interest in mixed-species plantations in the tropics has increased because they appear to provide a wider range of options, such as yield, biodiversity, nutrient cycling, and C sequestration than pure stands. Pure stands of Pinus patula Schlecht. and Charm., Juniperus procera Hochst., and Grevillea robusta A. Cunn., and mixed stands of P. patula / G. robusta, P. patula / J. procera, and P. patula / Podocarpus falcatus R. Br. at Wondo Genet in S Ethiopia were studied to examine (1) the impact of mixed-species plantations on soil chemical properties, and (2) the impact of mixed-species plantations on the nutritional status of constituent trees. Soil (0–50 cm depth) and foliage samples were collected from four random plots (100 m 2 ) in each of the pure and mixed-species plantations. Soil samples were analyzed for organic C, N, and base cations. Foliage samples were analyzed for nutrients (N, P, K, Ca, and Mg). There were little significant differences in soil chemical properties and foliar nutrient concentrations of trees between the pure and mixed stands. Among pure stands, J. procera and G. robusta differed in soil exchangeable Ca ++ and K + at 0–5 cm soil depth and in foliar P and Ca concentration. After 18 and 24 y, mixed stands did not influence soil chemical properties and tree nutrition differently than pure stands. This may be due to additive interaction in mixed-species stands and the similarity of the constituent tree species in foliar nutrient concentration and their impact on soil chemical properties.

Beschreibung: A greenhouse experiment was conducted to investigate the immediate effect of application of mono-ammonium phosphate (MAP), single superphosphate (SSP), and triple superphosphate (TSP) fertilizers containing varying concentrations of Cd on (1) chemical speciation of Cd and Zn in soil solution by chemical-equilibrium calculations (MINEQL+4.6 model), (2) growth of barley plants, (3) concentrations of Cd, P, and Zn in soil solution and plant tissue, as well as total plant accumulation of Cd, P, and Zn, and (4) monitoring pH and element changes during incubation periods following phosphate application. Results show that, in general, the pH of soil solution increased during the first 40 d of incubation, then declined. Also, at the end of incubation period, pH of soil solution was affected by fertilization source and fertilization rate. The concentration of Cd in soil solution changed with time. Phosphate fertilization ( p 〈 0.05) or fertilizer source ( p 〈 0.05) showed consistent effects. Also, the application of phosphate fertilizers with three rates significantly increased Zn concentrations in soil solution during the first half (0–30 d) of incubation period and then decreased but still more than in the control. In general, application of different sources of phosphate at 100 g kg –1 did not change the dominant forms of Cd in soil solution during all incubation time intervals. Speciation of Zn in the control after 30 d of incubation had changed, in comparison to 10 d of incubation, and the dominant forms were Zn 2+ , ZnOH + , ZnHCO 3 , ZnCO 3 (aq), and Zn(OH) 2 (aq). Adding phosphate fertilizer significantly increased both shoot and root dry weight compared to control, indicating P was a growth-limiting factor in the control plants. The Zn concentrations in shoot and root were lower in the TSP- and SSP-fertilizers treatment than those in the MAP and fertilizer treatments at all rates of fertilization. Adding phosphate increased the Cd : Zn and P : Zn ratios in the shoot and root tissue, with the effect being greater with increasing fertilization rate. Phosphate fertilization greatly increased the total accumulation of Cd of barley compared with the control plants ( p 〈 0.001), with the effect being greater with increasing fertilization rate. Source and rate of fertilizers, and their interactions had significant effect ( p 〈 0.05) on Cd accumulation in the whole plant.

Beschreibung: The effects of intensive banana production with high mineral-fertilizer application and of extensive pastures were compared regarding water quality in a lowland region of SE Mexico. We monitored NO , NO , and PO 4 3– concentrations in groundwater (80 m depth), subsurface water (5 m depth), and surface water (open-ditch drainage) at monthly intervals for a one-year period. Irrespective of the land use, the NO concentrations in all water bodies were lower than the threshold value for drinking water and aquatic life. Particularly in areas with intense banana production, the NO contents in water exceeded the safety thresholds for drinking water of 1.0 mg L –1 ( WHO , 2006) and aquatic ecosystems of 0.2 mg L –1 ( OATA , 2008). Water from pastureland showed significantly higher PO 4 3– concentration than that from the banana plantation, indicating a high risk of eutrophication. There is a need to provide recommendations for optimal time and amount of N application in commercial banana production and for limitation of P inputs in pasturelands to avoid further contamination of water bodies.

Beschreibung: Plants in arid or semiarid areas often experience simultaneous salt and boron (B) stress. Interactive effects on stress responses have been clearly established, but results are inconsistent and variably indicate antagonistic or synergistic interactions even within the same plant species. In this study, five differently B- and salt-resistant wheat genotypes were grown hydroponically at low and high B supply. The effect of increasing NaCl salinity on plant growth, boron uptake rates, shoot B concentrations, and transpiration was determined under both B regimes. The interactive effect of salt and B was different under low and high B supply. Boron-uptake rates were reduced with increasing salt concentration only under high B supply, and reductions correlated significantly with decreases in leaf area and shoot B concentrations. Under low B supply, however, salt-induced effects on B-uptake rates were variable and not significantly correlated with leaf-area reductions. These results suggest that under high B supply, when B uptake is predominantly passive by diffusion or channel-mediated via aquaporins, transpiration-driven water flow is the dominant factor for B accumulation in arial plant parts. Under low B supply, when a significant portion of B can be taken up via active pathways, transpiration is not the decisive factor for B accumulation. Under these conditions, the salt sensitivity of a genotype is a modifying factor of salt–B interactions, because salt-induced growth inhibition can result in a concentration effect, offset the reduction of B-uptake rates, and result in increased shoot B concentrations. Contradictory reports on the nature of salt–B interactions might in part be related to low levels of B supply chosen as control treatments and concomittant differences in predominant B-uptake pathways.

Beschreibung: Potassium (K) deficiency is one of the main limiting factors in cotton ( Gossypium hirsutum L.) production. To study the mechanism of high K-use efficiency of cotton, a pot experiment was conducted. The experiment consisted of two cotton genotypes differing in K-use efficiency (H103 and L122) and two K-application levels (K 0 : 0 g (kg soil) –1 ; K 1 : 0.40 g (kg soil) –1 ). Root-hair density and length, partitioning of biomass and K in various organs, as well as K-use efficiency of the two cotton genotypes were examined. The results show that there was no significant difference in K uptake between the two genotypes at both treatments, although the genotype H103 (high K-use efficiency) exhibited markedly higher root-hair density than genotype L122 in the K 1 treatment. Correlation analysis indicates that neither root-hair density nor root-hair length was correlated with plant K uptake. Furthermore, the boll biomass of genotype H103 was significantly higher than that of genotype L122 in both treatments, and the K accumulation in bolls of genotype H103 was 39%–48% higher than that of genotype L122. On the other hand, the litter index (LI) and the litter K-partitioning index (LKPI) of genotype H103 were 14%–21% and 22%–27% lower than that of genotype L122. Lastly, the K-use efficiency of total plant (KUE-P) of genotype H103 was comparable with that of genotype L122 in both treatments, but the K-use efficiency in boll yield (KUE-B) of genotype H103 was 24% and 41% higher than that of genotype L122 in K 0 and K 1 treatments. Pearson correlation analysis indicated that KUE-P was positively correlated with BKPI and negatively correlated with LKPI, while KUE-B was positively correlated with BKPI and boll-harvest index (HI B ), and negatively correlated with LKPI. It is concluded that there were no pronounced effects of root-hair traits on plant K uptake of the two genotypes. The difference in K-use efficiency was attributed to different patterns of biomass and K partitioning rather than difference in K uptake of the two genotypes.

Beschreibung: Previous greenhouse studies have demonstrated that photosynthesis in some cultivars of first- (GR1) and second-generation (GR2) glyphosate-resistant soybean was reduced by glyphosate. The reduction in photosynthesis that resulted from glyphosate might affect nutrient uptake and lead to lower plant biomass production and ultimately reduced grain yield. Therefore, a field study was conducted to determine if glyphosate-induced damage to soybean ( Glycine max L. Merr. cv. Asgrow AG3539) plants observed under controlled greenhouse conditions might occur in the field environment. The present study evaluated photosynthetic rate, nutrient accumulation, nodulation, and biomass production of GR2 soybean receiving different rates of glyphosate (0, 800, 1200, 2400 g a.e. ha –1 ) applied at V2, V4, and V6 growth stages. In general, plant damage observed in the field study was similar to that in previous greenhouse studies. Increasing glyphosate rates and applications at later growth stages decreased nutrient accumulation, nodulation, leaf area, and shoot biomass production. Thus, to reduce potential undesirable effects of glyphosate on plant growth, application of the lowest glyphosate rate for weed-control efficacy at early growth stages (V2 to V4) is suggested as an advantageous practice within current weed control in GR soybean for optimal crop productivity.

Beschreibung: Ongoing global warming may result in colder soil and thawing cycles and will increase the frequency of soil freezing-and-thawing-treated cycles (FTCs) during winter in the cool-temperate and high-latitude regions. The purpose of this study was to determine the effects of repeated freeze–thaw cycles on the solubility and adsorption of P in lab and field experiments on Pellustert, Argiustoll, Haplustept, Fluvaquent, and Calciorthid soils, the major soil groups in E Turkey. The results demonstrated that, depending on the soil type, the freeze–thaw cycle could increase the adsorption and desorption of P within a certain temperature range. Repeated freezing and thawing decreased equilibrium P concentration (EPC) and increased P adsorption. EPC and P adsorption were strongly correlated with the number of FTCs. The highest P adsorption and the lowest P desorption was found in Pellustert followed by Argiustoll, Calciorthid, Haplustept, Fluvaquent when refrozen at –10°C for 15 d, then thawed at +2.5°C for 18 h, and 9 times FTC. However, in the field study, the adsorption value was lower than the value obtained from the laboratory condition. It appears that increasing the frequency of freeze–thaw processes depending on increase in temperature that leads to decreased plant-available soil P pools, thus requires more P fertilizer in soil solution to supply adequate P during the plant-growth period.

Beschreibung: Bioenergy is becoming an important option in Global Change mitigation policy world-wide. In agriculture, cultivation of energy crops for biodiesel, biogas, or bioethanol production received considerable attention in the past decades. Beyond this, the cultivation of Miscanthus, used as solid fuel for combustion, may lead to an increase in soil organic matter content compared to other agricultural land use, since C-sequestration potential in soils of Miscanthus crops is high due to, e.g., high amounts of harvest residues. This may indirectly contribute to a reduction of atmospheric CO 2 concentration. The objective of the present work was to investigate the development of soil organic carbon and Miscanthus -derived C contents, as well as to estimate carbon stocks in soils cultivated with Miscanthus using 13 C-natural-abundance technique. The investigations were carried out in relation to soil depth up to 150 cm in a sequence of 2, 5, and 16 y of cultivation relative to a reference soil cultivated with cereals. Amounts of total organic C (TOC) and Miscanthus -derived C ( Miscanthus -C) increased with increasing duration of cultivation. For example, TOC increased from 12.8 to 21.3 g C kg –1 after 16 y of cultivation at the depth of 0–15 cm, whereby the portion of Miscanthus -C reached 5.8 g C kg –1 . Also within deeper soil layers down to 60 cm depth a significant enhancement of Miscanthus -C was detectable even though TOC contents were not significantly enhanced. At soil depth below 60 cm, no significant differences between treatments were found for Miscanthus -C. Within 16 y of continuous commercial farming, Miscanthus stands accumulated a total of 17.7 Mg C ha –1 derived from Miscanthus residues (C4-C), which is equivalent to 1.1 Mg C4-C ha –1 y –1 . The annual surplus might function as CO 2 credit within a greenhouse-gas balance. Moreover, the beneficial properties of Miscanthus cultivation combined with a low requirement on fertilization may justify the status of Miscanthus as a sustainable low-input bioenergy crop.

Beschreibung: Questions remain about the exact ultrasonic energy level that is required to effectively disperse soil aggregates and to what extent this is accompanied by physical damage to individual soil particles. We found maximum aggregate dispersion at energy levels of 1500 J cm –3 and no evidence for the disintegration of particles 〈 20 μm even at that energy level. Our findings suggest that sonication at energies much greater than those applied conventionally can disperse aggregates of high mechanical stability.

Beschreibung: Sulfur (S)-diagnostic tools are essential for rational use of S fertilizers. There is little information about the suitability of leaf greenness intensity to detect S deficiency in corn ( Zea mays L.). This work evaluates, under controlled S-stressed conditions, (1) the performance of leaf greenness intensity as an indicator of the degree of S deficiency in corn, and (2) the advantage of the upper leaves in relation to the middle leaves for S-deficiency determination. A pot experiment using sand as growth medium was conducted in greenhouse with corn at S rates of 0, 5, 10, 20, and 40 mg kg –1 and sufficiency of other nutrients. Measurements of aboveground biomass (AB), total nitrogen (N), and S concentrations, and chlorophyll-meter readings (CMR) in upper and middle leaves, were performed at the growth stages of 6–7, 11–12, and 14–15 fully expanded leaves (V6-V7, V11-V12, and V14-V15, respectively). Sulfur application significantly increased AB, leaf S concentration, and CMR. Significantly positive relationships were obtained between leaf S concentration and CMR. A sulfur-sufficiency index (SSI) based on CMR measured in upper and middle leaves was significantly associated with AB ( R 2 = 0.58 and 0.62 for the middle and upper leaves, respectively). It is concluded that under sufficiency of other nutrients and high-S-stressed conditions, leaf greenness intensity could be a good indicator of corn S status, although little or no advantage was found for taking CMR from the upper leaves.

Beschreibung: Despite the importance of biological soil crusts (BSC) for ecosystem functions in arid and semiarid areas, little information on their mechanical stability is available. Goal of this study was to develop a micropenetrometer (EMP) that allows to determine BSC stability at high spatial resolutions. First results show that differences in BSC stability at 39 μm resolution can be detected and that cyanobacterial BSC has an average penetration resistance of 0.75 MPa.

Beschreibung: Agricultural practices may lead to excessive phosphorus (P) accumulation in soil. The effects of excessive P on Chinese flowering cabbage ( Brassica campestris spp. parachinensis ) were investigated by exposing plants for 4 weeks in solution containing 1, 2, 3, 5, and 7 mM NaH 2 PO 4 . Phosphorus concentrations [P] greater than 3 mM produced significantly stunted growth, together with reduced appearance quality due to overaccumulation of anthocyanin in the epidermis of flower stalk. Nitrate concentrations in the flower stalk decreased with increasing solution [P]. Nitrogen (N) concentrations in the roots and potassium (K) concentrations in the leaves, stems, and roots all decreased at [P] higher than 3 mM. Increasing P supply caused great enhancement of root and stem [P], but decreased total plant and root N : P ratios. A positive linear relationship between solution [P] and anthocyanin concentration and a negative linear relationship between root N : P ratio and anthocyanin concentration were also observed. In addition, 3 to 7 mM P caused decreased levels of indole-3-acetic acid (IAA) and gibberellin (GA 3 ) in the leaves, but promoted ethylene production. The average gibberellin concentration was generally correlated with the plant's relative growth rates. Ethylene was negatively correlated with plant growth parameters except for the last day of the experiment. In conclusion, N : P ratio and endogenous phytohormones may be involved in the development of P toxicity in Chinese flowering cabbage plants.

Beschreibung: An essential prerequisite for a sustainable soil use is to maintain a satisfactory soil organic-matter (OM) level. This might be achieved by sound fertilization management, though impacts of fertilization on OM have been rarely investigated with the aid of physical fractionation techniques in semiarid regions. This study aimed at examining changes in organic C (OC) and N concentrations of physically separated soil OM pools after 26 y of fertilization at a site of the semiarid Loess Plateau in China. To separate sensitive OM pools, total macro-OM (〉 0.05 mm) was obtained from bulk soil by wet-sieving and then separated into light macro-OM (〈 1.8 g cm –3 ) and heavy macro-OM (〉 1.8 g cm –3 ) subfractions; bulk soil was also differentiated into light OM (〈 1.8 g cm –3 ) and mineral-associated OM (〉 1.8 g cm –3 ). Farmyard manure increased concentrations of total macro-OC and N by 19% and 25%, and those of light fraction OC and N by 36% and 46%, compared to no manuring; both light OC and N concentrations but only total macro-OC concentration responded positively to mineral fertilizations compared to no mineral fertilization. This demonstrated that the light-fraction OM was more sensitive to organic or inorganic fertilization than the total macro-OM. Mineral-associated OC and N concentrations also increased by manuring or mineral fertilizations, indicating an increase of stable OM relative to no fertilization treatment, however, their shares on bulk soil OC and N decreased. Mineral fertilizations improved soil OM quality by decreasing C : N ratio in the light OM fraction whereas manuring led to a decline of the C : N ratio in the total macro-OM fraction, with respect to nil treatment. Further fractionation of the total macro-OM according to density clarified that across treatments about 3/4 of total macro-OM was associated with minerals. Thus, by simultaneously applying particle-size and density separation procedures, we clearly demonstrated that the macro-OM differed from the light OM fraction not only in its chemical composition but also in associations with minerals. The proportion of the 0.5–0.25 mm water-stable aggregates of soil was higher under organic or inorganic fertilizations than under no manure or no mineral fertilization, and increases in OC and N concentrations of water-stable aggregates as affected by fertilization were greater for 1–0.5 and 0.5–0.25 mm classes than for the other classes. Results indicate that OM stocks in different soil pools can be increased and the loose aggregation of these strongly eroded loess soils can be improved by organic or inorganic fertilization.

Beschreibung: Knowledge of the soil hydraulic functions is required for various hydrological studies and for the simulation of water and solute fluxes in unsaturated soils. Sand/kaolin boxes are frequently used to determine these properties in the low-tension range. For higher tensions the pressure plate extractor is mainly applied. The extended evaporation method allows a more efficient determination of the water-retention curve in an adequate range. Besides this method enables to quantify simultaneously the unsaturated hydraulic-conductivity function. The objective of this study was to compare the water-retention curves obtained from the standard methods (STM) with those determined with the extended evaporation method (EEM). A set of 90 natural soil samples of different texture and origin was analyzed, and the agreement between the methods was statistically evaluated. The average water-content deviation (AWCD) of all samples was 1.83 vol.%, and the root mean square error (RMSE) 2.08 vol.%. The deviation of soil water-storage capacity in the pore-size classes 0–6, 6–30, 30–500, 500–1500 kPa varied between minimum –0.17 and 0.25 vol.% and maximum –2.89 and 2.36 vol.%, and confirmed the good comparability among the adopted methods. Systematic deviations between the methods were not found.

Beschreibung: Among energy crops, short-rotation coppices (SRC) are recommended to provide renewable energy. Compared to annual crops, willows and poplars are regarded as plants with low requirements for nutrients, herbicides, pesticides, and soil maintenance. However, only little is known about N-fertilizer effects on SRC and the few studies are even inconsistent. Therefore, we studied the effects of N on yields of willows and poplars in a field experiment. The effects of N fertilization on nitrate leaching and nitrous oxide emissions from the loamy-sand soil were also measured. Cuttings of willows ( Salix viminalis clone Inger) and poplars ( Populus maximovizcii × P. nigra clone max 4) were planted on farmland in 2008. The experiment was arranged in a random block design with three levels of N fertilizer (0, 50, and 75 kg N ha –1 y –1 ). After 2 y, the trees were harvested for the first time. Fertilization did not affect the yields of willows or poplars. However, the application of 75 kg N ha –1 y –1 caused an average increase of N leaching in the willow and poplar plots of 25 kg N ha –1 y –1 and 40 kg N ha –1 y –1 , respectively. Emissions of N 2 O were increased by a maximum of only 0.2 kg N ha –1 y –1 . Further, the N fertilizer stimulated the growth of the weed biomass in case of the willow plots by 46% and of the weed N content by 52% ( r = 0.53). In conclusion, in the first 2 y, SRC could be produced in a more effective and environmentally friendly manner without mineral fertilizer.

Beschreibung: Enrichment of soil organic carbon (SOC) stocks through sequestration of atmospheric CO 2 in agricultural soils is important because of its impacts on adaptation to and mitigation of climate change while also improving crop productivity and sustainability. In a long-term fertility experiment carried out over 27 y under semiarid climatic condition, we evaluated the impact of crop-residue C inputs through rainfed fingermillet ( Eleusine coracana [L.] Gaertn.) cropping, fertilization, and manuring on crop yield sustainability and SOC sequestration in a Alfisol soil profile up to a depth of 1 m and also derived the critical value of C inputs for maintenance of SOC. Five treatments, viz., control, farmyard manure (FYM) 10 Mg ha –1 , recommended dose of NPK (50 : 50 : 25 kg N, P 2 O 5 , K 2 O ha –1 ), FYM 10 Mg ha –1 + 50% recommended dose of NPK, and FYM 10 Mg ha –1 + 100% recommended dose of NPK imposed in a randomized block design replicated four times. Application of FYM alone or together with mineral fertilizer resulted in a higher C input and consequently built up a higher C stock. After 27 y, higher profile SOC stock (85.7 Mg ha –1 ), C build up (35.0%), and C sequestration (15.4 Mg C ha –1 ) was observed with the application of 10 Mg FYM ha –1 along with recommended dose of mineral fertilizer and these were positively correlated with cumulative C input and well reflected in sustainable yield index (SYI). For sustenance of SOC level (zero change due to cropping) a minimum quantity of 1.13 Mg C is required to be added per hectare per annum as inputs. While the control lost C, the application of mineral fertilizer served to maintain the priori C stock. Thus, the application of FYM increased the C stock, an effect which was even enhanced by additional amendment of mineral fertilizer. We conclude that organic amendments contribute to C sequestration counteracting climate change and at the same time improve soil fertility in the semiarid regions of India resulting in higher and more stable yields.

Beschreibung: Limited information is available on biological effects of various levels of nickel (Ni) (deficiency to toxicity levels) on growth and yield of certain crops, particularly vegetables. In this sand-culture study, we investigated the effects of four levels of Ni (0, 50, 100, and 200 μM) on growth, yield, and fruit-quality attributes of two cucumber cultivars ( Cucumis sativus L. cvs. Super Dominus and Negin) supplied with urea or NH 4 NO 3 as nitrogen source. Addition of 50 μM Ni to the nutrient solution resulted in a significant increase of shoot and root dry-matter yield of cv. Negin although this increase was greater in the urea-fed plants than those fed with NH 4 NO 3 . In both cultivars, addition of 50 μM Ni increased urease activity and thereby decreased the urea concentration in the urea treatment. Addition of 100 and 200 μM Ni caused a significant decrease in root and shoot growth of cucumber although this decrease was insignificant for cv. Super Dominus in the 100 μM treatment. The highest fruit yield, total soluble solids (TSS), and fruit firmness were achieved at the 50 μM Ni treatment. Regardless of nitrogen source, Ni addition proportional to the concentration used increased leaf Ni concentration and fruit acid ascorbic concentration. The concentration of Ni required for optimum growth and yield of cucumber varied with cultivars. The level of 50 μM was sufficient for optimum growth of cv. Negin in nutrient-solution culture while lower concentration of Ni was required for cv. Super Dominus. While the beneficial effects of sufficient levels of Ni on growth and yield of urea-fed plants was greater than with NH 4 NO 3 -fed plants, the toxic effects of Ni in these plants were also greater.

Beschreibung: In this work, the use of an objective method, the formulation of the Rasch measurement model, which synthesizes data with different units into a uniform analytical framework, is considered to get representative measures of soil fertility potential in an experimental field. Thus, two types of information about the soil were obtained from soil samples taken at 70 locations: first, the textural components were determined, and, secondly, deep (ECa-90) and shallow (ECa-30) soil apparent electrical conductivity, approximately 0–90 and 0–30 cm depths, respectively, were measured. A latent variable, denominated soil fertility potential, was defined. It is supposed, and later it is verified, that all soil properties previously indicated have a marked influence on the latent variable. The adequate assignment of categorical values across properties measures and the good fit of the data are checked as a previous phase to properly compute the Rasch measures. After applying the Rasch methodology, it was obtained that both electrical conductivities are the most influential properties on soil fertility potential, getting moreover a ranking of all soil samples according to their fertility potential and the unexpected behaviors, called misfits, of some soil samples, which constitute a very useful information to better match soil and crop requirements as they vary in the field, being a rational basis for a site-specific crop management.

Beschreibung: A 3-year field experiment was carried out to determine the significance of root-growth characteristics contributing to N-uptake efficiency of two oilseed rape ( Brassica napus L.) cultivars differing in N efficiency. Two N treatments were applied, and the core and minirhizotron techniques were used to study root-length density and number of living roots, respectively. Fertilizer-N supply increased shoot dry matter, grain yield, total N uptake, and total soil N min contents particularly in the top soil. Although significant differences occurred in all parameters between years, the interactions between years and cultivars were mostly not significant. Compared to cv. Capitol, the N-efficient cv. Apex was characterized by a higher grain yield at N0 and a higher N uptake during reproductive growth. This genotype also had a higher root-length density and more living fine roots particularly in the topsoil layer. Root growth of this genotype was especially high from beginning of shooting to beginning of flowering, while shoot growth and N uptake during vegetative growth were comparatively low. Our results suggest that N-efficient cultivars can be characterized by a high investment in root growth during the vegetative stage with a comparatively slow shoot growth and N-uptake rate until beginning of flowering, which, however, continues during reproductive growth. High root production only during reproductive growth seems to be less effective to achieve high N efficiency, because this may lead to a shortage of assimilates for seed filling. High root-length density at vegetative stages may thus be advantageous for N uptake and reproductive growth and could be a useful morphological character for the selection and breeding of N-efficient cultivars.

Beschreibung: We investigated soil response to long-term cattle grazing at stocking rates 0 (CK), 2.4 (MG), and 4.8 (HG) animal unit months ha –1 on a Rough Fescue ( Festuca campestris Rydb.) grassland. Soil organic C and N stocks and available nutrients were not affected by grazing while soil bulk densities (0–30 cm) were higher and P stocks (15–30 cm) were lower under grazing than CK. The slow rate change of soil C and N suggest the rich black grassland soils appear to tolerate intensive grazing.

Beschreibung: The effect of K fertilization on microstructural soil stability is rarely analyzed until now although the ambiguous impact on bulk soil structure was reported quite often, e.g., with regard to higher erodibility on the one hand and higher water storage on the other. Soil material from different long-term fertilization trials in Germany was examined rheologically by means of an amplitude sweep test where the samples were subjected to oscillating shearing with increasing deflection. The resulting shear stress was recorded, and the maximum stress denoted the maximum shear strength of the sample. Results showed an ambiguous influence of K which depends strongly on the soil properties. On the one hand, an increased ion concentration in the soil solution leads to increasing attractive forces as defined by the DLVO theory and therefore higher shear resistance. With increasing desiccation, K + like other salts can precipitate at the contact areas between particles and lead to cementation. On the other hand, K + as a monovalent ion impedes covalent and ionic bonding between clay minerals which holds true for most of the examined soil types while only sandy soils showed an increase in soil strength due to K fertilization. Potassium depletion further resulted in increased interaction of fertilization with other impact factors, e.g., climate and soil properties. Thus, the destabilizing effect of K + was more pronounced under liming as without liming. Subsequent modeling with selected soil parameters confirmed the high influence of matric potential. The modeling also revealed the interactions with other soil parameters, e.g., pH, oxides, texture, exchangeable cations as well as lack or surplus of K in relation to recommended K content. In conclusion, microstructural stability of soil depends on several soil parameters and requires the inclusion of many chemical and physical soil properties.

Beschreibung: Crop growth in sandy soils is usually limited by plant-available nutrients and water contents. This study was conducted to determine whether these limiting factors could be improved through applications of compost and biochar. For this purpose, a maize ( Zea mays L.) field trial was established at 1 ha area of a Dystric Cambisol in Brandenburg, NE Germany. Five treatments (control, compost, and three biochar-compost mixtures with constant compost amount (32.5 Mg ha –1 ) and increasing biochar amount, ranging from 5–20 Mg ha –1 ) were compared. Analyses comprised total organic C (TOC), total N (TN), plant-available nutrients, and volumetric soil water content for 4 months under field conditions during the growing season 2009. In addition, soil water-retention characteristics were analyzed on undisturbed soil columns in the laboratory. Total organic-C content could be increased by a factor of 2.5 from 0.8 to 2% ( p 〈 0.01) at the highest biochar-compost level compared with control while TN content only slightly increased. Plant-available Ca, K, P, and Na contents increased by a factor of 2.2, 2.5, 1.2, and 2.8, respectively. With compost addition, the soil pH value significantly increased by up to 0.6 ( p 〈 0.05) and plant-available soil water retention increased by a factor of 2. Our results clearly demonstrated a synergistic positive effect of compost and biochar mixtures on soil organic-matter content, nutrients levels, and water-storage capacity of a sandy soil under field conditions.

Beschreibung: Soil P availability has been identified as one of the key factors controlling wetland productivity, structure, and function. Soil P fractions at different depths in newly formed wetlands along a salinity gradient in Yellow River Delta (China) were studied using a modified Hedley fraction method. The total P (P t ) content ranged from 471.1 to 694.9 mg kg –1 , and diluted HCl-extractable inorganic P (Dil-HCl-P i ) ranged from 324 to 524.2 mg kg –1 . The Dil-HCl-P i is the predominant P form in all profiles, with on average 70% of the P t extracted as P i . Organic P (P o ) comprised (4.2 ± 2.0)% (mean ± SD) of the P t , due to low organic-matter content in coastal salt marsh ecosystems. The labile P (resin-P, NaHCO 3 -P i , and NaHCO 3 -P o ) and moderately labile P (NaOH-P i and NaOH-P o ) concentrations were both low, ranged from 11.6 to 38.1 and 2.8 to 21.3 mg kg –1 , respectively, constituting (3.7 ± 1.1)% and (2.0 ± 0.7)%, respectively, of P t , suggesting low availability of P to plants in these soils. Our results suggested that vegetation cover significantly influenced soil P dynamics and availability. In particular, the labile P content under Tamarix chinensis increased significantly by 23.2%–145.5% compared with adjacent soils. These findings have important implications for wetland conservation or restoration and long-term sustainable management of newly formed wetland ecosystems in the Yellow River Delta.

Beschreibung: Cadmium (Cd) is toxic to plants, animals, and humans. However, different plant species growing on the same soil may have very different shoot Cd concentrations depending on properties such as size of the root system, Cd net influx, shoot-growth rate, Cd translocation from root to shoot, and the ability to affect Cd availability in the soil. To investigate possible reasons for different shoot Cd concentrations maize, sunflower, flax, and spinach were grown on an acid sandy soil (pH〈$〉_{{\rm{(CaCl}}_{\rm{2}} {\rm)}〈$〉 4.5, and C org 2.8%) in a growth chamber with Cd additions as Cd(NO 3 ) 2 of none, 14, and 40 μmol (kg soil) –1 resulting in Cd soil-solution concentrations of 0.04, 0.68, and 2.5 μM. Only the high Cd addition caused a significant growth reduction of flax and spinach. The shoot Cd concentration was up to 30 times higher in spinach than in maize; the other species were intermediate. Of the plant properties studied only the variation of the Cd net influx explained the differences in shoot Cd concentrations. This was due to a decreased (maize, sunflower) or increased (flax) Cd concentration in soil solution or more effective uptake kinetics (spinach).

Beschreibung: Anadenanthera peregrina is a Brazilian savanna tree species that occurs naturally in arsenic (As)-contaminated areas, and its As resistance has been associated with arbuscular mycorrhizal–fungi (AMF) symbiosis. A plant's ability to survive in stressful environments is correlated with its nutrition status, which can be affected by As uptake. The present study evaluated the influence of As on the concentrations and distribution of nutrients in the roots and shoots of A. peregrina grown in the absence of AMF. These plants were grown in substrates spiked with 0, 10, 50, and 100 mg As kg –1 for 25 d under greenhouse conditions, and the concentrations of essential macro- (P, K, Ca, Mg, N, and S) and micro- (Fe, Mn, Cu, Zn, B, and Mo) nutrients in the roots and shoots were then determined. Enhanced As levels increased the concentrations of P, S, and N and decreased Ca, Mg, and Fe. Although the deleterious effects of As on the plants were striking, the internal As levels were high, which indicated some tissue tolerance of A. peregrina.

Beschreibung: The use of suitable plants that can accumulate excess phosphorus (P) from contaminated soil may serve as an attractive method for phytoremediation. In this study, pot experiments were conducted to investigate the effects of P incorporation on P accumulation and physiological mechanisms of Polygonum hydropiper in a mining ecotype (ME) and nonmining ecotype (NME) from a phosphorus mining and a noncontaminated agricultural area, respectively. The results demonstrate that the ME of P. hydropiper growing in soil supplied with 0, 100, 200, 400, 800, 1600 mg P (kg soil) –1 showed a significantly higher biomass compared to the NME. Phosphorus accumulation of the ME was positively correlated with the soil P concentration. APase activity in roots of the ME significantly increased at 1600 mg P (kg soil) –1 and phytase activity of the ME increased with increasing P supply. APase activity of the ME was more than twice that of the NME on average. A significant increase of superoxide dismutase (SOD) was observed compared with the NME at all supplied P levels. Peroxidase (POD) activity of the ME was significantly higher at 200 and 400 mg P (kg soil) –1 . No statistical differences in the catalase (CAT) activity of the ME were observed compared with the control. Activity of CAT in the NME was obviously induced after exposure to 100–800 mg P (kg soil) –1 . Malondialdehyde (MDA) concentration in leaves of the ME decreased with increasing P supply to reach a minimum at 400 mg P (kg soil) –1 . In the NME, an increase in MDA concentration compared to the control was observed at higher P levels. The APase and phytase induction and antioxidative defense allowed for the high P accumulation of the ME.

Beschreibung: Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil-texture analysis is costly and time-consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot-scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air-dried soil. The soil samples used for this study originated from four different European regions (Hainich-Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air-dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air-dried soil samples ranged from 2.8 g kg –1 to 63.3 g kg –1 and the corresponding clay contents from 60.0 g kg –1 to 815.7 g kg –1 . A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air-dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine-textured than in coarse-textured soils. In this study, organic-C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse-textured soils was more sensitive to the amount of organic C than that of fine-textured soils. The results indicate that in our study the water content of air-dried soil samples was a good quantitative proxy of clay contents, especially useful for fine-textured soils.

Beschreibung: Potassium (K) deficiency is one of the main limiting factors in cotton ( Gossypium hirsutum L.) production. To study the mechanism of high K-use efficiency of cotton, a pot experiment was conducted. The experiment consisted of two cotton genotypes differing in K-use efficiency (H103 and L122) and two K-application levels (K 0 : 0 g (kg soil) –1 ; K 1 : 0.40 g (kg soil) –1 ). Root-hair density and length, partitioning of biomass and K in various organs, as well as K-use efficiency of the two cotton genotypes were examined. The results show that there was no significant difference in K uptake between the two genotypes at both treatments, although the genotype H103 (high K-use efficiency) exhibited markedly higher root-hair density than genotype L122 in the K 1 treatment. Correlation analysis indicates that neither root-hair density nor root-hair length was correlated with plant K uptake. Furthermore, the boll biomass of genotype H103 was significantly higher than that of genotype L122 in both treatments, and the K accumulation in bolls of genotype H103 was 39%–48% higher than that of genotype L122. On the other hand, the litter index (LI) and the litter K-partitioning index (LKPI) of genotype H103 were 14%–21% and 22%–27% lower than that of genotype L122. Lastly, the K-use efficiency of total plant (KUE-P) of genotype H103 was comparable with that of genotype L122 in both treatments, but the K-use efficiency in boll yield (KUE-B) of genotype H103 was 24% and 41% higher than that of genotype L122 in K 0 and K 1 treatments. Pearson correlation analysis indicated that KUE-P was positively correlated with BKPI and negatively correlated with LKPI, while KUE-B was positively correlated with BKPI and boll-harvest index (HI B ), and negatively correlated with LKPI. It is concluded that there were no pronounced effects of root-hair traits on plant K uptake of the two genotypes. The difference in K-use efficiency was attributed to different patterns of biomass and K partitioning rather than difference in K uptake of the two genotypes.

Beschreibung: To investigate the mechanism of cadmium (Cd) detoxification in rice ( Oryza sativa L.), a Cd-tolerant mutant cadH-5 , obtained by an Agrobacterium tumefaciens -based gene-delivery system, was used for a Cd-tolerance and accumulation study. After 15 d of exposure to 0.75 mM CdCl 2 , significant phenotypic differences were observed between the wild type (WT) and cadH-5. When exposed to 0.5 mM CdCl 2 , higher Cd levels were accumulated in cadH-5 root cell wall, root cytosol, and membranes than those in WT. However, Cd concentrations in root tissues varied in both WT and cadH5. No significant difference of hydrogen peroxide (H 2 O 2 ) concentrations was observed between WT and cadH-5 , while contents of cell-wall polysaccharides and phytochelatins (PCs) in the mutant were higher compared to WT. The ratios of reduced glutathione to oxidized glutathione (GSH : GSSG) and ascorbate to dehydroascorbate (ASC : DHA) were lower in WT than in cadH-5 , while the NADPH : NADP + ratio was different to the ratios of GSH : GSSG and ASC : DHA; the ascorbate peroxidase (APX, EC 1.11.1.11), glutathione peroxidase (GR, EC 1.6.4.2), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activities were lower in WT compared to cadH-5. Our results indicate that under long-term Cd stress, cadH-5 plants can accumulate more Cd with more PC. Also, the redox status of ASC-GSH cycle was more inhibited in WT than in cadH-5 plants, rendering WT less able to scavenge reactive oxygen species (ROS). The cadH-5 mutant maintains relatively high ASC, GSH, and NADPH concentrations, ratios of ASC : DHA, GSH : GSSG, and NADPH : NADP + , as well as antioxidative enzymatic activities and PC concentrations. Thus, it is tolerant of relatively high Cd accumulation.

Beschreibung: The hydraulic properties of soils, i.e., their ability to store and conduct water, mainly govern the availability of soil water for plants. Information on the hydraulic properties is needed, e.g., for the quantification of drought risk at a given site. Furthermore, knowledge of the water transport is the precondition for the estimation of element fluxes in the soil, e.g., when predicting element leaching from the root zone to the groundwater. For forest soils, only few systematic investigations of their hydraulic properties exist. Within the 2nd forest-soil survey of Germany, soil samples were taken along a regular 8 km × 8 km grid in the forests of the State of Baden-Württemberg and the hydraulic properties were estimated in the laboratory by multistep outflow experiments. Besides the soil-hydraulic measurements, numerous additional soil chemical and physical analyses were carried out and comprehensive profile descriptions were compiled and integrated in a hydraulic database. Based on this database, multiple-linear-regression techniques were used to develop pedotransfer functions for the water-retention curve and the unsaturated-hydraulic-conductivity curve using the parametric models of Mualem/van-Genuchten. Our work fills a gap since to our knowledge, no pedotransfer functions for the unsaturated hydraulic conductivity for forest soils exist so far. The predictive accuracy of the established pedotransfer functions, both for the water-retention curve and the hydraulic-conductivity curve, is in the range of (and in some cases better than) other published pedotransfer functions that were mostly derived for agricultural soils.

Beschreibung: The aim of this study was to improve the fertilizer-nitrogen-use efficiency (NUE) for a sustainable citrus production where yield, fruit quality, and environment are reconciled. A soil pot experiment was conducted using 5-year-old orange trees ( Citrus sinensis cv. Navel Lane Late) to determine the response of NUE to timing of N-fertilizer supply. An equal N rate (50 g tree –1 ) following two seasonal supply distributions was tested: (1) ENS (early supply from March to June of 75% of the N rate, with the remaining 25% administered between July and October) and (2) LNS (late supply of the bulk of the N rate with 25% between March and June and 75% between July and October). Labeled fertilizer (5 atom% 15 N excess) was applied in order to accurately quantify N uptake, its partitioning among plant–soil compartments and NUE at the end of fruit drop and at fruit maturity. LNS resulted in a significant increase in NUE in both stages (up to 19% at the end of fruit drop and 9% at fruit maturity), while also increasing summer/autumn flush development. ENS showed lower fruit abscission, an enhanced final fruit load (up to 45%), and a more profuse development of spring flush. It is worth mentioning that LNS led to higher 15 N content in the majority of the tree storage organs available for next spring growth resumption. The amount of 15 N remaining in the soil of ENS trees at the end of the trial, which represented 16% of the supplied 15 N, was 1.5-fold higher than that of LNS trees as a result of the lower NUE of the former. Irrespective of the seasonal distribution of the fertilizer, mean 15 N recovery in the soil–plant system at the end of the trial was about 71%. The results clearly confirm that the N seasonal distribution curve affects NUE in young citrus trees and NUE increases when the bulk of supply of the N rate is delayed to the summer months.

Beschreibung: Plants in arid or semiarid areas often experience simultaneous salt and boron (B) stress. Interactive effects on stress responses have been clearly established, but results are inconsistent and variably indicate antagonistic or synergistic interactions even within the same plant species. In this study, five differently B- and salt-resistant wheat genotypes were grown hydroponically at low and high B supply. The effect of increasing NaCl salinity on plant growth, boron uptake rates, shoot B concentrations, and transpiration was determined under both B regimes. The interactive effect of salt and B was different under low and high B supply. Boron-uptake rates were reduced with increasing salt concentration only under high B supply, and reductions correlated significantly with decreases in leaf area and shoot B concentrations. Under low B supply, however, salt-induced effects on B-uptake rates were variable and not significantly correlated with leaf-area reductions. These results suggest that under high B supply, when B uptake is predominantly passive by diffusion or channel-mediated via aquaporins, transpiration-driven water flow is the dominant factor for B accumulation in arial plant parts. Under low B supply, when a significant portion of B can be taken up via active pathways, transpiration is not the decisive factor for B accumulation. Under these conditions, the salt sensitivity of a genotype is a modifying factor of salt–B interactions, because salt-induced growth inhibition can result in a concentration effect, offset the reduction of B-uptake rates, and result in increased shoot B concentrations. Contradictory reports on the nature of salt–B interactions might in part be related to low levels of B supply chosen as control treatments and concomittant differences in predominant B-uptake pathways.

Beschreibung: Wettability is related to forces or surface tensions (σ) acting at the solid–liquid–vapor interface. Given that surface tensions are difficult to assess directly, contact angles (CA) are used as indicators of the balance of forces acting in the system. In this context, the ES theory was developed as an alternative to assess the σ parameters of the Young's equation. This research evaluates the applicability of a proposed equation of state (ES), which is in theory also able to predict the CA of a sample when two σ parameters of the Young's equation and two fitting parameters (β and α) of the function Φ = (σ SL ) are known (Φ: molecular interaction parameter, σ SL : solid–liquid surface tension). These parameters were determined by different experimental methods assessing the CA, in order to determine which method is more suitable to validate the ES theory: Capillary Rise Method (CRM) and Wilhelmy Plate Method (WPM). For WPM, two modes (advancing and equilibrium CA) were applied. Finally, results of CA between the experimental measurements obtained by WPM and those predicted by the ES were compared. Samples of coarse silt, fine sand, and nonporous glass beads with different levels of water repellency were used as test materials. In line with previous research, all methods showed lower values of σ for samples with increasing hydrophobicity. At the same time, Φ reduces consistently with higher hydrophobicity, up to ≈ 0.5–0.6 based on CRM and WPM-ECA data, and even lower (≈ 0.1–0.2) in WPM-ACA. α increased with higher hydrophobicity, having relatively stable values in samples having σ SV 〉 40 mN m –1 . β showed stable values for samples having σ SV 〉 35–40 mN m –1 . In hydrophobic samples (σ SV 〈 35 mN m –1 ), β decreased in calculations based on WPM-ACA data, and to a minor degree in WPM-ECA. The agreement between the CA directly measured (WPM) and those predicted by the ES was low, although better for the WPM-ECA, suggesting that this last approach can be considered more suitable to evaluate the ES theory.

Beschreibung: Today rapid survey methods of proximal soil sensing (PSS) provide an increasing number of different and highly resolved data. These multidimensional data sets can lead to multilayered and complex maps of parameters which are only indirectly related to soil properties and soil functions. However, in applications usually just one clear elementary map is required. It is of increasing importance to tackle this problem utilizing a cluster algorithm for the synthesis and reduction of multidimensional input variables. The cluster algorithm provides a partitioning of the investigated site whereby the units are characterized by the statistics of the PSS data. Therefore, the question that arises is how suitable is the suggested partitioning in terms of the delineation of different soil units. In this study, we investigate the suitability of cluster partitioning through a case study at a medium-scale test site (≈ 50 000 m 2 ). Two common PSS methods: electromagnetic induction (EMI) and gamma spectrometry (GS) will be employed to create a data set for partitioning by a K-means cluster. The result of the cluster analysis is a delineation of three different parts. In contrast to previous studies, we evaluate the generated partitions by independent soil properties such as grain size, horizon thickness, and color of stratified randomly taken soil samples. The soil analyses show that one of three clusters significantly differs from the others in terms of grain-size distribution and horizon thickness. The partitioning of the other two clusters could not be confirmed by the considered soil parameters. Nevertheless, the case study demonstrates the combination of different PSS data by K-means clustering as a potential approach for site partitioning. An evaluation of the results of the cluster analysis through the collection and analysis of soil samples is highly recommended.

Beschreibung: Abandonment of mountain grassland often changes vegetation composition and litter quantity and quality, but related effects on labile soil organic matter (SOM) are largely unknown. The aim of this study was to investigate the impacts of grassland management and abandonment on soil Carbon distribution in light (〈 1.6 g cm –3 ) particulate organic matter (POM) and aggregation along a gradient of management intensity including hay meadows, pastures, and abandoned grasslands. The reduction of management intensity is an interregional phenomenon throughout the European Alps. We therefore selected sites from two typical climate regions, namely at Stubai Valley, Austria (MAT: 3°C, MAP: 1097 mm) and Matsch Valley, Italy (MAT: 6.6°C, MAP: 527 mm), to evaluate effects of land-use change in relation to climate. Free water-floatable and free POM (wPOM, fPOM), and an occluded POM fraction (oPOM), were isolated from three water-stable aggregate size classes (2–6.3 mm, 0.25–2 mm, 〈 0.25 mm) using density fractionation. Aggregate mean weight diameter slightly decreased with decreasing management intensity. In contrast to absolute POM-C, fPOM-C increased in aggregates at both sites with abandonment. Because the oPOM-C was less affected by abandonment, the ratio of oPOM-C : fPOM-C shifted from 〉 1 to 〈 1 from meadow to abandoned grassland in aggregates at both sites and thus independent of climate. This suggests that in differently managed mountain grasslands free and occluded POM are functionally different SOM fractions. In bulk soil, the oPOM-C : fPOM-C ratio is better suited as an indicator for the response of SOM to management reduction in subalpine grasslands than the total soil C, absolute or relative POM-C content.

Beschreibung: There is lack of information available concerning the effect of humic substances (HS) applied via fertigation on plant growth in sandy soils. Therefore, a field experiment was carried out at El-Saff district (20 km southwest of Cairo), Egypt, to investigate the role of HS fertigation on water retention of a sandy soil, yield and quality of broccoli ( Broccoli oleracea L.) as well as on soil nutrient concentration retained after harvest. The experiment consisted of six fertigation treatments (50%, 75%, and 100% of the recommended NPK-fertilizer rate for broccoli combined with and without HS application at 120 L ha –1 ) in a complete randomized block design with three replicates. Humic substances affected spatial water distribution and improved water retention in the root zone. Furthermore, application of HS increased total marketable yield and head diameter of broccoli as well as quality parameters ( i.e., total soluble solids, protein, and vitamin C). Higher nutrient concentrations were found in the broccoli heads and concentrations of plant-available nutrients in soil after harvesting were also higher, indicating an improvement in soil fertility. In conclusion, HS fertigation can be judged as an interesting option to improve soil water and nutrient status leading to better plant growth.

Beschreibung: A survey on the endorhizal status of 39 fruit crops of 25 families, indicated that 22 fruit crops had arbuscular mycorrhizal (AM)–, four had dark septate endophyte (DSE)–fungal association, and 13 had dual colonization of AM and DSE fungi. Fruit crops were capable of forming Arum-, Paris -, or intermediate-types of AM morphologies of which intermediate-type was common. To our knowledge, we report for the first time AM in 10 fruit crops and DSE-fungal association in 17 fruit crops. The extent of AM- and DSE-fungal colonization ranged from 41% to 98% and 〈 1% to 89.9%, respectively, in different fruit crops. Arbuscular mycorrhizal–fungal spore numbers in the rhizosphere ranged from 6 to 61 spores per 25 g of soil. Arbuscular mycorrhizal–fungal spores belonging to Acaulospora, Glomus, and Scutellospora were isolated from the rhizosphere soil.

Beschreibung: Our contemporary society is struggling with soil degradation due to overuse and climate change. Pre-Columbian people left behind sustainably fertile soils rich in organic matter and nutrients well known as terra preta (de Indio) by adding charred residues (biochar) together with organic and inorganic wastes such as excrements and household garbage being a model for sustainable agriculture today. This is the reason why new studies on biochar effects on ecosystem services rapidly emerge. Beneficial effects of biochar amendment on plant growth, soil nutrient content, and C storage were repeatedly observed although a number of negative effects were reported, too. In addition, there is no consensus on benefits of biochar when combined with fertilizers. Therefore, the objective of this study was to test whether biochar effects on soil quality and plant growth could be improved by addition of mineral and organic fertilizers. For this purpose, two growth periods of oat ( Avena sativa L.) were studied under tropical conditions (26°C and 2600 mm annual rainfall) on an infertile sandy soil in the greenhouse in fivefold replication. Treatments comprised control (only water), mineral fertilizer (111.5 kg N ha –1 , 111.5 kg P ha –1 , and 82.9 kg K ha –1 ), compost (5% by weight), biochar (5% by weight), and combinations of biochar (5% by weight) plus mineral fertilizer (111.5 kg N ha –1 , 111.5 kg P ha –1 , and 82.9 kg K ha –1 ), and biochar (2.5% by weight) plus compost (2.5% by weight). Pure compost application showed highest yield during the two growth periods, followed by the biochar + compost mixture. biochar addition to mineral fertilizer significantly increased plant growth compared to mineral fertilizer alone. During the second growth period, plant yields were significantly smaller compared to the first growth period. biochar and compost additions significantly increased total organic C content during the two growth periods. Cation-exchange capacity (CEC) could not be increased upon biochar addition while base saturation (BS) was significantly increased due to ash addition with biochar. On the other hand, compost addition significantly increased CEC. Biochar addition significantly increased soil pH but pH value was generally lower during the second growth period probably due to leaching of base cations. Biochar addition did not reduce ammonium, nitrate, and phosphate leaching during the experiment but it reduced nitrification. The overall plant growth and soil fertility decreased in the order compost 〉 biochar + compost 〉 mineral fertilizer + biochar 〉 mineral fertilizer 〉 control. Further experiments should optimize biochar–organic fertilizer systems.

Beschreibung: Experiments to assess the rate of absorption and translocation of foliar-applied, isotopically labeled boric acid (BA) were carried out with lychee ( Litchi chinensis Sonn.) and soybean ( Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl 2 and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of 10 B to other leaf parts and no effect of adjuvants in increasing 10 B absorption were recorded. In contrast, 10 B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of 10 B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased 10 B absorption and enhanced acropetal 10 B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl 2 in combination with 500 mM sorbitol decreased the rate of 10 B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal 10 B translocation was very limited. A distinct effect of B-sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.

Beschreibung: The assessment of grassland degradation due to overgrazing is a global challenge in semiarid environments. In particular, investigations of beginning steppe degradation after a change or intensification of the land use are needed in order to detect and adjust detrimental land-use management rapidly and thus prevent severe damages in these sensitive ecosystems. A controlled-grazing experiment was established in Inner Mongolia (China) in 2005 that included ungrazed (UG) and heavily grazed plots with grazing intensities of 4.5 (HG4.5) and 7.5 (HG7.5) sheep per hectare. Several soil and vegetation parameters were investigated at all sites before the start of the experiment. Topsoil samples were analyzed for soil organic C (SOC), total N (N tot ), total S (S tot ), and bulk density (BD). As vegetation parameters, aboveground net primary productivity (ANPP), tiller density (TD), and leaf-area index (LAI) were determined. After 3 y of the grazing experiment, BD increased and SOC, N tot , S tot , ANPP, and LAI significantly decreased with increasing grazing intensity. These sensitive parameters can be regarded as early-warning indicators for degradation of semiarid grasslands. Vegetation parameters were, however, more sensitive not only to grazing but also to temporal variation of precipitation between 2006 and 2008. Contrary, soil parameters were primarily affected by grazing and resistant against climatic variations. The assessment of starting conditions in the study area and the application of defined grazing intensities is essential for the investigation of short-term degradation in semiarid environments.

Beschreibung: Acid phosphomonoesterase (APM) (E.C. 3.1.3.2) in soil is either of plant-root or microbial origin. Each of these sources may be dominant in certain ecosystems. Generally, extracellular APM in soil has been reported. However, the lack of suitable methods limits investigations of APM in soil. Root-derived APM comes from intact plant roots, root exudates, root apoplastic sap, root extracts, or mycorrhizal fungi. The significance of these sources of APM is discussed in this review being the highest in intact roots or root extracts, and within wall- and membrane-bound fraction of mycorrhizal fungi. Evaluation of the location of APM has been based on extraction of fractions of APM with different types of extractants. The suitability of individual extractants and lack of these procedures as well as the need to search for other suitable solutions to increase extraction efficiency, minimalize extraction of inhibitors and solubilization of organic compounds are discussed. As APM derived from roots and soil microorganisms show different kinetic properties, and differ in their response to environmental factors, determination of the significance of root and microbial APM within ecosystems requires further research aimed at evaluating the response of P transformation to climatic and other environmental changes.

Beschreibung: Red lead (Pb 3 O 4 )- and ZnO-containing anticorrosion paints in the past have been extensively applied to high-voltage steel pylons which has led to heavy metal (HM) soil contaminations in their vicinity. Since pylons are commonly found on agricultural land, there is a potential risk of HM plant uptake. This is promoted by the fact that in contrast to the moderate total Pb contents (several 100 mg kg –1 ) in three nutrient-poor and acidic pylon soils the Pb amounts extractable with NH 4 NO 3 were extremely high, reaching almost 20% of total Pb. A 18-week field pot trial (three harvests in a six-week interval) using Lolium multiflorum was conducted to study the HM plant uptake and the efficiency of the four soil additives, lime (LI), Novaphos (NP), water-treatment sludge (WS), and ilmenite residue (IR) in reducing the plant uptake and NH 4 NO 3 -extractability of Pb and Zn in the soils. Lead concentrations in L. multiflorum shoots grown in the untreated soils reached maximum values of 128 mg (kg dry weight) –1 . Novaphos was most efficient in decreasing shoot Pb (–90%) followed by LI (–78%) and WS (–73%). For Zn, too, LI (–82%), NP, and WS (both –66%) substantially reduced plant uptake. Ilmenite residue was generally only poorly efficient. The dry-matter yield in the NP, LI, and WS treatments was significantly increased. While the relationship between Pb-NH 4 NO 3 and Pb-plant was high when considering the three harvests separately ( R 〉 0.93) a poor relationship ( R = 0.63) exists over all harvests together. This was attributed to different transpiration rates affecting the HM flux into the plants, since the temperature regime changed greatly during the cultivation period. For Zn, no such close relationship between the NH 4 NO 3 -extractable soil fraction and shoot Zn was found, most likely due to antagonistic effects from Mg which greatly varied in the three soils.

Beschreibung: The Argentine Pampa is one of the major global regions for the production of maize ( Zea mays L.) and soybean ( Glycine max L. [Merr.]), but intense management practices have led to soil degradation and amplified greenhouse-gas (GHG) emissions. This paper presents preliminary data on the effect of maize-soybean intercrops compared with maize and soybean sole crops on the short-term emission rates of CO 2 and N 2 O and its relationship to soil moisture or temperature over two field seasons. Soil organic carbon (SOC) concentrations were significantly greater ( p 〈 0.05) in the maize sole crop and intercrops, whereas soil bulk density was significantly lower in the intercrops. Soil CO 2 emission rates were significantly greater in the maize sole crop but did not differ significantly for N 2 O emissions. Over two field seasons, both trace gases showed a general trend of greater emission rates in the maize sole crop followed by the soybean sole crop and were lowest in the intercrops. Linear regression between soil GHG (CO 2 and N 2 O) emission rates and soil temperature or volumetric soil moisture were not significant except in the 1:2 intercrop where a significant relationship was observed between N 2 O emissions and soil temperature in the first field season and between N 2 O and volumetric soil moisture in the second field season. Our results demonstrated that intercropping in the Argentine Pampa may be a more sustainable agroecosystem land-management practice with respect to GHG emissions.

Beschreibung: Willows ( Salix spp.) were supposed to be suitable candidates for the phytoremediation of polluted floodplain soils, but it is unknown how willow growth alters concentrations and mobility of pollutants under the conditions of ongoing periodically flooding. Therefore, effects of willow cropping on total concentrations and mobility of As and heavy metals and soil microbial properties were determined after three and four growing seasons under willows in comparison to native grassland in a flood channel of a River Elbe floodplain (Central Germany). After 4 y of willow coppice, the heavy metal concentrations (mg kg –1 ) were increased not only in the grass control plots (final Cu 274, Pb 276, Zn 935) but also under the willows (final Cu 248, Pb 251, Zn 779) compared to the initial concentrations (initial Cu 170, Pb 156, Zn 579). This increase might likely be caused by the ongoing sedimentation by flood events. The smaller increase under willows compared to grass might be related to an initial net effect of phytoextraction. The concentrations of the mobile fractions of Cd, Cu, Ni, and Zn were significantly lower under willows than under grass. Higher β-glucosidase activities under willows than under grass might indicate a starting net decomposition of organic matter. Therefore, the study of long-term and large-scale effects are recommend before an appropriate evaluation of willow short-rotation coppice for phytoremediation of polluted floodplains will be established.

Beschreibung: Acidification and eutrophication of soils had been the main activators for the implementation of forest soil monitoring in Central Europe. Thus, field and lab studies focused on gathering information that is essential for the evaluation of the chemical status and its trend. A systematic assessment of soil physical threats caused by machine use in forests has not been integrated yet into the soil-monitoring systems. In this study, a first approach to get a deeper insight into structure damages of forest topsoils was derived for 302 systematically distributed grid points in the Federal State of Baden-Württemberg (SW Germany) during the nation-wide soil survey performed from 2006 to 2008. We derived an approach to assess structure damage based on a key system using field information on structural and hydromorphic topsoil properties. It covers eight satellites surrounding the central monitoring soil pit at each grid point. Our survey focused on the mere stand area excluding visible damage and systematic skid trails. Analysis of structure-damage intensity and spatial distribution leads to the conclusion that damage caused by vehicle traffic off the skid trails is a wide-spread phenomena in Baden-Württemberg forests, where wheeling is not restricted by steepness of terrain. Although regulations to control machine use recommending vehicle traffic to skid trails and fortified roads have been in place since the early 1980s, soil-structure damages off these trails have reached significant levels. In the future, it will thus be indispensable to put more emphasis on the importance of soil-protection aims in the ranking of the economic objectives of forest organizations and forest owners.

Beschreibung: This study investigated the effect of nitrogen (N) fertilization on leaf and boll N and carbohydrate concentrations in the development of fiber quality. A two-year field study was conducted with two cotton ( Gossypium hirsutum L.) cultivars, Kemian 1 (average fiber strength 35 cN tex –1 ) and NuCOTN 33B (average fiber strength 32 cN tex –1 ) at five (2008) and four (2009) N levels. The relationship between leaf and boll N and carbohydrate concentrations was assessed from measurements of N, carbohydrates, chlorophyll (based on SPAD readings), and free amino acids in the leaf subtending the boll, together with fiber carbohydrates and development of fiber quality. Results indicate that leaf N concentration more accurately reflected boll N status than the concentration of chlorophyll or free amino acids. Leaf sucrose and nonstructural carbohydrate had a quadratic relation with leaf N concentration ( p 〈 1%). The optimal leaf N concentration ranged from 3.0% to 2.4%. During 24–38 d post-anthesis (DPA), fiber sucrose was positively related to leaf sucrose and nonstructural carbohydrate ( p 〈 5%), but was not correlated with leaf starch or total soluble carbohydrates. Fiber strength was positively correlated with fiber sucrose before 38 DPA, and it appeared to be more easily influenced by the fiber sucrose concentration than fiber length, fineness, or maturity. These results suggest that 24–38 DPA is a crucial period for fiber development which might be significantly influenced by physiological and ecological factors. In addition, sucrose or nonstructural carbohydrates in the subtending leaf could be used as a monitoring index to evaluate sucrose levels in the developing fiber, and also for predicting the final fiber strength.

Beschreibung: Apparent electrical conductivity of soil (ECa) is a property frequently used as a diagnostic tool in precision agriculture, and is measured using vehicle-mounted proximal sensors. Crop-yield data, which is measured by harvester-mounted sensors, is usually collected at a higher spatial density compared to ECa. ECa and crop-yield maps frequently exhibit similar spatial patterns because ECa is primarily controlled by the soil clay content and the interrelated soil moisture content, which are often significant contributors to crop-yield potential. By quantifying the spatial relationship between soil ECa and crop yield, it is possible to estimate the value of ECa at the spatial resolution of the crop-yield data. This is achieved through the use of a local regression kriging approach which uses the higher-resolution crop-yield data as a covariate to predict ECa at a higher spatial resolution than would be prudent with the original ECa data alone. The accuracy of the local regression kriging (LRK) method is evaluated against local kriging (LK) and local regression (LR) to predict ECa. The results indicate that the performance of LRK is dependent on the performance of the inherent local regression. Over a range of ECa transect survey densities, LRK provides greater accuracy than LK and LR, except at very low density. Maps of the regression coefficients demonstrated that the relationship between ECa and crop yield varies from year to year, and across a field. The application of LRK to commercial scale ECa survey data, using crop yield as a covariate, should improve the accuracy of the resultant maps. This has implications for employing the maps in crop-management decisions and building more robust calibrations between field-gathered soil ECa and primary soil properties such as clay content.

Beschreibung: We determined the impact of different fertilization, namely organic vs. mineral fertilization, on the mesoscale parameter cyclic compressibility as well as on rheology of soil samples as a microscale parameter and how these parameters are related. Therefore, undisturbed samples were taken from a long-term fertilization trial at the Dikop farm near Bonn (Germany) and tested for their mechanical and hydraulic properties. This paper examines the sensitivity of the soil towards cyclic loading (mesoscale) and oscillatory shearing at the microscale by means of an amplitude sweep test and the resulting parameter maximum shear stress. Fertilization increased cyclic compressibility and thus revealed structural weakness of fertilized soil samples, so did shear stress at the microscale. The main reason for this was a decrease in bulk density in the wake of fertilization. However, within the range of fertilized soil samples, the soil structure became less susceptible towards cyclic loading and oscillatory shearing, respectively, the more organic matter the soil contained (equivalent to the fertilization level). This was assumedly caused by enhanced cementation due to organic substances that could partly substitute the direct grain–grain contacts generally contributing to soil strength. The similar behavior of cyclic compressibility and maximum shear stress enabled a first approach to relate soil mechanical parameters at the microscale to those at the mesoscale.

Beschreibung: Lower P-input levels in organic than conventional farming can decrease soil total and available P, which can potentially be resupplied from soil organic P. We studied the effect of 30 y of conventional and organic farming on soil P forms, focussing especially on organic P. Soil samples (0–20 cm) were taken in a field experiment with a nonfertilized control, two organic systems receiving P inputs as animal manure, and two conventional systems receiving only mineral P or mineral P and manure. Soils were analyzed for total, inorganic, organic, and microbial P, by sequential P fractionation and by enzyme additions to alkaline soil extracts. Samples taken prior to starting the experiment were also analyzed. Average annual P balances ranged from –20 to +5 kg ha –1 . For systems with a negative balance, labile and moderately labile inorganic P fractions decreased, while organic and stable inorganic P fractions were hardly affected. Similar quantities and proportions of organic P extracted with NaOH-EDTA were hydrolyzed in all soils after addition of an acid phosphatase, a nuclease, and a phytase, and enzyme-stable organic P was also similar among soils. Thus, neither sequential fractionation nor enzyme addition to alkaline soil extracts showed an effect of the type of applied P (manure vs. mineral) on organic P, suggesting that organic P from manure has largely been mineralized. Thus far, we have no indication that the greater microbial activity of the organic systems resulted in a use of stable P forms.

Beschreibung: Both earthworms and plant growth–promoting rhizobacteria (PGPR) are ubiquitous and important for promoting circulation of plant macronutrients. Two series of laboratory experiments were conducted to investigate the effects of earthworm casts and activities on the growth of PGPR, and the inoculation of earthworms and PGPR on the availability of N, P, and K in soils, respectively. During a short incubation period (0–34 h), the extracts of earthworm ( Pheretima guillelmi )-worked soil significantly ( p 〈 0.05) increased the abundance of the three species of PGPR, including N-fixing bacteria (NFB) ( Azotobacter chroococcum HKN-5), phosphate-solubilizing bacteria (PSB) ( Bacillus megaterium HKP-1), and K-solubilizing bacteria (KSB) ( B. mucilaginous HKK-1), in Luria-Bertani (LB) broth. There were synergistic effects of dual inoculation of earthworms and PGPR on increasing the concentrations of NH -N, (NO + NO )-N, NaHCO 3 -extractable P, and NH 4 OAc-extractable K in the corresponding soils. Bioavailable N (the sum of NH -N and [NO + NO ]-N) in the dual inoculation was 4 to 24 times those inoculated with earthworms or NFB alone, respectively. The significantly higher concentrations of bioavailable N and P in the dual inoculation of earthworms and NFB or PSB may be due to the higher abundance of PGPR and/or higher activities of urease and acid phosphatase than those of single inoculation of NFB or PSB, respectively. Dual inoculation of earthworms and PGPR would be most effective in reducing the need for chemical fertilizers in agriculture.

Beschreibung: Previous greenhouse studies have demonstrated that photosynthesis in some cultivars of first- (GR1) and second-generation (GR2) glyphosate-resistant soybean was reduced by glyphosate. The reduction in photosynthesis that resulted from glyphosate might affect nutrient uptake and lead to lower plant biomass production and ultimately reduced grain yield. Therefore, a field study was conducted to determine if glyphosate-induced damage to soybean ( Glycine max L. Merr. cv. Asgrow AG3539) plants observed under controlled greenhouse conditions might occur in the field environment. The present study evaluated photosynthetic rate, nutrient accumulation, nodulation, and biomass production of GR2 soybean receiving different rates of glyphosate (0, 800, 1200, 2400 g a.e. ha –1 ) applied at V2, V4, and V6 growth stages. In general, plant damage observed in the field study was similar to that in previous greenhouse studies. Increasing glyphosate rates and applications at later growth stages decreased nutrient accumulation, nodulation, leaf area, and shoot biomass production. Thus, to reduce potential undesirable effects of glyphosate on plant growth, application of the lowest glyphosate rate for weed-control efficacy at early growth stages (V2 to V4) is suggested as an advantageous practice within current weed control in GR soybean for optimal crop productivity.