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.