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  • Articles  (117)
  • nitrogen  (117)
  • Springer  (117)
  • National Academy of Sciences
  • 1995-1999  (116)
  • 1975-1979  (1)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (117)
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  • Articles  (117)
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  • Springer  (117)
  • National Academy of Sciences
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  • 101
    Electronic Resource
    Electronic Resource
    Tithonia and senna green manures and inorganic fertilizers as phosphorus sources for maize in Western Kenya (1998)
    Springer
    Agroforestry systems 44 (1998), S. 21-35 
    Details
    ISSN: 1572-9680
    Keywords: biomass transfer ; decomposition ; mineralization ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efforts to overcome declining soil fertility on small holder farms in western Kenya must be consistent with the reality of low utilization of inorganic fertilizers. Likewise organic inputs alone cannot supply adequate nutrients. The use of two organic resources, Tithonia diversifolia (tithonia) and Senna spectabilis (senna) leaves, and their combination with inorganic P for improving soil fertility and maize yields was investigated on a P limiting soil in Western Kenya. Treatments included: 1) control, no inputs; 2) 5 t ha−1 (dry matter) tithonia leaves; 3) 5 t ha−1 senna leaves; 4) 5 t ha−1 tithonia leaves + 25 kg P ha−1 as triple superphosphate (TSP); 5) 5 t ha−1 senna leaves + 25 kg P ha−1 (as TSP); and 6) 25 kg P ha−1 of TSP. Maize was used as a test crop. Decomposition and P and N release of tithonia and senna leaves were determined in a litterbag study. Tithonia + TSP applications tripled maize yields compared to the control, senna + TSP and tithonia sole application doubled yields, while senna sole applications did not increase yields substantially. A large residual yield was produced in the tithonia treatments in a subsequent crop. These yield results were consistent with the higher quality and faster release of N and P from the tithonia leaves compared to senna. The tithonia biomass transfer system can improve yields in the short term but has limitations because of the large amount of biomass and the associated labor requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006123404071
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  • 102
    Electronic Resource
    Electronic Resource
    Soil community composition and ecosystem processes: Comparing agricultural ecosystems with natural ecosystems (1999)
    Springer
    Agroforestry systems 45 (1999), S. 159-185 
    Details
    ISSN: 1572-9680
    Keywords: decomposition ; environmental monitoring ; fertiliser ; mineralisation ; nitrogen ; pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil organisms play principal roles in several ecosystem functions, i.e. promoting plant productivity, enhancing water relations, regulating nutrient mineralisation, permitting decomposition, and acting as an environmental buffer. Agricultural soils would more closely resemble soils of natural ecosystems if management practices would reduce or eliminate cultivation, heavy machinery, and general biocides; incorporate perennial crops and organic material; and synchronise nutrient release and water availability with plant demand. In order to achieve these goals, research must be completed to develop methods for successful application of organic materials and associated micro-organisms, synchronisation of management practices with crop and soil biota phenology, and improve our knowledge of the mechanisms linking species to ecosystem processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006299100678
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  • 103
    Electronic Resource
    Electronic Resource
    Response of young densely stocked stands of Pinus radiata to thinning and refertilization (1995)
    Springer
    New forests 10 (1995), S. 207-223 
    Details
    ISSN: 1573-5095
    Keywords: Fertilization ; foliar analysis ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of thinning and refertilization on growth of Pinus radiata in three experiments planted at 11 960 stems ha−1 were examined. Responses to thinning and refertilization were obtained at 3 or 5 years after planting despite heavy applications of fertilizer at establishment. During the 3 years following retreatment, trees which had been thinned to 2990 stems ha−1 had twice the sectional area increments of unthinned trees, while up to a 3-fold increase in increment was obtained on trees which had been thinned and refertilized. Responses to nitrogen were obtained in all experiments. Response to phosphate was dependent upon soil type and prior treatment. Foliar analyses do not appear to be reliable for predicting responses to fertilization applied in combination with thinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027924
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  • 104
    Electronic Resource
    Electronic Resource
    A concept of selection for 'low input' wheat varieties (1998)
    Springer
    Euphytica 100 (1998), S. 95-100 
    Details
    ISSN: 1573-5060
    Keywords: genetic variation ; wheat genotypes ; nitrogen ; phosphorus ; potassium ; breeding ; low-input cultivars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient efficiency in wheat is very complex. It includes two major types: nutrient acquisition efficiency and nutrient use efficiency. Various studies on wild, landraces, old, intermediate and new genotypes of cereals showed that the new varieties produced higher grain yields than the old varieties, and were also more efficient at using nutrients. Several spring wheat cultivars, representing almost all cultivars of spring wheat, released from the Federal Office for Cultivar Registration, Germany and published in the 'Descriptive List of Cultivars', were used to investigate the interactive effects between genotypes and the use efficiencies of the three macro nutrients N, P and K by the grain and straw. The results obtained in this study indicate that nutrient use efficiency of the single nutrients varies widely within recent cultivars. Some cultivars were identified as being multiple-nutrient use efficient. These are considered low-input cultivars. It appears that a special breeding programme of crop cultivars for low nutrient and stress conditions could be successful. Improved cultivar response to nutrients will help to reduce inputs and hence protect the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018308023391
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  • 105
    Electronic Resource
    Electronic Resource
    A novel method for characterisation and quantification of plant root exudates (1996)
    Springer
    Plant and soil 184 (1996), S. 97-104 
    Details
    ISSN: 1573-5036
    Keywords: C-budgets ; Festuca ovina ; nitrogen ; Plantago lanceolata ; root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A microcosm unit is described which readily allows manipulation of experimental conditions to enable the subsequent impact on root exudation release to be monitored with time. Festuca ovina and Plantago lanceolata seedlings were grown in this microcosm unit over a 34 day experimental period under conditions of high (3.75 mol m−3 N) or low (1.25 mol m−3 N) nitrate-nitrogen treatment. At the end of the experimental period the seedlings in the microcosms were labelled with [14C]-CO2 and the fate of the label within the plant and its release by the roots monitored. Total organic carbon (TOC) content of the collected exudate material was measured throughout the experimental period as well as during the 14C-chase period and comparison of plant C budgets using these two measurements is discussed. Nitrogen treatment as found to have a greater effect on exudate release by F. ovina than by P. lanceolata seedlings as indicated by both the total organic carbon and 14C results. The use and applications of the microcosm unit are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029278
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  • 106
    Electronic Resource
    Electronic Resource
    Grass species and soil type effects on microbial biomass and activity (1996)
    Springer
    Plant and soil 183 (1996), S. 61-67 
    Details
    ISSN: 1573-5036
    Keywords: denitrification ; mineralization ; nitrification ; nitrogen ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We evaluated plant versus soil type controls on microbial biomass and activity by comparing microbial biomass C, soil respiration, denitrification potential, potential net N mineralization and nitrification in different soils supporting four grass species, and by growing a group of 10 different grass species on the same soil, in two experiments respectively. In the first experiment, none of the microbial variables showed significant variation with grass species while all variables showed significant variation with soil type, likely due to variation in soil texture. In the second experiment, there were few significant differences in microbial biomass C among the 10 grasses but there were significant relationships between variation in microbial biomass C and potential net N mineralization (negative), soil respiration (positive) and denitrification (positive). There was no relationship between microbial biomass C and either plant yield or plant N concentration. The results suggest that 1) soil type is a more important controller of microbial biomass and activity than grass species, 2) that different grass species can create significant, but small and infrequent, differences in microbial biomass and activity in soil, and 3) that plant-induced variation in microbial biomass and activity is caused by variation in labile C input to soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185565
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  • 107
    Electronic Resource
    Electronic Resource
    15N natural abundance in forest and pasture soils of the Brazilian Amazon Basin (1996)
    Springer
    Plant and soil 182 (1996), S. 249-258 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; nitrogen fixation ; stable isotopes ; tropical forest ; tropical pasture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The natural abundance of 15N was examined in soil profiles from forests and pastures of the Brazilian Amazon Basin to compare tropical forests on a variety of soil types and to investigate changes in the sources of nitrogen to soils following deforestation for cattle ranching. Six sites in the state of Rondônia, two sites in Pará and one in Amazonas were studied. All sites except one were chronosequences and contained native forest and one or more pastures ranging from 2 to 27 years old. Forest soil δ15N values to a depth of 1 m ranged from 8‰ to 23‰ and were higher than values typically found in temperate forests. A general pattern of increasing δ15N values with depth near the soil surface was broadly similar to patterns in other forests but a decrease in δ15N values in many forest profiles between 20 and 40 cm suggests that illuviation of 15N-depleted nitrate may influence total soil δ15N values in deeper soil where total N concentrations are low. In four chronosequences in Rondônia, the δ15N values of surface soil from pastures were lower than in the original forest and δ15N values were increasingly depleted in older pastures. Inputs of atmospheric N by dinitrogen fixation could be an important N source in these pastures. Other pastures in Amazonas and Pará and Rondônia showed no consistent change from forest values. The extent of fractionation that leads to 15N enrichment in soils was broadly similar over a wide range of soil textures and indicated that similar processes control N fractionation and loss under tropical forest over a broad geographic region. Forest δ15N profiles were consistent with conceptual models that explain enrichment of soil δ15N values by selective loss of 14N during nitrification and denitrification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029056
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  • 108
    Electronic Resource
    Electronic Resource
    How do nutrients drive growth? (1997)
    Springer
    Plant and soil 196 (1997), S. 321-325 
    Details
    ISSN: 1573-5036
    Keywords: lettuce ; nitrogen ; phosphorous ; potassium ; nutrient limitation ; nutrient remobilisation ; relative growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relationship between plant nutrient concentration and relative growth rate (RGR) was studied under non-steady state conditions using data from a new N interruption experiment with young lettuce plants grown hydroponically in the glasshouse. RGRs estimated from the fit of a versatile growth model were shown to decline curvilinearly with plant N concentration as N deficiency increased. Similar curvilinear relationships were also derived when the same model was used to reanalyse data for N, P and K interruption treatments from other experiments previously published in the literature. These results clearly indicate that the rate of remobilisation of nutrient reserves varies with the nutrient status of the plant. This contrasts with the linear relationships observed where the changes in plant N concentration occurred solely as a response to increasing plant age, or when plants were grown under steady state conditions with constant relative nutrient addition rates. These differences in the pattern of response provide strong evidence to support the hypothesis that the form of the relationship between RGR and plant nutrient concentration can vary depending upon whether a plant's external supplies or internal reserves of a particular nutrient are more limiting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004240511210
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  • 109
    Electronic Resource
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    Effect of a dense Allium ursinum (L.) ground cover on nutrient dynamics and mesofauna of a Fagus sylvatica (L.) woodland (1997)
    Springer
    Plant and soil 189 (1997), S. 245-255 
    Details
    ISSN: 1573-5036
    Keywords: Allium ursinum ; acidification ; beech stand ; nitrogen ; nutrient leaching ; soil mesofauna ; soil solution chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aboveground biomass built up annually by Allium ursinum (L.) contains similar amounts of nutrients as the foliage of mature Fagus sylvatica (L.) stands. The decomposition of the A. ursinum stand in early summer provides N rich forage for grazing mesofauna, especially favouring collembolans and accelerating mineralization of soil organic matter. Short term decreases of soil pH had no negative effect on populations of collembolans. Synergistic effects from soil fauna and microbes may accelerate nitrogen release from decomposing leaf litter. A positive feed back may have emerged. High animal abundance and diverse mesofauna populations are capable of high rates of litter fragmentation. Consequently, favourable conditions for microorganisms are created and allow high rates of mineralization and release of nutrients. Our data show that substantial amounts of nitrogen are lost from the system. Undisturbed forest ecosystems are considered to recycle mineralized nitrogen efficiently though. But temporal uncoupling of the N cycle due to microbial activity and delayed or decreased N uptake of higher plants can cause enhanced leaching even from undisturbed systems. The tendency to loose nutrients is apparent from high nitrate concentrations in the soil solution throughout the year. When nutrient losses from A. ursinum subsystems are considered, lateral nutrient imports from adjacent parts of the ecosystem have to be taken into account. If lateral import does not counterbalance losses, maintenance of the soil nutrient status must occur by weathering or a decline is to be expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004223011834
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  • 110
    Electronic Resource
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    Fine root turnover of irrigated hedgerow intercropping in Northern Kenya (1998)
    Springer
    Plant and soil 198 (1998), S. 19-31 
    Details
    ISSN: 1573-5036
    Keywords: Acacia saligna ; agroforestry ; nitrogen ; root decomposition ; root distribution ; root turnover ; Sorghum bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fine root turnover (〈2 mm) was determined from repeated measurements of root distribution up to 120 cm soil depth by core sampling in four month intervals. Sole cropped Sorghum bicolor and Acacia saligna were compared with the agroforestry combination in an alley cropping system in semiarid Northern Kenya. Three methods for the calculation of root production were used: the max-min, balancing-transfer and compartment-flow method. The highest root biomass was found in the topsoil for all cropping systems, though trees had a deeper root system. Trees and crops had a similar amount of below-ground biomass during the vegetation period (0.3 and 0.4 Mg DM ha-1 120 cm-1), but in the agroforestry combination root biomass was more than the sum of the sole cropped systems (1.1 Mg DM ha-1 120 cm-1). The tree system showed a very static root development with little fluctuation between seasons, whereas root biomasses were very dynamic in the crop and tree + crop systems. Root production was highest in the tree + crop combination with 2.1 Mg DM ha-1 a-1, with about 50% less in sole cropped trees and crops. Root N input to soil decreased in the order tree + crop〉tree〉crop system with 13.5, 11.0 and 3.2 kg N ha-1 a-1, and cannot be estimated from total below-ground biomass or carbon turnover, as N is accumulated in senescing roots. Such low N input to soil stresses the need for investigating other processes of nutrient input from roots to soil. Areas of highest N input were identified in the topsoil under the tree row in the tree system. Resource utilisation and C and N input to soil were highest with a combination of annual and perennial crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004293910977
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  • 111
    Electronic Resource
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    Evaluation of the stem injection technique and subsequent15 N partitioning in red alder crowns (1998)
    Springer
    Plant and soil 198 (1998), S. 63-69 
    Details
    ISSN: 1573-5036
    Keywords: allocation ; Alnus ; nitrogen ; nitrogen fixation ; resorption ; translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Red alder (Alnus rubra Bong.) trees were labeled with15 NO- 3 or15 NH+ 4 using the stem-injection method. Leaves were sampled 3 and 15 months subsequent to injection within several crown positions, including top, bottom, proximal, medial, and distal. Stem injection of both15 NH+ 4 and15 NO- 3 at levels approaching 1% of crown N effectively labeled red alder trees. Although more variable, 15NO- 3 may have been more efficient in initial labeling. The distribution of 15N in the crown was uniform 3 months after labeling, but was diluted in the distal and top positions by the following year. In both years there was a clear increase in total N concentration toward the periphery of the tree. This increase became more pronounced with increasing crown size and crown closure. Crown position with respect to light availability may be the most important determinant in N allocation in red alder foliage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004275316217
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  • 112
    Electronic Resource
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    Changes in carbon, nitrogen and phosphorus levels due to deforestation and cultivation: A case study in Simlipal National Park, India (1998)
    Springer
    Plant and soil 198 (1998), S. 137-145 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; cultivation ; deforestation ; nitrogen ; phosphorus ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The study area, within the Simlipal National Park, India, provides a rare variety of soil sampling sites. These include virgin forests in the proximity of several cultivated areas (where no chemical fertilizers or any modern technology has been used and where periods of cultivation vary from 5 to a little over 100 yr); samples from evergreen forests, deciduous forests and natural grasslands could also be obtained. The availability of numerous such samples made it possible to use statistical methods to evaluate the changes. This study showed that deforestation and cultivation result in statistically significant (P0.05) reduction in organic C, total N and C:N ratios but no significant changes in total and available P levels; C:P and N:P ratios are also reduced. Loss of organic C and N occurs rapidly in the first 15 yr of cultivation and reaches quasi-steady state values around 1–2% organic C and 0.1–0.2% total N; extent of reduction is not related to initial levels. Significant reduction in C:N, C:P ratios following cultivation suggest that mineralisation losses of C are higher than loss of N whereas loss of P is lowest. Lack of significant correlation between organic C and P levels in all types of soils, suggests that the bulk of the P is in the inorganic form. Highest levels of organic C and N were observed in evergreen forests followed by deciduous forests, grasslands and cultivated areas in that order; total and available P levels, however, showed no significant differences. Evergreen vegetative cover appears to provide the ideal environment for organic matter accumulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004391615003
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  • 113
    Electronic Resource
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    Effect of tissue phosphorus concentration on the mineralisation of nitrogen from stylo and cowpea residues (1997)
    Springer
    Plant and soil 191 (1997), S. 139-146 
    Details
    ISSN: 1573-5036
    Keywords: cowpea ; crop residues ; mineralisation ; nitrogen ; phosphorusconcentration ; t Stylosanthes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory studies were conducted to investigate the effect of phosphorus concentration in residues of cowpea (t Vigna unguiculata, L. Walp) and stylo (t Stylosanthes hamata, L., cv Verano) on their rate of nitrogen mineralisation when incubated in a soil whose P status was deficient for plant growth. Residues with a range of P concentrations were obtained by applying varying rates of P to soil in which the plants were grown in the field or the glasshouse. Variations in P concentration of field- or glasshouse-grown residues were not accompanied by variations in other chemical components (C:N ratio, lignin and polyphenol concentrations). Both lignin and polyphenol concentrations were higher in the field-grown than in the glasshouse-grown residues. Lignin concentration was greater in cowpea than in stylo, but polyphenols were higher in stylo. Cowpea residues mineralised N less rapidly than stylo. N mineralisation from residues with low P concentration was consistently less than from those of higher P concentration; reduced mineralisation was observed for P concentration in the residues below 1.6 g kg−1. When inorganic P was added to the residue-soil systems, N mineralisation from the residues was increased, though no interaction between the effects of adding inorganic P and P concentration in the residues was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004261812861
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  • 114
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    Wildfire effects on carbon and nitrogen in inland coniferous forests (1999)
    Springer
    Plant and soil 209 (1999), S. 233-243 
    Details
    ISSN: 1573-5036
    Keywords: bioassay ; carbon ; erosion ; forest soil ; nitrogen ; wildfire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A ponderosa pine/Douglas-fir forest (Pinus ponderosa Dougl., Pseudotsuga menziesii (Mirb.) Franco; PP/DF) and a lodgepole pine/Engelmann spruce forest (Pinus contorta Loud., Picea engelmannii Parry ex Engelm.; LP/ES) located on the eastern slopes of the Cascade Mountains in Washington state, USA, were examined following severe wildfire to compare total soil carbon and nitrogen capitals with unburned (control) forests. One year after fire, the average C content (60 cm depth) of PP/DF and LP/ES soil was 30% (25 Mg ha-1) and 10% (7 Mg ha-1) lower than control soil. Average N content on the burned PP/DF and LP/ES plots was 46% (3.0 Mg ha-1) and 13% (0.4 Mg ha-1) lower than control soil. The reduction in C and N in the PP/DF soil was largely the result of lower nutrient capitals in the burned Bw horizons (12–60 cm depth) relative to control plots. It is unlikely that the 1994 fire substantially affected nutrient capitals in the Bw horizons; however, natural variability or past fire history could be responsible for the varied nutrient capitals observed in the subsurface soils. Surface erosion (sheet plus rill) removed between 15 and 18 Mg ha-1 of soil from the burned plots. Nutrient losses through surface erosion were 280 kg C ha-1 and 14 kg N ha-1 in the PP/DF, whereas LP/ES losses were 640 and 22 kg ha-1 for C and N, respectively. In both forests, surface erosion of C and N was ∼1% to 2% of the A-horizon capital of these elements in unburned soil. A bioassay (with lettuce as an indicator plant) was used to compare soils from low-, moderate- and high-severity burn areas relative to control soil. In both forests, low-severity fire increased lettuce yield by 70–100% of controls. With more severe fire, yield decreased in the LP/ES relative to the low-intensity burn soil; however, only in the high-severity treatment was yield reduced (14%) from the control. Moderate- and high-severity burn areas in the PP/DF were fertilized with ∼56 kg ha-1 of N four months prior to soil sampling. In these soils, yield was 70–80% greater than the control. These results suggest that short-term site productivity can be stimulated by low-severity fire, but unaffected or reduced by more severe fire in the types of forests studied. Post-fire fertilization with N could increase soil productivity where other environmental factors do not limit growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004602408717
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  • 115
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    Vertical and horizontal development of the root system of carrots following green manure (1999)
    Springer
    Plant and soil 212 (1999), S. 143-151 
    Details
    ISSN: 1573-5036
    Keywords: carrot ; green manure ; nitrogen ; organic production ; rooting depth ; root distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cover crops grown as green manure or for other purposes will affect nitrogen (N) distribution in the soil, and may thereby alter root growth of a succeeding crop. During two years, experiments were performed to study effects of nitrogen supply by green manure on root development of carrots (Daucus carota L). Total root intensity (roots cm−2 on minirhizotrons) was significantly affected by the green manures, and was highest in the control plots where no green manure had been grown. Spread of the root system into the interrow soil was also affected by green manure treatments, as the spread was reduced where spring topsoil Nmin was high. Although N supply and distribution in the soil profile differed strongly among the treatments, no effect was observed on the rooting depth of the carrot crops. Across all treatments the rooting front penetrated at a rate of 0.82 and 0.68 mm day−1 °C−1 beneath the crop rows and in the interrow soil, respectively. The minirhizotrons only allowed measurements down to 1 m, and the roots reached this depth before harvest. Extrapolating the linear relationship between temperature sum and rooting depth until harvest would lead to rooting depths of 1.59 and 1.18 m under the crop rows and in the interrow soil respectively. Soil analysis showed that the carrot crop was able to reduce Nmin to very low levels even in the 0.75 to 1.0 m soil layer, which is in accordance with the root measurements. Still, where well supplied, the carrots left up 90 kg N ha−1 in the soil at harvest. This seemed to be related to a limited N uptake capacity of the carrots rather than to insufficient root growth in the top metre of the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004646522369
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  • 116
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    The decomposition of sugar beet residues: mineralization versus immobilization in contrasting soil types (1997)
    Springer
    Plant and soil 192 (1997), S. 237-247 
    Details
    ISSN: 1573-5036
    Keywords: immobilization ; mineralization ; nitrogen ; residues ; sugarbeet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The leaves and crowns from 15N-labelled sugar beets were incubated in either a silty clay loam or sand soil for almost one year. Four additions of fresh, chopped residues mixed with soil were tested: 15N-labelled leaves alone, 15N-labelled leaves plus unlabelled crowns, unlabelled leaves plus 15N-labelled crowns, and 15N-labelled crowns alone; a control with no addition was also incubated. The C:N ratio of the leaves was 11 and that of the crowns 40. Incubations were carried out in pots kept at 20 °C and optimal moisture conditions. The leaves mineralized N from the start of the experiment but the addition of crowns to soil at first caused immobilization of nitrogen followed eventually by mineralization after 6 or 12 weeks depending on soil type. The extra amounts of mineral N found in soil at the end of the experiment where additions were made corresponded to the sum of the background mineralization and the addition; no priming effects were encountered. Very slight differences only were found between the initial rates of mineralization of C in all of the treatments. Although there was also little difference between the sand and silty clay loam soils in the direct mineralization of nitrogen from the sugar beet leaves, where N was first immobilized (i.e. from crowns or a mixture) re-release of N took place more quickly in the sand soil. The total recovery of15 N found in soils after 24 weeks incubation ranged from 70% to 90% with least being lost from the sugar-rich but N-deficient crowns. Where leaves plus crowns were incubated together both residues contributed to the microbial biomass N. In practice, immobilization of this magnitude and duration (expressed as a temperature sum) could exceed the growth period of a spring sown crop. The actual immobilization found in any one field is likely to depend on the C:N ratio of the residues and could account for much of the variation in the residual benefit of sugar beet residues reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004288828793
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    Electronic Resource
    Nitrate leaching from sandy loam soils under a double-cropping forage system estimated from suction-probe measurements (1997)
    Springer
    Plant and soil 195 (1997), S. 247-256 
    Details
    ISSN: 1573-5036
    Keywords: catch crop ; intensive dairy farming ; maize silage ; mineral nitrogen ; nitrogen ; slurry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrate leaching from a double-cropping forage system was measured over a 2-year period (June 1994–May 1996) in the Northwest region of Portugal using ceramic cup samplers. The crops were grown for silage making and include maize (from May to September) and a winter crop (rest of the year) consisting of a mixture of cereals and Italian ryegrass. The experiment was performed on two different sites with a history of many years under the same crop and fertiliser management, but differing in the amounts of N applied as fertiliser and by regular cattle slurry applications. The annual nitrate leaching losses measured ranged from 154 to 338 kg N ha-1. These amounts lead to annual mean concentrations between 22 and 41 mg $$NO_3^ - $$ -N L-1 in the drained water. The coarse textured soils (sandy loams) and the climatic conditions of the region with more than 600 mm of drainage concentrated between October and March, tended to promote the leaching of all the nitrate-N left in the soil after the maize crop plus the N released by mineralization during the winter period. On these soils, the minimum amount of drainage (necessary to provide the complete leaching of all the nitrate-N in the soil profile in the end of summer), seems to be between 300 and 400 mm. The winter crops removed important quantities of N (83–116 kg N ha-1) but, due to their late establishment in autumn they did not succeed in taking up the nitrate-N left in the soil after the maize crop. Approaches for reducing the nitrate leaching losses in this particular system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004289814201
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