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  • 1
    Electronic Resource
    Electronic Resource
    Dynamic model for the effects of K-fertilizer on crop growth, K-uptake and soil-K in arable cropping. 1. Description of the model (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. To provide a practical aid to improving fertilizer practice a mechanistic model was developed that can be readily calibrated for widely different crops. Most of the inputs are easy to obtain and the others, the amounts of fixed soil-K and the velocity constants for fixation and release of soil-K, can be readily measured by a novel procedure which is described.The model calculates for each day the potential increase in plant weight and the increment in root length, from the current plant mass, its %K and pan evaporation. It calculates the maximum amount of K that could be transported through soil to the root surfaces. It modifies this potential uptake by taking account of the ‘feedback’ of plant K on root absorption to give the actual uptake and a new %K in the plant. It calculates the radii of the depletion zones around each root increment and the interchange between the solution, exchangeable and fixed-K in these zones and also in the undepleted regions of soil. Routines are included for the effects of weather on the various processes. Differences between species are accommodated by selecting one of three algorithms for root growth and by adjusting the values of two crop-K parameters that define the decline in a critical and a maximum possible %K with increase in plant mass per unit area.A simplified version of the model runs interactively on the Internet at:
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00582.x
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic model for the effects of K fertilizer on crop growth, K-uptake and soil-K in arable cropping. 2. Field test of the model (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The validity of the model described in Greenwood & Karpinets (1997) was tested against the results of single year, multi level K fertilizer experiments. Measurements of plant mass, %K in the plant and K activity ratio in soil had been made at harvest and at intervals during the growing season on spring wheat, summer cabbage and turnips. Reasonably good agreement was obtained between these measurements and simulated values when the two ‘crop’ parameters (defining the dependence of critical and maximum possible %K on plant mass) were adjusted for each crop. Also good agreement was generally obtained for plant weight and plant %K at harvest in less detailed experiments on 10 other crops. Values of the two ‘crop’ parameters for 12 of the crops were strongly correlated with one another suggesting that a single ‘crop’ parameter may be all that is required to define most inter-species differences in plant-K demand.Simulations with the model indicate that, in central England, no response of 10 crops to K fertilizer would be likely on soils containing more than 170 mg of 1 M ammonium nitrate extractable-K/kg of soil and having clay contents of between 15 and 45%. Shortcomings of the model and opportunities for advance are discussed.A simplified version of the model runs on the Internet at:
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00583.x
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  • 3
    Electronic Resource
    Electronic Resource
    Aerobic Respiration in Soil Crumbs (1962)
    [s.l.] : Nature Publishing Group
    Nature 195 (1962), S. 161-163 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IN previous work1 a theory was developed to relate the aerobic respiration-rates of spherical soil crumbs to their size and the oxygen partial pressure surrounding them. The object of this communication is to correct an error in the formulation of the theory and to extend it to describe the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/195161a0
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  • 4
    Electronic Resource
    Electronic Resource
    Response of winter wheat to N-fertiliser: Quantitative relations for components of growth (1987)
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 119-137 
    Details
    ISSN: 1573-0867
    Keywords: fertiliser ; nitrogen ; regression ; response ; winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Measurements were made of yield of dry matter, plant-N content, and the distribution of mineral-N down the soil profile in 10 fertiliser-N experiments. In one of them detailed measurements were made throughout growth. Rate of N-uptake by the crop was unaffected by the amount of mineral-N in the upper 90 cm of soil when it was above about 30 kg N ha−1. The %N in plants that received ample N-fertiliser declined with increase in plant mass according to a previously derived equation. During senescence there was an apparent loss of N from the crop. N-nutrition in the different experiments had little effect on the partition of assimilate between grain and straw. At harvest grain and straw weights were well related by a linear model which had the same gradient but different intercepts for each experiment. Grain %N was about four times greater than straw %N. Regression analysis supported the view that high evaporative conditions or temperatures during the growing period induced earlier harvest dates, less grain relative to straw, and a higher %N in the plant when ample N-fertiliser was applied but not when N-fertiliser was withheld. Other analyses indicated that cereal roots were generally unable to extract mineral nitrogen from the soil when the concentration was less than about 0.18 kg N ha−1 cm−1, that at low levels of N-nutrition the recovery of available inorganic-N from soil by the grain and straw was about 80%, and that the average mineralisation rates from early spring to shortly after harvest date varied between 0.22 and 0.88 kg N ha−1 d−1 from site to site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048913
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental validation of an N-response model for widely different crops (1988)
    Springer
    Nutrient cycling in agroecosystems 18 (1988), S. 153-174 
    Details
    ISSN: 1573-0867
    Keywords: Simulation ; yield ; N-content ; vegetables ; inter-species variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A simulation model, developed from a previously published one generally gave a reasonably good description of the effects of N-fertilizer on plant dry weight and N-content of 12 different vegetable crops grown in 26 experiments on separate sites within the same field. Apart from standard weather and soil data, the model required as inputs, the maximum yield of dry matter, the fractional recovery of N by the crop (with minimum fertilizer), the plant mass and N content (at the time of planting or drilling), the dates of planting or drilling and of harvest. Simulations always started from the previous autumn. A constant value of soil mineral-N at that time and the same temperature dependent mineralization was assumed for all experiments. The validity of the model was tested by a range of statistical procedures. In 19 out of the 26 experiments there were no detectable trends in the deviations of the simulated from the measured dry matter yields with increase in fertilizer-N. The model over-estimated the %N in the dry matter of some crops at the highest level of fertilizer-N and was unsatisfactory for one of the crops. With these exceptions, the sum of squares of the differences between measured and simulated %N was 22% of the sum of squares of the measured values above the mean. When N-fertilizer was withheld, the average N-uptake over all experiments was 69 kg N ha−1, whereas that simulated was 59 kg N ha−1; the average difference between simulated and measured uptake for each experiment was 20 kg N ha−1. Simplification of the model by incorporating the same relationship between critical %N and plant weight for all crops did not lead to appreciable loss of accuracy. A user-friendly version of the model has been compiled so that it will run on IBM-compatible microcomputers with outputs that can be coupled with high level graphics packages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049511
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  • 6
    Electronic Resource
    Electronic Resource
    Fertilizer use and food production: World scene (1981)
    Springer
    Nutrient cycling in agroecosystems 2 (1981), S. 33-51 
    Details
    ISSN: 1573-0867
    Keywords: energy ; models ; N-fixation ; nutrients ; re-cycling ; yield ; food production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cereal yield per ha in the different countries of the world is almost proportional to the rate of fertilizer application. Yields in countries where most people live are severely limited by nutrient deficiencies. Unless steps are taken to rectify these deficiencies, crop yields will always be very poor, even if other improved agronomic practices are adopted. Much fertilizer is at present wasted because of difficulties in forecasting how to adjust levels and methods of application for differences in conditions. More widespread adoption of ‘mechanistic’ approaches to studying the problems than hitherto offers opportunities for improvement. Considerable scope also exists for saving fertilizer by more re-cycling of nutrients, by greater biological-N fixation and by the adoption of better cropping sequences. Only a minute fraction of the present consumption of fossil energy in the world is needed to manufacture all the required fertilizer. Adequate supplies of potassium and phosphate minerals probably exist to meet demand. The major problems in the future are likely to arise from the fact that essential resources are very unevenly distributed in relation to where they are needed to grow food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01072876
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement and simulation of the effects of N-fertilizer on growth, plant composition and distribution of soil mineral-N in nationwide onion experiments (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 305-318 
    Details
    ISSN: 1573-0867
    Keywords: N-response ; model ; critical %N ; nitrate ; soil mineral-N ; N-loss ; leaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To aid the development of simulation models for N-response, N-fertilizer experiments with onions (Allium cepa L.) were carried out on 5 different sites. In each experiment, there was little loss of fertilizer-N in soil during the period between application and rapid crop growth and little loss of mineral N by leaching at any time. Even so, a substantial proportion of the N applied as fertilizer could not be accounted for in the crop and soil at harvest; the sum of soil mineral-N plus crop N (excluding fibrous roots) was always linearly related to N rate applied over the entire range (0–300 kg N ha−1) and the gradient was always approximately the same, 0.64, irrespective of soil type or the amount of nitrate remaining in soil at harvest. Evidence was obtained that the phenomena resulted from roots retaining N and inducing immobilization at a rate proportional to soil nitrate concentration and that the proportionality constant was similar on all sites. Throughout plant growth there was little luxury consumption of N and the critical %N was related to plant mass by an equation previously deduced for other C3 crops (Plant and Soil 85, 163); plant nitrate concentration in the early stages increased with soil mineral-N (0–30 cm) to a maximum which varied from site to site but the nitrate concentration in the mature crop was always negligible. Plant yield in the early stages of growth generally declined with increase in fertilizer-N, despite the crops having been planted as sets and no more than 150 kg N ha−1 broadcast at one time; but at maturity, yield always increased asymptotically with increase in fertilizer-N. Mineralization rates were approximately the same in the first as in the second half of each experiment. At harvest, residual soil mineral-N in the upper 30, 60 and 90 cm of soil increased with increase in fertilizer-N even when crop demand for N exceeded supply. At harvest in every experiment, the ratio of crop dry weight in the absence of added N to the maximum obtained was approximately equal to the ratio of plant %N (with no fertilizer) to critical %N. The various phenomena concerning yields, plant-N contents, and values of soil mineral-N at harvest were quite well simulated by a slightly modified version of a previously published model (Fert. Res. 18, 153) with few site-dependent inputs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01051282
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  • 8
    Electronic Resource
    Electronic Resource
    Studies on the decomposition of amino acids in soils (1960)
    Springer
    Plant and soil 12 (1960), S. 69-80 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary 1. Anaerobic amino-acid breakdown in a garden soil was accompanied by the formation of large quantities of volatile fatty acid and ammonia (plus indole in the case of tryptophan). 2. Hydroxyproline, leucine, methionine, phenylalanine, proline, threonine, tryptophan, tyrosine, and valine were found to be “resistant” and decomposed more slowly than did alanine, arginine, aspartic acid, cystine, glutamic acid, glycine, histidine lysine, and serine. Casein hydrolysate was rapidly and completely deaminated. 3. The slow rates of breakdown of the “resistant” acids when tested singly could not be attributed either to the effects of adsorption on the soil surface or to elimination of an essential Stickland reaction. 4. The effect of glucose and of nitrate on anaerobic amino-acid metabolism have been tested. With the exception ofdl-methionine nitrate acted as an hydrogen acceptor in the anaerobic deamination of the “resistant” acids, glucose had no effect on their anaerobic metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01377762
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  • 9
    Electronic Resource
    Electronic Resource
    Report of the work group on cereal and grain crops (1982)
    Springer
    Plant and soil 67 (1982), S. 399-402 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Conclusions 1. Nitrogen balance studies are of considerable importance for predicting and understanding changes in the crop nitrogen cycle that take place as a result of different agronomic practices. 2. Too few detailed N-balance studies have been made of arable crops in Latin America. 3. Much useful information can be obtained by carrying out studies at different degrees of detail. Ideally,15N should be used for these studies, but we recognize that such experiments can be carried out at only a few sites because of economic limitations. We believe that considerable progress can nevertheless be made by using conventional methods of analysis to measure simultaneously at various sites major inputs and outputs of nitrogen and changes in soil organic-N (to the depth of rooting) over a number of years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182788
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  • 10
    Electronic Resource
    Electronic Resource
    Root development of vegetable crops (1982)
    Springer
    Plant and soil 68 (1982), S. 75-96 
    Details
    ISSN: 1573-5036
    Keywords: Assimilate ; Equations ; Models ; Partition ; Root decay ; Root distribution ; Root growth ; Vegetables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Measurements were made at intervals during the growth of seven different vegetable crops grown on the same soil to find how far root development and crop growth could be described by simply derived equations and to find how far the parameter values varied from crop to crop. For each crop K1 ln W+W, (where W is total plant dry weight, t ha−1 and K1 is equal to 1 t ha−1) was linearly related to time from emergence, as in past experiments. The derived equation $$\ln L = c_j + b_j \ln W - mt$$ where L is total root length per unit area, t is time from emergence, cj and bj are coefficients that depend on the crop (j) and m is a coefficient having the same value for all crops, removed 89.4% of the total variance in ln L. The best fit was obtained with a value of m that implied that about 3% of the root carbon was mineralized each day. Generally the logarithm of root density declined linearly with increasing depth. Most of the variation between the gradients of these relations for the different crops was removed by a single regression against logarithm of total root length. The main discernible differences between species in their rooting patterns were that root length for a given top weight of legumes was about half that of non legumes, that the development of storage roots was associated with a less steep decline in root density with depth than for other crops and that onions were exceptional in that the depth to which their roots penetrated did not change appreciably during much of the growing season. A single linear relationship between root depth and top weight (r 2=0.85) covered all non-leguminous crops except onions and another relationship (r 2=0.80) covered the legumes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374729
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