Ian E. Currah
Agronomic Computing Consultant,
Homepage: Model homepage: NCRM (N_ABLE) Nitrogen Online Model
In the model the soil is visualized as consisting of 20 consecutive 5 cm thick layers. Roots develop laterally and vertically in the soil. The volume of soil from which they can extract mineral-N increases with plant mass until a stage is reached at which further root development ceases or until the roots reach a hard pan or other barrier to root penetration.
Fertilizer and crop debris are incorporated in the uppermost layers of soil. Microbial breakdown of the endogenous soil organic matter always increases soil mineral-N. But mineral-N is either produced or immobilized during the decomposition of crop debris, depending on its C/N ratio. When mineral- N is released it is first converted to ammonium-N which is then nitrified to nitrate-N, which it is assumed, is not absorbed on soil. It can be taken up by plant roots, can be leached downwards during rain or can move upwards during evaporation from the soil surface.
Crucial to the estimation of plant growth are two crop-nitrogen parameters, the critical N concentration and the maximum possible N concentration, and the way they decline with increasing plant growth. This information is provided by a file ancillary to the program. Plant growth is calculated from the daily mean air temperatures, from the plant mass per unit area, and from its N concentration relative to the critical concentration for a plant of the same weight.
To calculate crop uptake first the potential demand of the crop for nitrogen is calculated from its mass per unit area, from its N content, from the maximum possible concentration for a plant of the same mass and from the potential maximum increment in weight. Then the maximum amount of N which the plant roots can extract from soil is estimated. If this is less than crop demand then it determines uptake.
Transpiration is calculated from fractional crop cover (derived from the plant mass), the rate of loss of water from an open water surface (a component of the weather file) and the amount of water in the rooting zone. Evaporation from bare soil likewise depends soil water distribution down the profile and on the evaporative conditions.
The foregoing processes are represented by equations and the calculations are repeated for each day and for each layer of soil.
The effects of water stress are assumed to be taken account of by the input of the maximum yield. It is assumed that crop growth and thus crop demand for N is more sensitive to dry conditions than the ability of the roots to extract that demand from soil. In consequence the model does not include routines for the effects of low soil moisture content on the transport of mineral-N to the roots.
The model has been developed for use of ammonium and nitrate based fertilizers. It does not include equations for any adverse effects of fertilizer-N on plant growth such as those caused by high osmotic stress or ammonia toxicity. Nor does it deal explicitly with ammonia volatilization.
Click this link for a simplified conceptual flow diagram of the Model.
Most of the algorithms in the model are given in GREENWOOD et.al. (1996), see the references at then end of this document.
The main exception is that most of the critical-N and maximum possible
N-concentrations in the plants and the way they decline with increase in plant
mass are taken from GREENWOOD, D. J. & DRAYCOTT, A. (1989a), see also among the
many other relevant references below.
NON-OBVIOUS APPLICATIONS OF THE MODEL
The displayed page shows four columns, namely: the day number of the year, the mean of the minimum and maximum temperature (deg. C), the evaporation from an open water surface (mm) and the rainfall (mm). You can save the page as a weather file or print it directly from your browser.
A drought warning then appears which gives an estimate of the maximum plant dry weight assuming that the crop is healthy and growth is never limited by shortage of either water or nutrients.
By setting the maximum yield to the low value of 0.1 t/ha (thus minimizing crop-N uptake) and running the model in the usual way the following may be estimated from the 10-day outputs:
This can be estimated for cropped soils by modifying the volumetric water content at field capacity according to the soil type (see table below) and by modifying the input monthly rainfall. It can also be estimated for fallow soils by making, in addition to the above changes, the maximum plant dry weight equal to 0.1 t/ha thereby minimizing the effect of plant growth on the calculated N-economy of the soil.
|SOIL TEXTURE AND FIELD CAPACITY|
|Silty clay loam||0.46|
Source of abstract: Description of the Nitrogen Model
Online: ONLINE Nitrogen Crop Response Model
Stand-alone version of the Nitrogen Model:
The Internet version of the Nitrogen Model (NCRM) is a simplification of N_ABLE, a stand-alone program developed at HRI, UK by Clive Rahn and Ann Draycott (based on research models of Duncan Greenwood and Ann Draycott) with funding from the UK Ministry of Agriculture Fisheries and Food. N_ABLE has more input parameters, and permits greater flexibility in the inputs than this Internet version. It also enables the users to run the model with their own weather data which is not practical over the Internet.
The stand-alone version of the Model is made available in the public domain for use in research.
A DOS EXE file of N_ABLE, an associated parameter file, and a manual will be supplied to any scientist requiring them solely for research or educational purposes. To obtain such a copy please write to Dr Clive Rahn, Horticulture Research International, Wellesbourne, Warwickshire, CV35 9EF, UK, stating the purpose for which it will be used. Please also enclose a cheque for 20 UK pounds, or equivalent, to cover the cost of administration and postage.
BURNS, I. G., RAHN, C. R., GREENWOOD, D. J., DRAYCOTT, A. and RICHARDSON, A. S. (1997). A user friendly decision support system for adjusting N fertiliser requirements to local conditions. In: Proceedings of a Conference on Managing Soil Fertility for Intensive Vegetable Production Systems in Asia, 4-10 November 1996, Taiwan: AVRDC, pp. 314-324.
GREENWOOD, D. J., NEETESON, J. J. & DRAYCOTT, A. (1985). Response of potatoes to N-fertilizer: Quantitative relations for components of growth. Plant and Soil, 85, 163-183.
GREENWOOD, D. J., NEETESON J. J. & DRAYCOTT, A. (1985). Response of potatoes to N-fertilizer: Dynamic model. Plant and Soil, 85, 185-203.
GREENWOOD, D. J., NEETESON J. J. & DRAYCOTT, A. (1985). Simulation of growth and nitrogen response of potatoes. In: Assessment of Nitrogen Fertilizer Requirement, (edt J.J. Neeteson & K. Dilz), The Netherlands: Institute for Soil Fertility, pp 159-168.
GREENWOOD, D. J., NEETESON J. J. & DRAYCOTT, A. (1986). An analysis of the dependence of yields of potatoes and vegetable crops on soil properties and weather conditions. Journal of the Science of Food and Agriculture, 37, 674-675.
GREENWOOD, D. J., NEETESON J. J. & DRAYCOTT, A. (1986). Quantitative relationships for the dependence of growth rate of arable crops on their nitrogen content, dry weight and aerial environment. Plant and Soil, 91, 281-301.
GREENWOOD, D. J., NEETESON J. J. & DRAYCOTT, A. (1986). Quantitative relationships for the dependence of growth rate of arable crops on their nitrogen content, dry weight and aerial environment. In: Fundamental, Ecological and Agricultural Aspects of Nitrogen Metabolism in Higher Plants, (edt H. Lambers, J.J. Neeteson & I. Stulen), Dordrecht: Martinus Nijhoff Publishers, pp 367-387.
GREENWOOD, D. J. & DRAYCOTT, A. (1987). Elements of similarity in the components of N-response of widely different crops. In: Meeting on Plant and Soil Nitrogen Metabolism, Sussex, September 1987, London: Agricultural and Food Research Council
GREENWOOD, D. J., NEETESON J. J.) & DRAYCOTT, A. (1987). Modelling the response of diverse crops to nitrogen fertilizer. Journal of Plant Nutrition, 10, 1753-1759.
GREENWOOD, D. J., VERSTRAETEN, L. M. J. & DRAYCOTT, A. (1987). Response of winter wheat to N-fertiliser: quantitative relations for components of growth. Fertilizer Research, 12, 119-137.
GREENWOOD, D. J., VERSTRAETEN, L. M. J., DRAYCOTT, A. & SUTHERLAND, R. A. (1987). Response of winter wheat to N-fertiliser: dynamic model. Fertilizer Research, 12, 139-156.
GREENWOOD, D. J. & DRAYCOTT, A. (1988). Recovery of fertilizer-N by diverse vegetable crops: processes and models. In: Nitrogen Efficiency in Agricultural Soils, (edt D.S. Jenkinson & K. A. Smith), Barking: Elsevier Applied Science, pp 46-61.
GREENWOOD, D. J. & DRAYCOTT, A. (1989a). Experimental validation of an N-response model for widely different crops. Fertilizer Research, 18, 153-174.
GREENWOOD, D. J. & DRAYCOTT, A. (1989b). Quantitative relationships for growth and N content of different vegetable crops grown with and without ample fertilizer-N on the same soil. Fertilizer Research, 18, 175-188.
GREENWOOD, D. J., KUBO, K., BURNS, I. G. & DRAYCOTT, A. (1989). Apparent recovery of fertilizer-N by vegetable crops. Soil Science and Plant Nutrition, 35, 367-381.
GREENWOOD, D. J., LEMAIRE, G., GOSSE, G., CRUZ, P., DRAYCOTT, A. & NEETESON J. J. (1990). Decline in percentage N of C3 and C4 crops with increasing plant mass.Annals of Botany,66, 425-436.
GREENWOOD, D. J., STONE, D. A. & DRAYCOTT, A. (1990). Weather, nitrogen-supply and growth rates of field vegetables. Plant and Soil, 124, 297-301.
GREENWOOD, D J., GASTAL, F., LEMAIRE, G., DRAYCOTT, A., MILLARD, P. & NEETESON J.J. (1991). Growth rate and percentage N of field grown crops; theory and experiments. Annals of Botany, 67, 181 - 190.
GREENWOOD, D. J., RAHN. C. R., DRAYCOTT, A., VAIDYANATHAN, L. V. & PATERSON, C. D. (1996). Modelling and measurement of the effects of fertilizer-N and crop residue incorporation on N-dynamics in vegetable cropping. Soil Use and Management , 12, 13-24.
GREENWOOD, D. J. (2001). Modelling of N-response of field vegetable crops under diverse conditions with N_ABLE: a review. Journal of Plant Nutrition 24, 1799-1815.
HINDE, C. J., ESCOBAR-GUTIERREZ, A. J., READER, R. L., PHELPS, K. & BURNS, I. G. (2001). Graphical modelling of nitrogen response in crops. Journal of Agricultural Science, Cambridge, 137, 121-122.
KARPINETS, T. V. & GREENWOOD, D. J. (2001) Potassium Dynamics. In "Processes in the soil -plant system: modelling concepts and applications. Ed R.Neider. Binghampton, New York. The Haworth Press. In Press.
LEMAIRE G. (1997) Diagnosis of the nitrogen status in crops. Springer, Berlin
LEMAIRE, G., GASTAL, F., CRUZ, P., GREENWOOD, D. J. & DRAYCOTT, A. (1990). Relationships between plant-N, plant mass and relative growth rate for C3 and C4 Crops. Proceedings of the First Congress of the European Society of Agronomy Paris, December 1990, Paper No. 05-07.
MacKERRON, D. K. L, GREENWOOD, D. J., MARSHALL, B., RABBINGE, R. & SCHOBER, B. (1991). Forecasting systems for the potato crop. Proceedings of the 11th Triennial Conference of the European Association for Potato Research, Edinburgh, July 1990, pp 85-105.
NEETESON J. J., GREENWOOD, D. J. & HABETS, E. J. M. H. (1986). Dependence of soil mineral N on N-fertilizer application.Plant and Soil, 91, 417-420.
NEETESON J. J., GREENWOOD, D. J. & HABETS, E. J. M. H. (1986). Dependence of soil mineral N on N-fertilizer application. In: Fundamental, Ecological and Agricultural Aspects of Nitrogen Metabolism in Higher Plants, (edt H. Lambers, J.J. Neeteson & I. Stulen), Dordrecht: Martinus Nijhoff Publishers, pp 439-442.
NEETESON J. J., GREENWOOD, D. J. & DRAYCOTT, A. 1987). A dynamic model to predict yield and optimum nitrogen fertiliser application rate for potatoes. Proceedings of the Fertiliser Society, No.262, 31 pp.
NEETESON J. J., GREENWOOD, D. J. & DRAYCOTT, A. (1988). A dynamic model to predict the optimum nitrogen fertilizer application rate for potato. In: Nitrogen Efficiency in Agricultural Soils, (edt D.S. Jenkinson & K. A. Smith), Barking: Elsevier Applied Science, pp 384-393.
NEETESON J. J., GREENWOOD, D. J. & DRAYCOTT, A. (1989). Een simulatiemodel voor de reactie van aadappelen op stikstefbernsting. Bestuur van de stichting Instituut voor Bodenvruchtbaarheid, 31/12/1989, pp 78-81.
NEETESON J. J., GREENWOOD, D. J. & DRAYCOTT, A. (1989). Model calculations of nitrate leaching during the growth period of potatoes. Netherlands Journal of Agricultural Science, 37, 237-256.
RAHN, C. R., VAIDYANATHAN, L. V. V. & PATERSON, C. D. (1992). Improving the prediction of fertiliser nitrogen for brassica crops. Proceedings of the 2nd Congress of the European Society of Agronomy, Warwick, 1992, pp 424-425.
RAHN, C. R., VAIDYANATHAN, L. V. V. & PATERSON, C. D. (1992). Nitrogen residues from brassica crops. Aspects of Applied Biology, 30, 263-270.
RAHN, C. R., GREENWOOD, D. J. & DRAYCOTT, A. (1996). Prediction of nitrogen fertiliser requirement with HRI WELL_N Computer Model. In: Progress in Nitrogen Cycling, (Proceedings of the 8th Nitrogen Fixation Workshop, Ghent, 5-8 September 1994, edt O. Van Cleemput, G. Hofman & A. Vermoesen), Kluwer, p255-258.
RAHN, C.R., GREENWOOD, D.J., and DRAYCOTT, A. (1996) Prediction of nitrogen fertiliser requirement with HRI WELL_N Computer Model. In: Proceedings of 8th Nitrogen Workshop, Ghent, 5-8 September 1994. In Progress in Nitrogen Cycling Studies p 255-258 Kluwer Netherlands.
RAHN C. R. (1998). Making the most of your nitrogen. The Grower 130, 22-23.
RAHN, C., MEADE, A., DRAYCOTT, A., LILLYWHITE, R. & SALLO, T. (2001) A sensitivity analysis of the prediction of nitrogen fertilizer requirement of Cauliflower crops using the HRI WELL_N computer model. Journal of Agricultural Science, Cambridge, 137, 55-69.
RAHN, C. (2001). Reducing nitrogen losses from field vegetable crops. Fruit & Veg Tech, 1, 34-37.
RILEY, H. & GUTTORMSEN, G. (1993). N requirements of cabbage plants grown in southern Norway. II Model predictions. Norwegian Journal of Agricultural Science, 8, 99-113
RILEY, H. and GUTTORMSEN, G. (1999). Alternative equations for critical N-concentration in Cabbage. Acta Horticulturae 506, 123-128.
SUTHERLAND, R. A., WRIGHT, C. C., VERSTRAETEN, L. M. J. & GREENWOOD, D. J. (1986). The deficiency of the 'economic optimum' application for evaluating models which predict crop yield response to nitrogen fertiliser. Fertilizer Research, 10, 251-262.
TEI, F., BENINCASA, P., GUIDUCCI, M. (1999). Nitrogen fertilization of lettuce, processing tomato, and sweet pepper: Yield, nitrogen uptake and the risk of nitrate leaching. Acta Horticulturae 506, 61-67.
YANG, J, WADSWORTH, G.A, ROWELL, D. L and BURNS, I.G. (1999). Evaluating a crop nitrogen simulation model, N_ABLE using a field experiment with lettuce. Nutrient Cycling in Agroecosystems 55, 221-230.
YANG,J., GREENWOOD,D.J., ROWELL,D.L., WADSWORTH,G.A., and BURNS, I.G. (2000) Statistical methods for evaluating a crop nitrogen simulation model, N_ABLE. Agricultural Systems 64, 37-53.
YANG, J., ROWELL, D.L., BURNS, I.G., GUTTORMSEN, G., RILEY, H. and WADSWORTH,G.A. (2002). Modification and evaluation of the crop nitrogen model N_ABLE using Norwegian field data. Agricultural Systems 72, 241-261.
source:Description of the Nitrogen Model