Keywords: Apparent nitrogen recovery (ANR), nitrogen use efficiency (NUE), water productivity, soil-crop models, grain yield, sustainability

Agronomically, farmers should aim at the minimum input of each production resource required to allow maximum utilization of all other resources (De Wit, 1992). Increased nitrogen use efficiency, raising the yield potential and closing existing yield gaps to avoid yield stagnation are pivotal components of a sustainable agriculture that meets human needs and protects natural resources (Cassman et al. 2003).

Improved crop yield, water productivity and nitrogen use efficiency are mutually related (Spiertz and De Vos, 1983). Matching nitrogen and water supply to the demand of the crop requires knowledge of crop growth processes and critical phonological stages in crop development (Slafer et al., 2005). The objectives are to develop tools to study water and nitrogen limitations on crop productivity. The apparent nitrogen recovery (ANR) was used as an indicator for quantifying plant-soil interactions in acquiring soil nitrogen.

A multi-scale approach to evaluate the efficiency of nutrient management in cropping and farming systems is recommended by Neeteson et al. (2002). Improved efficiency of nutrient use at a field and farm scale, both aiming at increasing crop yield and reducing losses, is dependent upon the magnitude of matching nutrient supply and demand of the crop. Irrigated lowland rice cropping systems show low ANR-values of about 0.30, while high-yielding wheat and maize crops can show values as high as 0.80. The agronomic nitrogen use efficiency, derived from ANR and PNUE, amounts to 0.50 on average for crops under temperate conditions. Water availability strongly affects N-uptake and -recovery.

The optimisation requires measurement and prediction of soil nutrient supply, crop uptake and their variability (Stockdale E.A. et al., 1997). A quantitative systems approach is needed to identify the prospects for improving the agronomic N-use-efficiency. Various mechanistic crop growth models have been developed (e.g. Jamieson and Semenov, 2000; Xinyou Yin and Van Laar, 2005). The state of the art will be discussed.

References

Cassman Kenneth G., Dobermann Achim, Walters Daniel T. and Yang Haishun, 2003.
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Jamieson, P.D. and M.A. Seminov, 2000. Modelling nitrogen uptake and redistribution in wheat. Field Crops Res. 68: 21-29

Neeteson, J.J.; J.J. Schröder and H.F.M. Ten Berge, 2002. A multi-scale system approach to nutrie management research in the Netherlands. NJAS Wageningen Journal of Life Sciences 50-2: 141-151

Slafer, G.A., J-L Araus, C. Royo and L.F. Garcia del Moral, 2005. Promising eco-physiological traits for genetic improvement of cereal yields in Mediterranean environments. Ann. Appl. Biol. 146:61-70

Spiertz, J.H.J. & N.M. De Vos, 1983. Agronomic and physiological aspects of the role of nitrogen in yield formation of cereals. Plant and Soil 75: 379-391

Stockdale, E.A.; J.L. Gaunt and J. Vos, 1997. Soil-plant nitrogen dynamics: what concepts are required? European Journal of Agronomy 7: 145-159

Yin Xinyou and H.H. van Laar, 2005. Crop Systems Dynamics: an ecophysiological simulation model for genotype-by-environment interactions. Wageningen Academic Publishers; 155 pp

Wit, C.T. de, 1992. Resource use efficiency. Agricultural systems 40: 125-151


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