Effect of nitrogen supply on maize yield. I. Modeling physiological responses.
Sinclair T.R. | Muchow R.C.
Much of the increase in maize (Zea mays L.) yields in recent decades has been closely associated with increased levels of N fertilizer application. Although many studies have documented yield responses to increased N levels in the soil, a mechanistic description of the physiological responses that influence crop growth under various levels of N has not been fully elucidated. The objective of this work was to develop a relatively simple, mechanistic model of maize growth and development to account for the influence of soil and crop N budgets. The soil N budget was simulated for two soil layers that incorporated fertilization, mineralization, denitrification, and leaching. Crop uptake rate of N was simulated by a supply function that depends on cumulative and daily thermal units, soil water content, and soil N availability. Comparison of simulated and experimental crop N uptake through the season showed especially good agreement for O to 12 g N m-2 fertilizer treatments. At 24 and 42 g N m-2, the simulated crop N uptake was greater than observed. Nevertheless, comparable seasonal patterns between simulations and observations at all fertility levels were obtained for accumulated total biomass and grain. Final grain yields for all fertility treatments were simulated to be within 8% of the observed. A sensitivity test was performed with the model to investigate the importance of various physiological parameters on biomass accumulation and yield. Yield estimates under low soil N levels tended to be most sensitive to minimum grain N concentration.
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