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Title: MODEL ANALYSIS OF SORGHUM RESPONSE TO NITROGEN IN SUBTROPICAL AND TROPICAL ENVIRONMENTS

Author
item Sinclair, Thomas
item MUCHOW, R. - CSIRO, BRISBANE AUSTRALIA
item MONTEITH, J. - INST TERR ECOL, SCOTLAND

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sorghum is a major crop world-wide, particularly in regions of limited rainfall. Determining the amount of nitrogen fertilization for the crop is difficult to resolve because of the influence of variable amounts of water available in individual experiments. To facilitate the understanding of sorghum growth and yield under these conditions, a simple, mechanistic model of sorghum was developed to consider the response of the crop to water and nitrogen availability in the soil. It was used to analyze the results of a number of experiments undertaken in three divergent environments. The sorghum model was able to reproduce observed crop behavior under the varying conditions and the simulations illustrated several important aspects of sorghum production. The model can now be used to analyze various management possibilities for sorghum in other water-limited environments.

Technical Abstract: Nitrogen fertilization is important in achieving high sorghum yields. However, under semi-arid conditions the response to N is confounded by seasonal differences in water availability. A simple, mechanistic model was developed to interpret measurements of the growth and yield of sorghum grown at different levels of N and water supply. After adjusting coefficients to describe leaf and grain development for sorghum, the model simulated crop nitrogen uptake, growth and grain yield. Analysis of the model results led to two interesting hypotheses concerning an experiment at Hyderabad, India: (1) the irrigation level of the well-watered treatment appeared to be inadequate to avoid drought stress at the end of the cropping season, and (2) there was seemingly about 4 g N m-2 of soil N unavailable to the crop in each of the irrigation treatments. Overall, the sorghum-N model proved useful in interpreting and analyzing field measurements of development, growth and yield of sorghum grown under diverse conditions.