Cereal growth, development and yield

Abstract

The objective of the CERES crop simulation models is to predict the duration of growth, the average growth rates, and the amount of assimilate partitioned to the economic yield components of the plant. With such a simulation system, optimizing the use of resources and quantifying risk related to weather variation is possible. The cereal crops included in the DSSAT (Decision Support System for Agrotechnology Transfer) v3 models are maize, wheat, barley, sorghum, millet (Pennisetum glaucum) and rice. A feature of each model is its capability to include cultivar specific information that make possible prediction of the cultivar variations in plant ontogeny and yield component characteristics and their interactions with weather. Biomass growth is calculated using the radiation use efficiency approach; biomass produced is partitioned between leaves, stems, roots, ears and grains. The proportion partitioned to each growing organ is determined by the stage of development and general growing conditions. The partitioning principles are based on a sink source concept and are modified when deficiencies of water and nutrient supplies occur. Crop yields in the CERES models are determined as a product of the grain numbers per plant times the average grain weight at physiological maturity. The grain numbers are calculated from the above ground biomass growth during a critical stage in the plant growth cycle for a fixed thermal time before anthesis. The grain weight in all the CERES models is calculated as a function of cultivar specific optimum growth rate multiplied by the duration of grain filling. Grain filling is reduced below the optimum value when there is an insufficient supply of assimilate from either the daily biomass production or from stored mobile biomass in the stem. The CERES models have been tested over a wide range of environments. Although there are improvements that can be made in the simulation procedures, results have shown that when the weather, cultivar and management information is reasonably quantified, the yield results are usually within acceptable limits of plus or minus 5% to 15% of measured yields.