Quantitative Method for Analysis of Grain Yield in Rice
- Shinichi Takami ,
- Tohru Kobata and
- C. H. M. Van Bavel
Cereal crop yields can be substantially reduced when drought occurs during grain filling. A mathematical expression is proposed to describe the effects of drought during the grain-filling stage of rice (Oryza sativa L.). The expression predicts the grain yield as a function of the total dry matter production during the grain filling with two parameters: potential yield, and amount of mobilizable reserves at anthesis, both to be determined experimentally. The proposed relation states that grain yield equals the potential yield when the total assimilate supply (the amount of mobilizable reserves at anthesis, plus the total dry matter produced during grain filling) is equal to, or greater than the potential yield. Below this level of assimilate supply, grain yield decreases in proportion to the total dry matter produced during grain filling. Drought is assumed to reduce the grain yield through dry matter production alone, without any effects on the potential yield and the amount of mobilizable reserves. The model was tested in an experiment in which the yield response of two different cultivars to six levels of water availability was measured. The theoretical generalization fits the experimental results. The model is useful in predicting the yield response of rice when the crop encounters drought stress during grain filling, provided the two parameters cited above can be measured or estimated at anthesis. It also could serve as a submodel for yield prediction in a mechanistic crop production model.
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