Growth of crop communities and the production of yield.

Abstract This chapter focuses on developing general model of community growth and the production of yield by grain crops. Murata's (1969) three-stage system provides such a model. It is useful because it is simple (only three stages), it applies equally well to all grain crop species (although there are some species variation in minor details), it clearly identifies the sequential nature of the yield production process and the three stages relate to the primary drivers of the yield production process at the community level. First, the crop must accumulate the leaf area that drives community photosynthesis (Stage I), then seed number is determined (Stage II), and finally seed filling occurs (Stage III) and the production of yield is finished. High yield of any variety/location combination requires, at a minimum: (i) the production of enough leaf area index (LAI) during Stage I to maximize solar radiation interception and community photosynthesis; and (ii) an absence of stress during Stage II to maximize seed number and during Stage III to allow the seeds to fill to their maximum potential size. The scheme provides a powerful framework for us to think about how management decisions and environmental conditions affect yield.