Abstract
We previously reported that deep-flood irrigation (DFI) is effective in reducing the occurrence of chalky grains compared to conventional water irrigation (CWI), which seems to be achieved by the suppression of inferior tillers. To investigate how the difference in tiller composition under DFI suppresses the occurrence of chalky grains, we examined the number of grains per panicle as well as factors related to source ability (nonstructural carbohydrate of leaf sheath and culm at full heading stage, nitrogen of leaf blade at full heading stage, and the leaf area at ripening stage) between superior main stem and inferior tillers including highest primary tiller and, in CWI, secondary tillers. Under DFI, the source ability per grain was increased not only in the superior main stem but also in the highest primary tiller, and hence chalky grains in both shoots were decreased. The results show that DFI increases source ability per grain in all stems and decreases chalky grains, regardless of superiority in stems. Moreover, the occurrence of chalky grains was suppressed, in spite of the higher number of grains per panicle with higher percentage of secondary rachis grains.
