Panicle emergence of tiller types and grain yield of tiller order for direct-seeded rice cultivars

Grain yield of rice (Oryza sativa, L.) tillers is critical to rice crop yield and quality but relatively little is known about variations that occur among panicles and grains for tiller types and emergence orders of direct-seeded rice cultivars. The objective of research was to examine how tillering may affect yield and quality at low plant population densities with profuse tillering. Single rice plants were grown in pots in a greenhouse in 1990 and in 1992 and in the field in 1991. The aim was to maximize tillering and thus better see effects of tiller emergence order and type on yield and panicle emergence. Culm and panicle emergence dates were successively later for primary, secondary, and tertiary tillers but with a smaller delay among panicle emergence dates than was observed for tiller emergence. Grain yield of tillers was related more to emergence order than to tiller type. Secondary and tertiary tillers in sufficient numbers could cause delays in crop grain maturity. Specifically, the beginning of grain-filling (closely following top anthesis) was 1 to 5 d later for primary tillers and 3 to 9 d later for secondary tillers, compared to main stems. These data indicate direct-seeded rice cultivars have partial but not complete synchrony of panicle emergence. Consequently, production strategies that increase preflood N to increase tillering in thin (sparsely populated) rice stands, could potentially delay maturity of the crop as well as increase yields.