PANICLE EMERGENCE OF TILLER TYPES AND GRAIN-YIELD OF TILLER ORDER FORDIRECT-SEEDED RICE CULTIVARS

Grain yield of rice (Oryza sativa, L.) tillers is critical to rice cro p yield and quality but relatively little is known about variations th at occur among panicles and grains for tiller types and emergence orde rs of direct-seeded rice cultivars. The objective of research was to e xamine how tillering may affect yield and quality at low plant populat ion 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. Th e aim was to maximize tillering and thus better see effects of tiller emergence order and type on yield and panicle emergence. Culm and pani cle emergence dates were successively later for primary, secondary, an d tertiary tillers but with a smaller delay among panicle emergence da tes than was observed for tiller emergence. Grain yield of tillers was related more to emergence order than to tiller type. Secondary and te rtiary tillers in sufficient numbers could cause delays in crop grain maturity. Specifically, the beginning of grain-filling (closely follow ing 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 indica te direct-seeded rice cultivars have partial but not complete synchron y of panicle emergence. Consequently, production strategies that incre ase preflood N to increase tillering in thin (sparsely populated) rice stands, could potentially delay maturity of the crop as well as incre ase yields.