Arranjo espacial de plantas e contribuição do colmo principal e perfilhos na produção e qualidade de grãos de arroz irrigado (Oryza sativa L.)

Abstract

The fieldwork aimed at defining the plant arrangement which provides an increase of productivity and quality of grains, as well as evaluating the main stem contribution in the productivity and quality of grains on four Oryza sativa cultivars, when compared to lateral sprouts. It was performed on the Embrapa Temperate Climate experimental area during the years of 2006/07 and 2007/08. The rice cultivars of BRS Atalanta, BRS, Firmeza, BRS Pelota and Br Irga 409 were utilized, as submitted to the following managements: two spacings between lines (12,5 and 17,5 cm), three seeding densities (90,120 and 150 kg ha-1 ) and two plant structures (main stem and sprouts). The experimental outlining was the one of random blocks and four repetitions. The parameters for evaluation were: plant height, stem diameter, number of stems, sprouts and panicles m-2, stem fertility, number of plant sprouts-1, panicle length and weight, sterile spikelet percentage, number of panicle grains-1, number of well shaped and default grains, the weight of 1000 grains, grain yield, polished grain dimensions, whole grain yield, white-core grains and plastered grains, grain amylose content, and gelatinization temperature. The results allowed one to conclude that: the four rice genotypes presented a grain yield increase with spacing reduction between lines; the gradual increase on the seeding density of 90, 120, and 150 hg ha-1, for the studied cultivars, produced an increase of 20 to 26% in the number of stems m-2 and 19 to 28% in the number of panicles m-2 . An opposite effect was observed for the number of stems plant-1 and grain panicles-1, with the variations of 6 to 20 % and 4 to 14%, respectively, however, did not show significant variation in the grain yield; for the BRS Atalanta and BRS Firmeza cultivars the contribution in the number of grains in the main stem and sprouts are equivalent. For the BRS Pelota and BR Irga 409, the participation of the number of sprout grains was 6% and 8% higher, respectively, to the number of grains in the main stem; the whole grain yield of the main stem and sprouts for the BRS Firmeza, BRS Pelota and BR Irga 409 presented significant differences, while the BRS Atalanta no differences were found. BRS Firmeza and BRS Pelota presented significant differences for the grains with white core and plastered characters coming from the main stem and sprouts; no significant differences were found between the main stem grains and those of the sprouts as to the amylose content and gelatinization temperature.