Response of lowland rice genotypes to plant arrangement

Grain yield increase of lowland rice can be obtained through manipulation o f plant arrangement. The objective of this research was to determine the re sponse of grain yield of lowland rice genotypes with different types of pla nt and yield potentials to plant arrangement. Three experiments were conduc ted in the field, in Cachoeirinha, RS, Brazil, in the 1994/95, 1997/98 and 1998/99 growing seasons. In the first year, treatments consisted of three r ow spacings (12.5, 20 and 30 cm), three seed rates (75, 150 and 225 kg/ha), and two rice varieties (BR-IRGA 410 and IRGA 416). In the other two experi ments, treatments consisted of four row spacings (12.5, 20, 30 and 40 cm), three seed rates (30, 90 and 150 kg/ha), and four rice varieties (959 line, XL-5 hybrid, BR-IRGA 410 and IRGA 416 commercial cultivars). In all experi ments, the reduction of row spacing increased grain yield, regardless of ri ce genotype. With efficient weed control and adequate water management, see d rate can be reduced.