GROWTH ANALYSIS IN RICE INFLUENCED BY SEEDING RATES (CROP GROWTH RATE, NET ASSIMILATION RATE AND PADDY YIELD)

Abstract

A field experiment was carried out at Field Crop Station of IPA Agricultural Research Center during the summer season of 1996. The aims of the study were to investigate the effects of seeding rates in some growth parameters and yield in nine genotypes of rice. The design of experiment was (RCBD) in split plot arrangement with four replicates. The seeding rates 120, 160 and 200 Kg/ha were the main plots, while the genotypes were sub plots. The growth parameters studied included crop growth rate (CGR), net assimilation rate (NAR), relative growth rate (RGR) and yield. The measurement began 55 days after planting until physiological maturity.The results showed that increasing of seeding rates caused significant increments for (CGR) (at the periods 55, 69 and 97 days after planting), the percentage increments were 37.9, 32.1 and 15.3% respectively when the seeding rates increased from 120 to 200 kg/ha, on the other hand increasing seeding rates caused significant reductions in (NAR) (at the periods 83, 97 and 111 days after planting) the percentage reductions were 25.6, 16.4 and 46.7% respectively, while (RGR) (at the periods 83, 111 and 125 days from planting) the reductions percentages were 16.3 and 26.6% and 7.14% respectively when the seeding rates increased from 120 to 200 kg/ha. Increasing of seeding rates caused significant increment in paddy yield (30.6%) when the seeding rates increased from 120 to 200 kg/ha. Significant differences among genotypes were found interms of (CGR), (NAR) and (RGR) at different periods as well as paddy yield. Higher (NAR) and paddy yield were obtained by genotypes RP20 and IR56 (4.56 and 4.13 gm/m2/days) and (4.77 and 4.27 t/ha) respectively. There were significant interactions between seeding rates and genotypes in paddy yield.Results of correlation study showed that significant positive relationship between paddy yield with (CGR), (NAR) and (RGR) at different growth periods.