Effect of different levels of nitrogen and plant spacing on yield, yield components and physiological indices in high-yield rice (number 843).

摘要

In order to study the effect of different levels of nitrogen and plant spacing on yield, yield components and physiological indices in high-yield rice (number 843), an experiment was conducted for a period of two years (2006-2007) at the Rice Research Station of Tonekabon (Chaparsar), Iran. The experimental design was split plot on basis of randomized block design with 3 replications. Three Nitrogen fertilizer levels consist of 200, 250 and 300 kg N ha-1 were applied in main plots and subplots which consisted of split application of spacing at four levels (11x30, 15x30, 20x20 and 25x25 cm2). Results showed that the rates of nitrogen fertilizer had significant effect on 1000-seed weight. Meanwhile different spacing had significant effects in the all mentioned traits. Statistical analysis indicated that grain yield decreased with increasing of spacing and the highest grain yield was obtained in 20x20 cm2 (8619.1 kg ha-1) spacing treatment. Grain yield increased with increasing nitrogen application but this increasing wasn't significant. The ideal spacing of 20x20 cm2 was determined with an efficient N dosage level of 200 kg N ha-1 for this promising rice line. Relative growth rate (CGR) graph has discount progress during growth season. Results showed that leaf area index (LAI), crop growth rate (CGR) and net assimilation rate (NAR) increased with increasing of density. Increasing of leaf area index in field lead to maximum photo assimilation rate and therefore increase crop photosynthetic capacity and finally resulted to high yield. Major part of increasing crop growth rate (CGR) was due to increase density for higher leaf area index (LAI). It is concluded that increasing grain yield in rice can be achieved through increasing total dry matter and improving physiological indices.