Effect of Nitrogen Rates and Split Application on Dry Matter Remobilization in Different Rice (Oryza sativa L.) Cultivars

To investigate the effect of nitrogen rate and split form of application on dry matter remobilization among different rice cultivars, a field experiment was carried out in the Rice Research Institute of Iran (Amol) – during 2005. A split–split experiment on the basis of a randomized complete block design with 3 replications involving 3 factors was employed in which fertilizer rates (100, 150 and 200 kgha-1 from urea source), split form of fertilizer application (in varied ratios at the stages of transplanting, tillering and heading namely: S1 (50%, 25% and 25%), S2 (25%, 50% and 25%) and S3 (25%, 25% and 50%)) and finally crop cultivar (Tarom, Shafagh and GRH1 Hybrid) constituted the treatments. Results indicated that nitrogen fertilizer rates and split application exerted a significant effect on dry matter remobilization in total shoot, stem and leaves (except flag leaf), in which among the experimented cultivars, Shafagh stood top in terms of stem and total shoot dry matter remobilization. Also, among the fertilizer rates application the highest rate of dry matter remobilization was related to the 100 kg nitrogen fertilizer level. Among split form of applications, the first form (50%, 25% and 25%) treatment resulted in the highest rate of dry matter remobilization. The highest rate of dry matter remobilization in other leaves and in flag leaf belonged to GRH1 hybrid. Based on the obtained results, dry matter remobilization of total shoot (r=0.60**), stem(r=0.62**) and other leaves (r=0.34**) had significant and positive correlation with paddy yield.