EFFECT OF NITROGEN FERTILIZER APPLIED AT MIDDLE AND LATE GROWING STAGES ON ~(15)NUPTAKE AND DISTRIBUTION IN RICE ( ORYZA SATIVA L.)

Isotopic 15 N micro plot experiment was conducted under field condition to investigate the effect and uptake of nitrogen applied at middle and late growing stages of rice. Results showed that nitrogen timing had an obvious effect on dry matter accumulation, fertilizer N uptake and its distribution in different parts of rice plant. With delayed fertilizer application dry weight of vegetative parts of rice plant (e.g. stalk and leaf) decreased obviously while spike dry weight decreased slightly. Compared with spikelet promoting fertilizer, amount of nitrogen accumulated in green leaf and leaf sheath decreased by 31.5% and by 37.70%, respectively, while that of stalk and spike increased slightly. Of total amount of 15 N accumulated in whole rice plant, green leaf (including its sheath) and spike accounted for 40% and 50%, respectively. Delayed fertilizer N application also resulted in the increase of 15 N uptake by spike and the decrease of that by green leaf. In this experiment, 15 N recovery of applied as spkelet promoting, spikelet sustaining and grain fertilizer was 32.7%, 30.0% and 23.7%, respectively.