Effect of time of nitrogen application on spikelet differentiation and degeneration of rice

A study was conducted in the field to identify the N application stages which greatly determine spikelet differentiation and degeneration of rice (Oryza sativa L.). Spikelet differentiation and degeneration were greatly influenced by time of N application. N application at the neck-node differentiation stage significantly increased spikelet differentiation and that at the active meiosis stage significantly reduced spikelet degeneration. N absorption at the spikelet differentiation and heading stages was significantly correlated with both greater spikelet differentiation and percent degeneration, respectively. Degeneration was mainly induced by the degeneration of spikelets on the secondary rachis-branch. Four equal splits of 100 kg N/ha at the early tillering, active tillering, neck-node differentiation, and active meiosis stages were found good for efficient rice production.