Plant Nitrogen Accumulation Dynamics in Rice in Response to Nitrogen Management

This study investigates the effect of rice nitrogen (N) management on the dynamics of plant nitrogen accumulation (PNA) during internodal elongation (IE) in relation to grain yield. Four field experiments were conducted in two soils with six preflood N treatments. The PNA was monitored for 3 weeks, starting at the beginning of IE (BIE). The PNA explained 54-72% of yield variability. The effect of midseason N application on yield varied with fields, indicating a need for assessing midseason N requirement for each field. One week after BIE was a better time to assess the N requirement of rice crop. The greatest grain yields in Cocodrie and Wells cultivars corresponded to PNA of 10.9 and 11.1 g m(-2) at BIE. A midseason application of 50 kg N ha(-1) as urea at 7-10 days after BIE increased the rice yield in the Glossaqualfs field when the PNA at BIE was less than 8.3 g m(-2).