Nitrogen management in direct seeded rice, agronomic, physiological and economical perspectives

Site specific nitrogen (N) management require development of plant based approaches for wide scale recommendation. Among different splits, two N splits (sowing and anthesis) showed growth, yield and total N uptake similar to three splits (sowing, tillering and anthesis) in direct seeded rice.

Increasing N supply from 80 to 160 kg N ha -1 improved recovery efficiency while reduced agronomic efficiency attributed to low soil NH4+ -N subjected to unaccounted gaseous losses. Positive association of NDVI at booting stage with leaf N contents and of total N uptake with grain yield suggest to predict economical N application using this index. NDVI and SPAD-chlorophyll at booting did not vary for two or three N splits, however, response was genotype specific with highest N requirement for coarse than medium grain rice types.