EFFECT OF INTEGRATION OF FERTILIZER AND GREEN MANURE NITROGEN ON YIELD ATTRIBUTES, NITROGEN UPTAKE AND YIELD OF LOWLAND RICE (ORYZA-SATIVA L)

Field experiments were conducted at Tamil Nadu Rice Research Institute , Aduthurai, India, during the wet seasons of 1992 and 1993 to study t he effect of full and partial substitution of fertiliser N with green manure N (Sesbania rostrata) on nitrogen uptake, yield attributes and yield of rice. The experiment consisted of eight treatments with two l evels of N (100 and 200 kg ha(-1)) and three sources of N application viz., fertilizer, integrated (1:1 fertilizer and green manure N) and g reen manure N compared to the recommended practice (150 kg fertilizer plus 6.25 t ha(-1) (72 kg N) green manure) and a no N control. Nitroge n application markedly increased the N uptake. Combined use of the two N sources at 200 and 222 kg N ha(-1) and of single fertilizer N at 20 0 kg N ha(-1) recorded the maximum N uptake, increased the yield attri butes such as number of panicles per unit area, weight per panicle, nu mber of total and filled grains per panicle and test weight. At 200 kg N ha(-1) full substitution of N by green manure reduced the grain yie ld bur only partial substitution of N by green manure resulted in almo st similar yield as single fertilizer N. Thus 200 kg N ha(-1) applied in equal proportions of fertilizer and green manure N can be recommend ed for medium duration rice cultivars.