Effects of gibberellic acid spray on nitrogen yield efficiency of mustard grown with different nitrogen levels

Mustard is cultivated throughout the world for oil in its seeds. Itrequires high nitrogen input for improved productivity but the nitrogen appliedto the soil is not fully utilised by the crops due to various constraints. Theobjective of the reported research was to determine if foliar- appliedgibberellic acid (GA^sub 3^) could enhance crop growth and increasenitrogen-use efficiency. A field experiment was conducted during 1997-98in which GA^sub 3^ (10^sup -5^ M) was applied tofoliage at 40d after sowing (pre-flowering) to mustard grown with 0, 40(sub-optimal), 80 (optimal) and 120 (supra-optimal) kgN ha^sup -1^. Foliar spray of GA^sub 3^ was effectiveonly when plants received sufficient N (80 kgN ha^sup -1^). GA^sub 3^ sprays significantly enhancedplant dry mass, leaf area, carbon dioxide exchange rate, plant growth rate,cropgrowth rate and relative growth rate. GA^sub 3^ -treated plants showedenhanced nitrogen-use efficiency through redistribution of N to seeds.[PUBLICATION ABSTRACT]