Seed production of dhaincha (Sesbania aculeata) as influenced by nitrogen and phosphorus fertilization

A field experiment was carried out under protective irrigation during kharif (June-November) seasons of 2009 and 2010 at New Delhi in a sandy loam soil low in available nitrogen (173 kg/ha) and medium in available phos- phorus (13.2 kg/ha) to study the effect of levels of phosphorus (0, 13.2 and 26.4 kg/ha in main plots) and nitrogen (0, 30 kg at sowing, 15 kg each at sowing and flowering and 30 kg at flowering in sub-plots) fertilization on seed production of dhaincha [Sesbania aculeata (Wills.) Poir.] in a split plot design with three replications. The results indicated significant impacts of nitrogen (N) and phosphorus (P) fertilization on growth, nodulation, biomass and seed production of dhaincha. On an average, application of 13.2 and 26.4 kg P/ha has increased the seed yield of dhaincha by 241 and 113 kg /ha over no P (1,040 kg/ha) and 13.2 kg P application, respectively. Net returns ( 17.47 103/ha) were highest with application of 26.4 kg P while the agronomic P use efficiency was highest with 13.2 kg P application. Application of 30 kg N at sowing (1,340 kg/ha) or 15 kg each at sowing and flowering (1,320 kg/ha) being at par enhanced the seed yield of dhaincha on average by 221 kg/ha over no N application (1,118 kg/ ha). Net returns ( 17.64 103/ha) and agronomic N use efficiency were highest with 30 kg N application at sow- ing. Both P (26.4 kg/ha) and N (30 kg/ha at sowing) fertilization have significantly improved nodulation in dhaincha as evident from increased nodule number (108.1 and 106.1) and nodule weight (1.91 and 1.87 g) at 90 days after sowing over control (70.8 and 1.28 g). Interaction of nitrogen and phosphorus fertilization indicated that applica- tion of 30 kg N at sowing along with 26.4 kg P resulted in the highest seed yield (1,486 kg/ha) and thus is recom- mended for seed production of dhaincha.