Influence of Foliar Application of Mineral Nutrients on Biological Nitrogen Fixation of Rainfed Soybean

Abstract

A field study investigated the effect of foliar nutrients on nitrogen fixation of soybean grown under subtropical rainfed conditions. Three soybean varieties viz. NARC-2, Ajmeri-1 and Rawal-l were sown with and without foliar application of nutrients (Mn, Fe, Cu, Zn, P and Ca) in a sandy loam soil (Typic Ustorthents). The spray applied 0.7 g ha-1 Mn, 0.7 g ha-1 B, 0.7 g ha-1 Cu, and 1 g ha-1 Zn besides 59 g ha-1 P, and 27 g ha-1 Ca. Foliar application enhanced the nitrogen fixation in all the soybean varieties. Increase was 98% in NARC-2, 84% in Rawal-1 and 70% in Ajmeri-1. The highest N2 fixation of 68 kg ha-1 was observed in NARC-2 with foliar application of nutrients. Nodule numbers increased from 0.12 plant-1 without nutrients spray to 0.99 plant-1 with nutrients spray. Number of pods increased 7.5 % to 45% with foliar application of nutrients. The highest number of pods (74 per plant) was recorded for Ajmeri-1 with foliar application spray. Increase in biomass yield with foliar application of nutrients was 18 % to 112%. The highest biomass yield was 4.8 t ha-1 from Rawal-1 with nutrients application. Increase in grain yield with foliar application of nutrients ranged between 19.5% and 132%. The highest seed yield was produced by NARC-2 (2.19 t ha-1) with foliar application of nutrients. The study clearly concludes that foliar application of nutrients significantly increased biological nitrogen fixation, number of pods per plant and finally grain yield in soybean