Bio-inoculant improves nitrogen-use efficiency and cotton yield in saline soils

Improved nutrient-use efficiency is important to sustain agricultural production. The goal of our study was to investigate the effects of Azovit (R) (Azotobacter chroococcum) inoculation of seed with N fertilization on crop yield, nutrient uptake, and N-use efficiency (NUE) of irrigated cotton (Gossypium hirsutum L. cv. C-6524) in secondary saline soil under continental climatic conditions of Uzbekistan. A randomized complete block design in a 4 x 2 split-plot experiment was established in the fall of 2013. The main plot was N fertilization (0, 140, 210, and 280 kg ha(-1)) and the subplot was Azovit inoculation. Azovit inoculation consistently increased the seed and lint yields of cotton by 25 and 27.9%, respectively, at 210 kg N ha(-1) compared to the respective control. Azovit with 210 kg N ha(-1) significantly increased the cotton harvest index by 21%, when compared to the control. Likewise, nutrient uptake and NUE of cotton were higher when N (210 kg ha(-1)) was applied with Azovit, as compared to other treatment combinations. An extrapolation of the relationship of relative yield vs. N fertilization showed that Azovit at 210 kg N ha(-1) was sufficient to obtain near-maximum cotton production (90%) with highest NUE, as compared to the respective control. The results suggest that Azovit with 210 kg N ha(-1) produces cotton yield higher and/or comparable with the currently used rates of 280 kg N ha(-1) or higher, suggesting savings of 70 kg N ha(-1) for cotton production in saline soils under continental climatic conditions.