Wheat yield in the Cerrado as affected by nitrogen fertilization and inoculation with Azospirillum brasilense

Abstract

The objective of this work was to evaluate the effect of inoculation with Azospirillum brasilense, associated with N rates and sources, in soil of the Cerrado (Brazilian savanna), on the grain yield of irrigated wheat (Triticum aestivum). The experiment was carried out under a no-tillage system in a Typic Haplustox. The experimental design was randomized complete blocks with four replicates, in a 2x5x2 factorial arrangement: two N sources (urea and urea with NBPT urease inhibitor); five N rates applied as topdressing (0, 50, 100, 150, and 200 kg ha^-1); and with or without seed inoculation with A. brasilense. The increase in the N rates positively affected spike length, number of spikelets and of grains per spike, number of spikes per meter, N accumulation in the straw, leaf chlorophyll content, and grain yield of irrigated wheat, regardless of the use of NBPT urease inhibitor with conventional urea. Singly, inoculation with A. brasilense does not affect production components and grain yield, despite the increase in N content in wheat straw. The inoculation with A. brasilense, associated with the application of 140 kg ha^-1 N, provides the highest grain yield of irrigated wheat cropped after corn in low-altitude Cerrado.