Abstract
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.
Highlights
In the 2015 harvest season in Brazil, wheat (Triticum aestivum L.) was grown in 2.5 million hectares of land, where 6.7 million tons of grain were produced, with an average yield of 2.7 Mg ha-1
The efficiency of N fertilization can be increased with the inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), which can delay the hydrolysis of urea and significantly reduce the loss of ammonia in regions with a predominance of high temperatures, including the low-altitude Cerrado region (Valderrama et al, 2014)
Most studies conducted in Brazil showed that urea combined with a urease inhibitor as well as conventional urea have a similar efficiency in N nutrition and grain yield (Cantarella et al, 2008): the inhibitory activity of urease does not effectively reduce the losses by ammonia volatilization, which occurs when urea is applied to the soil surface
Summary
In the 2015 harvest season in Brazil, wheat (Triticum aestivum L.) was grown in 2.5 million hectares of land, where 6.7 million tons of grain were produced, with an average yield of 2.7 Mg ha-1. Most studies conducted in Brazil showed that urea combined with a urease inhibitor as well as conventional urea have a similar efficiency in N nutrition and grain yield (Cantarella et al, 2008): the inhibitory activity of urease does not effectively reduce the losses by ammonia volatilization, which occurs when urea is applied to the soil surface This can be explained by the fact that the action of NBPT depends on: environmental conditions, such as temperature and rainfall; physical and chemical characteristics of acid and weathered soils; and cultivation system, which is the no-tillage system with straw (a source of urease) on soil surface in most of the Cerrado region
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