Avaliação de trigo de duplo propósito inoculado com Azospirillum brasilense

Abstract

The use of dual-purpose wheat genotypes is one alternative to minimize the impact of forage lack and even to produce grains. However, to maximize forage yield and grains yield are used highs doses nitrogen fertilizer. This practice increased costs and environmental impacts. Thus, the use of biostimulants based diazotrofic bacteria Azospirillum brasilense is able to be an alternative to reduce the costs and impacts. This study evaluated the forage yield and grain yield of “BRS Tarumã” dual-purpose wheat genotype inoculated with Azospirillum brasilense and fertilized with different doses of nitrogen subjected to cuts and grazing with lactation cows. Initial study was performed under cuts conditions in years 2016 and 2017 evaluating the forage yield and grain yield. In this study the trial was carried out in a completely randomized block design with four replicates, using a 2 (qualitative) x 4 (quantitative) factorial arrangement. The qualitative and quantitative factors corresponded to the use or not of inoculation and N rates (0, 50, 100 and 150 kg of N ha-1), respectively. In 2017, a second study was conducted under grazing conditions with lactating cows. This study evaluated the 100 kg N ha-1 been associated with inoculation (100+I) and fertilization with 150 kg N ha-1 (150+I). These treatments were chosen based on the results of the initial study. In this condition were evaluated forage yield, grain yield, pasture characteristics and responses of lactating cows. In the study under cuts, there was no difference forage yield between treatments with inoculation +100 kg N ha-1 and without inoculation + 150 kg N ha-1 (4.7 vs. 4.1 t de MS ha-1), respectively. There was no effect of inoculation on grain yield. In the study under grazing, forage mass, structural compositions, daily accumulation rate of forage and leaf blade, forage yield and leaf blade biomass yield, stocking rate, forage allowance and leaf blade allowance, grazing efficiency, forage intake, grain yield. No difference were obtained forage yield, leaf blade yield and stocking rate, grain yield and hectoliter weight with mean values of 3.6 t MS ha-1, 3.4 t MS ha-1 , 1.95 UA ha-1 dia-1, 75 kg hl-1 and 0.9 t ha-1. Significant difference was found in grazing efficiency (50.5% vs 36.6%) in third grazing cycle for wheat inoculated and fertilized with 100 kg de N ha-1. Under cutting conditions, the inoculation use increase forage yield and straw yield. The inoculation no influence in grain yield. Under grazing conditions, the fertilization with 100 kg N ha-1 associated with inoculation is equivalent fertilization with 150 kg N ha-1 without inoculation for the pastures response and grain yield.