Technical and economic viability of cowpea co-inoculated with Azospirillum brasilense and Bradyrhizobium spp. and nitrogen doses

Fernando S Galindo,Guilherme C Fernandes,Willian L Rodrigues,Marcelo C M Teixeira Filho,Salatiér Buzetti,Edson C Da Silva

doi:10.1590/1807-1929/agriambi.v24n5p304-311

Abstract

ABSTRACT Biological nitrogen fixation efficiency can be increased by co-inoculation with Bradyrhizobium spp. and Azospirillum brasilense, allowing even greater uptake of water and nutrients, leading to higher yields and enabling the insertion of unusual crops, such as cowpea (Vigna unguiculata L. Walp.), in the agricultural production system in the Cerrado region of Brazil. Thus, this study aimed to evaluate the technical and economic viability of cowpea in the Cerrado region, as a function of N doses and co-inoculation of seeds with Azospirillum brasilense and Bradyrhizobium. The study was carried out in a no-tillage system in Selvíria, MS, Brazil. The experimental design was a randomized block design, with four repetitions, arranged in a 3 x 5 factorial scheme, corresponding to three types of inoculation (without inoculation - control, with two strains of Bradyrhizobium spp. SEMIA 6462 and SEMIA 6463 - the conventional inoculation of cowpea, and these two strains of Bradyrhizobium spp. plus A. brasilense strains Ab-V5 and Ab-V6); and five N doses (0, 20, 40, 80 and 160 kg ha-1), as urea, applied as topdressing. The following evaluations were performed: grain yield, total operating cost, effective operating cost, gross revenue, operating profit, profitability index, equilibrium price and equilibrium yield. Co-inoculation with A. brasilense increases cowpea grain yield, which makes cowpea production in the Cerrado region of Brazil technically and economically viable, without the need to apply N fertilizers in topdressing.

Highlights

Due to its wide genetic variability, tolerance to unfavorable climate conditions, N2 fixation, high yield potential plus an excellent nutritional value, cowpea
Biological nitrogen fixation efficiency can be increased by co-inoculation with Bradyrhizobium spp. and Azospirillum brasilense, allowing even greater uptake of water and nutrients, leading to higher yields and enabling the insertion of unusual crops, such as cowpea
Considering the main current and potential limitations of Biological Nitrogen Fixation (BNF) in cowpea and the benefits, in various crops, by inoculation with Azospirillum brasilense, especially greater root system development and, higher absorption of water and nutrients, it can be deduced that joint co-inoculation of Bradyrhizobium spp. and A. brasilense can enhance crop performance, in an approach that respects the current demands for agricultural, economic, social and environmental sustainability (Hungria et al, 2013; Galindo et al, 2018a)

Summary

Introduction

Due to its wide genetic variability, tolerance to unfavorable climate conditions, N2 fixation, high yield potential plus an excellent nutritional value, cowpea In Brazil, it is estimated that about 1.5 million hectares of cowpea are cultivated, with an average yield of approximately 520 kg ha-1 (CONAB, 2018), well below the potential of the crop, which can reach yields greater than 2000 kg ha-1 (Ferreira et al, 2013; Marinho et al, 2017). Considering the main current and potential limitations of Biological Nitrogen Fixation (BNF) in cowpea and the benefits, in various crops, by inoculation with Azospirillum brasilense (free-living diazotrophic bacteria), especially greater root system development and, higher absorption of water and nutrients, it can be deduced that joint co-inoculation of Bradyrhizobium spp. and A. brasilense can enhance crop performance, in an approach that respects the current demands for agricultural, economic, social and environmental sustainability (Hungria et al, 2013; Galindo et al, 2018a)

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