Influência do Biochar na interação rizóbio feijão-caupi em dois solos do sertão do São Francisco

Abstract

Cowpea is one of the most adapted and nutritious legumes among cultivated bean species. The low rhizobial selectivity on the part of this culture, makes necessary the selection of fixing bacteria, which present good symbiotic efficiency. The use of pyrolysed biomass, known as Biochar, has emerged as an efficient soil conditioner. Its application to the soil has been used as a valuable method of carbon sequestration, decreasing beyond CO 2 emissions, other compounds with CH4 and N2O. This work aimed to evaluate the effect of biochar application and inoculation on the development of cowpea and GHG emission in this type of crop, as well as to observe the genetic diversity and efficiency of agronomic parameters of the bacterial isolates captured in different soils of the Valley of San Francisco. An experiment was carried out in pots using a Vertisol from the Mandacarú Experimental Station in Bahia and an Argissolo from the Experimental Station of Bebedouro in Pernambuco, both belonging to Embrapa Semiarid, the experiment followed a factorial scheme of 2 x 2 x 4, two solos , two applications of biochar (presence or absence) in a dosage of 15 g / kg soil-1 and four nitrogen treatments, being them; two inoculants, one commercial (BR 3267) and one still in the test phase by Embrapa Semi- arid (ESA 17), an application of mineral N at a dosage of 80 kg / ha-1 and an absolute control. It was also measured the GHG fluxes (CO2, CH4 and N2O) obeying the treatments. In addition, 79 cowpea bacteria were isolated for the two soils, the isolates had their DNA extracted and through the IGS-RFLP and BOX-PCR techniques and a subsequent sequencing were classified by comparing the sequences generated with those available on GenBank. 30 selected isolates had their symbiotic efficiency compared. For the experiment testing the effects of biochar on the development of cowpea with the four inoculants and GHG emissions, it was observed changes in NN and MNS, as well as a slight visual difference of the numbers for MPAS mass, indicating significant effects of biochar on the development of cowpea in the two soils. The highest CO2 emissions and CH4 reduction were observed in the Vertisols. While the lowest emissions of N2O was observed in the Argisol. The clustering of the rhizobia isolates revealed by the restriction analysis of IGS and fingerprinting of BOX-PCR, by soils, suggest that the application of biochar had no influence on the rhizobia communities. In all, 6 rhizobia species were identified, divided into two genera, able to nodulate the cowpea. The emergence of microviruses indicates a high genetic variability of rhizobia in the soils of the São Francisco Valley and their low similarity with species of the same genus indicates which may be a species not yet described The isolates submitted to the efficiency test were statistically different, presenting good results for MPAS, NN, NTOT and EN, in some cases being the reference and the nitrogen control.