Diversidade e eficiência de bactérias de nódulos de leguminosas em cultivos solteiros e consorciados com gramíneas

Abstract

Biological nitrogen fixation (BNF) is a natural process that occurs between plants and bacteria in an ecological relationship called symbiosis that presents great capacity to minimize the use of nitrogen-rich fertilizers in agricultural systems. Legumes and grasses are important plants in both the socioeconomic and environmental senses in relation to the reduction of impact from agricultural practices on the environment in addition to their ability to fix N together with diazotrophic bacteria, as well as cultivated in intercropping that can affect diversity and efficiency. The aim of the present study was to evaluate the diversity and efficiency of rhizobia obtained from root nodules of leguminous cowpea and pork bean in intercropped and single crops with maize grasses (Zea mays L); sorghum, (Sorghum bicolor (L.) Moench); or millet, (Pennisetum glaucum (L.) R. Br.), as well as whether nodules in consortium alter diversity and efficiency. The experiment was carried out in the field after the process of isolation, authentication and selection of bacteria, using samples of the top layer of a Planossol, following a randomized block design with 5 repetitions and 4 treatments. The diversity indices were calculated and presented averages for: Shannon-Weaver index (H ’) 1.80, Simpson index with 0.78, Margalef index with 2.95 and Pielou Equability Index with 0.95. The evaluation of the average efficiency in the N2 fixation process found that none of the treatments was considered inefficient, the B1T17 treatment was considered efficient with 63.03.18% in relation to the control, whereas the B1T12 treatment was efficient with 100% of efficiency in relation to control and the recommended strain for cowpea showed 83.18% efficiency. At the level of average productivity, the B1T17 treatment produced the highest average with 520 Kg / ha-1 being above the national average, while the B1T12 treatment produced 360Kg / ha-1 and finally the nitrogen treatment (N) with 450 Kg / ha -1.