Biomassa e dinâmica de nutrientes em leguminosas, em resposta à adubação nitrogenada e à inoculação com Rhizobium

摘要

Green manuring is recognized as a viable alternative in the pursuit of sustainability of agricultural soils. Legumes have been preferred for green manuring for associating the symbiotic diazotrophic bacteria to fix atmospheric nitrogen. The root system of legumes can reach over 80 cm depth, being able to return to the surface layers of soil nutrients such as NO3-, K+, Ca2+ and Mg2+, leached to deeper layers. Among the factors that can interfere with the activity of diazotrophic bacteria is the existence of strains of the bacteria in the soil and its efficiency in the infection process. The aim of this experiment was to evaluate the dry matter (DM) yield and accumulation of N, P, K, C, Ca, Mg, Fe, Mn, Zn and Cu in shoots of four species of legumes in response to nitrogen and / or inoculation with nitrogen fixing bacteria. The experimental design was a randomized complete block in a split plot, the parcels formed with legumes: jack bean (Canavalia ensiformis (L.) DC.), dwarf pigeon pea (Cajanus cajan var. Flavus DC.), dwarf velvet bean (Mucuna deeringiana (Bort) Merr.) and sunnhemp (Crotalaria juncea L.) and subplots in a factorial 2 x 2 for nitrogen fertilization (with and without nitrogen) and inoculated with bacteria (with and without inoculation), installed with four replications for the 16 treatments, totaling 64 experimental units. Comparisons between plants with and without inoculation and / or with and without N application, within each species, as well as comparisons between the mean yields of the species were obtained by means of contrast arising from the deployment of three degrees of freedom for treatments. The experimental results show that no effects were identified nitrogen or inoculation with N fixing bacteria in the DM production or accumulation of nutrients C, N, P, K, Ca, Mg, Zn, Mn and Cu in legumes studied, in climate and soil conditions of this test is not recommended fertilization or inoculation with N fixing bacteria, for the cultivation of leguminous species studied in this trial; the sunnhemp is legume that present the highest values for DM production and accumulation of C, K, Mg, Fe, Zn and Mn; and dwarf velvet bean is less efficient in the legume DM production and accumulation of C, N, P, K, Ca, Mg and Zn.