Nodulação e desenvolvimento do feijão-caupi em função de diferentes doses de P, Co e Mo

Abstract

The cowpea bean is a legume that has a wide economic potential, but it has not been explored efficiently. For this reason it has shown a yield potential far from the expectations of a so efficient legume in NBF as can be. The objective of this study is to obtain appropriate levels of P, Co, Mo nutrients. It is believed that these nutrients can optimize nodulation, nitrogen biological fixation and the growth of cowpea bean plants in representative soils from Cerrado, Mato Grosso. Based on the chemical analysis from the soil cited before, calculations for fertilization and liming were made. From the results obtained, were established doses for the elements of the present work (P, Co and Mo). The experiment was conducted in a greenhouse conditions and performed in a randomized block design. It was used a factorial arrangement 2 x 5 (2 soils; five doses of each element of the present study – inoculated with 3262 strain) + 1 + 3 replicates. The additional treatment (+1) was included to evaluate crop performance when applied 50 Kg.ha-1 of nitrogen. The study was split in two trials. In the first trial, different dosages of phosphorous were tested: control (without Phosphorus application); low (44 mg.vase-1 of P), medium (88 mg.vase-1 of P), medium-low (130mg.vase-1 of P) and high (175 mg.vaso-1 of P). These tests were made to obtain a optimum dosage. In the second trial, cobalt and molybdenum nutrient was tested as the following levels respectively: 0, 2, 3, 4, 6 mg and 0, 8, 16, 32 and 64 mg. In the thirty-fifth day, the experiment developed in a greenhouse was collected. From the plants were evaluated height and plant diameter, nodulation (dry matter and number of nodules), shoot dry matter, root dry matter, chlorophyll content and N accumulation in shoot. The 88mg of P.vase-1 dosage that corresponds to 200 kg.ha-1 of P2O5 and the medium-high Cobalt and Molybdenum dosage that corresponds the application of 32g of Mo.ha-1 + 4g.ha-1 of Co provided higher nodulation in cowpea bean plants with consequent increase of biomass and nitrogen accumulation. The site where soil was collected had influence on the development and on the nodulation of the cowpea bean crop, when submitted to different dosages of P and Co+Mo.