Avaliação de adubos verdes no Norte de Minas Gerais

Abstract

The objective was to evaluate the behavior of some legumes used as green manures and its potential for soil coverage, content and accumulation of nutrients in the North of Minas Gerais. The treatments, distributed in delineate in randomized blocks, with three replicates were: spontaneous vegetation (witness), Crotalaria juncea (Crotalaria juncea L.), pigeonpea (Cajanus cajan (L) Millisp.) velvet bean (Mucuna aterrima (Piper & Tracy) Holland);gray-mucuna (Mucuna pruriens L.); black-mucuna (Mucuna deeringiana (Bort.) Merr.) lab-lab (Lablab purpureus L. Sweet), pig bean (Canavalia ensiformis (L.) DC), cowpea (Vigna unguiculata (L) Walp) and cocktail (crotalaria, pig bean, pigeon pea, mucuna, lab-lab and cowpea). At the full flowering stage, the plant height, fresh mass (FM) and dry mass (DM), nutrient quantity and accumulation and soil cover porcentages (59, 80 and 125 days after sowing) were measured. We evaluated the levels of fertility in the lines and between-lines of plants in the layer 0-20 cm at 125 days after sowing of green manures (DAS) besides being determined the contents of macronutrient and micronutrient, remaining phosphorus (P-rem) and total nitrogen in the soil in layers 0-5 and 5 - 10 cm depths to 83 days after cutting the green manures (DAC), which were left on the soil. The crotalaria was the one that provided the fastest growing in the field, but the spontaneous vegetation more the gray-mucuna to 125 days after sowing were the species with more soil coverage. Higher yields of FM were found in the spontaneous vegetation, crotalaria and bean of pig, showing values between 10520 kg ha-1 and 12540 kg ha-1 and DS in the treatments with crotalaria and spontaneous vegetation, showing 3760 kg ha-1 and 3325 kg ha-1, respectively. The crotalaria got higher nutrient contents in the aerial part, especially the N, P, Ca, Mg and B, minus K, which was higher in the spontaneous vegetation. The greater efficiencies in extraction of nutrient were demonstrated by crotalaria (N, P, Ca, Mg, S, B, Zn and Mn) and spontaneous vegetation (K, Mg, and Fe). The maintenance of soil coverage in the form of fallow (with or without legumes), contributes to the maintenance of organic matter, in addition to providing nutrients such as K and Mg. The management of green manures, at 83 DAC was enough for significant increments in relation to pH, Ca, the H + Al, sum of bases, the potential CTC and base saturation in the layer 0-5 cm and Ca, Mg, sum of bases, potential CTC and base saturation in the layer 5-10 cm soil depth. In conditions of Northern Minas Gerais, the use of legumes in areas of fallow in family farms can be one for strategies for the maintenance and improvement of soil chemical conditions.