Adequação da adubação verde para o cultivo de milho verde em sistema orgânico de produção no Município de Chapada dos Guimarães - MT

Abstract

The major nutrients source for crop maize in organic units in the Chapada dos Guimarães City, MT, is industrial poultry litter, however, in some cases can occur legal restrictions for its use. Thus, in this work have been hypothesized that the introduction of legumes as nutrients source in areas of green maize production under organic management could replace totally or partially poultry litter as nutrients source in order to contribute to a positive N balance in these systems. In this way, have been established the objective as follow: to evaluate the intercropping use of Crotalaria juncea, jack bean and fertilization with poultry litter in an organic production system of green corn (Zea mays) in the Chapada dos Guimarães City - MT. The experiment was carried out in an area of organic production located at Site Monjolinho, Chapada dos Guimarães City – MT, by using a completely randomized block design with six treatments and four replications. The evaluated treatments consisted as follow: T1 – crop maize intercropped with Crotalaria; T2 – crop maize intercropped with Crotalaria + additional fertilization with poultry litter (rate of 40 kg N ha-1); T3- crop maize intercropped with jack bean; T4 – crop maize intercropped with jack bean + additional fertilization with poultry litter (rate of 40 kg N ha-1); T5 – single crop maize total fertilized from poultry litter (80 kg N ha-1); T6 – single crop maize without nitrogen fertilization. The legumes were managed for use as green fertilization through harvest 30 days after sowing, in which the biomass was left in topdressing over the soil. The corn used was the variety AG1051(nontransgenic). The variables evaluated in the legumes were biomass productivity and chemical composition. The corn was harvested at 82 days after plantation when the grains presented milky stage, green corn point, have been evaluated the follow characteristics: a) number of marketable husked spikes; b) total weight of marketable husked green spikes and accumulated biomass in the shoot; c) length and diameter of husked green spikes; d) partial nutrients balance. According with results, the tested hypothesis, which stated that green fertilization in the first crop maize cycle, could replace or reduce the topdressing fertilization from chicken litter was not confirmed when cut 30 days of growing. The legumes supplied nitrogen that contributed to become N balance less negative in the treatments which topdressing fertilization was omitted or when only a half of recommended dose was used. The poultry litter dose currently used by farmer results in a positive potassium balance of about 100 kg ha-1, which however can permit high losses this nutrient by leach. The maize productivity observed in the present study was considered high, regardless of use of the green fertilization or poultry litter