Milho orgânico em consórcio com adubos verdes perenes : produtividade, nutrição e supressão de plantas espontâneas

Abstract

Maize can be intercropped with green manures, which in addition to performing the coverage and soil protection, the weeds control, also cycle nutrients and perform nitrogen biological fixation. This study aimed at evaluating the growth, yield of grains and straw, the content of macronutrients of maize and the weeds control in intercropping with perennial green manures sown at two different maize growth stages. The experiment was conducted in the agricultural year of 2014/2015, at UFSCar/Araras-SP, in randomized complete blocks in factorial scheme 3 x 2 + 1 with 4 repetitions. The factors were: 3 species of green manures (calopogonio (Calopogonium mucunoides Desv.); kudzu (Pueraria phaseoloides (Roxb) Benth.) and perennial soybean (Neonotonia wightii (Wight & Arn) Lackey.) and two green manures sowing times (sowing at the V4 - four expanded leaves and VT – bolting of maize). And a control treatment, maize monoculture. The evaluations were: in the R1/R2 of maize stage - milky/doughy grain (height (ALT); diameter (DIA); specific leaf area (AFE); leaf area index (IAF); stalk dry matter (MSC), leaves (MSF) and total (MST) of maize; Falker chlorophyll index (ICF); number of leaves above the upper ear (FAS)); in the R5 of maize stage – chalky grain (dry mass of green manure (MSA); total dry mass maize intercropping/green manure (MSTC); percentage of land cover (PC) and dry mass of weeds (MSE)); in the R6 – maize harvest (final plant stand (EST); prolificacy (PROL); number of rows per ear (NFE); number of kernels per row (NGF); yield of grain (PROD); weight of 100 grains (P100) and content of macronutrients of maize). It was found higher production of EF with the sowing of green manures in the V4 stage (69,814 plants ha-1), being the intercropping maize/calopogonio with higher values of MSA and PC, with 1002.00 kg ha-1 and 35.63%, respectively. The highest P100 occurred in the VT (32.89 g). There was not difference for the other variables. The PROD was 9.04 t ha-1 and 7.0 t ha-1 of MSTC. The smallest leaf N content was observed in the intercropping with calopogonio in V4 (22.75 g kg-1). The Ca had smallest levels for the perennial soybean in the VT and kudzu in the V4. The smallest Mg content was in intercropping with the soybean perennial in the VT, in the P was in the intercropping with calopogonio and S, when the sowing of the green manures occurred in V4 of maize. For K, there was not statistical difference. The MSTC production was not affected by green manures, with maize straw production in monoculture and in the intercropping systems exceeding the minimum amount recommended for ground cover (6.0 t ha-1). The green manures negatively affect the content of P, K, Ca, Mg and S in maize and calopogonio sown in the VT, the kudzu and the soybean perennial sowing in the V4 and VT, contributed to provide N to maize.