Manejo orgânico da cultura da couve em rotação com o milho, consorciados com leguminosas para adubação verde intercalar em plantio direto

Abstract

Human being has been searching for health foods and environmental conservation in a crescent path. Is this way, organic agriculture activities are showing good results. Nevertheless, several techniques need to be improved for farm adoption. The objective of this work was to evaluate a collard greens and green corn rotation intercropped with legume plants for green manuring in a no tillage system. This work started in May 2003 with the rotation of collard-corn-collard for two years in a SIPA (Integrated Agroecological Production System, Seropédica, RJ). Mucuna deeringiana and Crotalaria spectabilis intercropped with collard, and C. juncea e M. pruriens intercropped with corn were used. Surface application of 0 and 200 kg ha-1 N-equivalent as poultry bed manure at 6th and 16th harvesting time (100 kg in each application) in 2003; 0 and 100 kg ha-1 of N at 10th harvesting time in 2004 for collard were used. The experimental design was a randomized complete block design, a factorial 3 x 2 with four replications. Treatments were kept in the same plots during all three cropping periods. Leaf number, yield, specific leaf area, leaf area index, and nutritional analysis were performed for collard, as well as number of corn spikes and nutritional status for corn. In the second collard cropping year chemical analysis and chemical fractionation analysis of soil were performed. Plant biomass, legume plant nutrient level, and biological nitrogen fixation (BNF) rate were determined. M. deeringiana and C. spectabilis yielded 1.5 Mg ha-1 of dry plant biomass where intercropped with collard, but BNF was significantly higher for Crotalaria sp. M. pruriens over C. juncea yielded 2.8 and 5.6 Mg ha-1 of dry plant biomass respectively where intercropped with corn. The presence of legume plants intercropped with collard promoted higher numbers of leaf and yield in 2003 and 2004. In 2004, collard leave from plots intercropped with M. pruriens were larger and more turgid, and with better nutritional status. Surface fertilization for collard increased yield, leaf number, leaf area index, and specific leaf area. Residual fertilization from collard cropped in 2003 affected positively corn plants, but there was no residual effect from legumes. Corn plants showed nutritional N deficiency symptoms. This indicated that residual effect from surface fertilization or green manuring were not sufficient for N supply to the crop. Soil carbon level increased on green manure and poultry bed surface fertilization plots. Preference for humin and humic acid formation, and higher levels of N, P, K, Ca e Mg occurred on places where surface organic fertilization was performed. Levels of Ca, K, carbon, and humin occured from starting to the ending point of the second cycle of collard cropping period, demonstrating the enrichment of the soil fertility.