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abstRact:The cultivation of different species of cover crops enables the improvement and conservation of soil and organic matter, in addition to promoting significant yield increases in subsequent crops, with significant economic gains. The objective of this study was to evaluate the growth and productivity of green corn on different soil covers in an organic no-tillage system. The work used a randomized block design, with 6 repetitions and 5 treatments, consisting of 3 soil covers in an organic no-tillage system, with black oat straw, white lupine straw and straw of the intercropping oat/lupine, as well as 2 systems without straw and with revolved soil, an organic one and a conventional. Evaluations of culm diameter, plant height and insertion of the corn ears were carried out, at stages V5, V10 and R3, as well as of total number of marketable ears, the total productivity of ears with and without straw, average weight of ears with and without straw, productivity, average weight and percentage of marketable ears, length and diameter of marketable ears without straw. The organic no-tillage system on the white lupine straw in single and intercropped with black oat provided greater growth of corn plants at the early stages of culture. The use of white lupine single or intercropped with black oat showed itself as good option for straw training in an organic no-tillage system, ensuring satisfactory growth and productivity for the green corn crop.

Development of vegetables and soil characteristics after green manuring and organic composts under levels of NIn organic farming systems, the proper management of organic manure and nitrogen cycling strategies are very important to improve soil fertility and increase productivity. The aim of this study was to evaluate the impact of the green manure in pre-cropping, associated with organic compost with different nitrogen levels, on soil chemical properties and yield of cabbage and green corn crops in succession, from 2009 to 2012. The experimental design was a randomized blocks design in a split-plot with three replications. The plots consisted of two treatments (with and without leguminous) and the subplots consisted of five treatments with fertilization systems based on compost of different nitrogen levels: 1) Unfertilized (control); 2) Compost with 1.5% N; 3) Compost with 2.0% N; 4) Compost with 2.5% N; 5) Compost with 3% N. Green manuring with leguminous in pre-crops improved crop development cabbage and green corn, increased the levels of P and H + Al and reduced the levels of K, Mg and soil pH. The calcium content, sum of bases, cations exchange capacity and soil organic matter were not modified by green manuring. The fertilization with organic compost with higher levels of N provided elevations in the levels of P, K, Mg and T linearly and soil organic matter in a quadratic model. Plants fertilized with organic composts of higher levels of N increased the commercial yields in 92.4% for cabbage and 23.1% for green corn. Green manure, when associated with composts with 3% N, increased cabbage yield by 19.2% and the green corn on 4.5%.

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Hortic. bras., v. 26, n. 4, out.-dez. 2008 V isando garantir alimentação, proteção, transporte, saúde, diversão e outras funções e bens de consumo do ser humano, muita energia é gasta, independente da forma e da fonte energética. Nos agroecossistemas, a energia está na forma de radiação solar que alimenta a fotossíntese, gerando biomassa; na forma de trabalho humano, animal ou mecâni-co; ou ainda contida em combustíveis, adubos, ferramentas, sementes e demais insumos da agricultura (Mello, 1989 O Brasil gasta 2,6 kcal ao produzir 1,0 kcal de alimentos (balanço energético = 0,38). Os países desenvolvidos já estão gastando mais de 5,0 kcal; RESUMOOs insumos e serviços utilizados na produção vegetal representam custo energético. Dependendo desses fatores e das produtividades obtidas, a conversão da produção em energia determinará a eficiência energética do sistema. A agricultura orgânica somente atingirá a missão de preservação ambiental se tiver comprovada sustentabilidade energética. Neste trabalho, objetivou-se caracterizar os balanços energéticos dos cultivos orgânicos e analisar sua sustentabilidade, em comparação aos sistemas convencionais. Monitoraram-se campos de produção de dez culturas, de 1991 a 2000 em Domingos Martins-ES. Os dados do sistema convencional foram obtidos pelas médias dos coeficientes técnicos da região. Quantificaram-se os coeficientes técnicos, convertendo suas grandezas físicas em equivalentes energéticos, expressos em kcal. O sistema orgânico gastou 4.571.159 kcal ha -1 e apresentou 12.696.712 kcal ha -1 de energia inserida na colheita, mostrando balanço médio de 2,78. Esse valor foi similar ao obtido no sistema convencional (1,93). As participações dos componentes nos gastos do sistema orgânico foram embalagem (35,8%), composto orgânico (17,2%), irrigação (12,6%), sementes/mudas (12,4%) e mão-de-obra (11,0%), serviços mecânicos (5,0%) e frete (4,5%). Se os custos com embalagens fossem eliminados, os gastos do sistema orgânico seriam reduzidos para 2.930.113 kcal ha -1 , aumentando sua eficiência. A maioria dos cultivos orgânicos pode ser considerada sustentável em transformação de energia, com balanços superiores a 1,00 e produção média diária de 80.421 kcal ha -1 por dia, superior à necessidade mí-nima de 58.064 kcal ha -1 . Palavras-chave: Agricultura orgânica; produtividade; sistemas de cultivo; balanço energético. ABSTRACT Energetic balance and sustainability analysis in the organic production of vegetable cropsThe inputs used in crop production represent an energetic cost. Depending on the inputs and on the achieved yields, the conversion of the harvest into energy will determine the energetic efficiency of the system. Organic agriculture will fully meet the goal of environmental conservation only if its energetic sustainability is accomplished. The objectives of this study were to characterize the energetic balance of organic vegetable production and to analyze its energetic sustainability, compared to conventional vegetable crop production systems. Field data were collected fro...

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