Sequências de culturas em sistema de semeadura direta: II - decomposição e liberação de nutrientes na entressafra
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Data
2012-11-01
Autores
Marcelo, Adolfo Valente
Corá, José Eduardo [UNESP]
Fernandes, Carolina [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Ciência do Solo
Resumo
Os nutrientes acumulados nos resíduos das culturas, ao serem liberados no processo de decomposição, retornam ao solo e podem ficar disponíveis às culturas em sucessão. O objetivo deste trabalho foi avaliar a decomposição e liberação de nutrientes de resíduos vegetais de espécies utilizadas na entressafra em diferentes sequências de culturas em sistema de semeadura direta. O experimento foi conduzido em Jaboticabal-SP (48° 18' W e 21° 15' S), em um Latossolo Vermelho eutrófico. O delineamento experimental foi em faixas, com três repetições. Os tratamentos constituíram da combinação de três sequências de culturas de verão (rotação soja-milho e monoculturas de milho e de soja) com sete culturas de entressafra (milho, sorgo, girassol, crotalária, guandu, nabo forrageiro e milheto). O experimento foi iniciado em 2002, e o presente estudo refere-se aos anos agrícolas 2007/2008 e 2008/2009. Avaliaram-se a decomposição e a liberação de nutrientes utilizando sacolas de decomposição, com coletas aos 15, 30, 60, 120 e 180 dias após a trituração das culturas. A cobertura do solo foi avaliada após a trituração das culturas e ao final do ano agrícola. Os resíduos de crotalária, milho, sorgo, girassol apresentaram menores taxas de decomposição. Crotalária, guandu, nabo forrageiro e milheto proporcionaram resíduos que liberaram maior quantidade de nutrientes quando comparados ao milho, sorgo e girassol. Crotalária e milheto destacaram-se como as culturas mais adequadas para cultivo na entressafra, em especial a crotalária, devido à baixa taxa de decomposição e à elevada quantidade de nutrientes liberados na decomposição, e o milheto, em razão da elevada quantidade de nutrientes remanescentes nos resíduos no final do ano agrícola. Sequências de culturas que envolveram cultivo de girassol na entressafra proporcionaram menor cobertura do solo pelos resíduos vegetais.
Nutrients accumulated in dry crop residues and released in the decomposition process return to the soil and may become available to subsequent crops. The objective of this study was to evaluate the decomposition and nutrient release of plant residues of different no-tillage crop sequences in the second growing season. A field experiment was carried out on a Rhodic Eutrudox in Jaboticabal, SP, Brazil (48°18'W and 21°15'S), arranged in a randomized split-block design with three replications. The treatments consisted of combinations of three summer crops sequences (soybean-corn rotation, corn monoculture and soybean monoculture) with seven crops in the second growing season (maize, grain sorghum, sunflower, sunn hemp, pigeon pea, oilseed radish, and pearl millet). The experiment was initiated in 2002 and this study assessed the 2007/2008 and 2008/2009 growing seasons. The decomposition of plant residues was evaluated 15, 30, 60, 120, and 180 days after management, using litter bags. The soil cover was evaluated immediately after chopping the residues and at the end of the growing season. The release rates from sunn hemp, maize, grain sorghum, and sunflower residues were lowest. Sunn hemp, pigeon pea, oilseed radish, and pearl millet released the highest amounts of nutrients during the decomposition period. Sunn hemp and pearl millet were most suitable as second season crops. The soil cover was poorest in the crop sequences with sunflower in the second growing season.
Nutrients accumulated in dry crop residues and released in the decomposition process return to the soil and may become available to subsequent crops. The objective of this study was to evaluate the decomposition and nutrient release of plant residues of different no-tillage crop sequences in the second growing season. A field experiment was carried out on a Rhodic Eutrudox in Jaboticabal, SP, Brazil (48°18'W and 21°15'S), arranged in a randomized split-block design with three replications. The treatments consisted of combinations of three summer crops sequences (soybean-corn rotation, corn monoculture and soybean monoculture) with seven crops in the second growing season (maize, grain sorghum, sunflower, sunn hemp, pigeon pea, oilseed radish, and pearl millet). The experiment was initiated in 2002 and this study assessed the 2007/2008 and 2008/2009 growing seasons. The decomposition of plant residues was evaluated 15, 30, 60, 120, and 180 days after management, using litter bags. The soil cover was evaluated immediately after chopping the residues and at the end of the growing season. The release rates from sunn hemp, maize, grain sorghum, and sunflower residues were lowest. Sunn hemp, pigeon pea, oilseed radish, and pearl millet released the highest amounts of nutrients during the decomposition period. Sunn hemp and pearl millet were most suitable as second season crops. The soil cover was poorest in the crop sequences with sunflower in the second growing season.
Descrição
Palavras-chave
soil cover, Macronutrients, Winter crop, Cobertura do solo, Macronutrientes, culturas de inverno
Como citar
Revista Brasileira de Ciência do Solo. Sociedade Brasileira de Ciência do Solo, v. 36, n. 5, p. 1568-1582, 2012.