Nitrate role in basic cation leaching under no-till
Carregando...
Data
2011-12-01
Autores
Crusciol, Carlos Alexandre Costa [UNESP]
Garcia, Rodrigo Arroyo
Castro, Gustavo Spadotti Amaral [UNESP]
Rosolem, Ciro Antonio [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Ciência do Solo
Resumo
A correção da acidez subsuperficial tem sido um problema, principalmente, em sistemas com semeadura direta, em que se depende da lixiviação das bases, a qual tem sido associada à presença de ácidos orgânicos e de ânions acompanhantes. O objetivo deste experimento foi avaliar a lixiviação de bases no solo em função da calagem superficial e adubação nitrogenada em cobertura no milho e arroz. Foram aplicados 0, 1.500, 3.000 e 6.000 kg ha-1 de calcário, combinados com 0, 50, 100 e 150 kg ha-1 de N aplicados no milho e arroz, cultivados em anos consecutivos. As doses totais de N ao longo do experimento foram de 0, 100, 200 e 300 kg ha-1. A semeadura do milho foi realizada em dezembro, três meses após a calagem. em setembro do ano seguinte foi semeado o milheto, sem fornecimento de fertilizantes, que foi dessecado 86 dias após a emergência. em seguida, realizou-se a semeadura do arroz. Após a colheita do arroz e 18 meses transcorridos da calagem superficial, amostras de solo foram coletadas das camadas de 0-5, 5-10, 10-20 e 20-40 cm, para avaliação do pH, N-NO3-, N-NH4+, K, Ca e Mg. Também foram determinadas as produtividades de grãos do milho, do arroz e da matéria seca do milheto. Na presença da calagem na dose de 3.000 kg ha-1, foi constatada maior produtividade de milho com doses elevadas de N. Os melhores resultados obtidos para o arroz e milheto também foram resultantes dessa dose de calagem, independentemente das doses de N. Os íons K, Ca e Mg mostraram maior mobilidade no perfil do solo na presença de adubação nitrogenada em cobertura. A calagem superficial aumentou o pH das camadas superficiais, gerando intensa nitrificação e formação de nitrato, o qual foi lixiviado no perfil do solo com as bases.
Especially under no-tillage, subsuface soil acidity has been a problem, because it depends on base leaching, which has been associated with the presence of low molecular weigth organic acids and companion anions. The objective of this study was to evaluate exchangeable base cation leaching as affected by surface liming along with annual urea side-dressing of maize and upland rice. Treatments consisted of four lime rates (0, 1500, 3000, and 6000 kg ha-1) combined with four nitrogen rates (0, 50, 100, and 150 kg ha-1) applied to maize (Zea mays) and upland rice (Oryza sativa), in two consecutive years. Maize was planted in December, three months after liming. In September of the following year, pearl millet (Pennisetum glaucum) was planted without fertilization and desiccated 86 days after plant emergence. Afterwards, upland rice was grown. Immediately after upland rice harvest, 18 months after surface liming, pH and N-NO3-, N-NH4+, K, Ca, and Mg levels were evaluated in soil samples taken from the layers 0-5, 5-10, 10-20 and 20-40 cm. Higher maize yields were obtained at higher N rates and 3000 kg ha-1 lime. Better results for upland rice and pearl millet yields were also obtained with this lime rate, irrespective of N levels. The vertical mobility of K, Ca and Mg was higher in the soil profiles with N fertilization. Surface liming increased pH in the upper soil layers causing intense nitrate production, which was leached along with the base cations.
Especially under no-tillage, subsuface soil acidity has been a problem, because it depends on base leaching, which has been associated with the presence of low molecular weigth organic acids and companion anions. The objective of this study was to evaluate exchangeable base cation leaching as affected by surface liming along with annual urea side-dressing of maize and upland rice. Treatments consisted of four lime rates (0, 1500, 3000, and 6000 kg ha-1) combined with four nitrogen rates (0, 50, 100, and 150 kg ha-1) applied to maize (Zea mays) and upland rice (Oryza sativa), in two consecutive years. Maize was planted in December, three months after liming. In September of the following year, pearl millet (Pennisetum glaucum) was planted without fertilization and desiccated 86 days after plant emergence. Afterwards, upland rice was grown. Immediately after upland rice harvest, 18 months after surface liming, pH and N-NO3-, N-NH4+, K, Ca, and Mg levels were evaluated in soil samples taken from the layers 0-5, 5-10, 10-20 and 20-40 cm. Higher maize yields were obtained at higher N rates and 3000 kg ha-1 lime. Better results for upland rice and pearl millet yields were also obtained with this lime rate, irrespective of N levels. The vertical mobility of K, Ca and Mg was higher in the soil profiles with N fertilization. Surface liming increased pH in the upper soil layers causing intense nitrate production, which was leached along with the base cations.
Descrição
Palavras-chave
calagem, adubação nitrogenada, ciclagem de nutrientes, solos tropicais, lime, nitrogen fertilization, nutrient cycling, tropical soils
Como citar
Revista Brasileira de Ciência do Solo. Sociedade Brasileira de Ciência do Solo, v. 35, n. 6, p. 1975-1984, 2011.