Ciclagem e disponibilidade de fósforo para a soja em rotação com braquiária como espécie de cobertura
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Data
2012-03-02
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Universidade Estadual Paulista (Unesp)
Resumo
Os solos tropicais são carentes em fósforo (P), em consequência do material de origem e dos altos conteúdos de Fe e Al. Como o P é uma fonte mineral não renovável, as reservas mundiais são finitas e o custo da adubação é significativo, a utilização do nutriente deve obedecer a uma filosofia de maximização da eficiência. O uso do sistema de semeadura direta promove o aumento de matéria orgânica nos horizontes superficiais do solo, em decorrência da deposição de palhada, alterando a dinâmica do P e, recentemente, tem-se atribuído à braquiária a característica de disponibilizar P às culturas subsequentes. O objetivo principal deste trabalho foi avaliar o efeito do cultivo de braquiária como espécie de cobertura na ciclagem e disponibilidade de P no sistema, assim como na resposta da soja à adubação fosfatada, em sistema de semeadura direta. O experimento foi conduzido na Fazenda Experimental Lageado, na Faculdade de Ciências Agronômicas, UNESP-Botucatu, Estado de São Paulo. Constou de 3 tratamentos iniciais (adubação com Fosfato Natural e Solúvel, mais uma testemunha), presença ou não de braquiária e 3 doses de P na semeadura da soja. É uma área conduzida em semeadura direta com rotação de culturas há dez anos, sendo a braquiária introduzida nos últimos cinco anos, de modo que as aplicações de P na área até hoje já chegaram a 800 kg de P2O5 ha-1. Foram realizadas amostragens de solo na época da semeadura da soja (após a dessecação da braquiária), para fins de análise de fertilidade e determinação das formas de P presentes no solo, como: P microbiano, capacidade máxima de adsorção de fósforo (CMAP), índice de saturação de fósforo e também no estádio R6 (em plena maturação fisiológica) para avaliação do P microbiano e P disponível. A palhada de braquiária...
The Brazilian soils are deficient in phosphorus, as a result of the source material and the interaction strong with the ground. Considering that phosphorus is a finite mineral source, the introduction of a brachiaria as cover crop might increase the use of less labile soil P forms, increasing P availability to subsequent crops, which is a fundamental component of a sustainable crop rotation system. This work compares the ability of brachiaria to recycle phosphorus and increase soil P availability and its effects on soybean yields in no till systems. The experiment was carried out on Lageado Experimental Farm. This experimental area is conducted with no-tillage and crop rotation since 2000, and brachiaria introduced in the last five years. In another hands, the phosphorus application in area reaches 350 kg ha-1 of P. The treatments consisted of a control (0.0 P), soluble and reactive rock phosphate spread over the soil (80 kg ha-1 P2O5), and brachiaria was cropped in half of the plots. Soybean was fertilized with 0, 30 and 60 kg ha-1 of P2O5 as triple superphosphate. Brachiaria was chemically desiccated and soybean was planted over the straw in November. Soil samples were taken before soybean planting (November, 2010) and at the R6 stage (February, 2011). P was analyzed in the soil profile down to 40 centimeters in the first sample, and the second sample was soil profile until to 10 centimeters. The brachiaria straw was sampled and drying at before and 15, 30, 60 and 90 days after desiccation, to analyze the P accumulation. Phosphorus accumulation in soybeans, soybean production, dry matter and agronomy efficient of use of P in the system were determined. It´s conclude the phosphorus sources spread over the soil on total area without incorporation increases the P content in the soil profile and Brachiaria plant... (Complete abstract click electronic access below)
The Brazilian soils are deficient in phosphorus, as a result of the source material and the interaction strong with the ground. Considering that phosphorus is a finite mineral source, the introduction of a brachiaria as cover crop might increase the use of less labile soil P forms, increasing P availability to subsequent crops, which is a fundamental component of a sustainable crop rotation system. This work compares the ability of brachiaria to recycle phosphorus and increase soil P availability and its effects on soybean yields in no till systems. The experiment was carried out on Lageado Experimental Farm. This experimental area is conducted with no-tillage and crop rotation since 2000, and brachiaria introduced in the last five years. In another hands, the phosphorus application in area reaches 350 kg ha-1 of P. The treatments consisted of a control (0.0 P), soluble and reactive rock phosphate spread over the soil (80 kg ha-1 P2O5), and brachiaria was cropped in half of the plots. Soybean was fertilized with 0, 30 and 60 kg ha-1 of P2O5 as triple superphosphate. Brachiaria was chemically desiccated and soybean was planted over the straw in November. Soil samples were taken before soybean planting (November, 2010) and at the R6 stage (February, 2011). P was analyzed in the soil profile down to 40 centimeters in the first sample, and the second sample was soil profile until to 10 centimeters. The brachiaria straw was sampled and drying at before and 15, 30, 60 and 90 days after desiccation, to analyze the P accumulation. Phosphorus accumulation in soybeans, soybean production, dry matter and agronomy efficient of use of P in the system were determined. It´s conclude the phosphorus sources spread over the soil on total area without incorporation increases the P content in the soil profile and Brachiaria plant... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Soja - Semeadura, Solos - Acidez, Solos - Fertilidade, Adubação, Brachiaria crops, Soybean
Como citar
JANEGITZ, Moniki Campos. Ciclagem e disponibilidade de fósforo para a soja em rotação com braquiária como espécie de cobertura. 2012. xi, 78 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências Agronômicas de Botucatu, 2012.