Congo grass grown in rotation with soybean affects phosphorus bound to soil carbon

Abstract

SUMMARYThe phosphorus supply to crops in tropical soils is deficient due to its somewhat insoluble nature in soil, and addition of P fertilizers has been necessary to achieve high yields. The objective of this study was to examine the mechanisms through which a cover crop (Congo grass -Brachiaria ruziziensis) in rotation with soybean can enhance soil and fertilizer P availability using long-term field trials and laboratory chemical fractionation approaches. The experimental field had been cropped to soybean in rotation with several species under no-till for six years. An application rate of no P or 240 kg ha -1 of P 2 O 5 had been applied as triple superphosphate or as Arad rock phosphate. In April 2009, once more 0.0 or 80.0 kg ha -1 of P 2 O 5 was applied to the same plots when Congo grass was planted. In November 2009, after Congo grass desiccation, soil samples were taken from the 0-5 and 5-10 cm depth layer and soil P was fractionated. Soil-available P increased to the depth of 10 cm through growing Congo grass when P fertilizers were applied. The C:P ratio was also increased by the cover crop. Congo grass cultivation increased P content in the soil humic fraction to the depth of 10 cm. Congo grass increases soil P availability by preventing fertilizer from being adsorbed and by increasing soil organic P.Index terms: crop rotation, no-till, organic P, phosphorus fractionation.RESUMO: Brachiaria ruziziensis CULTIVADA EM ROTAÇÃO COM SOJA INTERFERE NO FÓSFORO LIGADO AO CARBONO DO SOLO O fornecimento de P para as culturas em solos tropicais é deficiente em razão da sua natureza pouco solúvel no solo; e a adição de fertilizantes fosfatados é necessária para obter-se alta produtividade. O objetivo deste estudo foi examinar os mecanismos pelos quais uma planta de cobertura (Braquiária -Brachiaria ruziziensis) cultivada em rotação com soja A relação C/P também foi aumentada pela planta de cobertura. O cultivo de B. ruziziensis elevou os teores de P na fração húmica do solo. A B. ruziziensis aumenta a disponibilidade de P no solo por prevenir a fixação do P aplicado como fertilizante e manter o P em formas orgânicas.Termos de indexação: fracionamento do P, fósforo orgânico, rotação de culturas, semeadura direta.

Adubação do milho com superfosfato triplo em Latossolo Vermelho sob efeito residual de fontes alternativas de fósforo

“…P sources with lower solubility are a great fertilization alternative, and their efficiency may be equal to soluble phosphates in the medium and long-term (RESENDE et al 2006). These sources are regularly surface-applied in pastures (OLIVEIRA et al 2014), mainly for Brachiaria genus grazing areas (MERLIN et al 2014).…”