Formas de fósforo em latossolo sob diferentes sistemas de manejo e de plantas de cobertura em rotação com milho

Frações de P desempenham papel fundamental na manutenção da produtividade dos Latossolos ácidos do Cerrado e são influenciadas pelas práticas de manejo. O objetivo deste estudo foi quantificar as diferentes formas de P em um Latossolo Vermelho-Amarelo do Cerrado, sob sistemas de manejo com plantas de cobertura em rotação com milho. Três plantas de cobertura (Canavalia brasiliensis, Cajanus cajan (L.) e Raphanus sativus L.) foram estudadas. Essas plantas de coberturas foram comparadas com vegetação espontânea. As formas inorgânicas NaHCO3-iP e NaOH-iP representaram mais da metade do P total nas amostras coletadas na profundidade de 5-10 cm, durante a estação chuvosa, quando o milho foi cultivado. A concentração de P inorgânico de maior disponibilidade (NaHCO3-iP e NaOH-iP) foi maior no solo sob plantio direto na profundidade de 5-10 cm, durante a estação chuvosa. As concentrações de P orgânico foram maiores durante a estação seca, quando as plantas de cobertura foram cultivadas. Nessa estação, o P orgânico constituiu 70 % do P lábil no solo plantado com C. cajan, sob plantio direto. As plantas de cobertura foram capazes de manter maiores frações de P disponível para o milho, resultando em redução de perdas de P para compartimentos indisponíveis, principalmente em sistemas de plantio direto.Phosphorus fractions play a key role in sustaining the productivity of acid-savanna Oxisols and are influenced by tillage practices. The aim of this study was to quantify different P forms in an Oxisol (Latossolo Vermelho-Amarelo) from the central savanna region of Brazil under management systems with cover crops in maize rotation. Three cover crops (Canavalia brasiliensis, Cajanus cajan (L.), and Raphanus sativus L.) were investigated in maize rotation systems. These cover crops were compared to spontaneous vegetation. The inorganic forms NaHCO3-iP and NaOH-iP represented more than half of the total P in the samples collected at the depth of 5-10 cm during the rainy season when the maize was grown. The concentration of inorganic P of greater availability (NaHCO3-iP and NaOH-iP) was higher in the soil under no-tillage at the depth of 5-10 cm during the rainy season. Concentrations of organic P were higher during the dry season, when the cover crops were grown. At the dry season, organic P constituted 70 % of the labile P in the soil planted to C. cajan under no-tillage. The cover crops were able to maintain larger fractions of P available to the maize, resulting in reduced P losses to the unavailable pools, mainly in no-tillage systems

Forms of phosphorus in an oxisol under different soil tillage systems and cover plants in rotation with maize

Phosphorus fractions play a key role in sustaining the productivity of acid-savanna Oxisols and are influenced by tillage practices. The aim of this study was to quantify different P forms in an Oxisol (Latossolo Vermelho-Amarelo) from the central savanna region of Brazil under management systems with cover crops in maize rotation. Three cover crops (Canavalia brasiliensis, Cajanus cajan (L.), and Raphanus sativus L.) were investigated in maize rotation systems. These cover crops were compared to spontaneous vegetation. The inorganic forms NaHCO3-iP and NaOH-iP represented more than half of the total P in the samples collected at the depth of 5-10 cm during the rainy season when the maize was grown. The concentration of inorganic P of greater availability (NaHCO3-iP and NaOH-iP) was higher in the soil under no-tillage at the depth of 5-10 cm during the rainy season. Concentrations of organic P were higher during the dry season, when the cover crops were grown. At the dry season, organic P constituted 70 % of the labile P in the soil planted to C. cajan under no-tillage. The cover crops were able to maintain larger fractions of P available to the maize, resulting in reduced P losses to the unavailable pools, mainly in no-tillage systems