Em solos agrícolas que recebem aplicação de lodo de esgoto pode ocorrer, quando sujeitos à erosão hídrica, intenso transporte de fósforo (P) para trechos inferiores da paisagem e, eventualmente, para os corpos de água. O objetivo com este trabalho foi avaliar a distribuição espacial de P em um Latossolo Vermelho eutroférrico, cultivado com milho. Os tratamentos foram avaliados com aplicação de adubo mineral (AM) e de lodo de esgoto (LE). Amostras de solo foram coletadas seguindo uma grade amostral de 69 pontos em cada tratamento, em duas épocas, no início e no final do ciclo da cultura, em uma área experimental com 10% de declividade. No tratamento AM houve dependência espacial moderada de P no solo ocorrendo maiores concentrações de P na parte inferior do talhão, causada pela erosão do solo. O mesmo padrão foi observado para soma de bases, capacidade de troca catiônica e matéria orgânica do solo. Por outro lado, a aplicação de LE, feita de maneira não uniforme, resulta em sítios com maiores teores de fósforo aleatoriamente distribuídos e correlacionados com a matéria orgânica do solo.

In agricultural soils receiving sewage sludge and subjected to water erosion, may occur intense transport of phosphorus (P) to the lower parts of the landscape and eventually to water bodies. The objective of this study was to evaluate the spatial distribution of P in an Oxisol cultivated with maize. The treatments were evaluated with application of mineral fertilization (MF) and sewage sludge (SS). Soil samples were collected following a sampling grid of 69 points in each treatment at the beginning and at the end of the crop cycle, in an experimental area with 10% slope. There was a moderate spatial dependence of P in the soil in the treatment of MF, resulting in higher concentrations of P in the deeper layers of the soil caused by erosion. The same standard was observed for the soil attributes sum of bases, cation exchange capacity and soil organic matter. Conversely, when SS was applied there was a randomized distribution of P in the plots because of the non-uniform manner of its application. Such random distribution of P showed correlation with soil organic matter.

The maintenance of sugarcane (Saccharum spp.) straw on a soil surface increases the soil carbon (C) stocks, but at lower rates than expected. This fact is probably associated with the soil management adopted during sugarcane replanting. This study aimed to assess the impact on soil C stocks and the humification index of soil organic matter (SOM) of adopting no-tillage (NT) and conventional tillage (CT) for sugarcane replanting. A greater C content and stock was observed in the NT area, but only in the 0-5 cm soil layer (p < 0.05). Greater soil C stock (0-60 cm) was found in soil under NT, when compared to CT and the baseline. While C stock of 116 Mg ha-1 was found in the baseline area, in areas under CT and NT systems the values ranged from 120 to 127 Mg ha-1. Carbon retention rates of 0.67 and 1.63 Mg C ha-1 year-1 were obtained in areas under CT and NT, respectively. Laser-Induced Fluorescence Spectroscopy showed that CT makes the soil surface (0-20 cm) more homogeneous than the NT system due to the effect of soil disturbance, and that the SOM humification index (H LIF) is larger in CT compared to NT conditions. In contrast, NT had a gradient of increasing H LIF, showing that the entry of labile organic material such as straw is also responsible for the accumulation of C in this system. The maintenance of straw on the soil surface and the adoption of NT during sugarcane planting are strategies that can increase soil C sequestration in the Brazilian sugarcane sector.

Como a dificuldade da semeadura da soja sob grande quantidade de palha do milho safrinha intacta, sem a fragmentação ou incorporação dos resíduos, em solos muito argilosos, tem desmotivado a utilização do sistema plantio direto pelos agricultores da região paulista do Médio Paranapanema, objetivou-se, com este trabalho, comparar o desempenho quanto ao embuchamento, bem como avaliar a qualidade da semeadura entre semeadoras-adubadoras original e adaptada, na cultura da soja. O sistema modificado proporcionou menor número de paradas do conjunto trator-semeadora, em função de embuchamento. As freqüências de solo exposto e profundidades de deposição da semente e do sulco em ambas as semeadoras e, ainda, o número de plantas emergidas para a semeadora-adubadora modificada, apresentaram diferença significativa entre as linhas de semeadura. O desempenho das duas semeadoras-adubadoras avaliadas não foi satisfatório quanto à largura de revolvimento do solo e à uniformidade da profundidade de deposição da semente.

Soybean sowing under great amount of intact residues of off-season maize, without cutting or incorporation of residues in highly clayey soils has discouraged the farmers to adopt no-tillage (direct planting) in Médio Paranapanema region, São Paulo State, Brazil. The aim of this study was to compare the performance of an original and a modified no-tillage planter by minimizing the straw accumulation, and to evaluate the sowing quality. The modified planter system provided less number of stops due to straw accumulation. Both planter systems showed that uncover soil frequencies and depths of seeding and furrow presented significant differences between the sowed lines. The modified planter system expressed significant difference for number of emerged plants between the sowed lines. The performance of the both planters was not satisfactory for soil revolving width and uniformity of the depth of seeding.