RESUMO A adubação orgânica das culturas agrícolas com resíduos oriundos da suinocultura e da avicultura resulta em ganhos de produtividade e redução nos custos de produção, porém, pode alterar as propriedades físicas e o comportamento mecânico do solo, aumentando ou reduzindo a sua qualidade. Objetivou-se investigar a influência da aplicação superficial de doses crescentes de dejetos líquidos de suínos (160 m³ ha-1 ano-1, 320 m³ ha-1 ano-1 e 480 m³ ha-1 ano-1) e de cama de aviário (6 Mg ha-1 ano-1, 12 Mg ha-1 ano-1 e 18 Mg ha-1 ano-1), ao longo de quatro anos, sobre as propriedades físico-mecânicas e carbono orgânico de um Latossolo Vermelho muito argiloso. As aplicações de dejeto líquido de suínos e de cama de aves aumentaram os teores superficiais de carbono orgânico do solo. A densidade do solo reduziu-se, enquanto a porosidade total e a macroporosidade aumentaram, em função das adições de dejeto líquido de suínos e de cama de aves. Não houve alterações significativas na suscetibilidade do solo à compactação.

ABSTRACT In agricultural crops, the use of swine and poultry waste as organic fertilizers results in gains in the productivity and reduction of production costs, but it may also change the physical properties and mechanical behavior of the soil, either increasing or reducing its quality. This study aimed to investigate the influence of applying increasing doses of liquid swine manure (160 m³ ha-1 year-1, 320 m³ ha-1 year-1 and 480 m³ ha-1 year-1) and poultry litter (6 Mg ha-1 year-1, 12 Mg ha-1 year-1 and 18 Mg ha-1 year-1), along four years, on the physical-mechanical properties and organic carbon content of a very clayey Rhodic Eutrudox. The application of liquid swine manure and poultry litter increased the surface soil organic carbon contents. The soil density decreased, whereas the total porosity and macroporosity increased, with the addition of liquid swine manure and poultry litter. There were no significant changes in the soil susceptibility to compaction.

ABSTRACT Water and oxygen deficiencies in the soybean crop cultivated on lowland soils are an important topic of research. The objective of this study was to investigate changes in water and oxygen supply and soybean yield caused by soil management in lowland soils. A soybean crop was grown under four soil conditions: no-tillage (NT), chiseling (CH), ridge tillage on no-tillage (NTR), and ridge tillage on chiseling (CHR). Soil bulk density, total porosity, macro- and microporosity, air permeability, and saturated hydraulic conductivity were measured at 0.05, 0.15, 0.25, and 0.35 m depths. Soil volumetric water content was monitored at the same depths every 30 min during the soybean cycle. The transpiration coefficient was calculated from volumetric water content to express both water and oxygen deficiency. The groundwater level was monitored throughout the soybean cycle. Plant performance was evaluated by measuring plant population, shoot dry matter, yield, and taproot depth. Soil porosity, air permeability, and saturated hydraulic conductivity were most improved in CH and CHR, and less in NTR. Nonetheless, expected improvement in soil aeration in CH, CHR, and NTR was eliminated when the water table raised to near the soil surface. The transpiration coefficient indicated that CH decreased oxygen deficiency, but caused little water deficit. The CH also provided the highest yield (4,610 kg ha-1), which was not surpassed by the addition of ridge tillage on chiseled soil (CHR) (4,001 kg ha-1). The lowest yields were observed in NT (2,842 kg ha-1), and NTR (3,565 kg ha-1), in which oxygen deficiency was more severe. Lower oxygen deficiency for soybean in chiseled lowland soil is regulated by the water table. As the transpiration coefficient is dependent on all the processes determining soil water dynamics, it is more informative than soil structural properties regarding water and oxygen deficiency in soybean in lowland soil.

Resumo: O objetivo deste trabalho foi avaliar o efeito de diferentes quantidades de palha de aveia-preta (Avena strigosa) em cobertura do solo sobre a temperatura do solo em diferentes profundidades. Os tratamentos consistiram de 0, 3, 6 e 9 Mg ha-1 de palha. A temperatura do solo foi medida a cada hora por meio de termopares inseridos em diferentes profundidades (0, 5, 15, 30 e 50 cm) e usada para ajustar uma equação que correlaciona a temperatura do solo coberto com a do solo descoberto. A partir dessas correlações, foi possível observar um valor pontual de temperatura (temperatura de inversão do efeito da palha), abaixo do qual a presença de palha atua positivamente na manutenção da temperatura do solo e acima do qual a presença de palha atua negativamente no aquecimento do solo.

Abstract: The objective of this work was to evaluate the effect of different amounts of black oat (Avena strigosa) straw covering soil surface on soil temperature at different depths. The treatments consisted of 0, 3, 6, and 9 Mg ha-1 straw. Soil temperature was measured hourly by a thermocouple inserted at different depths (0, 5, 15, 30, and 50 cm) and was used to adjust an equation correlating the temperature of covered soil with that of bare soil. With the correlations, it was possible to observe a point value of temperature (inversion temperature of straw effect), below which the presence of straw acts positively on the maintenance of soil temperature and above which the presence of straw acts negatively on soil heating.