Influence of cover plants on water balance in the soil under no-tillage and conventional tillage crop rotation

Foi realizado experimento em um Latossolo Vermelho Distrófico argiloso a muito argiloso no Centro Experimental Central do Instituto Agronômico em Campinas, São Paulo, com o objetivo de avaliar a influência de plantas de cobertura no balanço de água no solo de uma cultura de verão (feijão) e uma cultura de inverno (triticale) sob plantio direto consolidadoe preparo convencional do solo recém mobilizado e avaliar atributos físicos do solo dosdiferentes sistemas de produção agrícola utilizados. O delineamento experimental em blocos casualizados foi composto por três blocos com parcelas subdivididas, sendo o fator da parcela o manejo do solo (plantio direto e preparo convencional) e o fator da subparcela a cobertura do solo (gramínea, leguminosa e pousio). As parcelas experimentais foram instrumentalizadas com tensiômetros às profundidades de 0,70 e 0,90 m. O balanço de água no solo foi realizado em períodos de tempo de aproximadamente 15 dias, num volume de solo delimitado pela superfície do solo a profundidade de 0,80 m, englobando o ciclo do feijão e o ciclo do triticale. Paraestimar a drenagem interna foi calculada diariamente a densidade de fluxo de água naprofundidade considerada, pela equação de Darcy-Buckingham. Para isso foram obtidas curvas de retenção da água no solo e foi medida a condutividade hidráulica em função do conteúdo de água no solo pelo método do perfil instantâneo. A evapotranspiração foi determinada por diferença, como incógnita da equação simplificada do balanço de água no solo. Foram também avaliadas a eficiência do uso da água pelas culturas do feijão e do triticale, os componentes de rendimento destas culturas e a produção de matéria seca das plantas de cobertura. Os atributos físicos do solo avaliados foram: densidade do solo, porosidade, macroporosidade, microporosidade e resistência do solo à penetração das raízes. Os resultados obtidos mostraram que: os resíduos culturais da espécie de leguminosa sobre a superfície do solo no plantio direto promoveu menor densidade do solo e menor resistência do solo à penetração das raízes e maior porosidade total e macroporosidade, indicando melhorias das propriedades físicas do solo em relação à sua incorporação no preparo convencional. Na cultura de verão (feijão), a maior perda de água por drenagem interna ocorreu no preparo convencional sob pousio e a manutenção de resíduos vegetais na superfície do solo não significou aumento de evapotranspitação e de produtividade da cultura. A menor utilização de água em profundidade pela cultura do triticale (ascensão capilar) ocorreu nos tratamentos que utilizaram planta de cobertura gramínea. Maior evapotranspiração e maior produtividade em termos médios, foram encontradas em pousio sob plantio direto e preparo convencional, indicando que o déficit hídrico da estação modifica o balanço de água no solo de culturas de inverno.An experiment was carried out on a clayey to very clayey Rhodic Hapludox soil at the Central Experimental Center of the Agronomic Institute in Campinas, São Paulo, with the aim of evaluating the influence of cover plants on soil water balance processes, of a summer crop (bean) and a winter crop (triticale) under consolidated no-tillage and conventional tillage and also evaluating the physical attributes of the soil of the different agricultural production systems used. The randomized block experimental design was composed of three blocks with subdivided plots. The plot factor was soil management (no-tillage and conventional tillage) and the subplot factor was soil cover (grass, legume and fallow). The experimental plots were instrumented with tensiometers at depths of 0.70 and 0.90 m. The soil water balance was carried out over periods of approximately 15 days in a volume of soil delimited by the soil surface and the depth of 0.80 m, including the bean and the triticale cycles. To estimate the internal drainage, the water flow density was calculated dayly at the considered depth, by the Darcy-Buckingham equation. For this, soil water retention curves were determined and the soil hydraulic conductivity as function of soil water content was evaluated by the instantaneous profile method. Evapotranspiration was determined by difference as unknown of the simplified no lateral water flow equation of soil water balance. The water use efficiency by bean and triticale crops, the yield components of these crops and dry matter yield of cover plants was also evaluated. The soil physical attributes evaluated were: bulk density, porosity, macroporosity, microporosity and soil resistance to penetration. The results obtained showed that: the maintenance of crop residues of the legume species on the soil surface under no-tillage promoted lesser bulk density and soil penetration resistance and greater total porosity and macroporosity, indicating better conditions to the soil physical properties in relation to their incorporation in the soil under conventional tillage. In the bean crop, the greatest internal drainage occurred in conventional tillage under fallow and the maintenance of crop residues onthe soil surface did not necessarily meant higher evapotranspitation and crop productivity; in triticale crop, the lower use of water in depth (capillary rise) occurred in treatments that used grass cover plants. Higher evapotranspiration and higher productivity in average terms, were found in the fallow areas under no-tillage and conventional tillage, indicating that the water deficit in the winter season changes the soil water balance

Soil physical quality in crop-livestock systems in a beef cattle-rearing pasture

Crop-livestock systems (CLS) using no-tillage systems have been used to reform and recover degraded pastures, allowing farmers greater profitability and improving soil health. In an experiment with the purpose to evaluate four models of CLS in rearing of cows Nellore, comparing them with the rebuilds performed in permanent pasture, soil physical attributes of quality (density-Db, microporosity-Mi and diameter weighted aggregates-DWA) were evaluated in three soil layers (0-10, 10-20 and 20-40 cm) six years after implantation.  The experiment was located in the Research Unity of São José do Rio Preto/APTA, in an Ferrasol, texture sandy/medium. The 26 ha-area was divided into 24 plots, distributed according to a randomized block design, with four replications and six treatments: (T1) permanent pasture with moderate fertilization (application of 45 kg of N/ha/year); (T2) permanent pasture with fertilizer intensive (90 kg of N/ha/year divided into two applications), and four CLS models with fertilization equal to the second treatment: (T3) one year of maize followed by two pasture; (T4) one year of corn and one of pasture, (T5) two consecutive years of corn followed by a pasture and (T6) two consecutive years of corn followed by two years of pasture. The goal was to provide information to identify environmental gains of CLS models with their long-term use. Changes were observed in the size and shape of the aggregates and the presence of roots in the aggregates. Permanent pastures (T1 and T2) form larger aggregates, at right angles, with fewer roots, while aggregates in the soil managed with CLS (T3 to T6) aggregates are smaller, rounder, with more roots and more darkened color. These observations are supported by the DWA aggregates, since the permanent pasture treatments (T1 and T2) showed higher values when compared to soils with CLS. Regarding the soil layers, there was higher aggregate stability in the surface layer (0-10 and 10-20 cm) due to the higher input of organic matter and increased soil structural arrangement given by the presence of roots. Treatments with CLS values present slightly higher Db in relation to permanent pasture maintained with moderate fertilization. Higher Db can result from machine traffic areas. Soil microporosity, however, was lower in the soil with CLS, indicating rearrangement of the structure. Thus, CLS, regardless of the sequence or number of grain crops and pastures not significantly alter the Db and the Mi soil in relation to the permanent pasture. The DWA was the attribute that has been shown more sensitive to changes in soil by implementation of CLS

Qualidade física do solo de pastagens em sistemas de integração lavoura pecuária para recria de bovinos de corte

O artigo não apresenta resumo em português

Qualidade física do solo de pastagens em sistemas de integração lavoura pecuária para recria de bovinos de corte

O artigo não apresenta resumo em português

Capacidade de suporte de carga de Latossolo Vermelho cultivado com cana-de-açúcar e efeitos da mecanização no solo

The objective of this work was to determine the load support capacity (LSC) of an Oxisol and, through compressibility models, relate it to wheel-soil interactions under management systems with one and three sugarcane crop cycles, with mechanized harvest. LSC evaluations were carried out on undisturbed soil samples, collected at planting row and bed, in four layers: 0.00-0.10, 0.10-0.20, 0.20-0.30, and 0.300.40 m. The contact area between wheels and soil was determined in order to estimate the contact pressure by agricultural machinery on the soil. Pre-consolidation pressures were used to determine LSC. The system with three cycles showed higher LSC than the system with only one cycle. The load support capacity of the soil evaluated in the range of friability is greater than the contact pressures applied to the soil by the wheels of the studied agricultural machines.O objetivo deste trabalho foi determinar a capacidade de suporte de carga (CSC) de Latossolo Vermelho e, por meio de modelos de compressibilidade, relacioná-la às interações rodado-solo em sistema de manejo com um e três ciclos de cultivo de cana-de-açúcar, com colheita mecanizada. As avaliações da CSC foram realizadas em amostras de solo indeformadas, coletadas na linha de plantio e no canteiro, em quatro camadas: 0,00-0,10, 0,10-0,20, 0,20-0,30 e 0,30-0,40 m. Determinou-se a área de contato dos rodados com o solo, para a estimativa da pressão exercida pelas máquinas agrícolas no solo. As pressões de preconsolidação foram usadas para determinar a CSC. O sistema com três ciclos apresentou maior CSC do que o sistema com apenas um ciclo. A capacidade de suporte de carga do solo avaliado na faixa de friabilidade é maior que as pressões de contato aplicadas ao solo pelos rodados das máquinas agrícolas estudadas

Soil compaction on traffic lane due to soil tillage and sugarcane mechanical harvesting operations

Mechanical sugarcane harvesting increases soil compaction due to the intense traffic of agricultural machinery, reducing longevity of sugarcane crops. In order to mitigate the harmful effects caused by agricultural traffic on the soil structure in sugarcane fields, this study evaluated impacts of mechanical sugarcane harvesting on traffic lane under two soil tillage systems based on load bearing capacity models. The experiment was carried out in the region of Piracicaba, state of São Paulo, Brazil, on a Rhodic Nitisol, under conventional tillage (CT) and deep strip-tillage (DST). For CT soil tillage was applied to the entire area with a heavy disk harrow, at operating depths from 0.20 to 0.30 m followed by a leveling harrow at a depth of 0.15 m. For DST, soil tillage was performed in part of the area at a depth of 0.80 m, forming strip beds for sugarcane planting, while the traffic lanes were not disturbed. Undisturbed soil samples from traffic lanes were used in the uniaxial compression test to quantify preconsolidation pressure and to model the soil load bearing capacity. The surface layer (0.00-0.10 m) was most susceptible to compaction, regardless of the tillage system (CT or DST) used. In the DST, the traffic lane maintained the previous soil stress history and presented higher load bearing capacity (LBC) than the traffic lane in the CT. As in CT the soil was tilled, the stress history was discontinued. This larger LBC in DTS minimized the impacts of the sugarcane harvest. Under CT, additional soil compaction due to mechanical sugarcane harvesting in the traffic lane was observed after the second sugarcane harvest. There was a reduction in load bearing capacity from 165 kPa to 68 kPa under CT and from 230 kPa to 108 kPa under DST, from the first to the second harvest at surface layer. Water content at mechanical harvesting was the most relevant factor to maximize impacts on the soil structure in traffic lanes, for both tillage systems