Erosão hídrica em diferentes sistemas de cultivo e níveis de cobertura do solo

The objective of this work was to evaluate, under simulated rainfall, the effect of soil cover on the erosion of a Typic Hapludalf erosion, in the state of Mato Grosso do Sul, Brazil, in the following crop systems: soybean, under conventional tillage; soybean, under no-tillage; established pasture, without cattle trampling; and exposed soil, as a comparison standard. Digital photographs were taken every 20 days for soil cover estimate, and 60 mm h-1 simulated rainfall was applied on the experimental plots, using a portable sprinkler infiltrometer. Soil losses, quantified every 2 min, ranged from 3.10 to 11.40 Mg ha-1, in exposed soil, and from 0.03 to 0.19 Mg ha-1, in established pasture; water losses ranged from 300 to 555 m3 ha-1, in exposed soil, and from 63 to 229 m3 ha-1, in soybean cultivation under no-tillage. Soil losses decreased with the increase in vegetation cover. In the pasture, the maximum vegetation cover was 98.10%. Conventional tillage has temporary positive effects, which makes the soil more susceptible to erosion than the conservationist systems.O objetivo deste trabalho foi avaliar, sob chuva simulada, o efeito da cobertura vegetal sobre a erosão de um Argissolo Vermelho, no Estado de Mato Grosso do Sul, nos seguintes sistemas de cultivo: soja, com preparo convencional; soja, em plantio direto; pastagem estabelecida, sem pisoteio animal; e condição desolo exposto, como padrão de comparação. A cada 20 dias, foram tiradas fotografias digitais para a estimativa da cobertura do solo, e chuvas simuladas de 60 mm h-1 foram aplicadas às parcelas experimentais, com uso do simulador portátil de chuvas. As perdas de solo, quantificadas a cada 2 min, variaram de 3,10 a 11,40 Mg ha-1, no solo exposto, e de 0,03 a 0,19 Mg ha-1 na pastagem; as perdas de água variaram de 300 a 555 m3 ha‑1, no solo exposto, e de 63 a 229 m3 ha-1, no cultivo de soja sob plantio direto. As perdas de solo diminuíram com o aumento da cobertura vegetal. Na pastagem, a máxima cobertura foi de 98,10%. Os efeitos benéficos do preparo convencional são temporários, o que torna o solo mais suscetível à erosão do que os sistemas conservacionistas

Efeito de resíduos vegetais de cana-de-açúcar no controle da erosão hídrica entressulcos

The cultivation of sugarcane uses different cropping systems that result in varying quantities of crop waste, this may influence soil erosion. The objective of this study was to evaluate the loss of soil and water, the infiltration rate, and soil surface roughness in an area cultivated with sugarcane (Saccharum spp.). Six treatments with different levels of plant waste were evaluated: sugarcane without plant waste; sugarcane with 4.0 Mg ha-1 of waste; sugarcane with 8.0 Mg ha-1 of waste; sugarcane with 12.0 Mg ha-1 of waste; sugarcane with 16.0 Mg ha-1 of waste; and burned sugarcane. The treatments were arranged in a randomized block design with four replications, totalling 24 experimental plots. As soil depth increased, there is reduction in macroporosity, total soil porosity, organic carbon content, mean geometric diameter and weighted mean diameter of the soil aggregates, whereas the bulk density of the soil displays the opposite trend. The presence of sugarcane waste on the soil surface increases the time required for the initiation of surface runoff. Sugarcane waste does not alter soil surface roughness, and at the minimum amount of waste administered (4 Mg ha-1) reduces losses of soil and water and increases the infiltration rate. The lack of soil surface coverage after harvesting the sugarcane contributes to soil and water loss, and reduces the rate of stable infiltration of water into the soil.O cultivo da cana-de-açúcar utiliza diferentes sistemas de colheita, resultando em quantidades variadas de resíduos vegetais, que podem influenciar no processo erosivo. O objetivo foi avaliar as perdas de solo e de água, a taxa de infiltração e a rugosidade superficial do solo em área cultivada com cana-de-açúcar (Saccharum ssp.). Foram utilizados seis tratamentos com diferentes níveis de resíduos vegetais: cana crua sem resíduo vegetal; cana crua com 4,0 Mg ha-1 de resíduo; cana crua com 8,0 Mg ha-1 de resíduo; cana crua com 12,0 Mg ha-1 de resíduo; cana crua com 16,0 Mg ha-1 resíduo e cana queimada. Os tratamentos dispostos no esquema experimental de blocos casualizados, com quatro repetições, totalizaram 24 parcelas experimentais. Com o aumento da profundidade do solo verifica-se redução da macroporosidade, da porosidade total do solo, do teor de carbono orgânico, do diâmetro médio geométrico e do diâmetro médio ponderado dos agregados do solo enquanto os valores de densidade do solo apresentam comportamento inverso. A presença de resíduos vegetais de cana-de-açúcar sobre a superfície do solo aumenta o intervalo de tempo necessário para o início do escoamento superficial. A palhada de cana-de-açúcar não altera a rugosidade superficial do solo e a quantidade mínima avaliada, de 4 Mg ha-1 de resíduo, apresenta eficiência na redução das perdas de solo e de água e no aumento da taxa de infiltração. A ausência de cobertura do solo após a colheita da cana-de-açúcar, favorece a ocorrência das perdas de solo e de água e reduz a taxa de infiltração estável de água no solo

Soil physical properties and interrill erosion in agricultural production systems after 20 years of cultivation

Agricultural management significantly influences soil physical properties and soil erosion. However, there are few studies investigating the long-term effects of agricultural management on soil erosion and physical properties. Here, we assessed the impacts of 20-year agricultural land uses under different management practices on soil physical properties and interrill erosion. This study was conducted on an experimental farm of the Embrapa Western Agriculture, Brazil, and the treatments consisted of soybean cropping under conventional tillage (CT) and no-tillage (NT), crop-livestock integration during the cropping phase (CL-C) and the livestock phase (CL-L), and Brachiaria decumbens pasture under rotational grazing (PP). Soil samples were taken to evaluate the soil physical properties, and 25 rainfall simulations with an intensity of 60 mm h -1 were carried out by using a portable rainfall simulator with runoff plots of 0.7 m 2 to quantify surface runoff and interrill erosion. After two decades, the crop-livestock systems (CL-L and CL-C) presented better soil physical properties in the topsoil layer (0.00–0.05 m) with a higher level of aggregation. Soil and water losses ranged from 4.7 to 14.4 × 10 -3 kg m -2 and 4.9 to 12.4 mm, respectively. A higher reduction in soil erosion was observed in NT, while CT showed the highest soil erosion rates. These findings indicate an opportunity for a reduction of soil erosion by 60 % by adopting crop-livestock integration comparing CL-C with CT, while livestock under an integrated system (CL-L) decreased water loss by 30 % compared with PP. This study is a starting point for future research, and the findings reveal the potential to minimize the agriculture footprint