ABSTRACT The native field area in southern Brazil has been reduced due to cultivation, and part of the remainder is traditionally burned and may increase water erosion and soil degradation. In this research, the soil chemical composition and water erosion, under natural rainfall, were evaluated in an Inceptisol, in the south of the Santa Catarina state plateau. The treatments consisted of native field, field mowed and burned once a year, and field cultivated under no-tillage conditions, in plots of 3.5 x 22.1 m and average slope of 10 %. The water erosion was evaluated between November 2016 and September 2018, when there were 61 erosive rainfalls, totaling 1,997 mm and 8,472 MJ mm ha-1 h-1. The soil losses were 82 kg ha-1 in the cultivated field, 55 kg ha-1 in the burned field and 24 kg ha-1 in the native field; and the water losses, in relation to the total rainfall, were 2.2 % in the native field and cultivated field and 1.2 % in the burned field.

RESUMO A área de campo nativo no Sul do Brasil foi reduzida devido ao cultivo, e parte do remanescente é tradicionalmente queimada, podendo aumentar a erosão hídrica e a degradação do solo. Avaliou-se a composição química do solo e a erosão hídrica, sob chuva natural, em um Cambissolo Húmico, no sul do planalto Catarinense. Os tratamentos consistiram de campo nativo, campo roçado e queimado uma vez ao ano e campo cultivado em condição de semeadura direta, em parcelas de 3,5 x 22,1 m e declividade média de 10 %. A erosão hídrica foi avaliada entre novembro de 2016 e setembro de 2018, quando ocorreram 61 chuvas erosivas, totalizando 1.997 mm e 8.472 MJ mm ha-1 h -1. As perdas de solo foram de 82 kg ha-1 no campo cultivado, 55 kg ha-1 no campo queimado e 24 kg ha-1 no campo nativo; e as perdas de água, em relação ao total precipitado, foram de 2,2 % no campo nativo e campo cultivado e de 1,2 % no campo queimado.

Abstract The application of pig slurry (PS) to soil is known to change its chemical and physical properties. However, little is known about the alterations that PS causes in pore morphology and water erosion. This research evaluated the influence of PS on the morphology of the pores in the surface layer of the soil and on water erosion in an Inceptisol subjected to simulated rainfall. The soil was cultivated with black oats and the treatments (doses) 0, 50, 100 and 200 m3 ha-1 of PS were applied to the crop residue. The experimental design was completely randomized. Six simulated rainfall lasting 60 minutes and planned constant intensity of 65 mm h-1 were applied to the treatments. Undisturbed soil samples were collected in the 0-0.05 m layer, 24 h before and 24 h after the first, third and sixth rainfall events. Image analysis was performed, determining the percentage of macropores and mesopores, number, diameter and shape of the pores, using the micro morphometry technique. PS doses of 100 and 200 m3 ha-1, combined with simulated rainfall, favored surface sealing and pore rearrangement. There was an increase in the number of small and rounded pores, without interconnection between them, with a consequent increase in water erosion until the moment of stabilization of the superficial crust.

Resumo O dejeto líquido de suínos (DLS) aplicado no solo reconhecidamente altera as propriedades químicas e físicas. Porém, ainda são pouco conhecidas as alterações que o DLS causa na morfologia dos poros e na erosão hídrica. Com esta pesquisa objetivou-se avaliar a influência do DLS na morfologia dos poros da camada superficial do solo e na erosão hídrica, em um Cambissolo submetido à chuva simulada. O solo foi cultivado com aveia preta e os tratamentos (dose) 0, 50, 100 e 200 m3 ha-1 de DLS foram aplicados sobre o resíduo da cultura. O delineamento experimental foi o inteiramente casualizado. Seis chuvas simuladas com duração de 60 minutos e intensidade constante planejada de 65 mm h-1 foram aplicadas aos tratamentos. Amostras indeformadas de solo foram coletadas na camada de 0-0,05 m, 24 h antes e 24 h após o primeiro, terceiro e sexto eventos de chuva. Foi realizada análise de imagem, determinando-se a porcentagem de macroporos e mesoporos, número, diâmetro e forma dos poros, pela técnica de micromorfometria. As doses 100 e 200 m3 ha-1 de DLS, combinadas com a chuva simulada, favoreceram o selamento superficial e o rearranjo dos poros. Houve aumento do número de poros pequenos e arredondados, sem interligação entre eles, com consequente aumento da erosão hídrica até o momento de estabilização da crosta superficial.

Abstract Water infiltration into soil varies significantly with soil type and management practices. Management practices alter soil physical properties, such as porosity and pore size distribution, which play an important role in infiltration. This study was conducted to assess the effect of the long-term use of two different soil tillage systems (conventional, CT, and no-tillage, NT) on soil structure and water infiltration to understanding of the relationship between physical conditions induced by tillage and water infiltration. The experiments were carried out on a Humic Cambisol in southern Brazil from 1995 to 2016. Soil density, porosity, aggregate diameter and soil water infiltration were evaluated under conventional tillage right after one plowing and two subsequent discings (CT0), and six months after these tillage operations (CT6). The results show that different management systems affect differently soil physical properties and, thus, water infiltration. By mechanical mobilization CT brings about modifications in soil structure which promote an increase in total porosity and mesopority, and a decrease in soil microporosity. This in turn results in an increase in the proportion of larger pores in the plow layer and a decrease in soil density, but also in a decrease in aggregate stability. The CT0 measurements showed the highest infiltration rates which were up to 15 times greater than in the NT treatment. The higher infiltration rate in CT0 wears off with time, but in the CT6 measurements six months after tillage it was still 2 times higher than under NT. Tillage, at least initially, increases total porosity and mesoporosity, while at the same time decreasing microporosity. This results in a larger saturated hydraulic conductivity (K). An increase in total porosity alone does not necessarily increase K, if there is an increase in small pores at the cost of decreasing the number of larger pores.

Abstract Improper management degrades the soil, decreases corn productivity and is reflected in the cost of production. The objective of this research was to evaluate the soil recovery in non-conservationist treatments after the change of management and cultivation to the conservation condition direct sowing, and compare these systems to consolidated direct seeding; This evaluation was based on the soil responsiveness to crop production and water erosion control, and based on the financial cost of soil recovery and corn production when soil management was converted from non-conservationist (tillage rotation - RT, minimum tillage - MT, conventional tillage - CT and bare soil - BS) to no-tillage (NT) condition, in a Humic Cambisol. The transition from managements to no-tillage occurred in 2015 year, after 27 years of conducting the preexisting managements. The chemical recovery was carried out with the application of limestone, phosphorus, and potassium. At the end of the research the yield of the corn crop, the cost of recovering the soil fertility and the cost of crop production were evaluated. Previous soil management influenced the cost of soil chemical recovery. The cost of production showed a financial loss for the previous treatments CT and BS, on the average of the three corn crops.

ABSTRACT: The conversion of native grassland into farmland causes changes in the soil. Tillage has profound effects on soil organic matter. The intensification of soil tillage decreases soil quality by reducing aggregate stability. Soil aggregate stability and soil organic matter are key indicators for soil quality and environmental sustainability in agro-ecosystems. The aim of the present study is to evaluate the total organic carbon content and the physical and chemical fractions of the organic matter in a soil under different uses and types of management over 27 years. Four soil tillage treatments with two annual crops were evaluated (no-tillage, NT; rotating tillage, RT; minimum tillage, MT; and conventional tillage, CT), as well as bare soil (BS) (standard plot of the Universal Soil Loss Equation - USLE) and natural grassland (NG) as a reference area. The experiment was carried out in an Inceptisol (Cambissolos) in southern Brazil. We determined total organic carbon (TOC) and particulate organic carbon (POC), and organic carbon associated with soil minerals (OCam). The chemical fractionation of carbon was into fulvic and humic acids, and humin. In addition, soil aggregates were divided into five size classes. The type of soil tillage affected the soil organic carbon content, namely TOC, POC, and OCam, as well as the composition of the physical and chemical fractions and their distribution in the arable soil layer. There was a positive relationship between stable aggregates and organic carbon in the soil: the higher the proportion of aggregates in class 1, the higher the organic carbon content. The results support the hypothesis that the carbon stock depends on intensification of a conservation tillage system with a continuous input of C through biomass, which maintains and supplies a continuous flow of C to the carbon transformation processes in the soil.

ABSTRACT Water erosion degrades the soil and contaminates the environment, and one influential factor on erosion is slope length. The aim of this study was to quantify losses of soil (SL) and water (WL) in a Humic Cambisol in a field experiment under natural rainfall conditions from July 4, 2014 to June 18, 2015 in individual events of 41 erosive rains in the Southern Plateau of Santa Catarina and to estimate soil losses through the USLE and RUSLE models. The treatments consisted of slope lengths of 11, 22, 33, and 44 m, with an average degree of slope of 8 %, on bare and uncropped soil that had been cultivated with corn prior to the study. At the end of the corn cycle, the stalk residue was removed from the surface, leaving the roots of the crop in the soil. Soil loss by water erosion is related linearly and positively to the increase in slope length in the span between 11 and 44 m. Soil losses were related to water losses and the Erosivity Index (EI30), while water losses were related to rain depth. Soil losses estimated by the USLE and RUSLE model showed lower values than the values observed experimentally in the field, especially the values estimated by the USLE. The values of factor L calculated for slope length of 11, 22, 33, and 44 m for the two versions (USLE and RUSLE) of the soil loss prediction model showed satisfactory results in relation to the values of soil losses observed.

ABSTRACT Water erosion is the main cause of soil degradation and is influenced by rainfall, soil, topography, land use, soil cover and management, and conservation practices. The objective of this study was to quantify water erosion in a Humic Dystrudept in two experiments. In experiment I, treatments consisted of different rates of fertilizer applied to the soil surface under no-tillage conditions. In experiment II, treatments consisted of a no-tillage in natural rangeland, burned natural rangeland and natural rangeland. Forage turnip, black beans, common vetch, and corn were used in rotation in the treatments with crops in the no-tillage during study period. The treatments with crops and the burned rangeland and natural rangeland were compared to a bare soil control, without cultivation and without fertilization. Increasing fertilization rates increased organic carbon content, soil resistance to disintegration, and the macropore volume of the soil, due to the increase in the dry mass of the crops, resulting in an important reduction in water erosion. The exponential model of the ŷ = ae-bx type satisfactorily described the reduction in water and soil losses in accordance with the increase in fertilization rate and also described the decrease in soil losses in accordance with the increase in dry mass of the crops. Water erosion occurred in the following increasing intensity: in natural rangeland, in cultivated natural rangeland, and in burned natural rangeland. Water erosion had less effect on water losses than on soil losses, regardless of the soil management practices.