Soil loss by water erosion in areas under maize and jack beans intercropped and monocultures

Adequate soil management can create favorable conditions to reduce erosion and water runoff, consequently increase water soil recharge. Among management systems intercropping is highly used, especially for medium and small farmers. It is a system where two or more crops with different architectures and vegetative cycles are explored simultaneously at the same location. This research investigated the effects of maize intercropped with jack bean on soil losses due to water erosion, estimate C factor of Universal Soil Losses Equation (USLE) and how it can be affected by soil coverage. The results obtained also contribute to database generation, important to model and estimate soil erosion. Total soil loss by erosion caused by natural rain, at Lavras, Minas Gerais, Brazil, were: 4.20, 1.86, 1.38 and 1.14 Mg ha(-1), respectively, for bare soil, maize, jack bean and the intercropping of both species, during evaluated period. Values of C factor of USLE were: 0.039, 0.054 and 0.077 Mg ha Mg-1 ha(-1) for maize, jack bean and intercropping between both crops, respectively. Maize presented lower vegetation cover index, followed by jack beans and consortium of the studied species. Intercropping between species showed greater potential on soil erosion control, since its cultivation resulted in lower soil losses than single crops cultivation, and this aspect is really important for small and medium farmers in the studied region

Assessment of soil erosion in olive orchards (Olea europaea L.) under cover crops management systems in the tropical region of Brazil

In the tropics, water erosion is one of the most important factors leading to the degradation and deterioration of agricultural land. Olive orchards have a low canopy coverage, especially during the first years after planting, due to the low density of olive trees. Given the fast expansion of olive orchards in Brazil, this study aimed to evaluate the effect of cover vegetation on soil and water losses under natural rainfall. In addition, it was assessed the crop performance and the vegetation cover index in different management systems in olive orchards. The study was carried out in soil erosion plots, where water and sediment were sampled and measured over two crops season, under the following treatments: in the first season, bare soil with olive cultivation (OBS); olive trees intercropped with spontaneous vegetation (OSV); olive trees intercropped with jack beans (OJB); olive trees intercropped with millet (OM) and, as a control, only bare soil (BS). In the second season, the OM treatment was replaced by olive trees intercropped with sunn hemp (OSH). On bare soils, soil loss was the highest reaching 303.9 Mg ha(-1) yr(-1) and where the surface runoff amounted to 484.8 mm yr(-1). However, in the absence of competition for resources with other crops, olive trees performed best under this system. The olive orchards planted in shallow and sloping soils without cover crops showed unsustainable soil loss, crusting, and sealing in the superficial soil layer, which can progress quickly for soil degradation in the future. The efficiency in the reduction of loss in relation to bare soil was 4.11 and 12.93 % for the soil loss and 12.15 and 25.17 % for water loss, respectively, for olive with spontaneous vegetation and olive with jack beans. Cover crops combined with olive trees, and reconciled with the crop performance aspects of cultivation in tropical regions, is of great relevance for improving sustainability, especially regarding the reduction of soil and water losses due to water erosion

Áreas de risco de erosões do tipo movimento de massa do solo em Lagoa Dourada, Minas Gerais – Brasil / Erosion risk and soil mass movement areas in Lagoa Dourada, Minas Gerais – Brazil

A identificação de áreas de risco de erosão do tipo movimentos de massa de solo em centros urbanos é de suma importância para a prevenção de desastres socioambientais. Neste estudo foram utilizados dados de declividade estruturados em quadrículas no formato GeoTiif do portal TOPODATA, visando a identificação das áreas de risco localizadas no perímetro urbano do município Lagoa Dourada, Minas Gerais - Brasil. Para realizar o processamento das imagens, conversão para arquivos vetoriais e geração de mapas utilizou-se o software QGIS, SIG de código aberto. Os locais com declividades entre 20 e 30% e aqueles acima de 30% foram consideradas, respectivamente, como de risco “Forte” e “Muito Forte” de erosão do tipo movimento de massa de solo. Observou-se que a maioria das áreas de riscos estão localizadas nos arredores do perímetro urbano do município, ocorrendo em quantidades expressivas em Cambissolos, mesmo este apresentando menor abrangência em área quando comparado aos Latossolos. O alto índice pluviométrico no início de 2020, provocaram movimentos de massa de solo expressivos no município, sendo que a maioria destes deslocamentos estiveram nas áreas classificadas como sendo de risco, o que demostrou que os intervalos de declividade utilizados foram adequados e podem auxiliar na prevenção de desastres socioambientais e no planejamento urbano

Rainfall erosivity indices in the Goiânia region, Goiás State, Brazil

A medida do potencial erosivo da chuva vem se tornando objeto de muitos estudos, uma vez que este parâmetro é indispensável nos estudos de modelos para predição de perdas de solo por erosão hídrica. Objetivou-se, com este trabalho, determinar a erosividade da chuva na região de Goiânia (GO) mediante dados pluviográficos. O estudo foi realizado na estação experimental da EMGOPA/Embrapa-CNPS. A erosividade média anual das chuvas na região foi de 8.353,0 MJ mm ha-1 h-1 ano-1 e 129,8 MJ ha-1 ano-1 para os índices EI30 e KE>25, respectivamente. Os coeficientes de correlação mostraram que os parâmetros precipitação e coeficiente de chuva permitem estimar a erosividade da chuva na ausência de dados pluviográficos mais completos. O período crítico de erosão por ocorrência de chuvas erosivas é de setembro a fevereiro; neste período, ocorrem 85,70% e 84,05% do total anual de KE>25 e EI30, respectivamente. Durante este período, práticas conservacionistas são necessárias para reduzir a erosão hídrica, com vistas a manter a sustentabilidade dos solos.The measure of rainfall erosive potential is becoming object of many studies, since this parameter is indispensable in the studies of models for the prediction of soil losses through hydrical erosion. This study was carried out at EMGOPA/Embrapa-CNPS experimental station, to determine the rainfall erosivity for the Goiânia region, GO, Brazil, through rainfall graphical data. The rainfall annual average erosivity for the region was 8353.0 MJ mm ha-1 h-1 year-1 and 129.8 MJ ha-1 year-1, respectively for EI30 and KE>25. The correlation coefficients showed that the rainfall and rainfall coefficient allow to estimate the rainfall erosivity in the absence of more complete rainfall data. The erosion critical period, due to the occurrence of erosive rainfalls is from September to February, when 85.70% and 84.05% of the KE>25 and EI30 annual total, respectively, occurr. In this period, conservation practices are necessary in order to reduce the hydrical erosion, for the maintenance of soil sustainability

Predicting runoff risks by digital soil mapping

Digital soil mapping (DSM) permits continuous mapping soil types and properties through raster formats considering variation within soil class, in contrast to the traditional mapping that only considers spatial variation of soils at the boundaries of delineated polygons. The objective of this study was to compare the performance of SoLIM (Soil Land Inference Model) for two sets of environmental variables on digital mapping of saturated hydraulic conductivity and solum depth (A + B horizons) and to apply the best model on runoff risk evaluation. The study was done in the Posses watershed, MG, Brazil, and SoLIM was applied for the following sets of co-variables: 1) terrain attributes (AT): slope, plan curvature, elevation and topographic wetness index. 2) Geomorphons and terrain attributes (GEOM): slope, plan curvature, elevation and topographic wetness index combined with geomorphons. The most precise methodology was applied to predict runoff areas risk through the Wetness Index based on contribution area, solum depth, and saturated hydraulic conductivity. GEOM was the best set of co-variables for both properties, so this was the DSM model used to predict the runoff risk. The runoff risk showed that the critical months are from November to March. The new way to classify the landscape to use on DSM was demonstrated to be an efficient tool with which to model process that occurs on watersheds and can be used to forecast the runoff risk40113CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIG471522/2012-0; 201987/2012-0; 305010/2013-1Sem informaçãoCAG-APQ-01423-11; CAG-PPM-00422-1

Soil and water losses in eucalyptus plantation and natural forest and determination of the USLE factors at a pilot sub-basin in Rio Grande do Sul, Brazil

Monitoring water erosion and the factors that control soil and water loss are essential for soil conservation planning. The objective of this study was to evaluate soil and water losses by water erosion under natural rainfall in eucalyptus plantations established in 2001 (EF2), and 2004 (EF1), native forest (NF) and bare soil (BS), during the period of 2007 to 2012; and to determine the USLE factors: rain erosivity (R), erodibility (K) of a Red Argisol and the cover-management factor (C) for EF1, EF2 and NF at a pilot sub-basin, in Eldorado do Sul, RS, Brazil. The R factor was estimated by the EI30 index, using rainfall data from a gauging station located at the sub-basin. The soil and water losses were monitored in erosion plots, providing consistent data for the estimation of the K and C factors. The sub-basin presented an average erosivity of 4,228.52 MJ mm ha-1 h-1 yr-1. The average annual soil losses em EF1 and EF2 (0.81 e 0.12 Mg ha-1 year-1, respectively) were below of the limit of tolerance, 12.9 Mg ha-1 year-1. The percentage values of water loss relating to the total rainfall decreased annually, approaching the values observed at the NF. From the 5th year on after the implantation of the eucalyptus systems, soil losses values were similar to the ones from NF. The erodibility of the Red Argisol was of 0.0026 Mg ha h ha-1 MJ-1mm-1 and the C factor presented values of 0.121, 0.016 and 0.015 for EF1, EF2 and NF, respectively

Assessing sediment yield and streamflow with SWAT model in a small sub-basin of the Cantareira System

Hydro-sedimentological models might be useful tools for investigating the effectiveness of soil and water conservation practices. However, evaluating the usefulness of such models requires that predictions are tested against observational data and that uncertainty from model parameterization is addressed. Here we aimed to evaluate the capacity of the SWAT model to simulate monthly streamflow and sediment load in the Posses creek catchment (12 km2), Southeast Brazil. The SUFI-2 algorithm from SWAT-CUP was applied for calibration, testing, uncertainty, and sensitivity analysis. The model was calibrated and initially tested using discharge and sediment load data, which were measured at the catchment outlet. Additionally, we used soil loss measurements from erosion plots within the catchment as independent data for model evaluation. Average monthly streamflow simulations obtained satisfactory results, with Nash-Sutcliffe coefficient (NSE) values of 0.75 and 0.51 for the calibration and testing periods, respectively. Sediment load simulations also displayed satisfactory results for calibration (NSE = 0.65) and testing (NSE = 0.52). However, the comparison with independent plot data revealed that SWAT severely overestimated hillslope erosion rates and compensated it with high sediment channel deposition. Moreover, the model was not sensitive to the parameters used for calculating hillslope sediment yields. Therefore, it should be used with caution for evaluating the interactions between land use, soil erosion, and sediment delivery. We found that the commonly used outlet-based approach for model calibration and testing can lead to internal misrepresentations, and models can reproduce the right answer for the wrong reasons