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

Nutritional limitations for initial growth of four native woody species in a Red-Yellow Latosol

Avaliaram-se, pela técnica de "diagnose por subtração", os requerimentos e limitações nutricionais das espécies arbóreas nativas canafístula [Senna multijuga (L.C. Rich) Irwin & Barneby], cedro (Cedrela fissilis Vellozo), pau-ferro (Caesalpinea ferrea Martius ex Tul. var. leiostachya Bentham) e jacaré [Piptadenia gonoacantha (Martius) MacBride] em um Latossolo Vermelho-Amarelo, de textura média, fase cerrado, dos Campos das Vertentes, MG. O estudo foi conduzido por 170 dias, em casa de vegetação, no Departamento de Ciência do Solo da Universidade Federal de Lavras, MG. Os tratamentos consistiram de testemunha sem adição de nutrientes, adubação completa com macronutrientes e micronutrientes (C), e adubação com omissão individual de cada um dos macronutrientes e micronutrientes do tratamento (C). Verificou-se elevada resposta das espécies à adubação completa. A produção de matéria seca de canafístula, cedro, pau-ferro e jacaré neste tratamento, foi aumentada, respectivamente, 67, 17, 82 e 8 vezes em relação à da testemunha. A omissão de N, P ou S do tratamento (C) resultou em grande redução no crescimento das espécies estudadas, evidenciando as exigências destas e as limitações do solo em fornecer estes nutrientes. Apesar da baixa disponibilidade de K no solo (15 μg/g solo), sua omissão não restringiu o crescimento de nenhuma espécie. Apenas o pau-ferro teve seu crescimento reduzido pela omissão de micronutrientes. O crescimento destas espécies no solo estudado só será possível se o solo for adequadamente adubado com N, P e S.Through the "missing element" technique, the nutritional requirements and limitations of the native woody species, canafístula [Senna multijuga (L.C. Rich) Irwin & Barneby], cedro (Cedrela fissilis Vellozo), pau-ferro (Caesalpinea ferrea Martius ex Tul. var. leiostachya Bentham) and jacaré [Piptadenia gonoacantha (Martius) MacBride] were evaluated in a medium texture, cerrado phase, Red-Yellow Latosol (Oxisol) from Campos das Vertentes, MG, Brazil. This study was conducted during 170 days under greenhouse conditions at the Soil Science Department of the Federal University of Lavras, MG, Brazil. The treatments consisted of the control without addition of nutrients, complete fertilization with macronutrients and micronutrients (C) and omission of nutrients of the (C) treatment. A high response of the species to complete fertilization was observed. The dry matter production of canafístula, cedro, pau-ferro and jacaré was increased in 67, 17, 82 and 8 fold, respectively, over the non-fertilized control. The omission of N, P or S from the (C) treatment resulted in great reduction of growth for the studied species, evidencing their requirement and soil limitations. In spite of the low K availability in the soil (15 μg/g of soil), its omission did not reduce plant growth. Pau-ferro had its growth reduced by omission of micronutrients. The growth of these species in the studied soil will be possible only if adequate N, P, and S fertilizers are supplied

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

Aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse

Soil aggregation is a very complex issue related to important soil attributes and processes. The aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse were evaluated using ultrasonic energy. Vinasse is an important byproduct of sugarcane industries, intensively applied to soils in Brazil as liquid fertilizer. Samples of two Oxisols and one Ultisol were used in this study. The physical and chemical characterization of soils was performed, and the 1 to 2 mm size aggregates (200 g) were packed in PVC columns (6.0 cm high and 4.0 cm internal diameter) and incubated with sugarcane vinasse under lab conditions for 1, 30 and 60 days. After incubation, aggregates were submitted to levels of ultrasonic energy, and the particle size distribution (53 to 2,000 µm, 2 to 53 µm, and < 2 µm fractions) was quantified. Mathematical equations were used to relate the mass of aggregates in each of these fractions to the applied ultrasonic energy, and parameters related to aggregate stability were then obtained. Soils showed an aggregate-hierarchy resulting in a stepwise breakdown under ultrasonic agitation. Considering this soil-aggregation hierarchy, vinasse contributed even in a short time to the bonding between and within 2 to 53 µm aggregates, mainly in the Oxisols. This may be related to organic compounds present in the vinasse, cementing soil particles. Potassium enrichment of soil samples did not contribute to soil dispersion

Soil type spatial prediction from Random Forest: different training datasets, transferability, accuracy and uncertainty assessment

Different uses of soil legacy data such as training dataset as well as the selection of soil environmental covariables could drive the accuracy of machine learning techniques. Thus, this study evaluated the ability of the Random Forest algorithm to predict soil classes from different training datasets and extrapolate such information to a similar area. The following training datasets were extracted from legacy data: a) point data composed of 53 soil samples; b) 30 m buffer around the soil samples, and soil map polygons excluding: c) 20 m; and d) 30 m from the boundaries of polygons. These four datasets were submitted to principal component analysis (PCA) to reduce multidimensionality. Each dataset derived a new one. Different combinations of predictor variables were tested. A total of 52 models were evaluated by means of error of models, prediction uncertainty and external validation for overall accuracy and Kappa index. The best result was obtained by reducing the number of predictors with the PCA along with information from the buffer around the points. Although Random Forest has been considered a robust spatial predictor model, it was clear it is sensitive to different strategies of selecting training dataset. Effort was necessary to find the best training dataset for achieving a suitable level of accuracy of spatial prediction. To identify a specific dataset seems to be better than using a great number of variables or a large volume of training data. The efforts made allowed for the accurate acquisition of a mapped area 15.5 times larger than the reference area

Calagem e adubação fosfatada corretiva na cultura da mandioca em Latossolo Vermelho-Escuro Distrófico textura muito argilosa fase cerrado

A field experiment to evaluate the effects of liming and phosphate fertilization for cassava (Manihot esculenta Crantz) growth was carried out in a dystrophic, very clayey, Dark-Red Latosol, originally under cerrado vegetation, in the Experimental Farm Station of Felixlândia, MG, Brazil. After the chemical and physical characterization of the soil, the liming rates based upon the Al, Ca + Mg method were established at four levels: 0, 0.5, 1.0, 1.5 times the normal rate, equivalent to 0, 1950, 3900, 5850 kg/ha of dolomitic lime, having 80% of relative power of total neutralization. The phosphorus as triple superphosphate was applied at six P2O5 levels: 0 - 125 - 250 - 500 - 1000 - 2000 kg/ha. The maximum harvest estimated by regression analysis was 20,58 ton of roots/ha with 1448.6 kg of P2O5. The obtained data evidenced that under these conditions soil correction through liming and phosphate fertilization for cassava growth did not bring compensational benefits in terms of root and branches productivity. The greater Zn amounts in peciole and leaf were registered in the absence of liming and phosphate fertilization, suggesting that on soils under cerrado vegetation, where its availability is low, the occurrence of Zn deficiency symptoms can be induced by application of high corrective rates. Um experimento para avaliar os efeitos da calagem e da adubação fosfatada corretiva, em um Latossolo Vermelho-Escuro distrófico textura muito argilosa, fase cerrado, relevo suave ondulado, para o cultivo da mandioca (Manihot esculenta Crantz), foi conduzido na Fazenda Experimental de Felixlândia, no Estado de Minas Gerais. Após a caracterização química e física do solo, determinou-se a necessidade de calagem pelo método do Al, Ca + Mg e estabeleceram-se 4 níveis: 0, 0,5, 1,0 e 1,5 vezes a calagem normal, equivalentes a 0, 1.950, 3.900, 5.850 kg/ha de calcário com PRNT 80%. A calagem foi feita com calcário dolomítico, simultaneamente com a adubação fosfatada na forma de superfosfato triplo, em seis níveis de  P2O5: 0 - 125 - 250 - 500 - 1.000 - 2.000 kg/ha. A produção máxima estimada pela análise de regressão foi de 20.58 t de raízes com 1.448,6 kg/ha de P2O5. Os resultados obtidos evidenciaram que, nestas condições, a correção do solo através da calagem e fosfatagem para o cultivo da mandioca não trouxe benefícios compensadores na produtividade de raízes e ramas. Na ausência de calagem e fosfatagem registraram-se os maiores teores de Zn no pecíolo e no limbo, sugerindo que nos solos sob cerrado onde sua disponibilidade é baixa, o aparecimento de sintomas de deficiência deste micronutriente pode ser induzido pela aplicação de altas doses de corretivos.

Intervalo hídrico ótimo como indicador de melhoria da qualidade estrutural de latossolo degradado.

As pastagens de gramíneas, quando bem formadas e manejadas, representam um componente ambiental importante em razão do papel que exercem na cobertura dos solos, na formação e estabilização dos agregados e na redução do adensamento ou da compactação. Os objetivos deste estudo foram quantificar o intervalo hídrico ótimo (IHO), para um Latossolo Vermelho-Amarelo degradado fisicamente e cultivado com Coastcross (Cynodon spp.), e utilizar o IHO como indicador de alteração da estrutura desse solo. Amostras indeformadas foram coletadas em anéis volumétricos de 0,025 m de altura e 0,065 m de diâmetro, nas profundidades de 0–0,05 e 0,20–0,25 m e no horizonte Bw (0,80–0,85 m), na ausência de tráfego de máquinas agrícolas, durante a estação chuvosa de 2008/2009, nos meses de novembro de 2008, março de 2009 e maio de 2009. Essas amostras foram utilizadas para determinar a curva de retenção de água, a curva de resistência à penetração, a densidade, o IHO e a densidade crítica do solo (Dsc). O IHO revelou-se um adequado indicador da alteração da estrutura de Latossolo. O Coastcross apresenta potencial para melhoria da estrutura, sendo sugerida sua utilização como alternativa ao uso de implementos agrícolas nesse contexto. A Dsc de 1,24 M g m-3 é limitante ao adequado crescimento e desenvolvimento da forrageira no solo em estudo

Spatial prediction of soil properties in two contrasting physiographic regions in Brazil

This study compared the performance of ordinary kriging (OK) and regression kriging (RK) to predict soil physical-chemical properties in topsoil (0-15 cm). Mean prediction of error and root mean square of prediction error were used to assess the prediction methods. Two watersheds with contrasting soil-landscape features were studied, for which the prediction methods were performed differently. A multiple linear stepwise regression model was performed with RK using digital terrain models (DTMs) and remote sensing images in order to choose the best auxiliary covariates. Different pedogenic factors and land uses control soil property distributions in each watershed, and soil properties often display contrasting scales of variability. Environmental covariables and predictive methods can be useful in one site study, but inappropriate in another one. A better linear correlation was found at Lavrinha Creek Watershed, suggesting a relationship between contemporaneous landforms and soil properties, and RK outperformed OK. In most cases, RK did not outperform OK at the Marcela Creek Watershed due to lack of linear correlation between covariates and soil properties. Since alternatives of simple OK have been sought, other prediction methods should also be tested, considering not only the linear relationships between covariate and soil properties, but also the systematic pattern of soil property distributions over that landscape