Impacto da aplicação de dejetos de suínos nas perdas de solo e água: comparação com uma série histórica

[Abstract] Water erosion in soil is influenced by several factors, including rain, relief, cover, and management and conservation practices. Also, erosion is affected by pig slurry (PS) applied to the soil as a fertilizer. The objectives of this research were i): to evaluate water erosion in a Humic Cambisol cultivated with Zea mays L., Avena strigosa, Glycyne max L., and Raphanus sativus in rotation after PS dispersal under different tillage treatments, namely: no-tillage (NT), minimum tillage (MT), rotation tillage (RT) and conventional tillage (CT) , and ii): to compare erosion before and after PS application in a single dose of 50 m3 ha-1 in each crop, soon after the germination of the crops. NT had lower soil and water loss, which were reduced by 81 and 13%, respectively, in relation to CT. Differences in soil and water losses were lower between MT and RT, than between other treatments. The contents of phosphorus (P) and potassium (K) in the superficial layers of the soil were higher under NT than under CT. The contents of P and K in the sediments were higher in the NT than in the CT treatment. Also, the contents of P and K were significantly higher in sediments than in water, especially under NT. The application of a single PS dose on the soil surface increased soil P and K contents and decreased water erosion compared to the 19-year historical series that preceded this research in different soil management systems without PS application.[Resumo] A erosão hídrica no solo é influenciada por diversos fatores, incluindo chuva, relevo, cobertura, e manejo e práticas conservacionistas. Ainda, a erosão é afetada pelo dejeto suíno (DS) aplicado ao solo como fertilizante. Os objetivos desta pesquisa foram i): avaliar a erosão em Cambissolo Húmico, após aplicação de DS sob diferentes tratamentos: plantio direto (PD), cultivo mínimo (CM), rotação de preparos (RP) e plantio convencional (PC), cultivados com Zea mays L., Avena strigosa, Glycyne max L., e Raphanus sativus em rotação, e ii): comparar a erosão antes e após a aplicação de DS em dose única de 50 m3 ha-1 em cada cultivo, logo após a germinação das culturas. O PD apresentou menor perda de solo e água, reduzindo em 81 e 13%, respectivamente, em relação à PC. Diferenças nas perdas de solo e água foram menores, entre CM e RP, do que nos outros tratamentos. O teor de fósforo (P) e potassio (K) nas camadas superficiais do solo foi maior em PD do que em PC. Os teores de P e K nos sedimentos foram maiores no PD que no PC. Ainda, os teores de P e K foram significativamente maiores nos sedimentos do que na água, especialmente PD. A aplicação da dose única de DS na superfície do solo melhorou os teores de P e K do solo e diminuiu a erosão hídrica em relação ao histórico de 19 anos que antecederam esta pesquisa, em diferentes sistemas de manejo do solo e sem aplicação de DS

Simulador de chuva tipo empuxo com braços movidos hidraulicamente: fabricação e calibração

O uso de simuladores de chuva é fundamental em estudos de erosão hídrica pluvial. Com eles é possível controlar as condições experimentais, principalmente as características da chuva, e compreender melhor o processo erosivo do solo. Vários tipos de simulador de chuva foram desenvolvidos desde 1930 no mundo. Atualmente, o tipo Swanson é o mais utilizado. No entanto, um pequeno número desses simuladores está em pleno funcionamento no Brasil, devido ao alto grau de desgaste e às dificuldades de manutenção. O objetivo deste trabalho foi desenvolver um novo modelo de simulador de chuva, construído predominantemente em alumínio, desprovido de motor para rotação dos braços e movido hidraulicamente por empuxo. O simulador de chuva movido hidraulicamente por empuxo mantém em geral as características do modelo Swanson, sobretudo aquelas relacionadas às características de chuva produzida, tendo sido minimizados seu excesso de peso e a necessidade de uso de um motor a gasolina para movimento dos braços, denominado "Tipo Empuxo". Essas características tornaram o novo modelo mais leve, econômico, silencioso e de fácil manejo na área experimental do que o modelo Swanson, sendo possível deslocá-lo com apenas quatro pessoas. A intensidade da chuva correlacionou-se linear e positivamente com a pressão da água no manômetro

WATER INFILTRATION IN TWO CULTIVATED SOILS IN SOUTHERN BRAZIL

Infiltration is the passage of water through the soil surface, influenced by the soil type and cultivation and by the soil roughness, surface cover and water content. Infiltration absorbs most of the rainwater and is therefore crucial for planning mechanical conservation practices to manage runoff. This study determined water infiltration in two soil types under different types of management and cultivation, with simulated rainfall of varying intensity and duration applied at different times, and to adjust the empirical model of Horton to the infiltration data. The study was conducted in southern Brazil, on Dystric Nitisol (Nitossolo Bruno aluminoférrico húmico) and Humic Cambisol (Cambissolo Húmico alumínico léptico) soils to assess the following situations: simulated rains on the Nitisol from 2001 to 2012 in 31 treatments, differing in crop type, sowing direction, type of soil opener on the seeder, amount and type of crop residue and amount of liquid swine manure applied; on the Cambisol, rains were simlated from 2006 to 2012 and 18 treatments were evaluated, differing in crop, seeding direction and crop residue type. The constant of the water infiltration rate into the soil varies significantly with the soil type (30.2 mm h-1 in the Nitisol and 6.6 mm h-1 in the Cambisol), regardless of the management system, application time and rain intensity and duration. At the end of rainfalls, soil-water infiltration varies significantly with the management system, with the timing of application and rain intensity and duration, with values ranging from 13 to 59 mm h-1, in the two studied soils. The characteristics of the sowing operation in terms of relief, crop type and amount and type of crop residue influenced soil water infiltration: in the Nitisol, the values of contour and downhill seeding vary between 27 and 43 mm h-1, respectively, with crop residues of corn, wheat and soybean while in the Cambisol, the variation is between 2 and 36 mm h-1, respectively, in soybean and corn crops. The Horton model fits the values of water infiltration rate into the soil, resulting in the equation i = 30.2 + (68.2 - 30.2) e-0.0371t (R2 = 0.94**) for the Nitisol and i = 6.6 + (64.5 - 6.6) e-0.0537t (R2 = 0.99**) for the Cambisol

Nutrient and Organic Carbon Losses, Enrichment Rate, and Cost of Water Erosion

ABSTRACT Soil erosion from water causes loss of nutrients and organic carbon, enriches the environment outside the erosion site, and results in costs. The no-tillage system generates increased nutrient and C content in the topsoil and, although it controls erosion, it can produce a more enriched runoff than in the conventional tillage system. This study was conducted in a Humic Cambisol in natural rainfall from 1997 to 2012 to quantify the contents and total losses of nutrients and organic C in soil runoff, and to calculate the enrichment rates and the cost of these losses. The treatments evaluated were: a) soil with a crop, consisting of conventional tillage with one plowing + two harrowings (CT), minimum tillage with one chisel plowing + one harrowing (MT), and no tillage (NT); and b) bare soil: one plowing + two harrowings (BS). In CT, MT, and NT, black oat, soybean, vetch, corn, turnip, and black beans were cultivated. Over the 15 years, 15.5 Mg ha-1 of limestone, 525 kg ha-1 of N (urea), 1,302 kg ha-1 of P2O5 (triple superphosphate), and 1,075 kg ha-1 of K2O (potassium chloride) were used in the soil. The P, K, Ca, Mg, and organic C contents in the soil were determined and also the P, K, Ca, and Mg sediments in the runoff water. From these contents, the total losses, the enrichment rates (ER), and financial losses were calculated. The NT increased the P, K, and organic C contents in the topsoil. The nutrients and organic C content in the runoff from NT was greater than from CT, showing that NT was not a fully conservationist practice for soil. The linear model y = a + bx fit the data within the level of significance (p≤0.01) when the values of P, K, and organic C in the sediments from erosion were related to those values in the soil surface layer. The nutrient and organic C contents were higher in the sediments from erosion than in the soil where the erosion originated, generating values of ER>1 for P, K, and organic C. The value of the total losses of nutrients in the form of triple superphosphate fertilizer, potassium chloride, and urea and limestone by water erosion was higher in CT than in NT. For triple superphosphate, the cost of erosion losses was 29 % higher in NT than in CT, while in urea and limestone, the effectiveness of NT in reducing costs was 65 and 50 %, respectively

Water erosion in surface soil conditions: runoff velocity, concentration and D50 index of sediments in runoff

Water erosion and contamination of water resources are influenced by concentration and diameter of sediments in runoff. This study aimed to quantify runoff velocity and concentration and the D50 index of sediments in runoff under different soil surface managements, in the following treatments: i) cropped systems: no-tilled soil covered by ryegrass (Lolium multiflorum Lam.) residue, with high soil cover and minimal roughness (HCR); no tilled soil covered by vetch (Vicia sativa L.) residue, with high soil cover and minimal roughness (HCV); chiseled soil after ryegrass crop removing the above-ground residues and keeping only the root system, with high roughness (HRR); chiseled soil after vetch crop removing the above-ground residues and keeping only the root system, with high roughness (HRV); ii) bare and chiseled soil, with high roughness (BHR). The research was conducted on a Humic Dystrupept under simulated rainfall. The design was completely randomized and each treatment was replicated twice. Eight rainfall events of controlled intensity (65 mm h−1) were applied to each treatment for 90 minutes. The D50 index, runoff velocity and sediment concentration were influenced by crop and soil management. Runoff velocity was more intensely reduced by cover crop residues than by surface roughness. Regardless of surface condition, the D50 index and concentration of sediment in runoff were lower under ryegrass than vetch crop. Runoff velocity and the D50 index were exponentially and inversely correlated with soil cover by residues and with surface roughness, while the D50 index was positively and exponentially correlated with runoff velocity