Romeu de Souza Werner

Erosão hídrica associada a algumas variáveis hidrológicas em pomar de maçã submetido a diferentes manejos do solo

Soil management in perennial crops such as orchards can influence erosion. This study evaluated soil and water losses from an Oxisol under simulated rain, from August 2007 to April 2008, at the experimental station of Embrapa Uva e Vinho, in Vacaria (RS). On the 3.5 m x 11 m plots, rains of one hour were simulated at a constant intensity of 70 to 88 mm h-1. In the apple orchard, the following soil management systems were studied: i) manual weeding under apple trees and spontaneous grass and legume cover in the rest of the area (ST), ii) undesiccated oat cover, hoeing the seeds into the soil at weeding in the entire area, two months before the first rain test (NO), iii) oat cover chemically desiccated seven days before the first rain test, planted by a rotary hoe to incorporate seeds into the soil in the entire area, two months before the tests (DO); and iv) uncovered soil with removal of the previously desiccated spontaneous cover from the soil surface by weeding the entire area with a hoe, one day before each rain test (BS). The management systems related to the soil cover in the apple orchard and the rain tests influenced water erosion. Soil losses varied considerably in the treatments, more than water losses. Even with soil mobilization in the entire area for oat planting in the NO and DO treatments the control effectiveness of water erosion was equal to the ST treatment in which the soil was mobilized only under the trees. The removal of the soil cover from under apple trees greatly increased soil losses in relation to the cover maintenance, but had only little influence on water losses. The runoff duration influenced soil loss; an increase of this variable was observed with increasing runoff duration until a certain moment and, from then on, it decreased independently of the treatment; water loss increased until a certain moment and stabilized. An inverse relationship was observed between soil and water losses, independently of the soil management system under apple trees, adjusting to an exponential model.

Comprimento crítico de declive relacionado à erosão hídrica, em três tipos e doses de resíduos em duas direções de semeadura direta

Under conservation tillage systems, the effectiveness of crop residues in reducing water erosion decreases if the mulch is carried away by runoff and/or if the runoff furrows the soil. This phenomenon is called mulch failure, characterizing the critical slope length, i.e., the distance on the ground after which the runoff shear stress is sufficient to overcome the resistance of the mulch to be carried away and/or the resistance of the soil to furrowing. The objective of this study was to define critical slope lengths in two sowing directions under different types and doses of crop residues, under no-tillage. The field work was conducted from May 2009 to May 2011, on a Nitosol (Alfisol) in Sao Jose do Cerrito, Santa Catarina, Brazil, in experimental units (3.5 x 11 m) with a mean slope of 0.144 m m-1. Transverse (contour) and parallel sowing directions (up-and-down) to the slope were tested using maize (Zea mays), wheat (Triticum aestivum) and soybean (Glycine max) mulches at doses of 50 and 100% of the total residue produced. During the research, rainfall was simulated using a rotating-boom rainfall simulator, with a rain intensity of 65 mm h-1 in 90 min, which was the time required until the runoff rate became constant. At the end of 90 min of rain, without disconnecting the rainfall simulator, increasing levels of extra flow of clean water were applied at the upper part of the plots, simulating additional runoff from longer slopes. The mulch failure was evaluated based on the theory of erosion, using the relationship between erosion rate (Dp) x runoff rate (qm) and sediment concentration in runoff (C) x runoff rate (qm). In all treatments the critical slope lengths were determined, and, in general, contour sowing and higher amounts of crop residues increased the critical slope length in relation to the up-and-down sowing and the lowest residue dose, respectively. These critical lengths ranged from 35 to 155 m. The point of failure of the theory of erosion was best identified by a combined analysis of the relationships Dp x qm and C x qm.

Erosão hídrica em campo nativo sob diversos manejos: perdas de água e solo e de fósforo, potássio e amônio na água de enxurrada

Native pastures in southern Brazil are used for cattle and sheep grazing. The forage offer in the spring-summer season is greater than the animal requirement, so the forage left over is usually burned. Pasture burning mineralizes nutrients and leaves the soil bare, triggering water erosion. This study aimed to quantify total soil and water losses and P, K and NH4+ contents in the runoff water from an Oxisol with native pasture. In the treatments, the native pastures, were i) unburned and unfertilized, ii) unburned and P-fertilized, iii) burned and unfertilized, and iv) burned and P-fertilized. Rain was simulated at an intensity of 75 mm h-1 and duration of 3 h on the plots (11 m long along the slope and 3.5 m wide). Burning of the native vegetation decreased the times until runoff began and peaked and reduced soil water infiltration, but increased the maximum runoff rate, soil and water losses by water erosion and the P, K and NH4+ concentration and total losses in the runoff water, compared to no burning. The runoff sediment concentration was higher in the treatment with vegetation burning than without. The highest and lowest values of sediment concentration were detected after a shorter runoff period in the treatment with vegetation burning than in that without, which is related to the 8.9 times higher total soil loss from burnt than from unburnt grassland. The P concentration and total loss in the runoff water were higher in the treatment with than without phosphate fertilizer, in the treatment with burning as well as that without. For K and the NH4+ , the concentration and total losses were higher in the treatment with burning than in that without. Phosphorus, K and NH4+ concentration in the runoff water fit the exponential model y = ae-bx in relation to runoff duration (p < 0.01).

Influência das condições de superfície e do cultivo do solo na erosão hídrica em um cambissolo húmico

The soil cover by crop residues dissipates the kinetic energy of raindrops, while, the surface roughness dissipates the kinetic energy of runoff, therefore, both store water and retain sediments on surface, decreasing water erosion. The objective of this study was to determine the persistence and the influence of crop residues and surface roughness in cultivated soil on soil and water losses, compared to bare and uncovered soil under the following treatments: i) cultivated soil: covered by ryegrass mulch (Lolium multiflorum), with minimal roughness (RMC); covered by vetch mulch (Vicia sativa), with minimal roughness (VMC); chiseled after ryegrass cultivation in the absence of residues above-ground crop and presence of plant roots, with high roughness (RHR); chiseled after the vetch cultivation in the absence of above-ground crop residues and presence of plant roots, with high roughness (RHV); ii) bare soil: uncovered, chiseled, with high roughness (RHU). The experiment was carried out from May 2011, to December 2012, in experimental plots of 38.5 m2 (11 m along the slope and 3.5 m width). In these treatments, eight simulated rainfall testes were applied, with 90 min of duration and planned to a constant rain intensity of 65 mm h-1 , using a rotating boom simulator rainfall moved by hydraulic thrust. The residue mass and the surface soil roughness decrease over time, especially in the vetch treatments, with more intense decrease in soil roughness in the first simulated rainfall test and in residues mass in the second rainfall test. The cultivation decreases soil losses relative to bare chiseled soil, independent of the surface conditions. Ryegrass and vetch residues reduce soil losses relative to chiseled treatments, and ryegrass reduces soil losses relative to vetch, independent of the soil management. The cultivated treatments show increasing soil loss during the time, mainly when soil was chiseled. The water losses by runoff follow the same tendency of soil losses, however, with lower differences between treatments.

Erosão hídrica em semeadura direta de milho e soja nas direções da pendente e em contorno ao declive, comparada ao solo sem cultivo e descoberto

Soil and water loss data from rainfall erosion studies are fundamental for the planning of soil conservation. Despite the implantation of no-tillage systems, introduced in the 1970s, conservation practices, e.g., contour cropping and terracing, are still required for an effective control of rainfall erosion, especially in areas with high rainfall amounts. Another alternative for erosion control is the planting of cover crops for soil protection. The objective of this study was to quantify water and soil losses by rainfall erosion from a soil under no-tillage soybean and maize, sown along and perpendicularly to the slope contour lines. The experiment was conducted on an Inceptisol, in the 2010/2011 growing season, with application of four simulated rainfall tests. There were five treatments, in two replications: soybean sown perpendicularly to the contour lines (SD); soybean along the contour lines (SC); maize perpendicular to the contour lines (MD); maize along the contour lines (MC); and control - no crop and bare soil (T). The crops were planted on wheat crop residues in the no tillage system. Soybean along the contour lines was more effective in controlling soil loss than soybean perpendicular to the contour. Maize was more effective in controlling soil loss than soybean, regardless of the form of seeding, and both were more effective than the control. Water losses were only influenced by the form of sowing and negatively correlated with soil moisture before the onset of the rains and the beginning of runoff.

Cobertura do solo, produção de biomassa e acúmulo de nutrientes por plantas de cobertura

The use of cover crops is an important strategy for maintaining the productive capacity of agricultural land. This research aimed to determine the soil coverage, biomass production and accumulation of N, P, K, Ca and Mg in plant tissue of different species of cover crops on the southern plateau of Santa Catarina, Brazil. The experiment was conducted in a Humic Cambisol (Inceptisol) with the following treatments: i) BO - black oat (Avena strigosa); ii) WR - wild radish (Raphanus sativus L.); iii) CV - common vetch (Vicia sativa); iv) IS - intercropping of the three species; and v) WF - winter fallow with spontaneous vegetation. The use of cover crops has potential for high biomass production, canopy cover and nutrient accumulation by plant tissue, higher than winter fallow. In the early stage of plant development the highest growth rates and soil coverage occur in WR and IS, while at the end are higher in CV and IS. The crops of BO, CV and IS produce large amounts of dry shoot mass and BO produces greater dry root mass. In general, the CV and IS treatments and the shoot accumulate greater amounts of nutrients in plant tissue as compared to other treatments and the roots, respectively.