Renato Levien

Managing grazing animals to achieve nutrient cycling and soil improvement in no-till integrated systems

Crop-livestock systems are regaining their importance as an alternative to unsustainable intensive farming systems. Loss of biodiversity, nutrient pollution and habitat fragmentation are a few of many concerns recently reported with modern agriculture. Integrating crops and pastures in no-till systems can result in better environmental services, since conservation agriculture is improved by system diversity, paths of nutrient flux, and other processes common in nature. The presence of large herbivores can positively modify nutrient pathways and soil aggregation, increasing soil quality. Despite the low diversity involved, the integration of crops and pastures enhances nature’s biomimicry and allows attainment of a higher system organization level. This paper illustrates these benefits focusing on the use of grazing animals integrated with crops under no-tillage systems characteristic of southern Brazil.

Erosão hídrica em diferentes preparos do solo logo após as colheitas de milho e trigo, na presença e na ausência dos resíduos culturais

A rotating-boom rainfall simulator, operating at a constant rainfall intensity of 64 mm h-1 for sufficient time to runoff reaches steady-rate, was used to investigate water erosion and other related parameters in three tillage systems. The experiments were carried out immediately following corn and wheat harvesting, in a sandy loam Red-Yellow Podzolic soil (Paleudult) with a 0.066 m m-1 average slope, in Eldorado do Sul, State of Rio Grande do Sul, Brazil, from 1992 to 1994. No-tillage, chiselling and disk-plowing followed by disking, were studied in the presence and absence of fresh crop residues. Results showed that no-tillage and disk plowing followed by disking, combined with residues maintained on the surface, reduced soil losses more efficiently than when the residues were removed. No-tillage, with residues maintained, was the most efficient system to control erosion, while disk plowing followed by disking, without residues, was the least efficient. Water losses followed the same tendency of soil losses, although being less affected by the treatments.

Evolução de atributos físicos de solo em sistema de integração lavoura-pecuária

The objective of this work was to assess the effect of sward height and successive grazing cycles over soil physical attributes in an integrated crop-livestock system. The experiment was established in 2001, in the Planalto Medio region, RS, Brazil, in a Rhodic Hapludox (Oxisol), with annual ryegrass (Lolium multiflorum) intercropped with black oat (Avena strigosa), under continuous grazing, during the winter, and single cropped soybean (Glycine max) during the summer. The treatments consisted of different grazing intensities, determined by sward height (10, 20, 30, and 40 cm), and a no-grazing area was used as a control. Soil bulk density and soil porosity were evaluated at the end of the grazing and soybean cycles, as well as soil resistance to mechanic penetration and aggregate stability in the seventh year of the experiment. No significant differences were found on soil bulk density and soil porosity after seven years under crop-livestock integration. Soil resistance to penetration is higher on the superficial layer after the grazing cycle. Soil aggregation increases in grazing areas, regardless of grazing intensities.

Demanda de tração em haste sulcadora na integração lavoura-pecuária com diferentes pressões de pastejo e sua relação com o estado de compactação do solo

An experiment was carried out with crop and cattle rotation in an Oxisoil, in Tupancireta - RS, which aimed to evaluate the draft effort in fertilizer direct drillings used in direct seeding, working at different depths and intensities of fields under different grazing pressures. Grazing pressure effects on soil compactness were also assessed. The main treatments were grazing maintaining 0.10, 0.20, 0.30, 0.40 m pasture (Lolium multiflorum + Avena strigosa) without grazing, height (adjusting the number of cows on the plots) and two working depths of fertilizer shanks: 0.12 m and 0.15 m. Root dry matter in the superficial layer (0.0 - 0.12 m) was increased when higher grazing pressures were used. Soil resistance to a penetrometer showed increased values at higher grazing pressures; it was detected until 0.12 m depth. Draft requirement of fertilizer shanks increased from 1,900 to 4,300 N (120%) when the working depth changed from 0.12 m to 0.15 m condition. Draft demand by fertilizer shanks was higher on soils under higher pressures as well, but the absolute values showed that only treatments with remaining heights of 0.10 and 0.20 m were different from those found without grazing systems. Soil resistance to penetrometer and power demand by fertilizer shanks was closely related.

PERDAS DE NUTRIENTES POR EROSÃO EM DIFERENTES MÉTODOS DE MELHORAMENTO DE PASTAGEM NATIVA NO RIO GRANDE DO SUL

Growth stagnation on native grassland during the winter season has stimulated the introduction of winter species in order to increase forage offer for animals in the State of Rio Grande do Sul, Brazil. To determine the nutrient losses by erosion as affected by different methods of native grassland improvement, an experiment was carried out at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul. A mixture of the winter forage species black oat, Italian ryegrass and arrowleaf clover was introduced on a Paleudult soil under long time native grassland use. Experimental plots of 3,5 by 11,0 m at 0.107 m m-1 of average slope were submitted to simulated rainfall of 64 mm h-1 average intensity and 75 minutes of duration in three different runs: 55 days after soil tillage and sowing; 125 days after soil tillage and sowing (right after the first grazing); and 175 days after soil tillage and sowing (right after the second grazing). The experimental design was completely randomized with five treatments for the introduction of winter species: Zero tillage (Control), No-tillage, Disking; Sub-soiling, and Conventional tillage. During each rainfall, runoff samples were collected every 15 minutes, and the available phosphorus, calcium, magnesium and potassium nutrient concentrations were determined by the extraction method of ionic exchange resin. There was a difference between the rain application runs and the treatments in relation to the nutrient concentrations and losses in the runoff. Highest losses occurred in the first run. In general, highest nutrient losses occurred in the Control treatment and lowest in Conventional tillage. These nutrient losses were not directly related with soil and water losses, but determined by soil surface conditions as well as fertilizer and lime application methods.

Força de tração e volume de solo mobilizado por haste sulcadora em semeadura direta sobre campo nativo, em função do teor de água no solo, profundidade e velocidade de operação

Direct drilling or no tillage systems are among the most successful agricultural alternatives regarding soil and water conservation, energy economy and operational capacity of machinery. Some areas where cattle raising and grain production share the same grounds, or where soils are trafficked in moist conditions they may show compaction of the upper layers. Compacted soil areas may not need to be chiseled or plowed, if seed germination and good growing standards are reached by the initial soil conditioning solely by planters coulters. The specific aims of the present work are to determine the knowledge of coulter draft requirements and the amount of displaced soil and tractor slippage on a Paleudult soil at different soil moisture condition, in direct planting on natural pastures chemically killed. Draft requirements increased with an increase in working depth. The increase of the ground speed had no effect on draft when soil was dry or moist; it increased however, on friable soil. Soil displacement was always higher with dry soil and at 12 cm working depth. When soil was friable or dry, the front wheels traction was needed to keep tractor slippage within acceptable levels.

Sistemas de preparo de solo: alterações na estrutura do solo e rendimento das culturas

A introducao e intensificacao no uso do sistema de semeadura direta no Brasil nas ultimas decadas desenharam um novo cenario na agricultura brasileira, aumentando a preocupacao com as caracteristicas fisicas dos solos. O objetivo deste trabalho foi avaliar a implicacao que diferentes sistemas de preparo de solo impoem sobre algumas caracteristicas fisicas de um Argissolo Vermelho inicialmente sob uso com campo natural. Cinco metodos de preparo de solo foram ensaiados: semeadura direta (SD), escarificacao (E), semeadura direta com escarificacao a cada dois anos (SDE2), escarificacao com escarificador munido de rolo destorroador (ER) e escarificacao seguida de gradagem (EG). Foram avaliados: densidade do solo, macroporosidade, microporosidade e porosidade total, resistencia mecânica do solo a penetracao, infiltracao de agua no solo e rendimento das culturas. Os valores de densidade do solo, resistencia mecânica do solo a penetracao e microporosidade aumentaram em detrimento da diminuicao da macroporosidade. A densidade do solo foi menor nos sistemas de preparo com maior grau de mobilizacao do solo, sendo os maiores valores observados para o sistema SD e os menores para o sistema EG. A taxa de infiltracao de agua apresentou-se maior no sistema ER, seguido pelos sistemas EG, SD e SDE2, ao passo que o rendimento das culturas foi maior nos sistemas com menor mobilizacao de solo.

Força de tração e mobilização do solo por hastes sulcadoras de semadoras-adubadoras

No tillage implies keeping the soil surface covered with crops or crop residues, which might influence planter performance. Using fixed shanks as furrow openers to place fertiliser is an alternative to minimize compaction, as it mobilizes the soil in the sowing line. The aim of this research was to evaluate the effect of different amounts of winter cover crop residues evenly distributed on the soil, the effect of the shanks working depth and quantity of planter lines on power demand, cross sectional furrow area and total volume of soil mobilized in the lines and corresponding wheel slippage in distrophic red Argisol. During winter, black oats and black oats plus turnip were used as cover crops before maize and beans, respectively. Increasing the working depth showed an increase in power demand, as measured directly at the shanks (three lines for maize and five for beans). There was also an effect of residue, increasing power demand on the shanks, but only measurable with the planter operating with three lines in maize sowing. Soil mobilization in the sowing lines was influenced by the amount of residues, the working depths of shank and the quantity of planter lines. Wheel slippage was higher with larger amounts of soil cover residues and when power demand was higher.

Densidade, agregação e frações de carbono de um Argissolo sob pastagem natural submetida a níveis de ofertas de forragem por longo tempo

The adjustment of animal quantity according to the herbage allowance is fundamental to the sustainability of natural pastures. The management of herbage allowance, besides affecting the plant species that compose the pasture, can also compromise soil properties, such as density and aggregation. This study aimed to evaluate the soil bulk density, weighted mean diameter of soil aggregates and carbon fractions under natural pasture, under varying grazing intensities for 22 years, represented by herbage allowance levels of 4, 8, 12, and 16 kg dry matter per 100 kg animal weight. Two ungrazed areas were included as references. Changes in soil properties were found, related to the grazing intensity. These changes occurred mainly in the soil surface layer (0-10 cm), where soil density increased with decreasing herbage allowance. The behavior of the weighted mean diameter of soil aggregates and the root mass in the layer 0 - 10 cm were inversely proportional to the herbage allowance. The carbon storage index indicated that under forage supplies of 12 % the soil C stock increased compared to the control, but decreased at other allowance rates. The index of carbon management shows that the highest herbage allowance (12 and 16 %) improved the system quality of natural pasture, while at the lowest allowance rate (4 %) the system lost quality and sustainability, as demonstrated by the substantial reduction of this index.

Produtividade de soja e milho após coberturas de inverno e descompactação mecânica do solo

The objective of this work was to evaluate the effect of soil winter covers and soil mechanical loosening on soybean and corn yield, in no-tillage system. Two experiments were carried oud in Rio Grande do Sul state, Brazil, in a compacted Argissolo Vermelho (Haplic Acrisol), in the 2005/2006 and 2006/2007 crop seasons. The first experiment was carried out in a complete block design, with a split plot arrangement. The treatments were two theoretical working depths of a driller chisel-type furrow opener (0.06 and 0.12 m, split plot), and three soil winter covers (main plot): fallow, black oat (Avena strigosa), and black oat+common vetch (Vicia sativa). In 2006, the soil cover black oat+common vetch was replaced by oilseed radish (Raphanus sativus). In the second experiment, in a complete block design, the soil was chiseled and treatments consisted of black oat or oilseed radish as winter cover crops. Cover crops reduced soil superficial (0-0,06 m) compaction compared to fallow and, in the 2005/2006-crop season, under low water availability, provided higher soybean and corn yields. In the 2006/2007-crop season, when water availability was higher, the same did not happen. Increasing working depths of the chisel-type furrow opener did not affect soybean or corn yields. Soil chiseling reduced soybean and corn yields in comparison to the continuous no-tillage system.