Short term changes on soil physical quality after different pasture renovation methods on a clayey oxidic Red Latosol

Abstract

Most of Brazilian agricultural land is occupied by pastures, which often show some degree of degradation. Grazing is usually associated to damages on soil structure because of soil compaction. The aim of this work was to evaluate short term changes on soil physical quality following different pasture renovation methods, including fertilization (FERT), conventional soil tillage (TILL) and two crop-livestock system (no-till and conventional tillage, respectively COTI and CONT), on a very clayey Red Latosol (Ustox), also comparing these to the original pasture and a nearby forest fragment. Bulk density and macroporosity were significantly different on the pasture sites (averaging 1.12 g cm -3 and 0.16 cm 3 cm -3 respectively) from that under the forest fragment (respectively 0.87 g cm -3 and 0.34 cm 3 cm -3 ); however, significant differences between the renovation methods and the original pasture were not observed. The load bearing capacity model (LBCM), which relates decrease on soil precompression stress (σ p ) with increase on water content (U), obtained for the original pasture, ORIG (σ p = 10 ), with the former being more resistant to compaction. When the ordinate pairs (U, σ p ) obtained from soil cores collected on the different renovation methods experimental plots were plotted on the LBCM from ORIG, an increase on soil strength could be noticed, but with small differences between renovation methods. This was because of higher stocking rates on FERT and TILL and corn harvest for silage production on COTI and CONT. Tillage failed to improve soil physical quality even on the short turn (only one growing season) and should be disregarded as a renovation method for pastures on initial stages of degradation, while soil fertility is the main limitation.Key words: load bearing capacity, precompression stress, soil compaction Alterações na qualidade física do solo no curto prazo após diferentes métodos de renovação de pastagens em um Latossolo Vermelho argiloso oxídico RESUMOAs pastagens ocupam a maior porção das terras agrícolas do Brasil e frequentemente apresentam algum grau de degradação. O pastejo animal geralmente está associado a danos à estrutura do solo, devido à compactação. O objetivo deste trabalho foi avaliar as mudanças no curto prazo na qualidade física de um Latossolo Vermelho muito argiloso, após diferentes métodos de renovação de pastagens, incluindo adubação (FERT), preparo convencional (TILL) e interação lavoura-pecuária (com preparo convencional do solo e em plantio direto, COTI e CONT respectivamente), comparando estes à pastagem original e a um fragmento de mata próximo. A densidade do solo e a macroporosidade nas áreas de pastagem (respectivamente 1,12 g cme 0,16 cm 3 cm -3 ) foram significativamente diferentes em comparação ao solo sob mata (respectivamente 0,87 g.cm -3 e 0,34); contudo, diferenças significativas entre os métodos de renovação e a pastagem original não foram observadas. O modelo de capacidade de suporte de carga (MCSC), que relaciona o decréscimo na pressão de pré-c...

Compressibility of a Cambisol Submitted to Periods of Rotational Grazing and Strategies to Avoid Additional Soil Compaction

“…Based on Pimentel-Gomes and Garcia [49], the coefficient of variation was high (between 20 and 30%) and very high (larger than 30%) for two-times grazing and low (smaller than 10%) and medium (between 10 and 20%) for three-times grazing (Table 2). Soil moisture is an important variable in the compaction process and soil compression behavior [23,24,[27][28][29][30][31], because it acts as a lubricant for solid particles, belonging to the easier rearrangement of soil particles [26,50], suggesting that controlling soil moisture is a key factor in mechanized operations and animal trampling [24,51] to avoid additional compaction and maintain the soil structure.…”

“…From the knowledge of the precompression stress and compression index, and their existing relationship with moisture and bulk density [23,24,[26][27][28][29][30][31], the soil and the traffic of machinery and animals trampling can be managed in order to avoid additional compaction. Soil bulk density is a good indicator of compaction [8], and some authors have verified a relationship between precompression stress and/or compression index with bulk density [23,24,26,29,32,33].…”

“…Despite studies solving soil compaction through tillage, such as chiseling, it is a costly operation, and the compaction returns after some period according to soil management [9,40]. In addition, the soil tillage exposes the topsoil to erosion [27]. Therefore, the best strategy is to prevent additional soil compaction through knowledge of precompression stress and monitoring soil moisture to define the most adequate moment for traffic of machinery and animal trampling.…”

Load-bearing capacity and critical water content of the coffee plantation soil with management in full sun and shaded

“…Load-bearing capacity is important in studies of soil compaction, sustainability of productive systems, evaluation of different agricultural management systems and traffic of machines and animals. In this regard, Tassinari et al (2015), Watanabe et al (2017) and Sousa et al (2019) are some examples of the soil LBC theory applied in agriculture. The capacity of a soil to support load depends on several factors, such as the drying and wetting processes of the soil, texture and mineralogy, soil bulk density, use and management adopted in the agricultural area, structure and soil water content, being these last two parameters of great contribution (Dias Junior et al, 2019).…”