Quantification of the soil physical quality of a tropical oxisol using the S index

Abstract

Soil physical quality is fundamental for the sustainability of agro ecosystems. Soil physical quality assessment must be developed using parameters that describe physical behavior. S, a new soil physical parameter has recently been introduced for assessing the soil physical quality. A good soil physical quality has been associated with values of S > 0.035 in soils from temperate climates. However, S has not been evaluated in tropical soils yet. Therefore we tested the hypothesis that S is a reliable soil physical quality indicator of a Typic Hapludox cropped with maize under notillage (NT) and conventional tillage (CT). Undisturbed samples were collected from each tillage system in the row and interrow positions. Soil bulk density was determined in the samples and the S parameter was calculated using a pedotransfer function from the same samples. The parameter S was able to differentiate tillage and position with S NT < S CT independent of the row and interrow sampling positions. Higher S values were verified in row position than in the interrow in both tillage systems. With the use of a pedotransfer function it was also possible to establish a negative relationship between S and soil compaction. The results confirmed our hypothesis and suggest that further studies should be carried out to evaluate S in other tropical soils and management systems. Key words: bulk density, tropical soils, no-tillage, soil water retention, soil structure QUANTIFICAÇÃO DA QUALIDADE FÍSICA DE UM LATOSSOLO UTILIZANDO O ÍNDICE SRESUMO: A qualidade física do solo é fundamental para a sustentabilidade dos sistemas agropecuários e deve ser feita por meio de parâmetros que descrevem o comportamento físico do mesmo. O índice S é um desses novos parâmetros, proposto para quantificar a qualidade física do solo. Valores de S > 0,035 têm sido associados com uma boa qualidade física relacionada à produção agrícola nos solos desenvolvidos em clima temperado. Contudo, S não tem sido avaliado em solos tropicais. Consequentemente, a hipótese deste trabalho é que S pode ser utilizado como indicador da qualidade física de um Latossolo Vermelho distroférrico cultivado com milho em sistemas de plantio direto (PD) e de preparo convencional do solo (PC). Amostras indeformadas de solo foram obtidas em PD e PC nas posições linha e entrelinha da cultura de milho. A densidade do solo foi medida e o índice S foi calculado usando uma função de pedotransferência obtida no mesmo, em condições experimentais. O índice S diferenciou os sistemas de preparo e posições de amostragem, sendo S PD < S PC independente das posições de amostragem linha e entrelinha. Na posição linha verificou-se maiores valores de S tanto em PD como em PC. O valor de S diminuiu com o aumento da densidade do solo, indicando a redução da sua qualidade física, associada à compactação do mesmo. Os resultados confirmam a hipótese estabelecida e sugerem que mais estudos devem ser conduzidos para quantificar o índice S em diferentes solos e sistemas de manejo sob condições tropicais. Pal...

Impacts of different management systems on the physical quality of an Amazonian Oxisol

“…Adjustment equations of macroporosity (MP) and total porosity (TP) as a function of the S index in the areas under no-tillage for eight years (NT8), no-tillage for four years (NT4), conventional tillage for two years (CT2), pasture, and forest that more than 72 % of the samples of an Oxisol under conventional tillage showed values of S> 0.035, and for no-tillage 55 % of the samples. These results demonstrate the great potential of the S index to identify variations in the soil quality of different tillage systems (Tormena et al, 2008). Noventa et al (2006) reported higher S indices in no-tillage soil with oats, due to the thin and aggressive root system that creates a series of long and thin channels resulting in better functionality to the soil structure.…”

“…Oliveira et al (2000) observed an increased bulk density after 17 years of grazing, which was however not significantly correlated with forage production. However, the pasture restoration benefits the soil structure, similarly as no-till systems improve it by OM accumulation (Colet, 2006) The influence of management on soil physical quality has been studied based on a number of physical properties, e.g., bulk density, soil moisture and penetration resistance, and even combined in the Least Limiting Water Range, and more recently, in Brazil, the S index (Machado, 2006;Tormena et al, 2008). This S index has been proposed as an indicator of the soil physical and structural quality, and is based on the parameters of the water retention curve in the soil (Dexter, 2004a, b, c).…”

Seasonal changes in soil physical properties under long-term no-tillage

“…Mohanty et al (1996) showed that water infiltration rate was highest in crop rows, while da Silva et al (1997) reported soil physical differences between row and inter-row zones. Tormena et al (2008) also found better soil physical quality within crop rows. What appears to be unknown is how soil physical properties change with lateral distance from the crop row due to both the intensity of soil disturbance by furrow opening and plant root growth.…”

Sediment transport in runoff on rugous soil surface submitted to simulated rainfall

“…Management practices applied to a soil over a time period can affect some of its physical properties which can be degraded due to the use of agricultural mechanization (Tormena et al, 2008), affecting runoff velocity and water erosion (Bertol et al, 1997;Cogo et al, 1983). Thus, each management practice causes additional effects on this surface roughness, especially related to mechanical till (Zoldan Júnior et al, 2008).…”