Abstract
Abstract The objective of this work was to evaluate the physical quality of an Oxisol under no-tillage subjected to different crop rotations and crop sequences. The experiment was carried out in a clayey Oxisol, during six years, in a randomized complete block design, with strip plots and three replicates. The following physical indicators of soil quality were evaluated: soil density and carbon content, as well as mean weight diameter and tensile strength of aggregates. Treatments consisted of three summer crop rotations - corn/corn (Zea mays), soybean/soybean (Glycine max), and soybean/corn - and of seven second crops (crop sequences) - corn, sunflower (Helianthus annuus), oilseed radish (Raphanus sativus), pearl millet (Pennisetum americanum), pigeon pea (Cajanus cajan), grain sorghum (Sorghum bicolor), and sun hemp (Crotalaria juncea). Crop rotations and sequences did not affect soil carbon contents. Corn, as a summer crop, increased the tensile strength and mean weight diameter of aggregates, similarly to pearl millet and sorghum as second crops. Soybean/corn rotation with sun hemp as a second crop increases soil physical quality, promoting higher tensile strengths and lower soil densities.
Highlights
Soil physical quality is strictly related with its organic carbon content, and reductions in this attribute often decrease crop productivity and enhance soil vulnerability to physical degradation.No-tillage systems can potentially reverse soil degradation in tropical regions and, with the intensification and proper use of crop sequences, it can increase soil organic carbon (SOC)
Information on which cropping system can promote more benefits to soil physical quality in tropical regions is still needed for a better adjustment to environmental specificities
Calonego & Rosolem (2008) reported that the variation in SOC must be considered in discussions on how crop sequences can increase soil quality, even when differences are not significant
Summary
No-tillage systems can potentially reverse soil degradation in tropical regions and, with the intensification and proper use of crop sequences, it can increase soil organic carbon (SOC). Physical quality of an oxisol under no-tillage subjected to different cropping systems lead to soil aggregation, reduced soil density, and greater least limiting water range (Seben Junior et al, 2014). Crop sequence arrangements with greater species diversity, for example, can improve SOC by 1.30 Mg ha-1 per year (Sá et al, 2013), increase biopores and the tensile strength of soil aggregates (Tormena et al, 2008), improve aggregate size (Martins et al, 2009), decrease soil density, and increase macro- and total porosity (Spera et al, 2009). Information on which cropping system can promote more benefits to soil physical quality in tropical regions is still needed for a better adjustment to environmental specificities
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