Physical attributes of yellow oxisol under different monocultures in the savanna of Piauí state, Brazil

Abstract

The objective of this study was to evaluate the physical attributes of an oxisol under soybean monoculture, eucalyptus monoculture, and pasture and native forest conditions at depths of 0-0.20 and 0.20-0.40 m. Disturbed and undisturbed soil samples were collected to perform physical analyses. Specific analyses included texture, soil density, macroporosity, microporosity, total porosity, aggregate stability index, weighted mean diameter, percentage of aggregates with a diameter of >2.00 mm, and soil penetration resistance (PR). The data were analyzed using the Tukey's test for the comparison of mean values and multivariate analysis. Different uses and management of the soil affected its physical attributes, resulting in the deterioration of soil quality in the soybean and pasture areas. Soil management systems in pasture and soybean areas also resulted in higher soil density and lower soil porosity. The eucalyptus monoculture showed soil aggregation equal to that of the native forest. There was a sharp increase in soil PR beyond the 0.15-m deep layer in the pasture and soybean management systems. Multivariate analysis identified variables that correlated with each type of soil management and the effects of changes in soil characteristics.

Impact of Converting Areas Cultivated With Sugarcane to Eucalypt Plantations on Soil Quality in Northeastern Brazil

“…Furthermore, the quality of organic residues also contributes to this behavior, since woody residues, such as litter, have higher concentration of phenols, cellulose and lignin; their decomposition supplies more nutrients to soil and to microorganisms (Barreto et al, 2014;Cook et al, 2016). These factors result in maintenance of uniform soil temperature and moisture overtime, which promotes a better development of root system and microorganism activity as well as a reduction of SOM mineralization in eucalypt forests (Rodrigues et al, 2013;Ibiapina et al, 2014). In this context, our results show that a correct management in eucalypt cultivation reduces BD and promotes a recovery of SOC, TN and biological parameters of soil, pointing to the great potential of planted forests in the sequestration of SOC (Table 1 and Figure 2).…”

“…The BD reduction and the increase of soil aggregates (MWD, GMD and ASI) found in E3 and E6 areas (Table 1) show that, despite the previous cultivation with sugarcane, over 3 years without intense anthropic actions, such as plowing and traffi c of machinery, as well as organic residues input on soil surface due to the growth and development of trees (Barreto et al, 2014;Zhang et al, 2019), are enough to improve physical quality of soil and, consequently, other properties, resulting in recovery of its structure (Rodrigues et al, 2013;Ibiapina et al, 2014).…”

“…These results are extremely important to the environment because eucalypt areas that show high aggregate stability are benefi ted, resulting in the recovery of the physical properties of soil, such as porosity, high infi ltration, and water retention, being resistant to soil erosion, which contributes to physical and chemical protection of SOM (Barreto et al, 2014;Ibiapina et al, 2014;Zhang et al, 2019). Our results are in accordance with those reported by Vicente et al (2019), since they found larger microaggregates (2000-250 μm) in eucalypt (Eucalyptus spp.)…”

“…During the recovery of soil properties, a substantial increase occurred in the physical, chemical and biological parameters in eucalypt cultivated areas (E3 and E6), which is justifi ed by several factors, for example, the continuous input of plant residues to the surface layer, the microclimate formed by the trees, which reduces direct contact of the solar rays, and the impact of rain on soil (Ibiapina et al, 2014;Zhang et al, 2019). Furthermore, the quality of organic residues also contributes to this behavior, since woody residues, such as litter, have higher concentration of phenols, cellulose and lignin; their decomposition supplies more nutrients to soil and to microorganisms (Barreto et al, 2014;Cook et al, 2016).…”

“…In order to evaluate the distribution of waterstable aggregates in soils, the method proposed by EMBRAPA (1997) was adopted, which uses the following diameter classes: 4.76-2.0 mm, 2.0-1.0 mm, 1.0-0.50 mm, 0.50-0.25 mm and <0.25mm. Data of dry mass were used to calculate weighted mean diameter (MWD), geometric mean diameter (GMD) and aggregate stability index (ASI), according to methodology proposed by Ibiapina et al (2014).…”