Abstract
ABSTRACT Soils in semi-arid regions have been degraded by overgrazing, which reduces the production capacity and, in certain situations, leads to desertification. An alternative to recover degraded areas is the fallow period, which works through the resilience of the soil itself, increasing the supply of organic matter and improving soil physical properties. Thus, the objective of this study was to test the hypothesis that 14-year grazing exclusion improves soil physical and chemical attributes in degraded areas under desertification. The study was conducted in Iraucuba, Ceara State, Brazil. The experimental design was completely randomized, in a 4 x 2 factorial scheme corresponding to four areas and two managements (overgrazing and fallow), with four replicates, plus an area with native vegetation (reference), with characteristics of secondary vegetation. Fallow led to improvements in soil physical and chemical attributes after 14 years; however, in comparison to the study conducted in the same area with a 7-year fallow period, there were few alterations. Organic carbon content was higher in fallow areas than in overgrazing areas, and the fraction in highest proportion was the mineral-associated organic carbon.
Highlights
Regions with arid and semi-arid climate are less tolerant to anthropic changes, being more prone to desertification
This study aimed to assess degraded areas under desertification after 14 years of fallow, in the municipality of Irauçuba, in order to evaluate the consequences through soil physical and chemical analyses, comparing areas under fallow and overgrazing
Interaction occurred for Ds and total porosity (TP), whereas particle density (PD) and degree of flocculation (DF) showed individual responses to the treatment factors (Table 3)
Summary
Regions with arid and semi-arid climate are less tolerant to anthropic changes, being more prone to desertification. Land use intensification, associated with deforestation, overgrazing and fire, exposes the soil to inclement weather, causing reduction of its quality (JÓRDAN; ZAVALA; GIL, 2010). Such reduction in quality results from effects on chemical, physical and biological attributes (WENDLING et al, 2010), decreasing the productive potential and increasing CO2 emission to the atmosphere (BRUUN et al, 2015). In addition to the natural problems and type of soil, this region faces problems such as deforestation, overgrazing and poor management of water resources Among these problems, overgrazing is the main responsible for desertification, due to the presence of animals, which compact the soil by grazing and consume vegetation, leading to losses of soil cover, with subsequent water runoff and losses of soil and nutrients through erosion (REYNOLDS et al, 2007). Overgrazing occurs in situations of plant exposure to intensive grazing for prolonged periods, or without sufficient periods to allow environmental recovery
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