Abstract
Soil erosion is one of the chief causes of agricultural land degradation. Practices of conservation agriculture, such as no-tillage and cover crops, are the key strategies of soil erosion control. In a long-term experiment on a Typic Paleudalf, we evaluated the temporal changes of soil loss and water runoff rates promoted by the transition from conventional to no-tillage systems in the treatments: bare soil (BS); grassland (GL); winter fallow (WF); intercrop maize and velvet bean (M+VB); intercrop maize and jack bean (M+JB); forage radish as winter cover crop (FR); and winter cover crop consortium ryegrass - common vetch (RG+CV). Intensive soil tillage induced higher soil losses and water runoff rates; these effects persisted for up to three years after the adoption of no-tillage. The planting of cover crops resulted in a faster decrease of soil and water loss rates in the first years after conversion from conventional to no-tillage than to winter fallow. The association of no-tillage with cover crops promoted progressive soil stabilization; after three years, soil losses were similar and water runoff was lower than from grassland soil. In the treatments of cropping systems with cover crops, soil losses were reduced by 99.7 and 66.7 %, compared to bare soil and winter fallow, while the water losses were reduced by 96.8 and 71.8 % in relation to the same treatments, respectively.
Highlights
Soil erosion is the main cause of land degradation (Eswaran et al, 2001; Lal, 2001) and one of the major environmental and food security threats mankind is facing (Pimentel, 2006)
(4) The periods in treatments bare soil (BS) and maize and velvet bean (M+VB) were not compared since no significant changes in water runoff rate over years were detected by regression analysis (Figure 2)
Means followed by the same uppercase letter for the same period are not different by the LS means test (p0.05) in the comparison among periods at the same treatment; NS not significant by the F test (p>0.05) in the comparison of the treatments WF, M+VB, M+JB, FR, RG+CV, and GL for the same period
Summary
Soil erosion is the main cause of land degradation (Eswaran et al, 2001; Lal, 2001) and one of the major environmental and food security threats mankind is facing (Pimentel, 2006). The increasing food demand of the growing world population will require an additional 1 billion hectares of agricultural lands by 2050 (Tilman et al, 2001). This process increases the pressure on agriculture soils to ensure food security and water quality and to meet emerging environmental demands, as for renewable energy production and mitigation of climate change (Lal, 2007). The introduction of no-tillage (NT) systems in crop and residue management is a key strategy for reducing soil erosion and water runoff in agriculture (Schuller et al, 2007)
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