Abstract
Purple soil is widely distributed in the hilly areas of the Sichuan basin, southwest China, and is highly susceptible to water erosion. The triggering of this process is related to slope, rainfall intensity and surface cover. Therefore, this study assesses the effects of different simulated rainfall intensities with different slopes on hydrological and erosional processes in un-mulched and mulched purple soils. Results show that the sediment and water losses increased with an increase of rainfall intensity and slope steepness. Generally, the slope contribution (Sc) on water and sediment losses decreased with increasing rainfall intensity and slope steepness under both un-mulched and mulched soil. In un-mulched conditions, water losses were independent of slope steepness (Sc < 50%) during the highest rainfall intensity. However, in mulched soil, the higher contributions of slope (Sc) and rainfall (Rc) were found for water and sediment losses, respectively, i.e., >50%, except during the increase in slope steepness from 15° to 25° under the highest rainfall intensity (120 mm·h−1). The effectiveness of mulch was more pronounced in reducing sediment losses (81%–100%) compared with water losses (14%–100%). The conservation effectiveness of mulch both decreased and increased with slope steepness for water and sediment losses, respectively, under higher rainfall intensities. Water infiltration and recharge coefficient (RC) decreased with an increase of slope steepness, while with an increase in rainfall intensity, the water infiltration and RC were increased and decreased, respectively, in both un-mulched and mulched soil. On the other hand, mulched soil maintained a significantly (α = 0.05) higher infiltration capacity and RC compared to that of the un-mulched soil.
Highlights
Purple soil occurs widely in the hilly areas of the Sichuan basin
In un-mulched soil, the runoff was significantly affected by rainfall intensity and slope steepness i.e., runoff was increased with increasing rainfall intensity and slope steepness (Table 1)
In un‐mulched treatments for all rainfall intensities, slope was the dominant factor in sediment loss, while the runoff process was independent of slope steepness for rainfall of high intensities
Summary
Purple soil occurs widely in the hilly areas of the Sichuan basin. It is one of the valuable agricultural soil resources in China, and its inherent natural fertility and high capability makes it suitable for intensive crop production [1]. Purple soil is highly susceptible to accelerated erosion, Water 2016, 8, 528; doi:10.3390/w8110528 www.mdpi.com/journal/water. Soils of the region are vulnerable to severe erosion because of steeper slopes and frequently intense rainfall throughout the year with a soil erosion rate of 3035 Mg/km in the area [3]. Slope and rainfall intensities are important factors influencing the erosion processes [4,5]. The mobilization of soil particles during rain-splash erosion depends on rainfall intensity [6]
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