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DOI:10.13522/j.cnki.ggps.2019317
The Resistance of Purple Soil Against Erosion Depends on Straw Removal Rate in the Hilly Regions in Southwest China
REN Tao1, HE Yuxin2*, ZHANG Peng1, LIU Chao2, LI Naiwen2, TAN Xiao2,REN Tao1, HE Yuxin2*, ZHANG Peng1, LIU Chao2, LI Naiwen2, TAN Xiao2,REN Tao1, HE Yuxin2*, ZHANG Peng1, LIU Chao2, LI Naiwen2, TAN Xiao2,REN Tao1, HE Yuxin2*, ZHANG Peng1, LIU Chao2, LI Naiwen2, TAN Xiao2,REN Tao1, HE Yuxin2*, ZHANG Peng1, LIU Chao2, LI Naiwen2, TAN Xiao2,REN Tao1, HE Yuxin2*, ZHANG Peng1, LIU Chao2, LI Naiwen2, TAN Xiao2
1.College of Water Resources and Hydropower Engineering, Sichuan University, Chengdu 610065, China; 2.State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
Abstract:
【Background】The hilly areas in mountainous region in southwest China are a unique terrain, the soil in which is dominated by purple soil. Over the past decades these areas have suffered serious water and soil losses due to erosion. Crop straw is a byproduct of agricultural production. It can provide nutrients the crops needs, but could also cause environmental pollution and soil degradation if managed badly. Improving straw management is hence essential to develop sustainable agriculture.【Objective】The overarching objective of this paper is to investigate the effect of straw removal after harvest on resistance of the purple soil against erosion in these hilly areas.【Method】 The field experiment was conducted at Jianyang city in Sichuan province. We measured five soil parameters in the experiment: soil moisture, dry volumetric soil mass, mass fraction, geometric mean diameter of water-stable aggregates, and saturated hydraulic conductivity, to represent the resistance of the soil against erosion. We compared five straw removal rates: 100%, 75%, 50%, 25% and 0%; the straws of winter rape and summer maize were removed during the planting time.【Result】The soil moisture content in the top 0~10 cm soil layer varied with the straw removal rate, peaking when the removal rate was 25%. The dry volumetric soil mass decreased as time elapsed. The ultimate decrease for the five removal rates was 5.5%, 4.6%, 2.1%, -5.2% and 0.4% in the top 0~5 cm soil, and 0.4%, 2.4%, 5.0%, 4.2%, 0.8% and 5.4% in the 5~10 cm soil, respectively. The mass fraction of the water-stable aggregates was highest when the removal rate was 25%, being 76.5%, 81.2%, 74.6% and 76.8% at the four sampling time points. When the removal rate was 75%, 50% or 25%, the average geometric diameter of the aggregates increased monotonically with time. When the removal rate was 100%, the average geometric diameter of the aggregates at three sampling time points increased by 31.2%, 14.7% and -42.0%, respectively, compared to the control. When the removal rate was 0%, the saturated hydraulic conductivity of the soil was 61.1mm/min, differing significantly from other removal rates.【Conclusion】Removing 25% of crop straws improved resistance of the soil against erosion in the hilly areas. It also increased soil aggregation and hydraulic conductivity, while in the meantime reduced soil crusting thereby increasing water infiltration and soil moisture. Removing 100% of straws made the soil susceptible to erosion and degradation. The results presented in this paper are helpful for understanding the impact of straw management on resistance of soil against water and soil erosion in hilly areas in southwest China.
Key words:  southwest hilly region; purple soil; straw removal; soil; sustainable development