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Study on appropriate straw mulching application rate on sloping farmland in karst area of Southwest China based on soil and water conservation function

ABSTRACT To systematically study the soil and water conservation functions of different straw mulching application rates on sloping farmland in karst area of Southwest China, the observation of runoff plots was carried out with natural rainfall. The effects of six mulching gradients (0, 1.111, 2.222, 3.889, 5.556, 6.944 Mg ha−1) on soil and water conservation functions (soil moisture, nutrients, runoff and sediment yields) were showed: with an increasing straw mulching, total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), soil moisture and available nutrients increased, and high straw mulching (SM4 and SM5) made them significantly higher than control, but there was no significant difference between SM4 and SM5; the contents of soil moisture, TOC, TN, TP and available nutrients of mulching treatments in 2019 except for total potassium (TK) were higher than those in 2018; with an increasing straw mulching, the runoff and sediment yields decreased exponentially, while the straw mulching reached 5.556–6.944 Mg ha−1, it didn’t change significantly. These results suggested that straw mulching about 6 Mg ha−1 should be adopted for sloping farmland in karst area of Southwest China, and appropriate K fertilizer should be added to maintain the balance of K in soil.