2. Soil characteristics
Soil characteristics were collected at the depts of 0–10, 10–30, 30–50, and 50–80 cm before started the research experiment. Soil samples were classified the types and analysed the properties included sand-silt-clay ratio, organic matter and carbon, total nitrogen (total N), total phosphorus (total P), available potassium (available K), available sulphur (available S), available zinc (available Zn), available boron (available B), field capacity, cation exchange capacity (CEC), electrical conductivity (EC), and soil pH.