2.3 Soil water content and nutrient analysis
The soil subsamples were weighed and oven-dried at 105°C for 24 h to a constant weight for soil water determination. Soil N was determined by the modified semi-micro-Kjeldahl method (Liao, 1981) and soil P was determined by NaOH digestion followed by quantification using colorimetry (Smith and Bain, 1982). The SOC was quantified using a modified Walkley-Black chromic acid wet oxidation method (Wang et al., 2012) and the soil K concentration was determined by the atomic absorption method (Bao, 2000).