Soil pH was measured in slurry with a soil-to-water ratio of 1:2 (10 g of soil in 20 ml deionized water) after shaking for 1 h at room temperature. Soil moisture was determined by calculating weight loss after drying 20 g fresh soil at 105°C for 24 h. Soil ammonium and nitrate were extracted with 2 M KCl by mixing 5 g fresh soil with 45 ml of KCl solution, followed by homogenization on a shaker at 50 rpm for 1 h and centrifuge at 3,000 g for 10 min. The supernatant was filtered through a 0.45 μm Nylon filter and the ammonium and nitrate concentrations were then determined colorimetrically following salicylate method (Bower et al., 1980 (link)) and VCl3-Griess method (García-Robledo et al., 2014 (link)), respectively. Total phosphorus (TP) and available phosphorus (AP) concentrations were measured using a continuous segmented flow analyzer (Auto Analyzer 3, Seal Analytical Inc., Mequon, WI, United States) following the EPA method 365.1 (Determination of Phosphorus by Semi-Automated Colorimetry, Revision 2.0). Soil organic matter (OM) content was measured by calculating loss on ignition and dissolved organic carbon (DOC) content was measured using a TOC analyzer (Shimadzu, Kyoto, Japan).
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