Soil urease kit

Soil total P content was measured using the sodium hydroxide melting-molybdenum antimony colorimetric method (Yang et al., 2018 (link)). Soil total C and N were milled using a ball mill (Retsch MM400; Retsch, Haan, Germany), and weighing 0.15 g of the sieved soil sample, wrapping it in the tin cup required by the instrument, and using the elemental analyzer (Vario MAX CNS, Elementar, Hanau, Germany). Soil ammonium N (NH⁴⁺-N) and nitrate N (NO³⁻-N) levels were measured after extraction using 50 mL of 2 mol/L KCl on a 10 g subsample and a potassium chloride leaching-flow-solution analyzer. Soil available P was measured using Xiao et al. (2018) (link) and Yang et al. (2018) (link). Soil urease enzyme (UE), and alkaline phosphatase activities (ALP) were examined using the Solarbio soil urease kit (Solarbio, BC0120, Beijing, China) and soil alkaline phosphatase kit (Solarbio, BC0280, Beijing, China), respectively.

To determine soil physical and chemical properties, we ground the air-dried soil samples and passed them through a 2.0 mm sieve before assessing their soil nutrient content. Soil pH was measured at a water: soil ratio of 1: 2.5. The total nitrogen (TN) was determined using the Kjeldahl method by an automatic Kjeldahl analyzer K1100F device (Jinan Hannong Instrument Company, Jinan, China; Wang et al., 2020 (link)). Soil organic matter (SOM), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and available potassium (AK) were determined according to the method described by Zhao M. et al. (2014) (link) and Wang et al. (2021) (link). Soil urease (S-UE), soil alkaline phosphatase (S-ALP), soil sucrase (S-SC), soil catalase (S-CAT), and soil polyphenol oxidase (S-PPO) activities were determined using Solarbio soil urease kit (Solarbio, BC0120), soil alkaline phosphatase kit (Solarbio, BC0280), soil sucrase kit (Solarbio, BC0240), soil catalase kit (Solarbio, BC0100) and soil polyphenol oxidase kit (Solarbio, BC0110). The above soil enzyme kits are manufactured by Solarbio (Beijing Solarbio Science & Technology Co., Ltd., Beijing, China). The specific methods and measurement procedures were carried out according to the instructions in the manual.