[Effects of Four Amendments on Cadmium Bioavailability and Enzyme Activity in Purple Soil].

In this study, the effects of four types of amendments on effective Cd and Cd content in different parts of prickly ash soil and soil enzyme activity were studied, which provided scientific basis for acidification improvement of purple soil and heavy metal pollution control. A field experiment was conducted. Six treatments were set up:no fertilizer (CK), only chemical fertilizer (F), lime + chemical fertilizer (SF), organic fertilizer + chemical fertilizer (OM), biochar + chemical fertilizer (BF), and vinasse biomass ash + chemical fertilizer (JZ). Soil pH; available Cd (DTPA-Cd); Cd content in branches, leaves, shells, and seeds of Zanthoxylum; as well as the activities of catalase (S-CAT), acid phosphatase (S-ACP), and urease (S-UE) in different treatments were studied, and their relationships were clarified. The results showed following:① The two treatments of vinasse biomass ash + chemical fertilizer and lime + chemical fertilizer significantly increased soil pH (P < 0.05) to 3.39 and 2.25 units higher than that in the control, respectively. Compared with that in the control treatment, the content of available Cd in soil under vinasse biomass ash + chemical fertilizer and lime + chemical fertilizer treatment decreased by 28.91 % and 20.90 %, respectively. ② The contents of Cd in leaves, shells, and seeds of Zanthoxylum were decreased by 31.33 %, 30.24 %, and 34.01 %, respectively. The Cd enrichment ability of different parts of Zanthoxylum was different, with the specific performances being leaves > branches > seeds > shells. Compared with that of the control, the enrichment coefficient of each part of Zanthoxylum treated with vinasse biomass ash + chemical fertilizer decreased significantly(P < 0.05)by 27.54 %-40.0 %. ③ The changes in catalase and urease activities in soil treated with amendments were similar. Compared with those in the control group, the above two enzyme activities were significantly increased by 191.26 % and 199.50 %, respectively, whereas the acid phosphatase activities were decreased by 16.45 %. Correlation analysis showed that soil available Cd content was significantly negatively correlated with soil pH value(P < 0.01), S-CAT and S-UE enzyme activities were significantly positively correlated with soil pH(P < 0.01), and the soil available Cd content was significantly negatively correlated (P < 0.01); the S-ACP enzyme showed the complete opposite trends. The application of lime and vinasse biomass ash to acidic purple soil had the most significant effect on neutralizing soil acidity. It was an effective measure to improve acidic purple soil and prevent heavy metal pollution by reducing the effective Cd content in soil and improving the soil environment while inhibiting the absorption and transfer of Cd in various parts of Zanthoxylum.

[Effects of Four Amendments on Fertility and Labile Organic Carbon Fractions of Acid Purple Soil].

The aim of this study was to explore the effects of four amendments on soil fertility and labile carbon fraction characteristics of acid purple soil, so as to provide scientific basis for nutrient management and carbon storage stability in purple soil. Field experiments were carried out, and six treatments were set up:no fertilization (CK), only chemical fertilizer (F), lime + chemical fertilizer (SF), organic fertilizer + chemical fertilizer (OM), biochar + chemical fertilizer (BF), and vinasse biomass ash + chemical fertilizer (JZ). The contents of soil organic matter, pH, available nutrients, soil integrated fertility index (IFI), dissolved organic carbon (DOC), microbial biomass carbon (MBC), particulate organic carbon (POC), their effective rates, and soil carbon pool management index (CPMI) under different treatments were studied to clarify their relationships. The results showed that:① the application of amendments significantly increased soil pH and the contents of organic matter, alkali-hydrolyzed nitrogen, available phosphorus, and available potassium (P<0.05). The OM and JZ treatments had the most significant increase in soil comprehensive fertility index (P<0.05), with increases of 1.96 and 0.77 and 170.43% and 66.96%, respectively. ② Compared with those in the control treatment, the contents of POC, MBC, and DOC in JZ and OM increased by 110.30% and 84.81%, 61.08% and 46.56%, and 195.87% and 141.67%, respectively. The application of amendments significantly increased the soil carbon pool index (CPI) and CMPI (P<0.05), in which the OM treatment showed the most significant increase, with soil CPI and CMPI values increasing by 107.34% and 90.75% compared with those of the control, respectively. ③ Soil organic carbon and its labile fractions were positively correlated with IFI (P<0.05), and redundancy analysis showed that there were significant differences among different treatments. The interpretation rates of soil IFI, pH, and available potassium to organic carbon and its components reached significant levels, and the order of interpretation rates was IFI(74.6%)>pH (11.7%)>AK(6.5%). The application of vinasse biomass ash and organic fertilizer to acid purple soil had the most significant effect on improving soil fertility and soil quality and was conducive to promoting the accumulation and activation of soil carbon fractions.