生物耕作对蔬菜田土壤养分及酶活性的影响

通过在上海市崇明岛西部设置的长期定位试验，探讨生物耕作对菜田土壤养分及酶活性的影响。3年结果表明，与免耕处理相比，生物耕作有助于土壤养分含量增加，其中土壤有机质、 全氮、 全磷最高增幅分别为1822%、 1745%和1332%，速效氮、 速效磷和速效钾最高增幅分别为125.0%、 432.5%和21.3%，最高值多出现在生物耕作两年和三年时，差异显著（P0.05）。同时，随生物耕作年限的增加，05 cm土层过氧化氢酶、 脲酶、 蔗糖酶和蛋白酶活性均呈增加趋势，最高增幅分别为27.78%、 951.11%、 16.11%和420.00%，分别出现在生物耕作的第三年和第二年，且差异显著（P0.05）。此系统中过氧化氢酶活性与有机质、 全磷、 速效氮、 速效磷、 速效钾和含水量等呈显著正相关，与土壤pH值呈显著负相关（P0.05）， 有机质等是土壤酶活性主要影响因子，它们单独或是综合影响酶活性; 生物耕作时间对酶活性直接影响力大小顺序为过氧化氢酶活性蔗糖酶活性脲酶活性蛋白酶活性，直接通径系数为分别为1.353、 1.070、 0.421和0.110，其主要通过有机质和速效氮正向影响酶活性。

Effects of earthworm tillage on soil nutrients and enzyme activities in vegetable fields

Long-term positioning experimental plots were carried out to study the effects of biological tillage on soil nutrients and enzyme activities of vegetable fields in west of Chongming Island, Shanghai. After three continuous years of the study, the results show that the contents of soil nutrients under the biological tillage are significantly higher than those of the no-tillage, the highest increasing rates of 182.2%, 174.5% and 133.2% in soil organic matter, total nitrogen, total phosphorus, and the highest increasing rates of 125.0%, 432.5% and 21.3% in soil available nitrogen, available phosphorus and potassium. The biological farming time could impact the changes of soil nutrients significantly (P<0.05), and tightest rates of soil organic matter, total nitrogen, total phosphorus are generally in the third or second years of the biological farming. The activities of catalase, urease and sucrose are increased under the biological tillage compared with the no-tillage, and the highest increased rates are 27.78%, 951.11%, 16.11% and 420.00%. The enzyme activities are different (P <0.05) in farming times and soil layers. The correlation analysis shows that there are significantly positive correlations between the catalase activity and soil organic matter, total phosphorus, available N, available P,available K and water content. The regression analysis shows that the main factors of impacting soil enzyme activities are available nitrogen, potassium, available phosphorus, total phosphorus and water content which affect enzyme activities with single or comprehensive factors. The path analysis shows that the biological cultivation time directly influences the enzyme activities, for example, the catalase activity > invertase activity > urease activity > protease activity. The direct path coefficients are 1.353, 1.070, 0.421 and 0.110 respectively, and the soil organic matter and the available nitrogen are main factors of impacting the enzyme activities with positive effects.