Effects of Excessive Mg~(2+) on the Soil Enzyme Activity

The research aims to reveal the effects of excessive Mg2+ on the soil enzyme activity including urease,phosphatase and catalase.Reagents MgCl2 with different concentrations was added to the clean soil and soil urease,phosphatase and catalase activity were calculated.On the 1st,3 rd,14th,28 th day of the 28 –day training,the samples were selected to calculate soil urease,phosphatase and catalase activity.Data analysis showed that magnesium ions were on urease activity.When the magnesium concentration was 0.6%,the soil urease activity improved most which was 91.6 percent.The urease activity increasing degree was:0.6%0.8%0.4%0.2%1.0%0,and the first day was the best time to observe the change of urease activity.Mg2+ could first activate phosphatase activity and then inhibit it,and the activity of phosphatase had substantial increase at the third day.But from the fourteenth day to the twenty-eighth day,the phosphatase activities of five soil samples which contained different qualitative percentage of Mg2+ were all lower than bank experiment.The catalase activities of all soil samples were inhibited all along.In conclusion,urease,phosphatase and catalase are sensitive to Mg2+,and Mg2+ can improve the soil fertility in a short period of time when the qualitative percentage of Mg2+ is 0.6%,but the soil fertility will be influenced negatively if Mg2+ is added to the soil in large quantity and for a long period of time.Thus Mg2+ can be considered as an eco-toxicological indicator of soil contamination by Mg.