Nitrate reductase activity in soil under shelterbelt and an adjoining cultivated field

摘要

Laboratory studies were conducted to evaluate the effect of moisture (field-moist and 15% moisture) and nitrogen concentrations (field content and after the addition of nitrogen in the form of 0.25 and 0.5% urea, respectively), pH and organic matter on the changes in nitrate reductase activity in soils under shelterbelt and an adjoining cultivated field. Shelterbelt consists mainly of Robinia pseudoaccacia. A first-order kinetics reaction model was fitted to the experimental changes in nitrate reductase activity over time data at different moisture and nitrogen content. Under shelterbelt, an increase in the soil moisture content from field-moist to 15% led to a 1.13-fold increase in the first-order reaction rate constant. However, under the adjoining cultivated field, an increase in the soil moisture content from field-moist to 15% increased the first-order reaction rate constant significantly more than in soil under shelterbelt. Changes in nitrate reductase activity for a 15% moisture content in soil under shelterbelt and in field-moist soil in the adjoining cultivated field were similar. Moreover, the addition of 0.25% nitrogen to the adjoining cultivated field with field-moist soil led to a 3.65-fold increase in the first-order reaction rate constant.