[Objective] The aim was to study on effects of "straw returning and ir-returning" and "irrigation with ground water and water in the Yellow River" on changes of enzyme activity in soils under wheat at different developmental stages. [Method] Jimai 22, a kind of winter wheat, was made use of in fields to study on effects of "straw returning and ir-returning" and "irrigation with ground water and water in the Yellow River" on changes of enzyme activity in soils under wheat in different developmental stages. [Result] With advancement of developmental stage, urease activity of wheat in the four groups all showed the trend of "increasing-decreasing-increasing" and activities of invertase and phosphatase both changed from increasing to decreasing. In addition, urease activities of soils in wheat roots were improved by straw returning in four developmental stages. Meanwhile, activity of soil enzyme was better promoted by irrigation with ground water than with water in the Yellow River, except in grain-filling stage. Before developmental stage, different processing methods had a significant effect on phosphatase activity, for example, straw returning and ground water significantly enhanced activities of two kinds of phosphatase and promoted P absorption and transferring by plants and microorganisms in jointing stage; activity of acid phosphatase was higher in the group where irrigation with ground water and straw returning were adopted than those in the rest three groups in booting stage. [Conclusion] The research laid a foundation for dynamic relationship among activity of soil enzyme, crop growth and microorganisms.
