Variation in Paddy Soil Nitrogen as Impacted by Combination of Deep Rainfall Storage and Controlled Drainage

Abstract

【Objective】 Nitrogen in paddy soil is modulated by both rainfall and drainage, and in this paper we present the results of an experimental studies on its response to controlled drainage and deep rainfall storage. 【Method】 The experiment was conducted in 2018 in field plots at the Feidong Irrigation Experimental Station. We compared two irrigation methods: alternate dry and wet irrigation (L1), and deep rainfall storage and controlled drainage irrigation (L2 and L3). Business as usual used by local farmers was taken as the control (CK). During the experiment we measured nitrogen changes in soil water and the drainage water at the depths from 50 cm to 150 cm, and analyzed the response of nitrogen dynamics to irrigation amount, drainage amount, as well as rice yield under different water managements. 【Result】 Compared with CK, L1, L2 and L3 reduced the irrigation water by 725 m3/hm2, 1 703 m3/hm2 and 2 304 m3/hm2, and increased the rainwater utilization by 11.8%, 19.0% and 25.9%, respectively. In the meantime, they also reduced the irrigation times by 1~3. Soil nitrogen content decreased as the soil depth increased, regardless of treatments. Compared to CK, L2 and L3 reduced the maximum total nitrogen (TN) compared to CK, and L1, L2 and L3 reduced TN pollution load by 21.3%, 26.7%, 31.5%, while no significant difference in the yield was found between them. 【Conclusion】 Increasing the upper limit of the rainfall storage and extending the interval, coupled with deep rainfall storage and controlled drainage, can effectively reduce irrigation requirement and drainage times, thereby improving rainwater use efficiency. It also reduced nitrogen pollution and can thus be used as an improved agronomic practice for rice production in paddy field.

Keywords

• rice
• paddy field
• controlled drainage and deep rainfall storage
• nitrogen
• soil water content