Nitrogen-Decreasing and Yield-Increasing Effects of Combined Applications of Organic and Inorganic Fertilizers under Controlled Irrigation in a Paddy Field

Inadequate fertilization may result in water pollution and nutrient leaching, especially in paddy fields. It is expected that the combination of organic and inorganic fertilizers reduces water pollution in addition to crop yield improvement. In this study, combined fertilization with organic and inorganic fertilizers was tested under controlled irrigation conditions. With the addition of organic fertilizer, the pH of paddy soil could be maintained in a rather neutral environment, and the soil organic matter concentration could increase especially under a controlled irrigation regime. Hydrolyzed nitrogen was noticed in the fertilized plots with an increasing trend compared to unfertilized plots. However, available phosphorus concentration decreased in all treatments after rice harvest. During the drainage process, the ammonium nitrogen was the main form of nitrogen loss. Organic fertilizer application significantly improved productive panicles and thus increased paddy yield. We concluded that with the combination of organic-inorganic fertilizer application and controlled irrigation, the pollutants can be removed to some extent and the rice yield can be increased significantly, which is favorable for environmental protection and yield promotion.