Effects and Utilization Techniques of Lime Nitrogen on Control of Volunteer Rice and Weedy Rice (Oryza sativa L.)

Abstract

The application of lime nitrogen (LN) after harvesting rice effectively controls volunteer- and weedy-rice growth, but the effects of LN vary greatly depending on field management conditions and environmental conditions. Varietal differences, the presence or absence of rice straw residue, the temperature and season of LN application, and soil moisture, and rainfall, as well as the tilling time, are factors that influence the effects of LN. For example, rice straw halves the LN effect, moderate water is required, and the LN effect increases along with temperature. A no-tillage period of 2 weeks or more after LN application is required, and immediate tilling after LN application does not suppress volunteer-rice growth. Based on these findings, the concepts and points to consider when using LN are summarized here. The effects of LN application are evaluated in comparison with those of effective herbicides, which have been used as control measures for volunteer- and weedy-rice growth during transplant-based rice cultivation. The control values of herbicides against volunteer and weedy rice were estimated to be 90 or greater, while the values of LN application were estimated to be 80–90 in general. Because LN acts as a beneficial nitrogen fertilizer, application of other fertilizers may be reduced during rice cultivation. On the basis of our current knowledge, future issues are discussed.