Mechanical deep placement of nitrogen in wetland rice

Deep placement of nitrogenous fertilizer (N) is an alternative for increasi ng the N use efficiency of wetland rice besides minimizing the adverse effe cts of fertilizers on the environment. It has been found to limit the loss of N due to surface runoff, leaching, volatilization and denitrification th at lead to reduction in applied N. Different machines as well as N material s (granular, urea supergranules or briquettes, liquid N) have been introduc ed for this method. Although deep placement of fertilizer increased N use e fficiency in rice-growing countries, the machines meant for this purpose ha ve not been well accepted due to problems in performance consistency and co mmercial unavailability or extra cost of recommended materials. Despite the se problems, however, several prototypes have shown potential but their acc eptance maybe limited unless these promising mechanisms are adapted into a system that addresses the field and socio-economic conditions of Asian farm ers. A fertilizer management system that combines machine deep placement, c rop establishment and farmers' timing of application using the commercially available materials could enhance adoption of the technology. Further refi nements of the promising devices as well as addressing farmers' constraints are, thus, recommended for a better acceptance of deep placement in the ri ce-growing countries of Asia. (C) 2001 Silsoe Research Institute.