Mechanical Deep Placement of Nitrogen in Wetland Rice

Deep placement of nitrogenous fertilizer (N) is an alternative for increasing the N use efficiency of wetland rice besides minimizing the adverse effects of fertilizers on the environment. It has been found to limit the loss ofA N due to surface runoff, leaching, volatilization and denitrification that lead to reduction in applied N. Different machines as well as N materials (granular, urea supergranules or briquettes, liquid N) have been introduced for this method. Although deep placement of fertilizer increased N use efficiency in rice-growing countries, the machines meant for this purpose have not been well accepted due to problems in performance consistency and commercial unavailability or extra cost of recommended materials. Despite these problems, however, several prototypes have shown potential but their acceptance maybe limited unless these promising mechanisms are adapted into a system that addresses the field and socio-economic conditions of Asian farmers. A fertilizer management system that combines machine deep placement, crop establishment and farmersʹ timing of application using the commercially available materials could enhance adoption of the technology. Further refinements of the promising devices as well as addressing farmersʹ constraints are, thus, recommended for a better acceptance of deep placement in the rice-growing countries of Asia.