The Effect of Azolla on Nitrogen Use Efficiency in Rice-wheat Rotations of Nepal

Book excerpt: The low productivity of the rice-wheat cropping system in Nepal is associated with a low efficiency of applied mineral N in rice. The aquatic fern Azolla was used to reduce N losses via ammonia volatilization from the flooded lowland rice in farmers' field conditions in Nepal. The Azolla cover changed the floodwater chemistry, thus reducing ammonia volatilization losses. The use of Azolla in combination with Urea increased rice yields by 15% and reduced urea-N losses from 17-38% to 2-8%. A combined use of Azolla and urea is a viable option to enhance the productivity of rice-wheat systems in Nepal.