Dry Matter and Nitrogen Distribution at Maturity of Three Rice (Oryza sativa L.) Cultivars Exposed to Ammonia at Two Growth Stages

A substantial proportion of ammonical fertilizers applied to lowland rice is lost as gaseous N from the soil–plant system. Besides various environmental factors, the low N use efficiency of flooded rice is also attributed to this factor. As atmospheric ammonia found in the leaf environment of the plants could also be responsible for differences in N use efficiency and fertilizer N losses from lowland rice, a greenhouse study was conducted on three rice cultivars varying in physio-morphological characteristics for their dry matter and nitrogen distribution to grains at maturity in response to ammonia (NH₃) exposure at tillering and anthesis growth stages. The results revealed that ammonia exposure of plants at two growth stages did not affect the total dry matter and total N yield of the rice cultivars at maturity; however, the grain yield and grain N yield were negatively effected by NH₃ exposure of the plants at anthesis. The variation observed in dry matter and N partitioning at maturity to grains/roots of the plants exposed to NH₃ at anthesis indicated that the growth stage of the plants at which they are exposed to NH₃ has an influence on N use efficiency of crop plants and subsequent vegetative as well as total N losses from the soil–plant system.