Studies on Nitrate Nitrogen Contents in Forage Crops : I. Effects of Varying Levels of Nitrogen on Nitrate Nitrogen Contents in Some Forage Crops

Abstract

One possible method of increasing yields of grasses would be to grow at high levels of nitrogen fertilization. However, nitrate nitrogen (NO3-N) has at times been observed to accumulate within plants to abnormally high concentrations, with results disastrous to animals fed these plants, or to animals and humans exposed to the gaseous decomposition products. The purpose of this investigation was to determine the effects of rate of nitrogen application on the nitrate nitrogen contents in some grasses. The nitrate nitrogen contents were determined in orchardgrass (Dactylis glomerata L.), Italian ryegrass (Lolium multiflorum Lam.) and hybrid sorgo (Sorghum vulgare Pers.), grown in National Hokkaido, Shikoku and Chugoku Agricultural Experiment Stations respectively. Those grasses were fertilized with various rates of nitrogen. Bahiagrass (Paspalum notatum Flugge) and bermudagrass (Cynodon dactylon Pers.) were planted in pots and grown under 15°, 20° and 30°C temperature glass chambers in phytotron, and NO3-N contents were determined in those grasses. The NO3-N contents increased with increasing rates of nitrogen application in these grasses, and this tendency was shown markedly in the grasses grown in warm season than those grown in cool ones. There were two types in accumulation patterns of NO3-N in those grasses. Orchardgrass, hybrid sorgo and bermudagrass increased in NO3-N contents with increasing rates of nitrogen, but Italian ryegrass and bahiagrass did not increased in NO3-N contents at lower levels of nitrogen and increased rapidly in the contents at higher levels of nitrogen. In bermudagrass and bahiagrass, application of nitrification inhibitor (N-serve) with nitrogen fertilizer did not increased in NO3-N contents for the effective period of N-serve in this experiment.