INTRODUCTION Rice (Oryza sativa L.) is one of the most important cereal crops of the world, grown in wide range of climatic zones, to nourish the mankind. Introduction of hybrid rice is an important step towards augmentation of rice yield. Hybrid rice yields about 15-20% more than the promising high-yielding commercial varieties. Earlier studies reveal that judicious and proper use of fertilizers can markedly increase the yield and improve the quality of rice [14].Given the importance of nitrogen fertilization on the yield in grain from the rice plant, it is necessary to know what the best dose is for each variety as well as its infl uence on components of yield and other agronomic parameters such as the cycle, plant height, lodging and moisture content of the grain, in order to obtain better knowledge of said productive response. Tanaka et al. (1966) showed that the height of a rice plant is positively correlated to the length of the maturation cycle. A taller plant is more susceptible to lodging and responds less well to nitrogen [25]. Panicles with a low percentage of sterile fl owers permit the application of higher doses of nitrogen and produce better yields [26]. Some factors, like early sowing, meet the twin objectives of producing higher yields and improving the grain quality[10, 2]. Other factors, like increased rates of fertilizer nitrogen, may increase the yield but reduce the quality of the grain [2]. An adequate supply of nitrogen to the crop plants during their early growth period is very important for the initiation of leaves and fl orets primordia [23].
INTRODUCTION Rice (Oryza sativa L.) is one of the most important cereal crops of the world, grown in wide range of climatic zones, to nourish the mankind. Introduction of hybrid rice is an important step towards augmentation of rice yield. Hybrid rice yields about 15-20% more than the promising high-yielding commercial varieties. Earlier studies reveal that judicious and proper use of fertilizers can markedly increase the yield and improve the quality of rice [14].Given the importance of nitrogen fertilization on the yield in grain from the rice plant, it is necessary to know what the best dose is for each variety as well as its infl uence on components of yield and other agronomic parameters such as the cycle, plant height, lodging and moisture content of the grain, in order to obtain better knowledge of said productive response. Tanaka et al. (1966) showed that the height of a rice plant is positively correlated to the length of the maturation cycle. A taller plant is more susceptible to lodging and responds less well to nitrogen [25]. Panicles with a low percentage of sterile fl owers permit the application of higher doses of nitrogen and produce better yields [26]. Some factors, like early sowing, meet the twin objectives of producing higher yields and improving the grain quality[10, 2]. Other factors, like increased rates of fertilizer nitrogen, may increase the yield but reduce the quality of the grain [2]. An adequate supply of nitrogen to the crop plants during their early growth period is very important for the initiation of leaves and fl orets primordia [23].
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