|Prudente, Jacqueline - LA. D.E.Q.|
|Kongchum, Manoch - S.P.E.S.S.M., LA.|
|Prudente, Alfredo - DEPT. FOOD AND SCI., LA.|
Submitted to: World Journal of Agricultural Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2009
Publication Date: February 10, 2009
Citation: Prudente, J.A., Sigua, G.C., Kongchum, M., Prudente, A.D. 2009. Improving yield and nutrient uptake potentials of japonica and indica rice varieties with nitrogen fertilization. World Journal of Agricultural Sciences. 4(3):326-332. Interpretive Summary: Agriculture remains as the key sector for the economic development of most developing countries in Southeast Asia where rice is the most important and dominant agricultural crop. Many factors influence the growth and yield of rice. One of the most important factors is N fertilization. High yields are dependent on increased N absorption at each growth stage without reducing the percentage of ripened grains. To avoid losses and use soil- and fertilizer-nitrogen efficiently, it is necessary to develop better ways of predicting the optimum amount of N needed by the rice plants. However, N needs and uptake patterns of rice vary among varieties, and ecosystems. Thus, this study was conducted: (1) to evaluate the effect of varying levels and split application of N on the growth and yield of rice; (2) to determine the relationship of N uptake to yield, yield component, and dry matter production of rice; and (3) to determine the N uptake patterns of japonica and indica rice varieties applied with different levels of N fertilizer. The N uptake of japonica and indica rice varieties increased with increase in levels of applied N. At the early growth stage, IR-13 was more responsive to N fertilization while Hatsuboshi was more responsive to N fertilization at the later stage until maturity. The yield and yield components were positively correlated to the amount of N applied. Topdressing of N significantly increased the yield of brown rice, weight of 1000 grains, dry matter production and panicle number. It also enhanced the tillering ability of the rice plant. Hence, such increase in the yield and other agronomic characters could be attributed to the increase in N uptake from the soil and from the applied fertilizer, regardless of the type or variety of rice.
Technical Abstract: The most important problem in achieving high yields in rice is how to increase the nitrogen (N) absorption at each growth stage without reducing the percentage of ripened grains. Proper amount and timing of application could reduce N losses and increase fertilizer use efficiency while cost of production is also reduced and yield is increased. In order to avoid losses and to use soil- and fertilizer-nitrogen efficiently, it is necessary to develop better ways of predicting the optimum amount of N needed by the rice plants. A field experiment was conducted to determine the effect of different levels of N on N uptake, yield components, and dry matter yield of japonica (Hatsuboshi) and indica (IR-13) rice varieties. Results showed an increasing trend in the N uptake, rice yield, panicle number, tiller number, and dry matter production, with increased amount of applied N fertilizer. The yield (brown rice) of the two varieties (Hatsuboshi, 3.2 - 6.5 tons ha-1; IR-13, 2.6 - 6.4 tons ha-1) did not differ significantly (p=0.05). However, the agronomic efficiency (AEN) of IR-13 was significantly higher than Hatsuboshi. There was a 30 kg ha-1 increase in the yield of brown rice and about 1.4% increase in the total N uptake for every additional kilogram of applied N ha-1. Higher correlations (p=0.001) were found between the yield (r = 0.96; r = 0.99), number of panicles (r = 0.98; r = 0.96) and number of tillers (r = 0.96; r = 0.97) and N uptake (r = 0.97; r = 0.95) of japonica and indica rice varieties and applied N, respectively. The increase in yield (ton ha-1) of japonica (y = 1.07x + 2.5) and indica (y = 1.24x + 1.5) could be attributed to the increase in N uptake with increased application of N and mineralized soil N after flooding. However, best timing and amount of N application should be determined to reduce N losses and increase soil and fertilizer N efficiency while cost of production is also reduced but yield is increased.