Nitrogen and Phosphorus Uptake and Utilization

Abstract

Developing nutrient efficient rice cultivars is an increasingly important objective as the continually increasing population worldwide needs to be fed from the decreasing arable land and declining natural resources. To deal with the demand, vast improvements in cultivars with higher yield potential per unit area (super rice for example) have being targeted in breeding programs. Traditionally, breeding selection is done on fully fertilized plots with a focus on potential for higher yield, making current commercial rice cultivars relatively inefficient at accessing applied fertilizers. The plants may only take up 10–15 % of applied phosphorus (P) fertilizer in the first year, with subsequent uptake rarely exceeding 50 % [17]. To obtain a higher yield, a great quantity of nitrogen (N) fertilizer has been applied during the past 20 years. The statistical data indicate that rice yield increased 26.5 % from 4,888 kg/ha in 1982 to 6,185 kg/ha in 2002, but consumption of nitrogen fertilizer increased 106.5 % in China [10]. Phosphorus is a nonrenewable resource. The exploitation of economically viable sources of rock phosphate is estimated to peak within this century [9], resulting in prohibitive prices for P fertilizer for many primary producers, especially in developing countries, increasing rice production costs. In addition, overapplication of N fertilizer often reduces rice grain yield because plants grown under excess N conditions are more susceptible to lodging and pest damage. Thus, developing crops that are less dependent on the heavy application of fertilizers is essential for the sustainability of agriculture [52].