Nutrient uptake and water use efficiency as affected by modified rice cultivation methods with reduced irrigation

A field experiment was conducted in 2005 to investigate the effects of modified rice cultivation methods on: water use efficiency, the uptake of nutrients (N, P and K) by plants, and their distribution within plants and their internal use efficiency. The treatments were modified methods of irrigation, transplanting, weeding, and nutrient management, comparing the System of Rice Intensification (SRI) with standard rice-growing methods including traditional flooding (TF). Results showed that the uptake of N, P, and K by rice plants during their growth stages was greater with SRI management compared to TF, except during the tillering stage. At maturity stage, SRI plants had taken up more nutrients in their different major organs (leaves, stems, and sheaths; panicle axis; and seeds), and they translocated greater amount of nutrients to the grain. Under SRI, the ratio of N, P, and K in seed grain to total plant N, P, and K was 4.97, 2.00, and 3.01% higher, respectively, than with TF. Moreover, under SRI management, internal use efficiency of the three macronutrients (N, P, and K) was increased by 21.89, 19.34, and 16.96%, respectively, compared to rice plants under TF management. These measurements calibrate the crop’s physiological response to differences in cultural practices, including the maintenance of aerobic versus anaerobic environment in the root zones. With SRI, irrigation water applications were reduced by 25.6% compared to TF. Also, total water use efficiency and irrigation water use efficiency was increased with SRI by 54.2 and 90.0%, respectively. Thus, SRI offered significantly greater water saving while at the same time producing more grain yield, in these trials 11.5% more compared to TF.