Deficit irrigation and nitrogen effects on nitrogen-use efficiency and grain protein of rice

To meet future food demand, world rice production must increase in the next few decades, which is possible only by effective use of soil and water resources and inputs. This research was conducted to investigate the effects of nitrogen, N, application and deficit irrigation treatments including a sprinkler, intermittent flooding and continuous flood irrigation, and their interaction with the N-use efficiency and grain protein of a local lowland rice cultivar. The results indicated that low (sprinkler irrigation) and high (continuous flood irrigation) applied water affected the plant and soil factors in N uptake and decreased N-use efficiency for rice. Therefore, optimum applied water was obtained in intermittent flooding (2-day interval). Reduction in nitrogen uptake at high applied water can be due to the effect of nitrate leaching in the root zone and the reduction in N uptake at low applied water can be due to the inability of the roots to absorb N and translocate it to the plant top. With respect to the relationship between N uptake and grain protein and leaf chlorophyll, these parameters can also be affected by applied water and N application. Appropriate linear models were proposed to show these relationships. At different times of soil nitrogen measurements and N application rates, maximum nitrogen leaching (about 50%) occurred in continuous flooding irrigation.