Agronomic Performance Of High-yielding And Water-saving/Drought(WDR) Varieties Under Different Water And Nitrogen Management Conditions

Rice production is seriously constrained by water shortage and excessive nitrogenous fertilizer application. It is important to develop suitable water-saving and efficiency nitrogen management strategies and select appropriate rice varieties for water-limited rice growing conditions in order to ensure national food security. This experiment aimed to evaluate agronomic performance of five rice varieties under different water and nitrogen managements, the results will provide the scientific basis to rice cultivation and breeding program for high water and nitrogen use efficiencies.This research was conducted to compare the grain yield, water productivity and nitrogen use efficiency of different varieties grown under continuously flooded (CF) and rainfed (RF) conditions as well as two nitrogen levels. High-yielding varieties (Huanghuazhan, HHZ, an inbred variety; Yangliangyou6, YLY6, a hybrid variety; Jinkeyou938, JKY938, a hybrid variety) and water-saving and drought resistant rice (WDR) varieties (Hanyou5919, HY5919, a hybrid variety; Hanyou3, HY3, a hybrid variety) were grown under CF and RF conditions in Wuxue, Hubei in2011and2012.The main objectives of this study were:(1) to determine the interaction effect of different water and nitrogen management conditions on grain yield and agronomic traits of different varieties;(2) to compare the differences of grain yield, water productivity and nitrogen use efficiency between high-yielding and water-saving and drought resistance rice varieties under different water and nitrogen management conditions;(3) to determine the agronomic traits of water-saving and drought resistant rice and high NUE varieties for breeding.The following results were obtained:(1) There was insignificant difference in the interaction effect of different water and nitrogen management conditions on grain yield and agronomic traits of different varieties. The difference in grain yield between CF and RF was5.7%(2011) and2.0%(2012), separately. Compared with CF, RF saved24.7-32.5%of total water input in the two years. Water productivity of RF was consistently higher than that of CF. Rainfed water management after crop establishment did not reduced grain yield in the rice growing area of southeastern Hubei province, and consequently increased water productivity compared with CF. (2) There was insignificant difference in grain yield of HHZ and YLY6between CF and RF. The grain yield of YLY6and HHZ were higher than HY5919and HY3in both water regimes across the two years. Hence, high-yielding rice varieties developed for CF condition also demonstrated yield superiority over WDR varieties under RF conditions.(3) The higher grain yield of high-yielding rice varieties were attributed to higher panicle number per m2, spikelet number per m2, biomass, grain filling percentage, and harvest index. For the development of WDR and high NUE varieties, high-yielding traits for CF such as high biomass production, large sink size, and high harvest index are still the targets for improvement. Compared with the high-yielding varieties, the crop growth rate of WDR varieties was higher, but there was insignificant difference in the radiation use efficiency between the two groups. Furthermore, the biomass translocation from straw to grain, tiller number and the ratio of grain number to leaf area of WDR varieties were lower than the high-yielding varieties. Our results suggest that biomass translocation efficiency, tillering capacity and sink/source ratio of WDR varieties need to be improved through crop breeding in order to further increase the yield potential of WDR varieties.