Productivity Of ‘Plant Once And Harvest Twice’ System With Water-saving And Drought-resistant Rice And Its Response To Different Water And Nitrogen Management Modes

Ratoon rice production,also known as‘plant once and harvest twice’plantation system,is considered to be a green and efficient production system that can effectively replace common double-season rice cropping system.It has obvious advantages with relatively higher annual productivity but lower agricultural input costs.In recent years,thanks to the breeding of a series of good cultivars with strong regenerative ability and the improvement of production techniques,the plantation area of ratoon rice system has been expanding in central China.However,the common lowland rice（CLR）is usually used in the current ratoon rice production,which makes up a restraint on expanding the plantation area of ratoon rice from water resource shortage.Water-saving and drought-resistant rice（WDR）,a new type of rice cultivars,has a good application prospect with high drought resistance and low water consumption in rice production,and helps expand the rice plantation scope.However,few attempts have been made to use WDR cultivars in the"plant once and harvest twice"production system.In this study,field experiments were conducted in Huanggang city and Wuhan city,Hubei Province in 2020 and 2021,respectively.The yield formation and water use efficiency（WUE）of‘plant once and harvest twice’plantation systems with WDR and CLR were compared using high-yield and high-quality WDR and CLR cultivars with high regenerative ability as materials.Meanwhile,the response and its physiological mechanism of the yield formation of‘plant once and harvest twice’system with WDR to different nitrogen（N）management modes were investigated under two water management modes,i.e.,water-saving irrigation（WSI）and conventional flooding irrigation（CFI）,respectively.The results of this study are expected to provide experimental basis for improving the productivity of‘plant once and harvest twice’system with WDR and establishing its high-yield and high-efficiency cropping system.The main results are as follows:1.The total water use efficiency for the WDR system were 17.3%and 25.7%higher than that for CLM system in the main and ratoon cropping season,respectively.The grain yield was not significantly different in the main season between WDR system under WSI and CLR system under CFI.Nevertheless,it was significantly lower in the ratoon cropping season in the WDR system than that in the CLR system,mainly due to smaller panicles and shorter growth duration.The high-node panicles on the stubble of the main season crops contributed more to the yield in the ratoon season for WDR system;while,the low-node panicles on the stubble contributed more in the ratoon season for CLR system.Therefore,it is an important way to enhance the productivity of"plant once and harvest twice"system with WDR by enhancing the regenerative ability of low nodes in the stubble of main season crops and prolonging the growth period in the ratoon cropping season.2.Water and nitrogen management significantly influenced the yield of Jieyou（JY804）in two seasons,there were obvious interacting effects of water and nitrogen management on grain yield.The highest yield was obtained in the main cropping season and annual yield when the panicle N fertilizer was split as panicle-promotion fertilizer:spikelet-protection fertilizer=1:1 under WSI,which was mainly due to the higher spikelets and filled grain number per panicle;Under CFI,the yield of the main cropping season and annual were the highest when the panicle N fertilizer was totally used as spikelet-protection fertilizer,which was mainly due to the higher filled grain number per panicle and 1000-grain weight in the main season cropping.During the nitrogen topdressing N fertilizer modes,the yield of ratoon season cropping under two water management conditions was the highest when the panicle fertilizer was totally used as spikelet-protection fertilizer,because the treatment had a higher increase in ratoon panicle per m^-2 and spikelet number per panicle.In all treatments,the mian season,ratoon season and annual yield were obtained the highest when the panicle fertilizer was totally used as spikelet-protection fertilizer combined with CFI.3.In terms of water management,the number of tillers,SPAD value of leaves,leave area index（LAI）,aboveground dry matter production and nitrogen use efficiency（NUE）in the main cropping season under WSI were lower than under CFI.Postponing N application could miantain the appropriate LAI at the late growth stage,and increase dry matter accumulation post full heading and aboveground dry matter production.In addition,postponing N application improved the nitrogen anronomic use efficiency,apparent use efficiency and partial productivity by promoting aboveground N uptake.However,under different water conditions,the demand ratio of panicle fertilizer for Jieyou804 was different.Otherwise,the advantage of postponing N application varies with water management mode.Under WSI,When the panicle N fertilizer was split as panicle-promotion fertilizer:spikelet-protection fertilizer=1:1 has a better increase in above parameters.Under CFI,the effect is best when the panicle fertilizer was totally used as spikelet-protection fertilizer.4.Under the two water management modes,when all panicle fertilizer was used as the spileket-protection fertilizer in the main cropping season,the highest regeneration ability was achieved among the treatments of N topdressing.The effect of water management on the regeneration ability of JY804 was inconsistent between the two years.The regeneration ability under CFI was 12.5%higher on average than that under WSI in 2020.Nevertheless,there was little difference in the regeneration ability between the two water management modes in 2021.The regeneration ability showed a close relationship with the nutritional status of stubble after harvest in the main cropping season under different water management conditions.In summary,the‘plant once and harvest twice’plantation system with WDR showed obvious advantages in saving water and resisting drought,but its productivity in the ratoon cropping season remains to be improved further.Under WSI,the high-yield,high-quality and high-efficiency production could be coordinately achieved for WDR in both cropping seasons under the N management mode that the panicle fertilizer was split to panicle-promotion and spikelet-protection fertilizers.