Agronomic Performance Of Green Super Rice And Super Rice Under Simplified And Reduced-input Practices

Low resource use efficiency,high environmental pressure,and high production cost and labor input are the main problems in China's rice production.To solve these problems,Prof.Qifa Zhang proposed to develop green super rice(GSR)in order to reduce the utilization of pesticides,fertilizers,and water while achieving a high grain yield and good grain quality in rice production.Currently,information about the performance of GSR and super rice(SR)under simplified and reduced-input practice(SRIP)is lacking.Seven GSR candidate varieties and 5 SR varieties were used in present study.There were two treatments,namely farmers' practice(FP)and SRIP.The seven GSR varieties were selected in our previous experiment and included Hanyou 549,9 You 6 Hao,Jinkeyou 651,Huanghuazhan,Luoyou 10,Huiliangyou 858,and Guangliangyou 476.The five SR varieties were Shenliangyou 5814,Fengliangyou 4,Yliangyou 1,Yangliangyou 6 and Yliangyou 900.Compared to FP,SRIP had reduced N rate,planting density,and water input,but longer seedling age.The objectives were to examine the difference between GSR and SR in grain yield and NUE(nitrogen use efficiency)under SRIP,and investigate the underlying physiological mechanisms.The main results are as follows:(1)Compared to the FP,the average grain yield of the varieties at SRIP was 10.0% and 5.5% lower in 2015 and 2016,respectively.This was resulted from significantly lower panicles number m-2,spikelets number m-2 and above-ground biomass.There was no significant difference in grain yield between GSR and SR at the two treatments in 2015.But in 2016,the grain yield of GSR was significantly lower than that of SR at both treatments.9Y6 H and YLY6 had relative high grain yield at the two treatments in the two years,which was due to their higher grain filling percentage and harvest index.GSR varieties such as HY549,JKY651,and HHZ produced higher grain yield under FP,but lower grain yield under SRIP.(2)Compared to the FP,nitrogen harvest index(NHI),nitrogen use efficiency for grain production(NUEg),nitrogen use efficiency for biomass production(NUEb),and the partial factor productivity of applied N(PFPN)at SRIP was lower by 13.8%,58.5%,79.9%,and 27.3%,respectively.In 2015,there were no significant differences in the NUE-related parameters between GSR and SR,but significant variation existed among varieties within each group.In 2016,GSR had lower PFPN and NUEb than SR at FP,whereas GSR had higher total nitrogen uptake(TN),but lower NUEg,NUEb,NHI and PFPN than SR at SRIP.In both years,variation in NUE-related parameters among the five SR varieties was relatively small.Compared to the SR varieties,GSR variety JKY 651 and HY 549 had higher TN at FP,and 9Y6 H had higher TN and PFPN at SRIP.Overall,no advantage was observed in NUE for the GSR varieties when compared to the SR varieties.(3)Compared to the FP,the economic input and output at SRIP were lower by 2256 yuan ha-1 and 1560 yuan ha-1,respectively.This resulted in a higher net income of 696 yuan ha-1 for SRIP over FP.Overall,the SRIP reduced the N rate,water input,and production cost.Grain yield of SRIP was lower than that of FP by 5.5-10.0%,while the economic return was increased by 696 yuan ha-1.In 2015 with normal climatic condition,there was no significant difference in grain yield between GSR and SR.In 2016 when high temperature stress occurred at the flowering stage,grain yield of GSR was significantly lower than that of SR.This indicated that SR had better adaptability and higher tolerance to abiotic stresses.Moreover,it is found that GSR had no advantage in NUE compared to SR.Our results suggest that screening the green traits among the SR varieties is feasible to identify GSR varieties.