| Rice is one of the most important staple crops in China.Optimizing crop management practices and rice cultivars planting have been paid more attentions by farmers with the goal of reducing production cost and increasing profit,amid a series of challenges including labor shortage and high production cost in rice production during the transition period.Therefore,farmers are increasingly adopting reduced-input crop management practices and replacing hybrid rice cultivars with inbred rice cultivars to reduce production cost.Previous studies demonstrated that tybrid rice has higher yield potential than inbred rice under optimum growing conditions with large amount of inputs.However,little attention has been paid to the performance of inbred and hybrid rice cultivars under reduced-input crop management practices(RCMP).Addtionally,assessments of energy use and energy use efficiency regarding rice production with inbred and hybrid rice cultivars under different crop management practices have not been performed in China.Therefore,widely grown inbred(Huanghuazhan,HHZ)and hybrid(Yangliangyou 6,YLY6)rice cultivars were used to investigate agronomic performace,nitrogen use efficiency,energy balance,and economic benefit in farmers’practice(FP)and and RCMP treatments under transplanted condition in Wuxue County,Hubei Province of China in 2014 and 2015.RCMP treatments used in this study included RCMP with reduced N input(RCMP_N),reduced water input(RCMP_W),older rice seedling(RCMP_S),reduced planting density(RCMP_D),and combined reduced nitrogen input,water input,planting density,and older rice seedling(RCMP_C).This study was conducted to identify whether inbred or hybrid rice is more suitable for RCMP to achieve sustainable rice production.The results of this study are as follows:(1)Average yield of six treatments of YLY6 was 16.9%and 5.9%significantly higher than HHZ in 2014 and 2015,respectively.Higher yield of YLY6 mainly attributed to 13.4%higher total dry weight,24.3%higher leaf area index,and 34.7%higher1000-grain weight than HHZ.Moreover,the yield stability across the crop management treatments and years of YLY6 was significantly higher than that of HHZ.Grain yield of YLY6 was 11.9%and 10.8%higher than HHZ in FP and RCMP(average of five RCMP treatments),respectively.It indicated that hybrid rice had superior yield pefromance as compared with inbred rice even in RCMP.The results showed that rice yield was significantly impacted by crop managmeent practice.Grain yield was reduced in RCMP_Nand RCMP_C and increased in RCMP_S with no yield change observed in RCMP_W and RCMP_D as compared with FP.In this study,the reduction in spikelets per m~2 was responsible for yield decline in RCMP_N and RCMP_C,while the increase in spikelets per m~2contributed to yield increase of RCMP_S as compared wit h FP.Significant interaction between rice cultivar and treatment was obersvered on grain yield.Yield reduction expressed as a percentage of the corresponding FP of YLY6 in RCMP_N and RCMP_C was lower and higher than that of HHZ,respectively.Compared with FP,yield increase in RCMP_S of HHZ was higher than that of YLY6.(2)On average,YLY6 had 11.2%,6.4%,5.5%and 6.0%higher partial factor productivity of applied N fertilizer,N use efficiency in biomass production,N use efficiency in grain production,and H harvest index than those of HHZ,respectively.N use efficiency was affected by N application rate with RCMP_N and RCMP_C had higher N use efficiency than FP.No significant effects of RCMP_W and RCMP_D on N use efficiency were found as compared with FP.N use efficiency of HHZ in RCMP_S was significantly higher than that in FP.(3)Energy inputs were 0.8-32.3%lower in RCMP_N,RCMP_W,RCMP_D,and RCMP_Cassociated with reduced input of N fertilizer,irrigation water,seeds,and labor force as compared with FP.There was no significant difference in energy input between HHZ and YLY6.However,energy output of YLY6 was 20.1%and 5.0%higher than HHZ in 2014and 2015,respectively.Therefore,YLY6 had higher net energy and energy use efficiency than HHZ.Energy use efficiency of YLY6 was 10.5%and 9.3%higher than HHZ in FP and RCMP,respectively.Energy use efficiency in RCMP_C was significantly higher than in FP for both HHZ and YLY6.Compared with FP,energy use efficiency was significantly higher in RCMP_N,RCMP_W,and RCMP_S for HHZ and YLY6.Significantly higher energy use effieicny in RCMP_S than FP was only observed for HHZ.(4)Given higher economic cost of YLY6 from seed,pesticides,and labor than HHZ,total production cost of YLY6 was 16.2%and 17.3%higher than HHZ in 2014 and 2015,respectively.Higher production cost of YLY6 from pesticides and labor was a consequence of higher pesticides usage resulted from higher disease pressure associated with dense rice canopy as compared with HHZ.No significant difference in gross return between HHZ and YLY6 was found in this study,so net return of HHZ was 27.2%and41.8%higher than YLY6 in 2014 and 2015,respectively.The benefit-to-cost ratio of HHZ was 1.40 in 2014 and 1.88 in 2015,which was 10.2%and 22.9%higher than YLY6,respectively.Comapred with FP,RCMP increased net return and benefit-to-cost ratio(except for RCMP_N),with reduced production cost(except for RCMP_S).Net return and benefit-to-cost ratio of HHZ was 39.0%and 15.4%higher in FP and 35.9%and 17.5%higher in RCMP than YLY6,respectively.This indicated that the economic advantage of HHZ than YLY6 still existed in RCMP.Overall,no significant yield losses were found in RCMP as compared with FP,with the expectation of RCMP_N.Furthermore,RCMP reduced energy input and increased resource use efficiency and economic benefit with reduced resource input and production cost.Hybird rice had higher grain yield,N use efficiency,and energy use efficiency than inbred rice under RCMP,indicating that hybrid rice is more suitable for RCMP than inbred rice from the perspective of achieving high yielding and ensuring national food security.Equally importantly,inbred rice has an economic advantage over hybrid rice under RCMP in terms of reducing production cost and increasing farmers’profit. |
PDF Full Text Request