Research On Water And Fertilizer Management Of Rice-crayfish Co-culture Mode Based On Water Saving And Efficiency Increasing

An integrated rice and fishery refers to a compound mode of planting and aquaculture that deeply integrates aquatic crop planting and aquaculture through necessary field engineering transformation.In a variety of rice-fishery modes,the area and aquatic product yield of integrated rice-crayfish(Procambarus clarkii)farming rank first in the integrated rice-fishery farming.Rice-crayfish co-culture is one of the integrated rice-crayfish farming modes.It is a production mode in which crayfish and rice grow in the same paddy field system during rice cultivation.This mode can reduce the input of chemical fertilizers and pesticides,reduce the input cost,improve the utilization rate of resources,and increase the economic benefits of farmers(the income of crayfish is about 2-3 times that of rice).However,there are also prominent problems such as excessive consumption of water resources,reduction of effective planting area of rice and decline of yield.In order to achieve high yield,green and sustainable development of rice-crayfish co-culture mode,a field experiment was carried out in the Science and Technology Park of Yangtze University from 2020 to 2022 to study the effects of nitrogen fertilizer application and water management on rice growth,dry matter accumulation,nitrogen utilization,rice yield and crayfish growth,so as to provide theoretical basis for optimizing water and fertilizer management,reducing resource consumption and ensuring rice yield in rice-crayfish co-culture mode.In the water-nitrogen coupling experiment,two water management and four nitrogen fertilizer treatments were designed.The two water management methods are conventional irrigation and optimized irrigation: 1)conventional irrigation water management for the rice-shrimp coppice model(CI);2)optimised irrigation water management for the riceshrimp coppice model(OI).Four N fertiliser treatments were set up: no N(N0),compound fertiliser(CF),controlled release fertiliser(CRF)and organic inorganic compound fertiliser(OCF).The main results were as follows.(1)In this experiment,application of N fertilizer could significantly increase rice plant height,tillering,leaf area index and SPAD;different types of N fertilizer had different effects on rice growth;application of compound fertilizer was beneficial to the growth of rice during the nutritional growth period,and application of controlled-release fertilizer was beneficial to the growth of rice during the reproductive growth period;optimal irrigation had a promotional effect on rice growth,but did not reach significant differences.(2)Nitrogen application significantly increased above-ground dry matter accumulation(DMA),and different N varieties showed different performance in different fertility stages of rice,with above-ground DMA showing compound fertilizer > organic inorganic compound fertilizer > controlled-release fertilizer > N0 at the tiller stage,compound fertilizer = controlled-release fertilizer > organic inorganic compound fertilizer > N0 at the nodulation stage,controlled-release fertilizer > organic inorganic compound fertilizer = compound fertilizer > N0 at the germination stage,and controlledrelease fertilizer > organic inorganic compound fertilizer > N0 at the tassel stage and maturity stage.Compared with conventional water management,optimized water management can increase the DMA of all organs at the tiller and tassel stage,at the gestation and spike stage,and at the gestation and spike stage.The DMA in the ears reached significant levels at the gestation and maturity stages.N fertilizer application significantly increased the total accumulated N in rice and significantly reduced the dry matter production efficiency of N.The apparent utilization rate of N fertilizer,the biproductivity of N fertilizer,the agronomic utilization rate of N fertilizer and the contribution rate of N fertilizer all showed that controlled-release fertilizer >organicinorganic compound fertilizer >compound fertilizer,and the significant difference was reached among the N fertilizer treatments.Productivity.(3)Application of nitrogen fertilizer can significantly increase rice yield,and different nitrogen fertilizer types have different effects on rice yield.In 2020,rice yield with controlled-release fertilizer is 17.13%-20.83% and 7.80%-8.08% higher than that with compound fertilizer and organic-inorganic compound fertilizer,respectively;in 2021,rice yield with controlled-release fertilizer is 19.48%-23.07% and 8.81% higher than that with compound fertilizer and organic-inorganic compound fertilizer,respectively.23.07%and 8.81%-8.08% respectively.Compared with conventional irrigation,the yield and effective number of spikes of optimally irrigated rice increased by 1.82%-19.77% and5.50%-9.29%,respectively,in 2020,and by 8.95%-24.20% and 1.03%-13.11%,respectively,in 2021.(4)Nitrogen fertilizer application could significantly increase crayfish yield,different nitrogen fertilizer types had no significant effect on crayfish yield,optimized irrigation reduced crayfish yield but did not reach a significant difference,irrigation method and nitrogen fertilizer type had no effect on crayfish size,nitrogen fertilizer had no significant effect on crayfish limb rate,but optimized irrigation significantly increased crayfish limb rate.In the nitrogen fertilizer reduction test,there were two water managements(conventional irrigation CI;optimized irrigation OI)and four nitrogen application levels which are no nitrogen fertilizer(N0),normal application of nitrogen fertilizer(FFP),nitrogen fertilizer reduction by 10 %(FFP-10%),nitrogen fertilizer was reduced by 20 %(FFP-20%).The main results are as follows:(1)Different water management and N fertilizer reduction had different effects on rice growth.Nitrogen fertilizer application could significantly increase rice plant height,tillering,SPAD and LAI,under the conventional irrigation pattern,compared with FFP,both FFP-10% and FFP-20% treatments significantly affected rice plant height,tillering,SPAD and LAI,under the Under optimal irrigation,compared with FFP,FFP-10%treatment had no significant effect on rice plant height,tillers,SPAD and LAI,while FFP-20% treatment significantly affected rice plant height,tillers,SPAD and LAI.Under the same N fertilizer management,optimized irrigation reduced rice plant height and increased rice tillers,SPAD and LAI(except at the tillering stage),but did not reach a significant level.(2)Rice nitrogen metabolizing enzymes(NR,GOGAT,GS)activities gradually decreased as fertility progressed,nitrogen fertilizer application could significantly increase rice leaf nitrogen metabolizing enzymes activities,nitrogen fertilizer application could increase enzymes activities,optimized irrigation could delay rice leaf senescence;rice,total root volume gradually increased as rice fertility progressed,nitrogen fertilizer application could significantly increase rice total root length,total root weight,total root surface area,total root The total root length,total root weight,and total root surface area of rice were greatest at the tillering stage with FFP-10% treatment,and at the nodulation,gestation and flush stages with FFP treatment.Under the optimized irrigation pattern,FFP-10% treatment had no significant effect on rice nitrogen metabolizing enzyme activity and rice root growth,and FFP-20% treatment significantly affected rice nitrogen metabolizing enzyme activity and rice root growth.(3)Nitrogen fertilizer application significantly increased rice yield and constitutive factors,and N fertilizer reduction under different water management had different effects on rice yield and constitutive factors.Under the conventional irrigation pattern,compared with farmers’ customary fertilizer application,both 10% and 20% reduction of N fertilizer application significantly reduced rice yield,with effective spike number reduced by 7.07%and 11.00%,and fruit set rate reduced by 8.60% and 10.86%,respectively.Under the optimized irrigation pattern,compared with farmers’ customary fertilizer application,10%reduction of N fertilizer application had no significant effect on rice yield,with effective spike number reduced by Under the optimized irrigation pattern,a 10% reduction in N fertilizer application had no significant effect on rice yield compared to farmers’ customary fertilizer application,with a 5.18% reduction in effective spike number and a0.62% increase in fruit set rate.At the same N fertilizer level,optimized irrigation increased rice yield by 16.72%-31.07% compared to conventional irrigation.(4)Application of nitrogen fertilizer significantly increased crayfish yield,and OI did not significantly decrease crayfish yield compared with CI.Application of nitrogen fertilizer increased the proportion of medium-and large-sized crayfish and decreased the proportion of small-sized crayfish,and application of nitrogen fertilizer decreased crayfish limb rate,and OI significantly increased crayfish limb rate compared with CI.