Analysis Of Hydrological Characteristics And Water Use Efficiency Of Rice-Crawfish Co-Culture System

The comprehensive cultivation of paddy fields is an important model of current national agriculture.It has developed rapidly in recent years.In particular,the rice-crawfish co-culture system has become a research hotspot.The environmental change of water resources and water use efficiency of rice-crawfish co-culture system relate to the sustainable development of this model.In order to understand the water balance and water production efficiency of rice-crawfish co-culture system under different environmental conditions in Hubei Province,field positioning test,fixed-point observation test and regional investigation test were set up in this experiment from 2017 to 2018.Simulation of water balance in different culture ditch widths and different landform types in Hubei Province were conducted by HYDRUS-1D model and calculate its water production efficiency.The purpose of this study is to investigate the characteristics of water production efficiency and water balance under the rice-crawfish co-culture system,make assessment of hydrological cycle characteristics and suitability of rice-crawfish co-culture system in different regions of Hubei Province.The research results are as follows:(1)Using the HYDRUS-1D model to simulate the soil volumetric water content of different culture ditch widths in field positioning experiments,and make analysis and evaluation of the width of four culture ditch by using efficiency model and evaluation index.The simulation results of 4 different culture ditch widths show:The Nash Sutcliffe Efficiency(Ens)results were 0.74,0.88,0.81,and 0.85,respectively;the root mean square error(RMSE)results were 6.38,5.87,4.51,and 3.44,respectively.The results show that the model can simulate the characteristics of soil water movement in the field,which means the model is applicative.(2)Field positioning experiments show:With the width of culture ditch increases,the water production efficiency of rice-crawfish co-culture system decreases.The datas are 0.81 kg/m~3,0.78 kg/m~3,0.69 kg/m~3 and 0.60 kg/m~3 respectively.The HYDRUS-1D model simulates the water balance of different culture ditch widths in field positioning experiments.The groundwater recharge is 3 m>2 m>1 m>CK,which datas are 83.0 mm,72.1 mm,62.5 mm and 55.6 mm respectively.The leakage is 3 m>2 m>1 m>CK,which datas are 319.9 mm,245.6 mm,135.5 mm and 68.1 mm respectively.With the width of culture ditch increases,the water storage capacity is108.3 mm,756.9 mm,1516.7 mm and 1873.5 mm respectively.(3)The fixed-point observation and regional survey studies show that the different geomorphological environmental characteristics and water and soil resources in Hubei Province restrict the application of the rice-crawfish co-culture system and affect its water management model.Jianghan Plain:Rice-crawfish co-culture system adopt a wide culture ditch mode(5 m-8 m).Water source is convenient for irrigation.Paddy field surface water depth is 10.62 cm and the field drying period is 46.39 days.After harvesting the rice for a period of time,the rice is covered with water to the height of the field,and gradually deepens to 30 cm-70 cm from March to June;Southeast hills Hubei:Rice-crawfish co-culture system adopt a narrow culture ditch mode(2 m-5 m).Part of the hilly areas set ecological pool to solve the crayfish problem in winter.The water source mainly comes from rainfall and reservoir rivers.Paddy field surface water depth is 7.61 cm and the field drying period is 55.76 days.After the rice is harvested,the lake area is generally covered with water until the surface is flush,and gradually deepens to 30 cm-75 cm from March and June.The hilly area is not covered with water in winter;North Central Hubei:Rice-crawfish co-culture system also adopt a narrow culture ditch mode(1 m-4 m).Water resources are relatively scarce and mainly using reservoir water,etc.Paddy field surface water depth is 8.14 cm and the field drying period is 25.67 days.The water is coverd with field to 10 cm after harvesting,gradually deepens to 20 cm-50 cm from March to June;Different types of water productivity show that North Central Hubei>Jianghan Plain>Southeast hills Hubei,they were 0.83 kg/m~2,0.79 kg/m~2 and 0.66 kg/m~2,respectively.Different types of water balance:Irrigation volume,groundwater recharge and storage capacity in Jianghan Plain are maximum amount,which were1553.7 mm,104.5 mm and 872.4 mm,respectively;The largest evapotranspiration is in the North Central Hubei,which is up to 725.3 mm.The rainfall and leakage in the Southeast hills Hubei were the highest,which were 789.0 mm and 830.4 mm,respectively.(4)Irrigation mode is optimized by simulating different irrigation volumes(culture ditch width).The Jianghan Plain area can increase the amount of irrigation based on the original irrigation amount(1.25 times to 1.5 times the original irrigation amount).The storage water can be increased by 457.33 mm-931.71 mm;It is suitable to maintain the existing irrigation amount or the width of the culture ditch in North Central Hubei;Because of the poor soil water retention in southeast hills Hubei,they can properly reduce irrigation water(0.75 times the original irrigation amount)and reduce leakage by 98.4 mm to achieve efficient use of water resources.(5)Analysis of the suitability of rice-crawfish co-culture system in Hubei Province show that:The Jianghan Plain is suitable for large-scale rice-crawfish co-culture system with the advantages of flat topography and convenient irrigation.Thousands of acres of contiguous farming can be adopted by using the village as a unit.The culture ditch can adopt more than 5m super wide ditch type.The suitable area for rice-crawfish co-culture system is 250,000 hm~2;It is suitable for a certain area of rice-crawfish co-culture system in North Central Hubei with easy water collection and abundant water resources.Usually based on family cooperatives and area controls in the range of 50 acres to 500 acres.The suitable area for rice-crawfish co-culture system is 30,000 hm~2;The water resources in the southeast hills Hubei are relatively abundant,which is also possible to develop a certain scale of rice-crawfish co-culture system.However,the amount of leakage is large,the area of the field and the culture ditch are not suitable for being too large.The suitable area for rice-crawfish co-culture system is 70,000 hm~2.