Study On The Optimized Irrigation Schedule Of Winter Wheat In Typical Regions Of North China Under The Constraints Of Irrigation Amount And Irrigation Technique

North China is a main area where produces winter wheat in China.The water demand of winter wheat cannot be satisfied by the precipitation in its growth period.Since the growth of winter wheat is heavily dependent on irrigation,surface irrigation remains a major means for irrigation winter wheat in this area.Nevertheless,there are two subject matters encountered by the agricultural production in North China,i.e.,shortage of total water resources and low irrigation water use efficiency.Based on the strategy of saving water-saving and containing over-exploitation of groundwater,how to increase the water use efficiency through optimizing the crop irrigation system and improve water management of surface irrigation with the control of the total water consumption for safeguarding peasant's interests is an urgent problem to be solved at present.Therefore,combining field experiment with numerical simulations,this paper determined variety parameters of tested winter wheat samples in the research area and the minimum irrigation water quota under the performance restraint of surface irrigation on the basis of evaluating advance ratio and applicability on parameters of the crop growth model and the surface irrigation simulating model.Besides,based on parameters of the crop growth model,an irrigation system simulating scenario scheme was determined through combining different precipitation level years,different growth periods,and check irrigation arrangement with the irrigation quota control indicator and the minimum irrigation quota limited by the surface irrigation performance as the upper limit and the lower limit,respectively,in the research area,so as to simulate the crop growth model.At last,an indicator system and an evaluation model for evaluating and filtering the irrigation system were proposed and constructed in accordance with the simulated results to evaluate and filtrate the simulation scheme.Main findings and innovations of this paper are mainly manifested in the following aspects:(1)The DSSAT crop model was utilized to determine model parameters and to evaluate the applicability of the model based on field trial data,so as to select the optimal set of parameters for the trial crop model.Experimental fields were set in multiple areas in this study,so as to analyze and determine genetic parameters of crop varieties in the mode of uniform variety planted,and four different cross-validation plans were adopted to adjust and verify parameters of the DSSAT crop model of the tested crops.The model was applied in simulating changes of soil and moisture of crops,which canobtain a high accuracy when irrigation system data are fully utilized for calibration and verification.The further from the surface soil,the higher the simulation accuracy will be obtained.It can be observed from the parameter calibration plan and results of model cross-validation that high simulation accuracy could be obtained in the phenological period and single grain weight of the test crops,while big error existed between the measured crop yield and the simulated one.All in all,after the parameter rating of the DSSAT model was corrected,the simulated result had good convergence and acstem.(2)The SISM model was employed to simulate the model.Also,the applicability of the model was verified by field trial data.Meanwhile,irrigation processes under different combination of technical elements were simulated to obtain the corresponding performance index values of border irrigation,and determine the minimum irrigation quotas for different combinations of irrigation technology in North China.Soil infiltration parameters of each irrigation event were estimated with field irrigation trial data obtained from winter wheat in different growth stages based on typical areas.Moreover,elements such as the length of border check,the field slope,the land leveling precision,the spatial variability of micro-topography,and border unit discharge were taken into account together with the status of border irrigation in North China.To this end,with the combinations of 53,088 irrigation technical elements in total,the whole piece of winter wheat field being covered by surface irrigation water flow and the minimum irrigation depth Zmin being larger than 0 were considered as control requirements.On this basis,the SISM model was adopted to simulate the irrigation processes in different technical elements,analyze the correspondence of technological elements and irrigation performance of border irrigation,and determine the minimum irrigation quotas under different element combinations of irrigation techniques.(3)The water consumption rule of winter wheat in the growth period was analyzed to prepare the scenario scheme for the irrigation system.And parameters of the calibrated crop growth model were simulated to analyze the influence of factors such as the crop growth period,irrigation water quotas in different growth stages,irrigation quotas and different precipitation years on the output and the evapotranspiration.According to the simulation results,with the increase of irrigation water quota,the corp transpiration capacity is increased,to varying degrees,while the soil evaporation capacity is varied insignificantly in four growth stages of winter wheat of different level years.Moreover,the sensitivity of water supply on crop yield in different stages is Jointing stage>Turning green stage>Overwintering stage>Grain filling stage,while the yield-increasing potential in different level years is low flow year>normal flow year>high flow year.The rule and amplitude of variation of the above affecting factors are consistent under three typical border lengths.And the irrigation at the greening-jointing and jointing-heading stages remarkably affects the yield increase of the corps.Thus,these two stages are critical water required periods.(4)The irrigation system scheme was optimized from the perspectives of crop yield-water use efficiency and net income-input-output ratio in accordance with scenario simulation results of the irrigation system,so that the optimal irrigation scheme at different level years and different typical length of border check.The optimal surface irrigation and border irrigation layout scheme in the study area is 50m in border length under two evaluation index systems.Irrigation systems corresponding to the three typical level years in high,normal,and low precipitation levels with the highest water use efficiency are 0+55+ 55+0(mm),0+75+55+0(mm),and 0+75+55+0(mm),that is,watering at sprouting stage and at jointing stage are required.The irrigation systems with the largest input-output ratio are 0+75+55+0(mm),55+75+55+0(mm),and 55+75+55+0(mm),that is,watering at sprouting stage and at jointing stage is required in the wet year,while watering at overwintering stage,at sprouting stage and at jointing stage is required in the dry year and the normal flow year.Regarding optimized elements for surface irritation and border irrigation,50m in border length is recommended for achieving an outstanding irrigation performance.The above research achievements can provide producers with strongly-practical border check layouts and irrigation system applying modes.Research findings being of strong practicability and promotion value,have important and realistic significance in easing the shortage of irrigation water sources as a whole and promoting the sustainable development of modem agriculture in North China.