Study On The Optimization Of Planting Structure Based On Crop Water Requirement

In recent years,with the mining of coal and other mineral resources,the groundwater level in Hebei Province has dropped seriously,and some areas are no longer suitable for planting crops due to problems such as water shortage and surface subsidence.At the same time,Hebei Province has also begun to implement the strictest water resources management system,and imposed restrictions on groundwater extraction,resulting in a prominent agricultural water use problem in Hebei Province.The southern plain area of Hebei Province is an important crop planting base in Hebei Province.How to effectively use the adjustment of planting structure to deal with the problem of regional water shortage has become an urgent problem to be solved in this region.In this thesis,the plain area of southern Hebei Province was selected as the study area.STSG filtering(integrating Spatio Temporal information with the Savitzky-Golay filter)was used to smooth the MODIS(Moderate Resolution Imaging Spectroradiometer)NDVI(Normalized Difference Vegetation Index)data in the study area for many years.The decision tree classification model was used to extract the main crop planting structure in the study area in 2001,2006,2012 and 2018.On this basis,according to the daily meteorological data of the corresponding years,the crop water requirement in the study area was calculated and analyzed based on the crop coefficient method.Finally,the linear programming model in operational research was applied to optimize the planting structure of the study area under ideal conditions.The main conclusions are as follows :(1)The planting area of winter wheat and summer maize in the study area was the largest,showing a fluctuating trend in 18 years,and the sowing range is wide,covering the whole study area;the planting area of spring maize and cotton is relatively small,and the planting area of both increases first and then decreases from 2001 to 2018.In the study area,spring maize is mainly planted in Cangzhou and Langfang,and cotton is mainly planted in Hanxing and Hengshui.(2)From the spatial distribution of crop water requirement per unit area,the overall performance of the four crop water requirement in the study area is mainly concentrated in Hanxing and Cangzhou,and the low value is mainly in the north of the study area.According to the average water requirement of each crop in different growth stages,the cotton water requirement is the highest in the initial growth stage.Rapid development period,spring maize > summer maize > cotton > winter wheat;in the middle and mature stages,the order of water requirement of each crop is the same,cotton water requirement is the largest,followed by spring maize,summer maize and winter wheat.From the perspective of the annual average water requirement of different crops in the whole growth period,the average water requirement of the four crops is above 450 mm as a whole.The water requirement of cotton is the largest,followed by spring maize,followed by winter wheat and summer maize.According to the inter-annual variation of total crop water requirement the total annual crop water requirement has maintained an upward trend from 2001 to 2012 and declined from 2012 to 2018.(3)According to the optimization results of crop planting structure,the planting area of winter wheat and cotton increased by 8.9 % and 21.9 %,respectively,and the area of maize decreased by 10.6 %.From the point of view of its optimization effect,the net income of crop planting has increased by 500 million yuan after optimization.At the same time,the total water requirement of crops has decreased after optimization,and the decrease is 1 million cubic meters.Overall,the goal of improving crop economic benefits under the condition of reducing crop water requirement is realized.