Distribution Changes Of The Main Grain Crops And Its Effects On The Farmland Nutrients Balance In West Liaohe River Basin

In recent years,due to the influence of climate and policies,the crop layout of the Xiliao River Basin has undergone significant changes.Changes in crop planting structure,layout,etc.are bound to have an impact on farmland nutrient balance.Based on the long-term sequence MODIS remote sensing data source,based on the collection of GPS data from the field,the decision tree extraction model is established by using the phenological information of the study area to interpret the spatial layout of the main food crops in the Xiliao River Basin from 2000 to 2015.Analysis of the temporal and spatial variation characteristics of main food crops in the West Liaohe River Basin from 2000 to 2015;Based on the remote sensing interpretation vector data from 2000 to 2015,the farmland nutrient input-output model was established to explore the spatial pattern change of the main food crops and the farmland nutrient balance.The result is as follows:(1)The statistics show that the average area accuracy of the classification is more than 80%,and the overall accuracy of the extraction accuracy of the crop planting pattern is above 84%,which indicates that it is feasible to use the phenological indicators for planting pattern and division,and the decision tree classification method can be applied to planting.Extraction of the pattern.(2)The crop planting area of the West Liaohe River Basin increased from 2000 to 2015,and the distribution of major food crops and the major tributaries of the Xiliao River Basin was consistent.The change of corn area is the most severe.The change of the total planting area of soybean,wheat and corn is not entirely due to the internal transfer change between the three crops.The internal transfer change between the main food crops and other cash crops,new development Or the increase or decrease of the area of major food crops caused by abandoned land is also an important factor causing the change in the total area of major food crops.(3)Total nutrient input-output of nitrogen,phosphorus and potassium in farmland nutrients in the West Liaohe River Basin increased from 2000 to 2015.Judging from the trend of planting area of grain crops and total input and output of farmland nutrients,the two showed good consistency.Affected by the layout and structure of the main crops,the input of nitrogen and phosphorus nutrients in the cultivated land area of the West Liaohe River Basin decreased first and then increased,and the potassium performance showed an upward trend.(4)The change of corn and soybean planting layout has significant influence on the farmland nutrient balance in the Xiliao River Basin.The change of corn planting layout plays a decisive role in the change of nutrient surplus per unit area in the Xiliao River Basin.At the same time,the change of farmland nutrient surplus in 2000-2015 is mainly concentrated in the violent area of corn planting layout change.(5)The nitrogen and phosphorus surplus of grain crops in the West Liaohe River Basin far exceeds the standard level,and the nitrogen and phosphorus inputs exceed the demand for crop production.The nutrient elements of the surplus are accumulated in the soil,and the rest are discharged through the gas.And leaching and runoff into the water body are the main factors causing environmental pollution.Therefore,it is necessary to reasonably control the nitrogen and phosphorus fertilizer application rates of food crops in the Xiliao River Basin.