Change Analysis Of Crop Planting Structure In Typical Black Soil Area Based On Remote Sensing

Crop identification and crop planting structure adjustment are the basic basis for the formulation of various national agricultural policies,as well as the basis for estimating yield information and planting area.Heilongjiang province is a major grain province in China,and its grain output ranks first in China for several years.At the beginning of 2016,the ministry of agriculture put forward the policy of "sickle bay".The development of corn in the sickle bend region was too fast,and the problem of single planting structure gradually emerged.Therefore,it is particularly important to accurately obtain crop planting information.The traditional method of obtaining crop species is based on ground sampling,which is then reported layer by layer and finally summarized.This method to obtain the types of crops results in detail,but time-consuming,laborious over-reliance on statistical data makes the results of the study and the method is relatively backward,so need time,manpower,strong objectivity,build a large range and high precision of classification,for planting area,yield crop allocations,information distribution,provide data support.It is of great significance for the adjustment of crop yield,growth,planting structure,fallow rotation,reduction of corn and rice,as well as solid progress of agricultural supply-side structural reform and efforts to improve the quality and efficiency of agricultural supply system.Due to the large amount of information,short cycle,large detection range,low cost and strong objectivity,remote sensing technology can save a lot of manpower,financial resources,material resources and time.Therefore,it is used in various links of agricultural production,such as:monitoring crop planting area,crop growth information,rapid monitoring and assessment of agricultural drought,pests and diseases and other disaster information,estimation of global,national and regional crop yield,to provide information for quantitative analysis and prediction and warning of food supply.Currently,LANDSAT,gaofen-1,env and SAR can provide us with ideal satellite data.In view of the diversity of remote sensing data,this paper USES the combination of non-optical data and optical data,takes the typical black soil area(Helen,wangkui and lanxi)as the research area,and USES MODIS data to compare the time-phase differences of reflectance spectra and vegetation index of different crops,so as to select the best time-phase for crop classification.In this study,different methods were adopted for crop classification and adjustment analysis of planting structure change,and the driving force of planting structure change was analyzed to observe the spatio-temporal dynamic changes of crop planting structure in three counties in the past three years.The main conclusions are as follows:(1)Crop varieties can be distinguished by analyzing the spectral characteristics of crops.Different crop canopy spectral reflectance and vegetation index is not at the same time under the phase differences,this paper adopts MODIS16 day data extraction different crops don't phase spectral reflectance and draw curves at the same time,determine the critical period of crop classification for 7,8,9 three month,at the same time,combining with the critical period of crop growth and different crop canopy spectral reflectance characteristics of different types for the determination of roughly to the crops.Among them because of the climate in northeast China,mostly in June for the paddy field irrigation,therefore upland and paddy field can be distinguished in this period,growth period,belong to the seeding in July it is difficult to distinguish the period of crop variety,mid to late August,soybean NDVI value is higher,the rice NDVI value is low,the critical moment of this time can be used as extracting soybean and land in remote sensing image as the bright red color,mid to late September in the mature period of corn,the corn NDVI value of the highest,can be a critical period,the identification of maize on the remote sensing image embodied in dark red,mature rice is also in the same period,The color is pink in remote sensing(2)The accuracy of supervised classification is higher than that of unsupervised classification.Supervised classification under the condition of classifying crop so far there are so many ways,this paper adopted two kinds of supervised classification and unsupervised classification method in the study area,map of wangkui,Nancy(Helen),after the results of comparison,and select the result of the high precision,and the classification results of cultivated land within the scope of precision evaluation and final selection results supervised classification method for subsequent research.The accuracy of supervised classification and unsupervised classification was 91.82% and 84.98%,respectively,and the Kappa coefficient was 0.88 and 0.78,respectively.(3)Analyze the change trend of planting structure adjustment from the perspective of time and space.As time goes by,the soybean area in the research area increases year by year,while the corn planting area decreases.However,soybean and corn are still important crops in the research area,and the area and proportion of rice and potato show an increasing trend within three years,and the increasing range is relatively stable.From the perspective of space,the planting structure of the research area is divided into eight planting areas: pure corn planting area,pure soybean planting area,pure rice planting area,corn planting area,soybean planting area,rice planting area,potato planting area and mixed planting area.In three years,the planting center of pure corn growing area tends to move southward.The center of gravity of the corn-dominated crop growing areas showed a trend of transferring from the north to the south,while that of the pure soybean growing areas as a whole showed a trend of moving from the north to the south.The center of gravity of the soy-dominated crop growing areas moved from the north to the south of hailun city,and there was a small distribution in the west of lanxi county.The spatial distribution of mixed cropping areas was widespread,showing a trend of migration from the west to the east of the study area.The area of pure rice planting area and rice-dominated planting area slightly changed,but thechange range was not large.(4)Planting structure adjustment and driving factors.By 2015,2016,2017,spatio-temporal changes of crop planting structure adjustment analysis showed that the three years of the study area is on the rise,the soybean acreage of corn area is on the decline,rice area is almost the same,fewer most corn,soybean area in 2015 because of corn,strong adaptability,can grow in various soil types,and high yield soybean soil the demand is higher,in 2016 began to study in the soybean acreage and proportion rising year by year,corn planting area and the proportion of decline year by year,the change of structural adjustment is most national policy guidance,At the same time,with the proposal and implementation of national policies,farmers actively respond to national policies,so as to improve their own income and realize the adjustment of planting structure.