Study On Parcel Scale Winter Oilseed Rape Waterlogging Monitoring Method By Remote Sensing

Oilseed rape(Brassica napus L.)is one of the most important wintering crops in the middle and lower reaches of the Yangtze River Basin,occupying an important position in China's grain and oil production.However,due to the wet and rainy season in the spring,oilseed rape at this region often suffered a large area of waterlogging stress,resulting in serious loss of yield.In the past,people obtained the data most by the methods of laboratory analysis and field survey and measurement.However,using these methods to collect data is time-consuming and difficult to collect large-scale data,and it is difficult to collect large-scale data.In recent years,with the rapid development of the ground observation technology,such as the satellite communication technology,space positioning technology,remote sensing technology and geographic information system and the intensified change of earth's environment,people's requirements for the quality and quantity of remote sensing satellite data continues to increase.In the field of agricultural remote sensing applications,the monitoring and analysis of crop growth,the prediction of pests and diseases,and the estimation of crops have made a high demand for the use of high temporal and high spatial resolution remote sensing images.This study on the strength of the high-resolution,multi-source,and multi-temporal satellite data,based on the experimental data,accurately obtained the oilseed rape growth information under waterlogging stress condition,and estimated the oilseed rape growth status under waterlogging condition by using various regression models;then,mapped the oilseed rape dynamic growth,and made qualitative analysis and quantitative study on the oilseed rape growth under waterlogging condition.The main research contents and conclusions are as follows:(1)This research studied the effects of waterlogging stress on the oilseed rape biomass,leaf area and yield at seedling stage and flowering stage through a pot experiment.Results showed that at seedling stage and flowering stage,the growth and development and yield of oilseed rape were affected by waterlogging stress,and the response to waterlogging stress at flowering stage was more sensitive than that at seedling stage.Therefore,during the growth and development of oilseed rape,especially at the flowering stage,drainage should be carried out in time to reduce the impact of waterlogging damage on oilseed rape growth.At the same time,when the oilseed rape suffering the waterlogging stress damage more than 15 days at seedling stage,and more than 10 days at flowering stage,there will have a significant impact on the growth and development of oilseed rape.(2)Through field experiments,different soil water content treatments were imposed at the seedling stage and flowering stage for 20 days,respectively.At the same time,the field LAI data were measured and the high resolution satellite remote sensing data were acquired.Then,we estimated the oilseed rape LAI growth before flowering stage by using exponential regression model,compared the field measured LAI with the vegetation indices that calculated from the high spatial resolution satellite data.Finally,results showed that the GNDVI-LAI exponential regression model had the best fit,and its validation accuracy was highest.Then we used the GNDVI-LAI exponential regression model to map the seasonal dynamic growth of oilseed rape.(3)Field experiment was carried out with different waterlogging treatments,during the seedling stage,flowering stage and podding stage,respectively,and the field AGB data and remote sensing data were acquired simultaneously.Five regression models were established,and the optimal regression model was used to estimate the AGB of winter oilseed rape.Results showed that power regression model established by NDVI and AGB had the the best,with the R~2 being 0.75 and the validation index RMSE being 100.45 g/m2 and rRMSE being 20%respectively.Simultaneously,we mapped the seasonal growth of oilseed rape AGB,studied the variability of oilseed rape AGB and monitored the oilseed rape growth under waterlogging stress.Results showed that high spatial resolution satellite could well show the growth difference of different waterlogging stress imposed on different growth stages of oilseed rape.And the results were in agreement with the results of pot experiment in the second chapter of this study,the effect of waterlogging stress on the oilseed rape at flowering stage was higher than that of seedling stage,and the effect of flooding treatment was greater than that of waterlogging treatment.