Remote Sensing Monitoring Of Biophysical And Biochemical Parameters Of Staple Rice In Key Growth Stages

Fast and accurate access to a wide range of crop nutrition and growth status has become an inherent requirement for the development of precision agriculture.Rice,as a staple food source,plays an important role in China’s food security,and the improvement of its output requires especially careful field management.The growth period,leaf area and canopy cover ratio,leaf chlorophyll,nitrogen,phosphorus,and potassium contents of rice are important parameters for monitoring rice growth status.The timely and effective acquisition of these parameters is of great significance for targeted field management of field rice.Satellite remote sensing monitoring technology has the advantages of low cost,high efficiency,and no damage compared with traditional nutrition diagnosis methods.It has become an important technical means for monitoring rice parameters in a large area.However,when the satellite remote sensing inversion model of regional field crops is constructed directly based on the ground point data,not only the monitoring accuracy is affected by the limited band range and the number of mixed pixels,but also because of the complex spatial scale conversion effects.The problem makes the relevant monitoring results difficult to apply to the precise management practices of regional field crops.This paper takes rice widely planted in the Jianghan Plain as the research object,uses ground digital images as intermediate variables,and compares and analyzes the application effects and existing problems of remote sensing monitoring models of key parameters of rice at different spatial scales to explore an appropriate A ground-space coupling model for high-precision monitoring of key parameters of rice in regional fields.The main contents of the research and the results achieved are as follows:(1)The process characteristics of key rice parameters were analyzed.The field canopy images,leaf scan images,field measurement data on the ground measured points,and field test and analysis data in the laboratory,etc.were used to determine the rice leaf size and canopy cover ratio,leaf chlorophyll nitrogen and phosphorus of different planting methods.The characteristics of key parameters such as potassium content in different growth periods were analyzed and studied.The results show that the time-series changes of each key parameter of rice have a high correlation with each other,and the rice parameters can be estimated based on this.The transplanted rice had a higher leaf area index than the sowing rice in the growth period before the jointing booting stage,but the planting density of the transplanted rice was lower than that of the sowing rice,which resulted in a lower canopy cover ratio at the seedling stage than the sowing rice.(2)The monitoring model of rice key parameters based on ground digital images is studied.The results show that the prediction results of SPAD and canopy coverage ratio(Ca)using digital images are better.Among them,the prediction results of SPAD and Ca based on scanned images have RMSE of 2.293 and 0.021,RE of 5.528% and 4.917%.Can be used for ground monitoring practice.The prediction results of other rice key parameter estimation models are relatively poor,which can only provide a certain degree of guidance for actual monitoring.In addition,compared with the canopy image,the scanned image has a stronger ability to monitor key rice parameters.(3)The key rice parameter monitoring model based on Sentry 2 image only was studied.The results showed that SPAD and Ca also achieved better model prediction results than other parameters,with RMSE of 3.799 and 0.033,and RE of 8.0065% and 7.610.The monitoring models of other rice parameters combined with RMSE and RE evaluation indicators are obviously inferior to SPAD and Ca.In addition,the accuracy of rice leaf chlorophyll inversion based on Sentinel 2 satellite images is higher than that of digital images,and the inversion of other key rice parameters is lower than that of digital images.(4)Integrating the performance characteristics of key rice parameters on ground digital images and satellite remote sensing images and the relationship between them,establishing a ground-air coupling monitoring model of key field rice parameters with leaf scanning images as intermediate variables,based on this It can realize high-precision satellite remote sensing monitoring of key rice parameters SPAD,Ca and K on the regional field scale.Comparative experiments show that the monitoring effect of the ground-air coupling model on these rice parameters is not only better than that of Sentinel 2 monitoring model,but also more accurate than the monitoring model based on single-source ground digital images.(5)The extrapolation application of the ground-air coupling monitoring model of key rice parameters in the study area was carried out.The results show that there are large spatial and temporal differences in key parameters such as the growth and development period of rice in the study area,which are mainly caused by the inconsistent planting preferences of farmers in various regions.