The Estimation On The Total Nitrogen Of The Rice Field By Remote Sensing In Lishui County, Nanjing City

The remote sensing is important in getting the fertility level of the cropland and plays an important role in the the fertilization. The Normalized Difference Vegetation Index (NDVI) has made great contribution in the monitoring of the earth vegetation cover. The kind of the vegetation cover in the paddy field is single, with few other affecting factors which makes monitoring the soil fertility indirectly with the monitoring of the rice growth vigour using NDVI. The paper focused on the monitoring of the soil fertility of the paddy soil in the county of Lishui, Nanjing city using the NDVI of the CBERS-2 CCD image. And the research showed that is possible. And the grade distribution figure of the total Nitrogen content of the study area is made, which makes the monitoring of the total Nitrogen in the paddy field possible with remote sensing.Soil is the material foundation and the headspring of human survival for the people living on the earth. As the agency which is very important for the crop growth and provides food for the world, soil is the plant base for its growth reproduction and biological production. And the content of various elements in the soil is the main factor affecting the soil fertility and deciding whether the srop has a high yield or not Therefor, understand the soil fertility and realize the crop restriction factor according to the basic nutritional requirement of the crop production is critical to the rational fertilization and the income increase of the crop.As there are spatial distribution differences of the soil fertility in the cropland, the traditional indistinctive fertilization may lead to agricultural no point pollution because of over fertilization in some area whereas can cause soil fertility exhaustion in other places. Besides, the content of various elements in the soil is a relative dynamic state which is a changing process. So it is necessary to real time monitor all kinds of nutrient elements in the soil because the soil fertility in the cropland must to be mastered if formulated fertilization want to be executed. The traditional monitoring to the soil fertility usually implemented through the steps of field sampling, air drying, soil grinding and the chemical analysis in the laboratory. On one hand, it will wast a mass of labours and material resources; on the other hand,the period of monitoring the soil fertility will last for long and that will make a bad time effectiveness. Therefore the peasants can not master the information of the soil fertility in the cropland effectively in time and it is hard to take efficient measures to execute rational fertilization for removing the soil restriction factor to the crops. So it is urgent to find a method to monitor the soil fertility quickly, effectively with low input.The remote sensing technology is a comprehensive detective technology which springed up in the sixties of the 20th century and then developed rapidly. It is a process to conclude earth surface parameters by the measure of the electromagnetic radiation obtained from the ground surface. As the common ground object, soil is very sensitive to the electromagnetic radiation of specific waveband. There is a remarkable correlation between soil electromagnetic radiation in some waveband and some physical-chemical parameters of the soil which is the internal mechanism of monitoring soil quality with remote sensing technology. But the soil in the cropland was usually covered by vegetation and the duration of the bare soil was short that affected the application of remote sensing technology in the soil fertility monitoring in the croplang. However, scholars at home and abroad have make remarkable achievements on the monitoring of crop growth status and its nutritional conditions. Because different physico-chemical properties of the soil and different levels of fertilization will affect the crop growth which reflects on the different electromagnetic radiation of the crop canopy finally, the existence of this mechanism make it possible to indirectly monitor the soil physico-chemical properties through vegetation spectrum properties obtained by remote sensing. The Normalized Difference Vegetation Index (NDVI) has made great contribution in the monitoring of vegetation coverage on the land surface. Because the single kind vegetation coverage in the paddy land is scarcely affected by other factors, it is feasible to indirectly monitor the soil fertility in the paddy land through monitoring the rice growth by NDVI.The application of remote sensing in the monitoring of the soil fertility status just can make up the defects of the traditional soil monitoring. Remote sensing technology has played an important role in the soil monitoring for its advantages such as the real time, persistence, large volume of data, wide range of observation and so on. The spatial distribution of the soil physical-chemical properties can be reflected using the remote sensing, so the soil in the same area could be monitored by using multi-temporal remote sensing images that will prevent the no_point pollution caused by over fertilization in some area and the soil fertility exhaustion in other places which can provide evidence for the rational fertilization.The research took paddyland of the rural area in Lishui County, Nanjing as research region, took the main index of the remote sensing image—NDVI as the research object. The correlation and regression analysis was make to connect organically the relationship between the micro monitoring data on the ground and the macroscopically monitoring data of the remote sensing on the purpose of probing into the sensitive wave band or wave band association of the main nutrient element of the soil-total nitrogen in rural area from China and Brazil Earth Resource Satellite 2 data (CBERS-2 data), studied the establishment of remote sensing monitoring speculating model of soil quality in rural district. At last, the established model was applied to monitor the soil fertility of the paddyland and the map of the total nitrogen content of the paddy soil in the research region was also made.The innovative point of this paper is that the soil total nitrogen content of the paddyland in Lishui County, Nanjing was estimated by the Normalized Difference Vegetation Index (NDVI) of the CCD data from the CBERS-2; and on this basis the grade distribution of the soil total nitrogen content in the research area was made; further more, the preliminary study of the founding of the technology system of the estimation of the soil elements in the rice field using remote sensing was also discussed. This paper reached the following conclusions by the study:(1)The NDVI of the CCD data from the CBERS-2 in the tillering stage of the rice can reflect the rice growth propertily and the total nitrogen level of the soil in the paddyland can also be indirectly reflected through that; (2)the semi-quantitative estimation of the soil total nitrogen in the paddyland could be realized using the CCD data from the CBERS-2; (3) regionalization mapping of the soil total nitrogen in the paddyland of the research region also can be achieved on the basis of the NDVI image; (4) it is basicly feasible to found the technology system of the estimation of the soil elements with remote sensing technology. On the basis of the research above, further research can be done to improve the precision of the estimation model,then the accurate monitoring to the soil elements can be realized. Furthermore found and perfect the technology system of the estimation of the soil elements with remote sensing technology through monitoring the content of other elements in the soil.