| Huabei region as a serious drought area in North China,Drought tendency is becoming more and more obvious,Xingtai area is located in the central part of Huabei region,drought and water shortage is very serious.The drought occurrence frequency,influence scope,duration and degree of hazard rank first in all kinds of natural disasters.In the growth period of summer maize,Xingtai area has more precipitation, but due to uneven temporal and spatial distribution of precipitation,it can not satisfy the requirements of water on each summer maize growth stages,leading to the drought of summer maize growth period,so still need irrigation to ensure high yield.The drought monitor of summer maize growth period were divided into two kinds which meteorological monitoring and remote sensing monitoring,there are some differences between the two different methods for drought monitoring,but overall it seems basically the same.Meteorological monitoring is based on the statistical analysis of the site data,the crop drought response is lack of comprehensiveness;Remote sensing monitoring is based on the surface monitoring,it can reflect the changes of crop drought from the whole.There are two parameters which vegetation index and land surface temperature can reveal the soil moisture information through the vegetation to drought stress responses to the environment,because of the limitations of the two separate use,therefore, it is necessary to combine them,the surface temperature vegetation index can not only indicator vegetation drought when the water heat stress environment,and reveal the vegetation in the stress environment showed symptoms,it can effectively improve the accuracy and efficiency of drought monitoring.In this paper,a systematic analysis of drought monitoring at home and abroad is carried out,to search for suitable crop drought monitoring method in Xingtai area.How to cope with drought has become one of the key problems urgently to be solved in Xingtai area sustainable development,in order to solve the problem of effective and comprehensive response to drought,this paper consider the three aspecrs whice are process of dynamic change of drought,impact factor, measures to deal with. Contents and procedures are as follows:(1) The MODIS remote sensing image through processing,calculation to obtain the land surface temperature,vegetation index data,the surface temperature and vegetation index data were processed by ENVI software,calculated TVDI value,to remote sensing and dynamic monitoring of summer maize drought in Xingtai area,to calculate the water demand and precipitation of summer corn,to obtaine various growth stages and different precipitation years fill rate,to conduct meteorological drought monitoring.(2) The validation of the model includes two aspects:firstly:firstly,the correlation which TVDI between LST and NDVI was analyzed by using SPSS software.The results showed that TVDI was positively correlated with LST and had a strong correlation,but had a negative correlation with the NDVI and had a weak correlation. The results showed that the surface temperature was better than the vegetation index,which indicated the change of drought occurrence.Secondly,the correlation analysis between TVDI and 20cm surface soil moisture. Using SPSS software to analyze the correlation between TVDI value and 20cm soil moisture at jointing stage of Summer Maize in 2005-2010,results show,TVDI and 20 cm surface soil moisture showed a negative and strong correlation,it shows that the TVDI index is reasonable to monitor the drought of Summer Maize in Xingtai area.(3) Changes of drought in different regions of the same growing period:From the drought level distribution diagram can be seen, sowing jointing stage,the drought of western hilly region and the eastern plain area are seriously in 2005-2009,the drought in the eastern plain area is relatively light in 2010.The jointing heading stage,the drought of Western Hills of northern is seriously in 2005、2007、2008 and 2009, the southern and easrhern of western hilly area has severe drought in 2006, the central plains area has severe drought in 2010. During the heading filling stage,the drought in the west of 2005-2008 was more serious,and the rest areas were mostly light and medium drought, and the drought in the eastern plain of 2009-2010 was relatively light.Grouting mature period, the western hilly region are severly drought in 2005、 2010, most of the region are mainly heavy drought in 2006、2009, the western hilly area and the eastern plain area are severly drought in、2007、2008.(4) From the meteorological drought monitoring map:Sowing to jointing stage,the Eastern Plain area of Linxi, Qinghe, Nangong have a high precipitation satisfaction rate and low in other counties in 2005、2007、2009、2010、2006,the Central Plains District Julu, Pingxiang have a high precipitation satisfaction rate in 2008,the remaining counties are relatively low. From jointing to heading stage,annual precipitation can meet the demand for water in 2006、2008、2009;Linxi、Qinghe of the Eastern Plain have a high precipitation satisfaction rate in 2005、2010,Shahe of the West hilly region,Linxi、Julu、Renxian of the Middle East Plains have a high precipitation satisfaction rate in 2006、2007、2008、2009,the rest of the county is low.During heading and filling stage,the amount of precipitation could not meet the requirement of Summer Maize water requirement in growing period of 2005-2010.During the grain filling stage and heading filling stage,the change of precipitation content was generally consistent,but the height was different. Only in 2009,it could meet the requirement of water in summer maize growing period.(5) The agricultural drought impact factors in Xingtai region mainly include three aspects:climate,underlying surface and irrigation factors.Climatic factors include precipitation and air temperature, and the underlying surface factors mainly include soil and topography.(6) The yield of summer maize was negatively correlated with the degree of drought distribution,high yield of Summer Maize in the region with low drought level,low yield of Summer Maize in the region with high drought level. Comparison of drought grade map and summer maize yield map can clearly know,Neiqiu、weixian、Shahe,in different years and each growing period have a relatively heavy drought,summer maize yield is relativel low,indicating that the distribution map of drought level was consistent with the yield of summer maize.(7) According to the different growth period of Summer Maize in Xingtai,this article puts forward different measures to deal with drought:optimal allocation of water resources、the introduction of advanced irrigation technology、according to the weather changes、adjust seeding time according to the change of weather、improve the effective utilization of natural precipitation、introduction of new variety with strong drought resistance and so on. |
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