Stablility classification of cultivated land based on crop growth difference in different annual precipitation type in semi-arid and sandy land area

Abstract: Water resource is the key factor affecting dry land maize growth in semi-arid and sandy land area. These areas are fragile in eco-environment and unreasonable land use has induced serious land desertification. So, it is significant to study crop growth status under different precipitations and to identify the unstable cultivated land for eco-environment rehabilitation in semi-arid and sandy land area. Taking Horqin Left Back Banner as a case study, firstly, this paper analyzed the precipitation types of maize growth period from 1980 to 2013 with precipitation data of Horqin Left Back Banner Weather Station. Secondly, dry land maize growth status was studied with the method of remote sensing technology and the crop production stability was analyzed. Thirdly, unstable cultivated land identification was performed according to dry land maize growth status under normal precipitation year and partially dry year. The results indicated that proportions of dry year, partially dry year, normal year, partially wet year, and wet year were 11.77%, 29.41%, 17.65%, 32.35%, and 8.82% respectively. The proportions of partially wet year and wet year, partially dry year and dry year were large. Precipitation fluctuation in maize growth period was dramatical in Horqin Left Back Banner. The sum of normalized difference vegetation index (NDVIsum) of cultivated land in partially dry year (2001), normal year (2013), and partially wet year (2008, 2012) were mostly distributed in 4，4.5), 4.5，5.5) and 4，5) respectively. There were big gaps in dry land maize growth condition in different precipitation types of maize growth period. In general, dry land maize growth status in partially dry year was worse than that under normal year. Precipitation in semi-arid and sandy land area could not meet the demand of dry land maize growth. And precipitation in partially dry year was less than normal year. These reasons made dry land maize growth in partially dry year worse than that under normal year. Dry land maize growth under normal year was better than that under partially wet year. Micro-terrain made the redistribution of precipitation and the cultivated land distributed at low terrain would be in waterlogging in much precipitation condition. So, dry land maize growth under partially wet year was worse than that under normal year. Dry land maize growth under partially dry year was worse than that under partially wet year. Area of cultivated land distributed on high terrain was larger than that on low terrain, and compared with the waterlogging, drought had a more wide effect on dry land maize growth. So, dry land maize growth under partially dry year was worse than that under partially wet year. According to the precipitation types and dry land maize growth status, crop production is unstable in semi-arid and sandy land area. Based on the difference of dry land maize growth under normal year and partially dry year, cultivated land was grouped into 4 types: extremely unstable cultivated land, unstable cultivated land, relatively stable cultivated land, and stable cultivated land. The areas of extremely unstable cultivated land and unstable cultivated land were 68.75 and 33918.75 hm2 respectively. By this study, the understanding of agricultural production in semi-arid and sandy land area has been deepened. Drainage facilities or water storage facilities should be constructed in low-lying area in semi-arid and sandy land area to avoid the effect of waterlogging on crop growth. Extremely unstable cultivated land and unstable cultivated land should be changed to achieve ecology restoration.