GIS Supported Cultivated Land Fertility Analysis And Soil Testing And Fertilizer Recommendation At County Level

Cultivated land is the essence and irreplaceable resource for agricultural production, and is also the important resource for sustainable development of our society and national economy. Therefore, The protection of cultivated land is our basic national policy. It is of great significance to know the quantity, quality and changes of cultivated land for the reasonable planning, utilization and effectively protection of cultivated land. Food security is important for the well-being of people,the country's prosperity and the social stability, while fertilization hold an important place for food security as the primary means for food production. A large number of researches show that the contribution rate of chemical fertilizers in the crop output is as high as 40%-50%. Under the condition of large population and serious shortage of land resources in China, it is meaningful for sustainable development so as to achieve high-yield crops and alternative strategies for water and soil resources through fertilization techniques. Taking Guangrao County as research area, this paper studied soil testing and fertilizer recommendation techniques for management and farmer purposes at county level based on GIS data analysis and fertility evaluation.The research firstly identified grading distribution of cultivated land in Guangrao County. Overlay method between soil map and land use map was adopted to produce evaluation units, evaluation factors were chosen by Delphi approach and cluster analysis with their weights determined by AHP method. Finally the grades of cultivated land fertility were evaluated by fuzzy discrimination method. Our results showed that the cultivated land fertility in Guangrao County was good in general with area of the first and the second grades 30.72% of the total area, the third and the fourth grades 46.59%, and the fifth and the sixth grades only 22.70% of the total area.Research of soil testing and fertilizer recommendations was based on soil testing and field examination. A system of technological fertilizer recommendations including amount, time and application method of nitrogen, phosphorus, kalium and microelement were proposed according to the requirement regulation of crops to soil nutrition, soil ability to supply nutritions and ration-effective use of organic fertilizers. Therefore, soil testing and fertilizer recommendation is a great measure to improve the integrated production capability of agriculture, increase the production of crops and make people become rich.In the research facing management level, using"fertility distribution and target yield"method supported by GIS, fertilizer recommendations were determined. On the basis of recommendation units, it was divided according to fertilizer grade map of cultivated land and crop layout, the parameters were obtained through field-testing, and the nutrient demands and fertilizer recommendations were calculated accordingly. Using GIS, coupling fertilizer recommendation unit map and corresponding attributes, recommendation map of fertilizers in Guangrao County was formed. The results showed that, the spatial distribution of nutrient contents was not uniform. The requirement amount of nitrogen was relatively less, mostly within 200kg·km-2; the requirement amount of phosphorus was great, the area bellowing 20kg·km-2 and more than 240kg·km-2 were large; the requirement amount of kalium varied widely, the southern region had the higher demand, more than 400 kg·km-2, and the northern part large area had lower demand to kalium. Overall, the general demand for nitrogen, phosphorus and kalium elements increased from north to south. There were 14 kinds of fertility recommendations, the proportion of N, P and K ranged in 1:0.04-1.53:0.05-0.82 with the proportion of 19.80% of the whole area. The largest area of the proportion of N, P and K was 1:0.22:0.19, other main proportion of N, P and K were 1:0.05:0.05, 1:1.53:0.82,1:0.004:0.13,1:0.94:0.66, the proportion of the whole area is 17.02%,14.62%,14.01% and 11.31% respectively. With the distribution map of requirement amount of fertilizer and fertility recommendation proportion map, we can know the overall fertilizer demand throughout the county. According to the requirement amount of fertilizer and fertility recommendation proportion, we can put forward the corresponding regional fertilizer recommendations to instruct farmers for reasonable fertilization. We can proposed the specialty fertilizer recommendations and organize agricultural technology sector and manufacturers to produce specialty fertilizer for regional intensive fertilization. The study combined the regional distribution and nutrient balance method, got the accurate regional fertilizer recommendations, and can provide fertilization regions and corresponding fertilization recommendations. It is also useful for the scientific management of cultivated land.In the research facing peasant household, based on the GIS, the maps were grided into size of 50m×50m, quantity for 1145×1684. The total area of the cultivated land is 62389.37 hectares; therefore each grid represents 0.486 Chinese acres. Fertilization quantity of N P K of ach grid can be calculated by nutrient balance model, consequently, the entire county distribution map of fertilization quantity of N, P and K can be obtained. Farmers can inquiry the precise fertilization quantity according to the position of their land. This research changed the present situation that the farmers apply fertilizer blindly and excessively. It is a positive instruction about cultivated land utilization and fertilizing management.