| Nitrogen(N) and phosphorus(P)are important environmental factors in terrestrial ecosystem, their content and migration can directly influence soil ecosystem productivity and water environmental quality, the storage of soil N and P has become a hot issue in ecological and environmental research. Based on the data of the second survey of soil samples in 1983 and the survey of samples of farmland capability in Tong'an district, Xiamen in 2007, the grid database of the storage and density of N and P in the plough horizon of farmland soil in Tong'an district in 1983 and 2007 was evaluated and established by GIS and mathematical model respectively in this study; The value of N and P of the soil in the plough horizon in Tong'an district was calculated by Soil nutrient price method. In addition, the grid database of the value of N and P about the farmland soil in Tong'an district in 1983 and 2007 was also established respectively. Then the temporal and spatial variation of the value of storage and density about N and P in this district was analyzed and the division was evaluated. The results of the study are as follows:1. In 1983 and 2007, the density of N in the soil of plough horizon in Tong'an district was between 0.10kg/m2-0.24kg/m2 and 0.12kg/m2-0.26kg/m2 respectively, and the average was 0.14kg/m2 and0.18 kg/m2 respectively. The spacial variation of the density of N in the whole district was distinct. The towns with lower include Hongtang, Xike Town and Fengnan farm in the south. The towns with higher density of N include Lianhua and Tingxi town in the north. In Tong'an district, the density of N in the north was higher than the south in both 1983 and 2007. 2. The total storage of N in the soil of plough horizon in Tong'an district was 12563.33t and 15815.30 t in 1983 and 2007 respectively. Both in 1983 and 2007, the mainly towns with higher storage of N are Lianhua and Wuxian, and the storage of N was lower in Xike and Fengnan farm, the storage of N in the north was also higher than the south in space.3. In 1983 and 2007, the density of P in the soil of plough horizon in Tong'an district was between 0.03kg/m2-0.20kg/m2 and 0.13kg/m2-0.37kg/m2 respectively and the average was 0.09kg/m2 and 0.23kg/m2 respectively. In 1983, the towns with lower density of P included Hongtang and Wuxi Town, the towns with higher density of P included Datong, Tingxi town and Fengnan farm. In 2007, the towns with lower density of P included Lianhua and Tingxi, the towns with higher density of P included Xiangping and Wuxian town. In Tong'an district, the density of P was higher in the north and lower in the south in 1983, but in 2007, the density of P was higher in the south and lower in the north.4. The total storage of P in the soil of plough horizon in Tong'an district was 8145.38t and 19903.14t in 1983 and 2007 respectively. Both in 1983 and 2007, the towns with higher storage of P are mainly Lianhua and Wuxian town, at the same time storage of P in Xike and Fengnan farm was lower, storage of P in the north was also higher than the south in space.5. In Tong'an district, the total value of N in the soil of plough horizon in 1983 and 2007 was 4.70×107 yuan and 5.92×107 yuan respectively. In 1983, the value of N in different town was between 1.24×106 yuan and 1.03×107 yuan with the average of 5.22×106 yuan. In 2007, the value of N in different town was between 1.51×106 yuan and 1.31×107 yuan with the average of 6.57×106 yuan. The in different town was also higher in the north and lower in the south.6. In Tong'an district, the total value of P in the soil of plough horizon in 1983 and 2007 was 2.57×107yuan and 6.29×107yuan respectively. In 1983, the value of P in different town was between 6.84×105yuan and 5.53×106yuan with the average of 2.86×106yuan. In 2007, the value of P in different town was between 1.77×106yuan and 1.52×107yuan with the average of 6.98×106yuan. The value of P was also higher in the north and lower in the south.7. In Tongan district, the area with higher Storage of N was 68.66hm2 and 1704.89hm2, took up 15.04% and 2.88% of the total arable land respectively in 1983 and 2007, Such area mainly located in Datong, Wuxian, Ximin Town. The area with medium Storage of N was 2684.64hm2 and 5349.59hm2, took up 62.66% and 65.08% of the region's total area of arable land respectively in 1983 and 2007, Such area mainly located in Lianhua, Tingxi and Wuxian town in 1983 while in Lianhua and Wuxian Town in 2007. The area with low Storage of N mainly located in Wuxian and Lianhua Town in 1983 and in Xinmin and Hongtang Town in 2007, and accounted for 66.51% and 14.18% of the total area of arable land in this region in 1983 and 2007 respectively. The area with low Storage of N was 5466.99 hm2 and 1165.87 hm2.8. In Tong'an district, there was no areas with high Storage of P reserved in 1983. The area with higher Storage of P was 1438.26hm2, took up 17.50% of the total arable land in 2007, Such area mainly located in Wuxian Town. The area with medium Storage of P mainly located in Datong Town in 1983 and in Lianhua and Wuxian Town in 2007, and accounted for 0.06% and 69.30% of the total area of arable land in this region in 1983 and 2007 respectively. The area of medium Storage of P was 4.55hm2 and 5696.38hm2. The area with low Storage of P was 8215.80hm2 and 1083.95hm2, took up 99.94% and 13.19% of the region's total area of arable land respectively in 1983 and 2007, Such area mainly located in Lianhua and Wuxian town in 1983 while in Lianhua and Tingxi Town in 2007.9. During 1983 and 2007, there was a general trend of increasing of the density of N, the storage and value of N in the arable layer of the farm land took up 96.78% of the total arable land in Tong'an district. The region where the density of N descended mainly in the northwest of Xinmi Town and parts of Datong street. The change of the storage of soil N and the value of N spatial were the same as the density of N from 1983 to 2007 in the whole area .10. During 1983 and 2007, there was a general trend of increasing of the density of P, the storage and value of P in the arable layer of the farm land took up 98.00% of the total arable land in Tong'an district. The region where P density descended mainly in the north of Tingxi Town with Mountain or Valley slope. The change of the storage of soil P and the value of P spatial were the same as the density of N during this 24 years.
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