Phosphorus Management In Chinese Agroecosystem Based On GIS And Outlook Of Phosphate Fertilizer Demand

It was designed a database for the utilization of phosphate fertilizers and the phosphorus balance in the soil of different countries in China based on the agricultural statistic data to analyze the spatio-temporal distribution of phosphorus in those areas by using GIS (Geographic Information Systems). The models of the balance and variation of phosphorus were simulated and validated in the field scale and the regional scale based on the phosphate variations integrating with the balance of phosphorus of soil in the long-term fertilization monitoring locations in China and Huanghuaihai plain. The characters of impact factors such as fertilization, local climate, soil physico-chemical status, and cultivation were analyzed, which provide a theory basis for the application and outlook of phosphate fertilizers in different region so that it could optimize phosphate fertilizer resources. The results are summarized as follows:1,According to study on the input and the balance of phosphorus in different countries in China in 1990, 1997, 2004, the input and the balance of phosphorus increased from 1990 to 2004 all over the country. The regional differnce enlareged gradually which indicated the input and balance of phosphorus more in the East and South and less in the West and North.2,The relationship between the balance of phosphorus and the change of the availabe phosphorus in the soil was analyzed from the results of 136 long-term located experiments in China. It showed that the profit and loss of the soil phosphorus had an effect on soil availabe phosphorus. Soil phosphorus could increase while the balance of field nutrients were surplus, and vice versa. In a county scale, there was no change obviously in the balance of soil phosphorus and the change of availabe phosphorus in the Huanghuaihai plain.3,According to the analyses of 136 long-term located experiments in China near 10 years, the results showed that the balance of the soil phosphorus increased on the whole, but there were regional differences, which was that the input of phosphorus per unit area was lower in the northwest and the northeast, and the highest input of phosphorus was in the north of China. The amount of the phosphorus balance per unit area was lower in the northwest and northeast and it was highest in the south of China. From the models of the phosphorus balance and the change of phosphorus, it could be concluded that different regions had different effects of the phosphorus balance on the available phosphorus. When the amount of the phosphorus balance was increased by 1 kg·hm-2, the content of the soil availabe phosphorus was increased 0.0349 mg·kg-1 in the northeast but only 0.0198 mg·kg-1 in the northwest and the average was 0.0251 mg·kg-1 all over the country. The more phosphate fertilizers were applied per unit area, the higher values of the phosphorus balance were got.4,According to the phosphorus balance in the Huanhuaihai plain, the surplus areas of soil phosphorus balance were widely larger than the deficiency areas. It also suggested that phosphorus resources of this region were always accumulated in the soil. The phosphorus balance per unit area also increased from 1997 to 2004. Compared to 1997, the content of soil available phosphorus increased in 2004 in most area, but the increase was small. It showed the more variation of available phosphorus with the higher phosphorus balance and the content of available phosphorus increased linearly with the increase of the phosphorus balance by analysis of the relationship between phosphorus balance and phosphorus variation.5,It was analyzed the impact factors of phosphorus balance such as phosphorus application rate, planting structure, economical reason, soil type, soil texture, soil fertility, soil pH and climate, The impact factors of the gain and loss of phosphorus was analyzed from six sides included phosphorus application rate, soil type, soil texture, soil fertility, soil pH and climate. It showed that the phosphorus balance and the phosphorus variation were correlated with phosphorus application rate, soil type, soil texture, average temperature and soil fertility but there was not correlated with soil pH and precipitation.6,The changes of soil available phosphorus could be estimated by the model of the phosphorus balance and the model of the phosphorus variation. It was also used to calculate the requirement of phosphate fertilizers in the future. The consumption of phosphate fertilizers would rise to 13.472 million ton after 10 years. The estimation for the requirement of phosphate fertilizers was similar with the results from other methods, which indicated the models can be used to predict the demand of phosphate fertilizers in China.