Spatio-temporal Variatio Variability Of Farmland Topsoil Phosphorus Of Sichuan Province

Soil phosphorus is not only a necessary nutrient element for plant growth and development,but also one of the main factors that lead to the eutrophication of rivers and lakes.The soil phosphorus reserves and its dynamic balance as an important index to reflect the soil quality of farmland topsoil have an important influence on maintaining soil fertility.In this paper,the spatial distribution of total phosphorus and phosphorus content in farmland topsoil of Sichuan province was analyzed by geostatistics and ArcGIS,and the spatial distribution of total phosphorus and phosphorus content of farmland soil in the two periods of 1979-1985 years?1980s?and 2005-2011 years?2000s?were analyzed by the method of Geostatistics and the combination of geostatistics.The spatial distribution characteristics of total phosphorus and effective phosphorus density in farmland soil were studied with four spatial prediction models,and the total phosphorus and available phosphorus reserves of farmland soil in two periods were estimated respectively.The main conclusions of the full text are as follows:?1?The total phosphorus content of farmland topsoil in 1980s province is 0.12-2.05g/kg,which is concentrated in the lack of grade,and the range of available phosphorus content is 0.5-38.2mg/kg,which is concentrated in the rich and lack grade.The concentration of total phosphorus of farmland topsoil in 1980s Provinces is 0.12-2.05 g/kg,while range of available phosphorus content is 0.5-38.2 mg/kg,which was concentrated in lack of grades.The total phosphorus content of farmland topsoil in 2000s province is0.01-2.72 g/kg,which is concentrated in the lack of and below the level,and the range of available phosphorus content is 0.1-80.2mg/kg,which is concentrated in the middle or above grade.In different periods,the total phosphorus content of farmland topsoil in the northern Sichuan Plateau and the northern Sichuan south mountain region decreased obviously,but the total phosphorus storage of farmland topsoil in the middle of the hilly region of the basin and the central of the Chengdu plain increased greatly.The content of available phosphorus decreased significantly in the southern part of the hilly region of the basin and in the central part of Southwest Sichuan.?2?The best prediction models of phosphorus density of farmland topsoil in different ecological zones were different.The total phosphorus density in 1980s soils was GWRK and the available phosphorus density was RK.The total phosphorus density in 20^thcentury soils of Chengdu plain region was RK,and the available phosphorus density was GWRK;The total phosphorus density in hilly region of the basin was GWRK and the available phosphorus density is GWRK;The total phosphorus density in South Sichuan mountain region is GWRK and the available phosphorus density is GWRK;The total phosphorus density in Northwest Sichuan Plateau is CK and the available phosphorus density is RK;The total phosphorus density in Around the basin region is RK and the available phosphorus density is GWRK.?3?Using the optimal prediction model,the spatial interpolation of phosphorus density in farmland topsoil was carried out.The results of 1980s farmland topsoil showed that the total phosphorus density in the whole Province varies from 0.061-0.648 kg/m2,and the variation range of available phosphorus density was 0.13-4.75 g/m2.The results of2000s farmland topsoil showed that the total phosphorus density in the whole Province varies from 0.001-0.584 kg/m2,and the variation range of available phosphorus density was 0.03-19.46 g/m2.In the different ecological region of 2000s,the variation range of total phosphorus density in the Chengdu plain region was 0.004-0.333 kg/m2,while the range of available phosphorus density was 0.49-19.46 g/m2.The variation range of total phosphorus density in Hilly region of the basin was 0.004-0.316 kg/m2,the variation range of available phosphorus density was 0.06-12.84 g/m2.The variation range of total phosphorus density in Around the basin region was 0.008-0.358 kg/m2,and the available phosphorus density was 0.03-11.85g/m2.The variation range of total phosphorus density in South Sichuan mountain region was 0.015-0.584kg/m2,the range of the available phosphorus density was 0.17-18.95g/m2.The variation range of total phosphorus density in Northwest Sichuan Platea was 0.001-0.278kg/m2.The variation range of the available phosphorus density is 0.42-18.95g/m2.?4?In 1980s soils,the total phosphorus and available phosphorus storage of farmland topsoil in the whole province was 9.790Tg and 105.783Gg respectively,and the proportion of available phosphorus in total phosphorus storage was 1.08%.In 2000s the total and available phosphorus storage of farmland topsoil in the whole province was 9.401Tg and239.218Gg respectively,and the proportion of available phosphorus in total phosphorus storage was 2.54%.The total phosphorus and available phosphorus storage in the farmland were consistent with the order in the ecological region,cultivated land and soil type.Hilly region of the basin>Around the basin region>Chengdu plain region>South Sichuan mountain region>Northwest Sichuan Plateau;and from the farmland type,the dryland>paddy field>water land;from the soil type,purple soil>paddy soil>yellow soil.At the same time,the total phosphorus storage in the farmland of 2000s province decreased by0.389Tg compared with 1980s,while the available phosphorus storage increased by133.435Gg.