Spatial Variability of Soil Available Phosphorus and Soil Available Potassium Contents in Agricultural Land in Danzhou,Hainan Province

Key words: 
• Agricultural land /
• soil available phosphorus /
• soil available potassium /
• spatial variability /
• Danzhou

Abstract: Understanding the spatial variation and distribution pattern of soil available phosphorus（SAP） and soil available potassium（SAK） contents is of great importance for sustainable development of agricultural land in a region.The spatial variation of SAP and SAK contents in agricultural land in Danzhou,Hainan was analyzed by using geostatistics and geographic information system（GIS） to provide information for preventing soil degradation.There were 2 597 soil samples（0-20 cm） collected from the agricultural land.The geostatistical characteristics,spatial trend and range of the SAP and SAK contents were analyzed using the Geostatistical Analyst,Arc GIS 9.0.For all the soil samples collected,the SAP content averaged 13.15 g·kg^-1,generally moderate in the soil,with an coefficient of variation（CV） being 163.99%.The spatial correlation distance（range） of the SAK content was 12.03 km,and the proportion of the semi-variogram model（C₀/（C₀+C）） was 66.68%,indicating a high semi-variogram value in the SAK content.The SAK content was 36.49 g·kg^-1 by average,generally low in the soil,and its CV was 78.02%.The spatial correlation distance of the SAK content was 12.10 km,and the proportion of the semi-variogram model was 63.80%,indicating a moderate semi-variogram value.These indicated that both the SAP and SAK contents had a moderate spatial correlation.The Kriging spatial interpolation showed both the SAP and SAK contents had a spatial nested distribution.The SAP content varied greatly,with the Grade 3 of the SAP content being most widely distributed in the agricultural land,higher in the central north and central east and gradually lower in the north,center,south and central west of Danzhou,while the SAK content varied less than the SAP content,and its Grade 5 was most widely distributed in the agricultural land,massively in the south,east and north of Danzhou.This spatial distribution may be related with landform,geological conditions,landuse,land management,etc.