Soil organic carbon and nutrient content under different land use patterns in Jingdian Irrigation Zone

Soil organic carbon and nutrient contents were analyzed under four different land use patterns of annual medlar field (AMF) and perennial medlar field (PMD) in secondary saliferous soil, wheat field (WF) in un-saliferous soil and alfalfa field (AF) in wasteland in Jingdian Irrigation Zone. The analysis shows that organic carbon content and density, total nitrogen and Olsen phosphorus for WF are the highest, while those for AF are the lowest in the 0～60 cm soil layer. Soil total nitrogen has a significant positive correlation with organic carbon (r = 0.791, P < 0.01). There is a generally low C/N ratio for all the soil samples, that for PMD is highest and that for AMF is lowest. There is no significant difference in available potassium among the land use patterns. Soil bulk density is signifi-cantly higher for AF, due mainly to the relatively low soil organic carbon content (r = 0.420, P < 0.01). Soil organic carbon content and density are significantly lower while total nitrogen and Olsen phosphorus are higher under AMF relative to WF. Organic carbon content and density are also higher, total nitrogen content significantly lower and Olsen phosphorus content significantly higher un-der PMD in relation to AMF. An important finding of the study is that farmland soils deteriorate following secondary salinization whereas planting medlars improves soil physical and chemical properties in the study area.