Study On Spatio-temporal Variability Of Soil Nutrients In Nanhu Area Of Jiaxing

The cultivated land resource is extremely deficient in China, which hasbeen decreasing in recent years. As a result, food safety has been more andmore concerned recently. The chemical fertilizer is one of the most importantinputs for agricultural production, which accounts for about one half of the totalproduction costs. Due to the low utilization efficiency of chemical fertilizers, theefficiency of agricultural production has been directly affected. Fertilizationrecommended based on soil tests has not been actually practiced because thespatial-temporal variability of soil nutrient distribution has not been wellunderstood in different areas. So, it is important for agricultural production tounderstand the content and spatial distribution of soil nutrients. In this paper,Nanhu District of Jlaxing City has been taken as an example, an elaborateinvestigation of soil nutrients was performed and its spatial-temporal variabilitywas studied with methods of geo-statistics and GIS to provide information forprecision agriculture and prevention of non-point pollution. The main resultsobtained are summarized as follows:1. Spatial variability of SOM (soil organic matter), TN (total nitrogen)and pH in Nanhu DistrictThe variability of soil pH was lowest, and the variability of soil TN contentwas highest with that of SOM content being intermediate. As for their spatialdistributions, SOM and TN displayed similar belt-shaped distribution trendsalong the southeast-northwest direction. However soil pH presented blockdistribution, with low value areas mainly located at north and south and highvalue area in the centre of Nanhu District.Compared with those data of the second soil survey in Zhejiang Province,soil pH decreased slightly, whereas SOM and TN increased significantly.Attention should be paid to the changes in future agricultural production.2. Spatial and temporal variability of soil available nutrients in NanhuDistrict Soil available nutrients in the study area presented great spatial variabilitywith certain distribution trends. The spatial variability of AP (availablephosphorus) was higher than that of AK (available potassium) in either 1984 or2003. In addition, the spatial variability for both AP and AK in 2003 was morecomplex than that in 1984.Soil available phosphorus content has increased significantly in the past20 years, whereas available potassium content has basically maintainedstable with slight increase or decrease in some areas. These results wereconsistent with fertilization practices (excessive application of P andinadequate application of K fertilizers) and emission of the domestic sewage inthe region.