Study on Soil Fertility Variation during Wetland Reclamation and Utilization in the Naoli River Watershed of the Sanjiang Plain

Variation in the fertility of wetland soil with different cultivated time is analyzed with methods such as correlation analysis and principal component analysis. It is found that soil degradation is evident after reclamation and during utilization. Decrease in the content of organic matter and total nitrogen is the main characteristic of soil degradation process. Organic matter and total nitrogen decrease by 6% and 3.1% in the 1～2 years after reclamation, and 63.6 % and 62.5 % after 5 years respectively. Variation in other soil fertility factors is mostly related to the variation in these two factors. In the end of the paper, some countermeasures are suggested.