Chemical soil properties of reclaimed marsh soil from Zhejiang Province P.R. China

Initial pedogenesis of reclaimed saline marsh soils was studied along a chronosequence of reclaimed land at Hangzhou Bay, Zhejiang Province, P.R. China. The objective was to compare soil development of these soils with processes known for natural saline marsh soil development and to evaluate the presented form of artificial land recovery against the background of increasing population densities in China. Electrical conductivity (water) and exchangeable sodium percentage decreased rapidly after reclamation started. The decrease in pH and carbonate content suggest an incipient decalcification. Soil organic carbon decreased in the first 30 cm within 20 years, caused by mineralization of the organic sea sediments. After this process an accumulation of soil organic carbon due to organic matter input as a result of farming was observed. At all sites total contents of calcium, magnesium and potassium were classified as elevated to high and decreased slightly within 31 years after reclamation and commencement of agricultural use. Only total phosphorus increased after construction of embankments, attributed to the application of fertilizer phosphorus. Available nutrient contents developed differently but none showed significant trends. Calcium slightly decreased as an effect of reclamation. Processes of pedogenesis were comparable to those known for natural marshes, but had an initial character. The reclamation of land in the presented manner is considered important to support high and growing population densities in China. However, agricultural management and fertilizer application has to be carefully evaluated.