Abstract:

In order to reveal the evolution trend and influencing factors of soil quality under the influence of human activities, soil chronosequence of 0, 60, 160, 280, 2 000 and 3 000 years were established in typical areas along the Yangtze River Plain in the lower reaches and the differences of soil physicochemical properties under different reclamation time and land use were analyzed. The survey results indicated that the carbonate in the surface soil was rapidly lost after reclamation, and the soil gradually changed from weakly alkaline to weakly acidic. After 3 000 years of reclamation, the pH value of the dryland soil decreases by about 2. Under the long-term rotation of water and drought, the degree of acidification is slightly lower due to the alternation of soil salinization and redox during the rice season. After a considerable period of time after reclamation, soil organic carbon (SOC), total nitrogen (TN), and available nitrogen (AN) contents showed a gradual accumulation trend. While the inorganic carbon in the surface soil gradually decreased, SOC overall increased compared with before reclamation, indicating that tillage and fertilization measures are beneficial to the accumulation of SOC and nutrients to a certain extent. However, the polder areas with the longest history of reclamation have varying degrees of decrease in SOC, TN, and AN contents. Total phosphorus(TP)and available phosphorus(AP)contents increase in the early stages of reclamation, but continue to decrease in the later stages. Under the use of water drought rotation, the problem of soil phosphorus depletion is particularly prominent, indicating that the input of nutrients in the farmland in the area is in a state of varying degrees of deficiency. Under the current management mode, the degradation of soil fertility quality should be paid enough attention.

Key words: alluvial plain, land use, soil quality evolution, soil chronosequence