Soil development under different cropping systems in a reclaimed coastal soil chronosequence

Dynamics of reclaimed coastal soils under cultivation has not been well understood. In this study, we analyzed major soil chemical properties under two cropping systems (rice-barley vs. cotton-barley cropping systems) along a 60-year soil chronosequence created by intermittent reclamation of coastal salt marshes in Shangyu, Zhejiang Province of China. Soil horizons were identified and selected pedogenic properties such as soil salinity, pH, organic carbon (Sac), nitrogen, phosphorus, potassium, manganese (Mn), zinc (Zn) and copper (Cu) were used to characterize the horizons. Results showed that the soil profiles with 36-year or longer cultivation durations included the soil horizon arrangement of A-B-C, while those with 28-year or shorter cultivation durations had the soil horizon arrangement of A-C. The paddy soil profiles showed the plow pan and redoximorphic features with rice-barley cropping system, but the upland soil profiles did not show redoximorphic features and a distinct plow pan with cotton-barley cropping system. Rice-barley cropping system significantly increased the contents of SOC, nitrogen, diethylenetriamine penta-acetic acid (DTPA)-Mn, DTPA-Zn, and DTPA-Cu in 0-20 cm soil depth, but significantly decreased soil pH, salinity and potassium in 0-20 cm soil depth. The chronosequence of soil development was obvious in terms of increasing the contents of SOC, nitrogen, phosphorus, DTPA-Mn, DTPA-Zn, and DTPA-Cu with cultivation time, and decreasing soil pH, salinity, and the contents of potassium, total Mn, total Zn and total Cu with cultivation time except for no obvious decreases of total Cu in the cotton-barley cropping systems. Thirty-six years of cultivation history seemed to be long enough to differentiate paddy profiles with rice-barley cropping system from upland ones with cotton-barley cropping system in terms of soil pH, salinity, and SOC contents. Therefore, the direction and intensity of soil development undergone by the reclaimed soils depend not only on their natural characteristics but also on the way and time that they are managed after land reclamation. The results of this work could be helpful for management plans in reclaimed coastal areas. (C) 2014 Elsevier B.V. All rights reserved.