Abstract:

To explore the variations in soil salinity, nutrient levels and carbon pool dynamics under various silage planting models, a series of comparative planting experiments were initiated in the Jiangsu costal reclamation area in October 2021. The experimental designs included a rapeseed-corn rotation (R—M), alfalfa interplanting-corn (A—M), and a monoculture of alfalfa (A—A). The results showed that: (1) soil salinity within the 0-40 cm depth exhibited similar patterns of fluctuation across different models until August. However, the R—M model demonstrated significantly higher soil salinity levels in comparison to the A—M and A—A models; (2) the soil samples from the 0-20 cm layer under A—A model recorded the highest levels of total nitrogen, alkali-hydrolyzed nitrogen, organic carbon and easily oxidized carbon. Furthermore, the total available nutrient pool capacity in A—M and A—A models was increased by 6.05% and 11.64% compared with R—M mode respectively. At the same time, there were no significant differences in soil pH, bulk density and available phosphorus under different planting models; (3) the carbon pool index (CPI) from the A—M and A—A models increased by 3.70% and 8.90%, respectively. The carbon pool activity index (AI) increased by 36.40% and 50.50%, and the carbon pool management index (CPMI) increased by 41.45% and 63.94%, respectively, compared with the forefield one year after planting. The AI and CMI from R—M model increased by 30.50% and 26.37%, respectively. Alfalfa silage planting or interplanting in coastal reclamation areas was conducive to decreasing soil salinity and the accumulation of effective nutrient in the short term, increasing soil carbon pool management index, and improving beach soil quality and fertility. The research results would provide data support for the future development of silage crop production and large-scale promotion.

Key words: coastal flat, active organic carbon, soil nutrient reservoir, salt change, carbon pool management index