Responses of soil organic and inorganic carbon to organic and phosphorus fertilization in a saline - alkaline paddy field

There is evidence of increased soil organic carbon (SOC) and inorganic carbon (SIC) under fertilization in dry croplands of arid and semi-arid areas. However, not much is known about the responses of SOC and SIC in coastal saline - alkaline paddy soils that undergo flooding - draining cycles. Here, we assess the impacts of various combinations of organic and phosphorus fertilization on SOC and SIC and other soil properties in a saline - alkaline paddy field of the Yellow River Delta. Our study showed that organic fertilization resulted in an increase of SOC by 11.9% over 0 - 20 cm and 13.3% over 20 - 100 cm (i.e., 140 - 250 g C m(-2)y(-1) over 0 - 100 cm) whereas phosphorus fertilization only led to a significant increase of SOC in subsoils (or similar to 75 g C m(-2)y(-1) over 0 - 100 cm). There were little differences in SIC over 0 - 20 cm among the treatments; but SIC showed a significant decrease over 20 - 100 cm under organic fertilization combined with lower rate of phosphorus fertilization. However, high rate of phosphorus fertilization combined with organic amendment led to an increase in SIC stock, but a decrease in SOC stock in the subsoil. There was a significant negative relationship between SIC and SOC stocks in this paddy soil. This study demonstrated that fertilization practices could have complex influences on SOC and SIC in saline - alkaline paddy fields due to the flooding - draining cycles that lead to changes in soil conditions.

Automated summary

There is evidence that organic and phosphorus fertilization can increase soil organic carbon (SOC) and inorganic carbon (SIC) in saline - alkaline paddy fields, but little is known about the effects of flooding - draining cycles on SOC and SIC.