Soil carbon mineralization, enzyme activities, and crop residue decomposition under varying soil moisture regimes

In the Lower Mississippi River Basin, farmlands are flooded in late fall and winter by impeding drainage to provide a habitat for migratory birds stopover. A laboratory incubation study was conducted to study the influence of temporary wetting of these soils on carbon (C) and nitrogen (N) mineralization from residue decomposition. Surface soils (0–15 cm) were collected from fields with clay and silty clay loam soils. Both soils were incubated with five crop residues—corn ( Zea mays ), soybean ( Glycine max ), cotton ( Gossypium hirsutum ), sorghum ( Sorghum bicolor ), and sweet potato ( Ipomea batatus )—at 50% and 100% water holding capacity (WHC). Soil carbon dioxide (CO 2 ) efflux was measured during 74 days of incubation. Soil moisture had the largest effect on soil CO 2 efflux and most of the enzyme activities followed by residue and soil type. Cumulative soil CO 2 efflux was reduced by 46% at 100% WHC compared to 50% WHC. Clay soil had higher cumulative CO 2 efflux, aryl sulfatase, aryl phosphatase, and β‐ N ‐acetyl glucose aminidase activities than silty clay loam soil. Residue type had the largest effect on post‐incubation soil inorganic‐N, remaining biomass, and residue C and residue N. Sweet potato residue had the lowest remaining biomass, significantly lower than cotton, corn, and sorghum, but statistically similar to soybean. After incubation, residue N concentration had a positive association with cumulative CO 2 efflux and a negative association with remaining residue biomass percentage. Winter flooding might limit the loss of soil C as CO 2 depending on the crops grown and soil type.