A new framework for simulating C decomposition and emissions from land applied biosolids and manures using the denitrification and decomposition model.

There is a need for modeling tools capable of estimating CO2 emissions from land application of biosolids and manure. The Denitrification and Decomposition model (DNDC) was improved for this capacity by adding a separate manure C pool to disaggregate manure decomposition from the soil organic matter pools. The effect of soil temperature on soil organic matter decomposition was also improved. Data collected from two climatically distinct sites in Montreal (Quebec) and Truro (Nova Scotia) with corn were used to test DNDC for simulating yield, soil temperature and moisture, and CO2 fluxes from soil amended with biosolids (mesophilic anaerobically digested, composted, or alkaline-stabilized). A third site in Harrow (Ontario) was used to verify the model for solid cattle manure applied to a corn-soybean field. Crop yields were well simulated by the improved model (rRMSE 4.1-30.1 %) for all sites. The model (0.78 ≤ d ≤ 0.93) outperformed the default version (0.61 ≤ d ≤ 0.9) in simulating CO2 fluxes across all sites. Similarly, the model effectively simulated both soil temperature (d ≥ 0.88) and moisture (0.53 ≤ d ≤ 0.91). The addition of an independent biosolids/manure C pool in DNDC resulted in more accurate simulation of seasonal soil C decomposition and CO2 emissions for alkalized and composted biosolids. The modified temperature function alleviated the over-prediction of CO2 emissions shortly after biosolid application and improved the timing of emissions during the growing season. The enhanced model will help simulate best management practices for integrated crop-livestock-manure systems, reducing reliance on nitrogen fertilizer.