Using the integrated farm system model to improve nitrogen management
Application of livestock manure to farm soils represents a priority nutrient management concern in the Chesapeake Bay Watershed. Historically strong emphasis has been placed on adding manure storage to dairy operations, and, there has been recognition that manure application methods can be improved.
In an article recently published in Agriculture and Environmental Letters, researchers report on the results of simulations from the Integrated Farm System Model to weigh environmentally and economically assess manure storage in combination with surface or injection manure application.
Converting the farm operation from daily haul to 6 months of storage with broadcast application did not substantially change N losses to the environment. However, switching to manure injection conserved ammonium-N and improved manure N use efficiency by crops, even though it increased N leaching by 27% with 6 months of storage and 13% with 12 months of storage. Increasing manure storage from 6 to 12 months with manure injection reduced nitrate-N leaching by 38% due to better timing of manure application to crop growth, but lowered annual net returns. Overall, combining manure storage with injection was the best environmental and economic option.
These findings illustrate that the benefits of investing in manure storage are incomplete without the additional use of manure injection to prevent ammonia losses to the environment.