Date of Award



Plant Biology; Crop, Soil, Environmental Management; Criminology and Criminal Justice

Faculty Advisor

Sadeghpour, Amir


Dairy farmers often surface apply phosphorus (P)-based liquid manure to corn (Zea mays L.) for silage, supplementing with N fertilizers for optimum corn nitrogen (N), optimizing crop production while decreasing P loss to the environment. However, injecting manure may further conserve losses and reduce synthetic N fertilizer need. An experiment was conducted on a dairy farm in Breese, IL from May 2019 to April 2022 with two main treatments including (i) surface application of manure at P-based rate supplemented with 123 kg ha-1 synthetic N and (ii) manure injection at P-based rate supplemented with 17 kg ha-1 of synthetic N fertilizer. Both treatments delivered 201 kg N ha-1 to meet corn N need. Our results indicated that yield and quality of silage corn and cereal rye were similar in both treatments. This suggests that injection can limit manure ammonium-N fraction losses and decrease the need for supplemental N fertilizer by 106 kg ha-1, which translates into up to $150 ha-1, while not affecting the quality and quantity of yields. Moreover, the effect of manure injection on soil test P (STP) was similar to that of surface application and did not increase STP over a three-year period. Elevated STP in high P-supplying soils can be an environmental concern, but our results show that neither treatment increased STP. Future research should focus on quantifying N loss through denitrification and leaching when manure is injected versus surface applied to provide a more holistic overview of the soil and environmental impact of each system.