Alfalfa yield impacts of low-disturbance manure application

Authors: Young, Eric

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 11/23/2021
Publication Date: 12/1/2021
Citation: Young, E.O. 2021. Alfalfa yield impacts of low-disturbance manure application. Forage Focus. December 2021. pg. 6.

Interpretive Summary:

Technical Abstract: Manure provides crops with needed nutrients and helps maintain soil quality with inputs of soil organic carbon, underpinning long-term soil quality/health. Several considerations should be evaluated for optimizing manure application benefits on forage crops (i.e., species, development stage, manure nutrient content/forms, application rates, soil tests, environmental risks, soil moisture, weather). Broadcast/surface application of liquid manure is a common practice after hay cuttings, however incorporating or injecting manure with low disturbance manure incorporation (LDMI) tools (i.e., banding, aeration-banding, shallow disk injection) is also possible. Compared to broadcast, LDMI can conserve more nitrogen (N) and phosphorus (P) than broadcast application via greater manure-soil interaction while reducing tillage disturbance. Research conducted at the Marshfield Agricultural Research Station in Stratford, WI and other ARS locations and university trials indicate greater overall soil N and P retention when manure is incorporated into hay forage crops with LDMI equipment compared to broadcast. Both shallow disk injection and aeration-banding significantly reduced dissolved P loss in runoff and maintained similar percentages of alfalfa, residue, and manure coverage. A second trial conducted at the Marshfield station measured ammonia, greenhouse gas fluxes, and alfalfa-grass dry matter yields over three seasons for broadcast and LDMI. While manure application tended to increase yield overall, application method had inconsistent impacts on yield. The Integrated Farm Systems Model developed at the USDA-ARS Pasture and Watershed System Laboratory calibrated with long-term field and farm economic data suggests similar yield potential and rates of return among LDMI methods compared to broadcast. LDMI methods show promise for conserving nutrients in dairysystems, however more research is needed to better assess effects on long-term forage yield and quality compared other viable application methods.