Impacts of Low Disturbance Liquid Dairy Manure Incorporation on Alfalfa Yield and Fluxes of Ammonia, Nitrous Oxide, and Methane

Surface applied liquid dairy manure application (i.e., broadcasting) after alfalfa ( Medicago sativa L.) harvest is a common practice. Low disturbance manure incorporation (LDMI) may offer multiple benefits including lower ammonia (NH 3 ), greenhouse gas (GHG) and hydrologic nutrient losses compared to broadcast. However, few studies have simultaneously quantified LDMI impacts on alfalfa yield, NH 3 and greenhouse gas (GHG) fluxes. We measured NH 3 , nitrous oxide (N 2 O), and methane (CH 4 ) fluxes for liquid dairy manure treatments applied to alfalfa plots for broadcast and LDMI over three seasons (2014 to 2016) in central Wisconsin, USA. There were minor differences in alfalfa yield and nitrogen (N) uptake across treatments and years. Shallow disk injection and aerator/band reduced NH 3 loss by 95 and 52% of broadcast, respectively, however both substantially increased N 2 O fluxes (6 and 4.5 kg ha −1 year −1 versus 3.6 kg ha −1 year −1 for broadcast, respectively). The magnitude and timing of N 2 O fluxes were related to manure application and precipitation events. Average CH 4 fluxes were similar among methods and increased with soil moisture after manure application. Results highlight the importance of quantitatively evaluating agri-environmental tradeoffs of LDMI versus broadcast manure application for dairy farms.