Submitted to: Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2021
Publication Date: 9/3/2021
Citation: Sherman, J.F., Young, E.O., Cavadini, J. 2021. Tillage and liquid dairy manure effects on overland flow nitrogen and phosphorus loss potential in an upper Midwest corn silage-winter triticale cropping system. Agriculture. https://doi.org/10.3390/agronomy11091775.
Interpretive Summary: Efficient recycling of on-farm nutrients through manure application and management is vital for crop production in the Upper Midwest and globally. Application of site-specific cropping and nutrient management systems contributes to greater nutrient use efficiency (amount of crop nutrient uptake as a proportion of the total applied) and farm sustainability. Winter cereal grains (wheat, triticale, and rye) can be effective cover crops during the corn phase of a crop rotation via their suppressive effects on erosion and nutrient loss potential, however few studies have compared different tillage regimes for integrating manure into a live cover crop. The objective this study was to evaluate field-scale nutrient and sediment losses using a portable rainfall-overland flow simulator to determine difference among the following treatments: 1) liquid manure application followed by one-pass chisel tillage (CT), 2) liquid manure application followed by one-pass vertical tillage (VT), 3) broadcast liquid manure application only (applied and left on the soil surface), and 4) a no manure control. VT had lower average total P, total N, and suspended solids loss, with 97 to 99% lower losses than broadcast for the first event (two days after manure application). Dissolved reactive phosphorus and ammonium-nitrogen concentrations for CT and VT were significantly lower than broadcast three weeks later. Both VT and CT substantially mitigated nutrient losses compared to broadcast, however VT resulted in lower triticale and surface residue disturbance than CT. Results show that the degree of manure-soil interaction as controlled by tillage implements is an important factor affecting nutrient loss potential in overland flow, and that a live cover crop alone may not sufficiently reduce nutrient loss risk from liquid manure applications in some settings.
Technical Abstract: Dairy manure is an important crop nutrient source in the upper Midwest, however it can contribute nitrogen (N) and phosphorus (P) to overland flow/surface runoff. Winter cereal grain cover crops and their residue can help reduce erosion and nutrient transport in corn systems, however few studies have compared tillage impacts on nutrient loss in live cover crop systems. The objective of this study was to evaluate vertical (VT) and chisel tillage (CT) effects on overland flow nutrient and sediment loss potential after spring-applied liquid manure. A broadcast manure application treatment and a no manure control were also included. After manure was applied and corn (Zea mays L.) planted into a live triticale (Triticale hexaploide L.) cover crop the same day, four artificial rainfall-overland flow events were generated (42 mm/hr for 30 min) on field-scale plots in central Wisconsin. Average loads for total P, total N, and suspended solids were consistently lower for VT at 2-days post-manure application (with 97 to 99% lower losses than broadcast, respectively). Dissolved reactive P and ammonium-N concentrations for CT and VT were significantly lower than broadcast three weeks after manure application. Both VT and CT mitigated nutrient losses compared to broadcast, however VT caused less physical disruption of surface soil/residue than CT. Results illustrate the importance of increasing manure-soil interaction for reducing N and P loss risk in overland land flows and that a cover crop alone may not adequately mitigate nutrient loss risk.