Runoff water quality following low-disturbance manure application in an alfalfa-grass hay crop forage system

Authors: Sherman, Jessica; Young, Eric; Coblentz, Wayne; CAVADINI, JASON - University Of Wisconsin

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2020
Publication Date: 2/5/2020
Citation: Sherman, J.F., Young, E.O., Coblentz, W.K., Cavadini, J. 2020. Runoff water quality following low-disturbance manure application in an alfalfa-grass hay crop forage system. Journal of Environmental Quality. 49(3):663-674. https://doi.org/10.1002/jeq2.20058.
DOI: https://doi.org/10.1002/jeq2.20058

Interpretive Summary: Managing manure to optimize nutrient use efficiency while minimizing environmental and health risks is an important challenge in dairy systems. While some form of manure incorporation mitigates nutrient losses in surface runoff water compared to unincorporated manure, less research has focused on specific types of incorporation or injection methods for optimizing manure benefits in forage and no-tillage systems. In contrast to annual crops and conventional tillage, manure applied in hay crop forage and no-till systems should cause minimal disturbance while still reducing nutrient loss potential. Low disturbance manure application methods are specifically designed to reduce disturbance and nutrient loss potential. Shallow disk injection, banding, and aeration with banding are promising low disturbance methods, however limited work has focused on runoff water associated with these methods in hay crop forages. Our objective was to evaluate runoff water quality (with simulated rainfall) from alfalfa-grass field plots after low disturbance application in relation to a no manure control and a surface broadcast treatment. Shallow disk injection had statistically lower mean runoff dissolved reactive P (bioavailable P) concentration than aeration/banding. Shallow disk injection also resulted in significantly lower cumulative total nitrogen, total phosphorus, and dissolved reactive runoff phosphorus loading than aeration/banding. Results indicate shallow disk injection may reduce runoff nutrient loss potential, however further characterization of longer-term agronomic, soil, economic, and farm system impacts is needed.

Technical Abstract: Impacts of low-disturbance manure application (LDMA) on runoff water quality in hay crop forage systems are not well known. Here, our objective was to determine surface runoff losses of total N (TN), ammonium-N (NH4-N), nitrate-N (NO3-N), total P (TP), dissolved reactive P (DRP) and suspended sediment from alfalfa-grass plots in central Wisconsin following application of liquid manure using traditional and LDMA methods. Manure application treatments consisted of: i) surface banding (BAND), ii) surface banding with aeration (A/B), iii) shallow disk injection (INJECT), iv) surface broadcast (BCAST), and v) no-manure control (CONT). Runoff events were generated (n = 7) from replicated plots following a standardized rainfall simulation protocol. While runoff was variable across plots and within treatments, INJECT had numerically lower loads and concentrations for almost all nutrients compared to other methods. Mean runoff concentrations of TN (P = 0.03), NH4-N (P = 0.03), TP (P = 0.001), and DRP (P < 0.0001) were lower for incorporated (INJECT and A/B) vs. unincorporated (BCAST and BAND) treatments. Additionally, INJECT had lower DRP concentration (P = 0.02) than A/B and was numerically similar to CONT. INJECT had lower cumulative TN (P = 0.05), TP (P = 0.07) and DRP (P = 0.01) loads than A/B. While INJECT and A/B mitigated N and P loss in runoff, longer-term LDMA effects on agronomic and farm systems in different regions are needed.