Varying Influence of Dairy Manure Injection on Phosphorus Loss in Runoff over Four Years

Abstract

Surface application of manure on no-till farms can exacerbate P losses in runoff, contributing to the eutrophication of surface waters. We monitored 12 400-m 2 field plots over 4 yr to compare P losses in surface runoff and lateral subsurface flow with shallow disk injection and broadcast application of dairy manure. Given the substantial variability in annual P losses, as well as a gradual, annual buildup of residual soil test P, significant differences in runoff P losses were detected in only 1 of 4 yr: in 2014, total P losses in runoff were 68% greater from broadcast manure plots than injected manure plots. Dissolved and particulate P were roughly even in their contribution to runoff. Even so, there were significant relationships between annual dissolved P losses and P in the soil surface, which pointed to soils as a regular source of P in runoff. Overall, results confirm the potential for injection to reduce P loss in runoff relative to broadcast application, but because in a few sampling dates injection resulted in greater losses, this study also highlights the importance of assessing mitigation benefits of manure application practices over longer timeframes.

Addressing the spatial disconnect between national‐scale total maximum daily loads and localized land management decisions

“…Because conventional tillage after manure broadcasting incorporates manure into the soil, injection does not provide considerable additional benefit over broadcasting immediately before conventional tillage. Disturbance due to injection can slightly increase the erosion risks, but the subsurface injection also impedes the runoff loss of nutrients (Jahanzad, Saporito, Karsten, & Kleinman, 2019). Average reductions of N runoff (0.1 kg ha −1 , 0.5%) and P loss (0.2 kg ha −1 , 3.6%), and average increases of N leaching (0.1 kg ha −1 ) were predicted in this study.…”

“…In the Spring Creek watershed, Jahanzad et al. (2019) compared manure injection and surface broadcast over 4 yr, and although P losses were variable and did not differ in 3 yr, P accumulated over time, and when P losses in runoff were greatest, manure injection reduced total P loss by 60% compared with surface broadcast application.…”

Manure management strategies are interconnected with complexity across U.S. dairy farms

“…The use of pasture and manure spreaders are associated with lower greenhouse gas emissions (CH 4 , N 2 O, CO 2 ) and ammonia as compared with anaerobic lagoon systems [ 13 ]. However, manure spreaders require significant time and management investments [ 39 ], and are most typically used in broadcast manure applications, which are associated with increased nutrient runoff [ 40 – 42 ] and fecal-coliform bacteria concentration [ 41 ]. Manure spreaders, and a lack of storage capacity, could also require a farmer to apply manure in non-optimal conditions, such as before rain or on frozen ground, both of which could also lead to additional runoff and potential eutrophication [ 43 ].…”

Tile Drainage Flow Partitioning and Phosphorus Export in Vermont USA

“…Increasing temporal and spatial contact between P and the soil matrix can result in lower P concentrations in runoff [24]. This is achieved by tillage and fertilizer incorporation, which also have the effect of disrupting PFP, thus reducing P loss to TD [23,25,26].…”

“…Manure injection (MI) is a BMP that incorporates manure P with the soil matrix with minimal aggregate disturbance [28]. MI can reduce P losses in surface runoff [29], however, it is still unclear the effect of MI on P losses via TD [24,30].…”