|Saporito, Louis - Lou|
Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2008
Publication Date: 12/24/2009
Citation: Kleinman, P.J., Sharpley, A.N., Saporito, L.S., Buda, A.R., Bryant, R.B. 2009. Application of manure to no-till soils: Phosphorus losses by sub-surface and surface pathways. Nutrient Cycling in Agroecosystems. 84:215-227. Available: http://www.springerlink.com/content/ll431535j5563388/fulltext.html
Interpretive Summary: The expansion of no-till management has created a dilemma with regard to manure management as surface application of manure to no-till soils can exacerbate environmental losses of nutrients. This study examined trade-offs in conventional no-till and conservation tillage approaches to manure management by quantifying phosphorus losses in surface runoff and subsurface flow under the two strategies. Results of the study point to benefits in using conservation tillage to incorporate manure where phosphorus leaching losses are of concern. These benefits are lost at sites where surface runoff of phosphorus is a concern, with little difference over the near term between no-till and conservation tillage approaches.
Technical Abstract: Concern over the acceleration of eutrophication by agricultural runoff has focused attention on manure management in no-till. We evaluated losses of phosphorus (P) in sub-surface and surface flow as a function of dairy manure application to no-till soils on a dairy farm in north-central Pennsylvania. Monitoring of a spring near fields receiving dairy manure revealed that over 36 months dissolved reactive P (DRP) concentrations increased by roughly four fold after manure was broadcast to field soils. A leaching study conducted with 30-cm diameter x 30-cm deep intact cores of two contrasting field soils confirmed leaching losses of manure P of 0.26 kg/ha over seven weeks in which columns were irrigated weekly with 2-cm water, comparable to natural rainfall averages. Simulating incorporation of manure by tillage significantly lowered P losses in leachate relative to broadcast application, presumably due to the destruction of preferential flow pathways with tillage. The sandy loam soil transmitted more manure P than did the clay loam soil, although differences in leached P between soils were not as great as those affected by application method. Rainfall simulations (7.5 cm/h) on 1 x 2-m runoff plots established on the two soils revealed that in the period of time shortly after manure was applied, P losses in surface runoff did not differ by application method but did differ by soil. However, mechanisms of P transport in surface runoff were different, with 87% of total P (TP) derived from DRP from broadcast manure compared with 24% from incorporated manure. Results of this study confirm the near-term benefits of incorporating manure by tillage to groundwater quality, but suggest that for surface water quality, avoiding soils prone to runoff is more important. Thus, this study highlights the trade-offs in water quality related to manure management in no-till systems, as well as the marked variability in P transport potential that exists within a single field.