Title: Assessing the impact of manure application method on runoff phosphorus using controlled and natural rainfall Authors
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 25, 2011
Publication Date: September 19, 2011
Citation: Veith, T.L., Kleinman, P.J.A., Shigaki, F., Saporito, L.S., Beegle, D. 2011. Assessing the impact of manure application method on runoff phosphorus using controlled and natural rainfall. In: International Symposium on Erosion and Landscape Evolution, September 18-21, 2011, Anchorage Alaska. Paper No. 11074. CDROM. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Land application of manure is a cost-effective method for recycling nutrients from livestock operations. Increasingly, there has been interest in promoting alternative methods of manure application that minimize nonpoint source phosphorus pollution. Watershed and nutrient trading programs rely upon empirical findings to determine which manure application methods to promote as well as to extrapolate the water quality benefits of practice adoption. Until now, assessments have primarily involved rainfall simulations to generate runoff under controlled conditions from small plots. To better understand the effect of assessment method on management recommendations, we compared edge-of-field findings from controlled rainfall events with those obtained under natural conditions. Eighteen field plot pairs were arranged in a randomized complete block designed with replications blocked by field strips farmed on the contour. Plots pairs consisted of one 2 X 10 m plot receiving artificial rainfall and one 10 X 10 m plot under natural rainfall, both with a 10-m slope. Effects of natural versus artificial rainfall on dissolved reactive P and total P losses from dairy manure were compared across five application methods: traditional surface application, surface application with incorporation, shallow disk injection, high pressure injection, and banded application with aeration. In both cases, manure application substantially reduced runoff. Incorporating the manure by tillage, aeration, or injection decreased total suspended solids and phosphorus levels in the surface runoff. Incorporation also greatly diminished the proportion of total phosphorous as dissolved reactive phosphorous in the runoff. Incorporation by chisel plow tillage and by shallow disk injection suggested the least overall loss of P and sediment from the fields through runoff. Shallow disk injection applies and incorporates the manure in the same operation, requiring fewer passes over the field, it may be economically preferable. While the artificial rainfall plots show more variation and reflect the effect of an intense rainfall event three days after manure application, they roughly mimic the results seen over two years of natural rainfall. Certainly, it is clear in either case that incorporation of manure on corn fields reduces both dissolved and total P losses from the field and in most cases also reduces erosion.