Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2005
Publication Date: July 20, 2005
Citation: Torbert III, H.A., King, K.W., Harmel, R.D. 2005. Impact of soil amendments on reducing p losses from runoff in sod. Journal of Environmental Quality. 34:1415-1421. Interpretive Summary: There is continuing concern regarding the environmental impact of nutrient loss from the long term application of animal waste to grass. This experiment was designed to evaluate whether the chemical materials of gypsum, lime, or ferrous sulfate could be used in conjunction with animal waste application on pastures and turfgrass to reduce the amount of soluble P that is potentially lost in a runoff event. In runoff events involving pasture and turfgrass the water runs over the surface and through the grass thatch layer. The addition of ferrous sulfate to the sod surface was so effective at reducing the soluble P that it was undistinguishable from no manure application. Further, in subsequent run-over events, no difference was observed from the treatments that received 13.5 Mg ha-1 of manure and those that received none when ferrous sulfate was added. This indicates that ferrous sulfate has a considerable potential to be used in conjunction with manure application on pasture, turfgrass, and filter strips to reduce the initial P losses to the environment.
Technical Abstract: Research was initiated to study the interaction between soil amendments (lime, gypsum, and ferrous sulfate) and dissolved molybdate reactive P (DMRP) losses from manure applications from concentrated runoff flow through a sod-covered soil surface. Four run-over boxes (2.2 m2 surface area) were constructed in a greenhouse and fitted with a water dispersion device to provide runoff. The boxes were prepared for each treatment with a bermuda grass (Cynodon dactylon (L.) Pers.) sod surface (using sod blocks) and composted dairy manure applied at rates of 0, 4.5, 9, or 13.5 Mg ha-1. The three soil amendments were then applied to the boxes at a rate corresponding to the stochiometric requirement to precipitate P at the highest manure application rate. Two run-over events, lasting for 30 min, were conducted and runoff water was routed to a tank which was continuously weighed. Water samples were collected at 10 minute intervals and analyzed for soluble P. Results indicate that the addition of ferrous sulfate was very effective at reducing the level of soluble P in runoff water. The lime and gypsum showed a small impact on reducing P in runoff water. Unlike the lime and gypsum additions, with the addition of ferrous sulfate, no significant differences were noted for soluble P concentrations between the boxes receiving 13.5 Mg ha-1 manure and those with no manure application. The results from this study indicate that the addition of ferrous sulfate in conjunction with manure application may greatly reduce P losses in runoff.