Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Soil and Water Conservation for Northwestern Irrigated Agriculture

Location: Northwest Irrigation and Soils Research

Title: Removal of vegetative clippings reduces dissolved phosphorus loss in runoff

Authors
item Ippolito, James
item Spackman, R. -
item Entry, J.A. -
item Sojka, R.E. -

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2013
Publication Date: May 28, 2014
Citation: Ippolito, J.A., Spackman, R., Entry, J., Sojka, R. 2014. Removal of vegetative clippings reduces dissolved phosphorus loss in runoff. Communications in Soil Science and Plant Analysis. 45(11):1555-1564.

Interpretive Summary: In soil-containing boxes, ryegrass was either maintained or clippings were removed or retained, with a rainfall simulator used to study vegetative conditions under which dissolved phosphorus losses are likely. Increasing the dead vegetative surface area for contact with water, and the amount of time for leaching to occur, resulted in the greatest dissolved phosphorus loss. Thus, management implications for vegetated areas should consider clippings removal, or perhaps no or reduced mowing during the growing season followed by end-of-season removal, to reduce dissolved phosphorus leaching losses.

Technical Abstract: Phosphorus-containing sediment entering surface water may degrade water quality and promote eutrophication. Grass is sometimes planted as a vegetated filter strip buffer along vulnerable receiving water to trap sediment and reduce the severity of phosphorus nutrient loading. However, eutrophication is still a problem in some waterways due to dissolved phosphorus leaching from senesced vegetation in grassed areas, independent of trapped sediment. A rainfall simulator (96 mm/h) was used to study the vegetative conditions under which losses of total dissolved phosphorus and filterable reactive phosphorus leaching are likely. Boxes containing a Portneuf silt loam soil (Xeric Haplocalcid) were planted with annual ryegrass (Lolium perenne) and cut at two different intervals prior to simulated rainfall 14 days apart. Grass clippings were removed from some boxes and retained on others. During the second simulated rainfall, total dissolved phosphorus and filterable reactive phosphorus in runoff were significantly greater for treatments cut the day before irrigation (0.95 and 0.74 mg/L, respectively) with clippings retained as compared to treatments cut the same day as irrigation with clippings retained (0.74 and 0.59 mg/L, respectively). Removing clippings yielded the lowest mean concentration for both total dissolved phosphorus and filterable reactive phosphorus (0.56 and 0.39 mg/L, respectively). Increasing the senesced vegetative surface area for contact with water, and the amount of time for leaching to occur, resulted in the greatest filterable reactive phosphorus loss. Results point to the potential for vegetation management programs to impact runoff water quality from vegetated buffers. Thus, management implications for vegetated filter strips should consider clippings removal, or perhaps no or reduced mowing during the growing season followed by end-of-season removal, to reduce filterable reactive phosphorus leaching losses.

Last Modified: 12/22/2014
Footer Content Back to Top of Page