Effects of sludge application on prairie establishment

Abstract

Native prairie in Iowa has all but disappeared since the development of agricultural land by European settlers over the past 165 years. Reconstructing prairie is one way to replace some of the acreage that was lost. A byproduct of settling an area is the generation of garbage and other wastes. Currently there is a surplus of sludge, the waste product of waste water treatment facilities. This material is usually disposed of in landfills, used on agricultural land or reclamation projects. A small area of prairie was reconstructed on the top of a closed portion of the Black Hawk County Solid Waste Landfill, Black Hawk County, Iowa. A mix of four grasses and 49 forbs was seeded on the 0.5 acre (0.2 ha) study site. The site was divided into four non-replicated plots including a control. Each of three plots received liquid sludge once per year for two years. Plot 1 received 1/2 load of sludge, Plot 2 received 1 load and Plot 3 received 1 1/2 loads of sludge. One load contains about 2000 gallons (7576 liters) of sludge. The effect of sludge on prairie establishment and growth was studied. Coverage and frequency of the prairie species and other species present were measured from June through September, 1996 and 1997. Importance value was calculated from this data. Graphical comparison of the September 1997 data showed that timothy (Phleum pratense) had a meaningful difference in plot means. The analysis of weeds showed no clear trend in plot means. There were no meaningful differences in plot means for native prairie. Some species showed an increase, some a decrease and others no clear trend in coverage. While other species were never found in sludge plots, and overall frequency of prairie species declined with increasing sludge application. Timothy (Phleum pratense) benefits from sludge application; sludge did not promote weed growth except at high application rates; and establishment of some prairie species did not appear to be affected by the application of sludge