Composted manure application promotes long-term invasion of semi-arid rangeland by Bromus tectorum

Authors: Blumenthal, Dana; Lecain, Daniel; Augustine, David

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2017
Publication Date: 10/3/2017
Citation: Blumenthal, D.M., Lecain, D.R., Augustine, D.J. 2017. Composted manure application promotes long-term invasion of semi-arid rangeland by Bromus tectorum. Ecosphere. 8(10):e01960. doi:10.1002/ecs2.1960.
DOI: https://doi.org/10.1002/ecs2.1960

Interpretive Summary: Composted organic matter derived from sewage treatment facilities or livestock manure from feedlots is often applied to rangelands of western North America to increase soil fertility, forage production, forage quality, and soil carbon (C) storage. This practice can have a number of undesirable side effects, however, including plant invasion. It is rare that both the beneficial and negative results of biosolid applications are monitored for more than a few years. In the North American Great Basin Cheatgrass (Bromus tectorum) has invaded tens millions of hectares of land. However, cheatgrass is less successful in the North American Great Plains, so far. Here we describe the long-term (17 and 22 year) effects of two types of biosolids – composted sewage sludge and composted cattle manure - as well as fresh cattle manure – on plant productivity and invasion in native mixed-grass prairie. Although biosolid additions increased plant productivity and forage quality in early years of the study (1994-1998), over time these effects declined while invasion by cheatgrass increased by up to 800%. These results show that biosolid application can cause invasion even in the relatively invasion-resistant grasslands of the western Great Plains. They also demonstrate that invasion can occur quite gradually and persist for decades following the initial application of biosolids. We recommend caution when considering application of biosolids to Great Plains rangelands as well as long-term monitoring for weed invasion.

Technical Abstract: Composted organic matter derived from sewage treatment facilities or livestock manure from feedlots is often applied to rangelands of western North America to increase soil fertility, forage production, forage quality, and soil carbon (C) storage. This practice can have a number of undesirable side effects, however, including plant invasion. While characteristics of both rangeland ecosystems and invasive plants suggest that applications of such composted biosolids (hereafter referred to as biosolids) might often promote invasion, results to date are mixed, perhaps due in part to the paucity of long-term studies. Here we describe the long-term (2, 4, 17, and 22 year) effects of two types of biosolids – composted sewage sludge and composted cattle manure - as well as fresh cattle manure – on plant productivity and invasion in native mixed-grass prairie. Although biosolid additions increased plant productivity and forage quality in early years of the study, over time these effects declined while invasion by Bromus tectorum (cheatgrass) increased. These results show that biosolid application can cause invasion even in the relatively invasion-resistant grasslands of the western Great Plains. They also demonstrate that invasion can occur quite gradually and persist for decades following the initial application of biosolids. Together, results from experimental additions of biosolids and nutrients to native rangelands suggest that risk of invasion is significant, and should be considered in programs that apply biosolids to rangelands of western North America.