Effect of Biosolids on Rangeland Forage Quality
Abstract:Biosolids land application was demonstrated to be a potentially cost effective approach for restoring forage productivity and enhancing soil moisture holding capacity on disturbed and/or marginal rangelands. By applying aerobically digested, anaerobically digested, composted and lime stabilized biosolids on rangeland test plots at rates of up to twenty times (20X) the estimated agronomic rate, forage yields were found to increase from 118.2 lbs/acre (control plots) to 1052.8 lbs/acre on rangeland plots receiving biosolids.
In spite of the economic and environmental benefits associated with increased forage yield (e.g., higher animal stocking rates, reduced soil erosion, improved drainage, etc.) the type of forage generated both before and after biosolids land application was found to be dominated by invasive weeds all of which were characterized as having fair to poor nutritional value. Of the nine dominant plant species identified including; 1) Cheatgrass, 2) Mouse Barley, 3) Bur Buttercup, 4) Mexican Fireweed, 5) Herb Sophia, 6) Bulbous Bluegrass, 7) Clasping Pepperweed, 8) Tall Tumblemustard and 9) Sticky Purple Geranium, only Sticky Purple Geranium is native to United States (US) rangelands. Furthermore, over 98% of the measured plant density on all rangeland test plots was characterized by invasive species regardless of the biosolids type or application rate employed. Opportunistic and shallow rooting invasive weeds not only have marginal nutritional value for support of wildlife and livestock, they also limit the establishment of native perennial grasses and thus, biodiversity. Many of the identified invasive species (e.g., Cheatgrass) also dry-out rapidly, a characteristic that significantly increases the fuel loads that currently support the increased frequency and extent of US wildfires.
In evaluating rangeland restoration approaches, the collected field data clearly demonstrated that biosolids land application provided vital nutrients and organic matter necessary for enhanced forage growth as well as improved soil and water management. However, vast areas of US rangeland (including the demonstration field plots) are characterized by extensive infestation by invasive weeds (biological pollution) whose presence is associated with a number of negative economic and environmental consequences including reduced: 1) forage quality, 2) biodiversity, 3) livestock health and 4) wildfire mitigation potential. Restoring and sustaining rangeland health will require a strategic and multi-Agency approach. Targeted reseeding of native grass species in combination with biosolids land application represents a potentially effective means to reversing the spread of invasive plant species while improving the environmental health, biodiversity and economic value of disturbed rangelands.
Document Type: Research Article
Publication date: January 1, 2008
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