Sierra Foothill REC: Quantifying IPM benefits in rangeland systems

Abstract

News from the RECs Sierra Foothill REC: Quantifying IPM benefits in rangeland systems T here’s a strong scientific case that integrated pest management strategies for rangeland weeds are effective — yet adoption of these practices on rangeland is extremely low. How come? One likely reason, says Jeremy James, director of Sierra Foothill Research and Extension Center (SFREC), is that it’s unclear whether investing in reducing weed populations makes financial sense. Microsoft, ESRI 174 CALIFORNIA AGRICULTURE • VOLUME 70 , NUMBER 4 Elena Zhukova running a series of experi- ments at SFREC. Beginning in 2013, the team manipulated pastures to have different degrees of weediness, measured by the percentage of land infested with medusahead, a com- mon rangeland weed. After 3 years, they had developed Medusahead (in green, above) is an a series of 13 experimental aggressive invasive annual grass that is 5-acre paddocks, with me- unpalatable to livestock for most of its “We have a good idea that invasive plants have negative dusahead coverage ranging life cycle. ecological impacts — but what we surprisingly do not know is from 11% to 50%. if there is actually any economic cost of having weeds on range- This spring, the researchers stocked the pastures with steers lands,” James said. from March through May and evaluated how weight gain var- A national assessment of rangeland integrated pest manage- ied with weed coverage. ment strategies like Results from this first season of tests indicate that weight targeted grazing, seed- gain does indeed suffer as weediness increases: for every N ing of desirable plants, 10% increase in weed cover, total weight gain was reduced by prescribed fire and the roughly 30 pounds per acre — a reduction in market value of use of selective herbi- $30 to $50 per acre at current prices. cides found abundant “For beef cattle production, those numbers are right in the evidence that these prac- middle of being something that might pencil out to treat,” said tices work (Sheley et al. James. “They’re not going to cause ranchers to go out of busi- 2011). However, the same ness, but at the same time they’re not negligible.” study also found that The study is scheduled to continue for at least another 2 that these practices are years. The team will replicate the spring grazing study and also little-used — in part be- assess the effects of weeds at other times of year, James said. cause of the difficulty of The project is part of a collection of studies funded by the assessing their economic U.S. Department of Agriculture that aims to quantify the value benefit. of the many ecosystem services that rangelands can provide. To better understand Some of these, like the effect of weeds on cattle weight gain, can the economic case for be directly quantified in economic terms. Others — such as the weed management, provision of habitat to support biodiversity or the benefits that James and a team of healthy soil can provide for groundwater infiltration — may be researchers — including more difficult to value but may still be desirable for ranchers to Tehama County live- support. The overall goal of the project, James said, is to docu- stock, range and natural ment the full suite of benefits that investments in rangeland resources advisor Josh management can deliver. c Paddock borders Davy, Stanislaus County — Jim Downing range and natural re- sources advisor Theresa Becchetti, Shasta County Reference livestock, range and Meters Sheley RL, James JJ, Rinella MJ, et al. 2011. Invasive plant management on antici- natural resources advi- pated conservation benefits: A scientific assessment. Chapter 7. In: Briske DD (ed.). The 13 test paddocks (nine of which are Conservation Benefits of Rangeland Practices: Assessment, Recommendations, and sor Larry Forero and UC shown here) enclose 5 acres each and Knowledge Gaps. US Department of Agriculture, Natural Resources Conservation Davis Plant Science pro- are infested with medusahead to varying Service. bit.ly/2c1H0s2. degrees — from 11% to 50% coverage. fessor Emilio Laca — are