Land Retirement Demonstration Project

Restoration of Retired Valley Farmlands Using Herbicides and Activated Carbon

Presented To:

Society for Ecological Restoration, California (SERCAL)
Bass Lake, California 2005

by

Howard, Adrian J. ¹ and Lair, Kenneth D. ²

1. C.S.U. Stanislaus, Endangered Species Recovery Program, Fresno, CA.

2. Bureau of Reclamation, Technical Service Center, Denver, CO.

Abstract

Restoration of former agricultural lands in the San Joaquin Valley has been extremely problematic, in large part due to an abundance of weeds. In situations like this where the native seed bank is depauperate a pre-emergent herbicide may be used, but unfortunately seeded species will also be impacted unless they are protected from the herbicide. In the 1970's researchers investigated the use of activated carbon (AC) to ameliorate negative effects from herbicides. Now it is a common agricultural practice in the Pacific Northwest to band AC over the seed row before applying herbicides to protect the seeded species. Our study evaluates whether such an approach may be useful in restoration. We drilled four native species (Great Valley phacelia, Phacelia ciliata; Great Valley gumweed, Grindelia camporum; bush seepweed, Suaeda moquinii; and allscale saltbush, Atriplex polycarpa) into a fallowed mustard-dominated site. Activated carbon was applied simultaneously, either by spraying a 1” band on the surface over the freshly drilled row or by incorporating it with the seed. Immediately following planting five herbicides were applied [Landmark MP (Sulfometuron methyl and Chlorsulfuron), Goal 2XL (oxyfluorfen), Telar DF (Chlorsulfuron), Cerano 5 MEG (Clomazone) and Broadrange 1.4% G (Sulfentrazone)]. Monitoring entailed estimating percent cover for all species. Three of the herbicides reduced the average cover of weeds to below 10%, whereas 100% non-native cover characterized the surrounding fields. In cases where the herbicide provided excellent weed control but also some target species control, surviving target species grew much larger than normal, probably due to the lack of competition in the bare, between-row spaces. Observationally, in some areas where the herbicide was applied at a lower rate or there was extra AC, we still achieved excellent weed control yet the target plants flourished. These patterns strongly suggest that with a refinement of herbicide and activated carbon rates, this approach could be extremely valuable in restoring weed-dominated lands.