Herbicides for Establishing Switchgrass in the Central and Northern Great Plains

Abstract

Weed interference limits switchgrass (Panicum virgatum L.) establishment from seed. Our objectives were to determine the effect of selected post-plant, preemergence herbicides on stand establishment and subsequent biomass yields of adapted upland switchgrass cultivars grown in three environments in the Central and Northern Great Plains. A separate experiment was conducted in eastern Nebraska to determine if there were any differences among switchgrass ecotypes for herbicide tolerance to the optimal herbicide combination. Herbicides applied immediately after planting were different concentrations of atrazine [Aatrex 4L \ ; 6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine], quinclorac (Paramount \ ; 3,7-Dichloro-8-quinolinecarboxylic acid), atrazine+quinclorac, imazapic {Plateau \ ; 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid}, and quinclorac+ imazapic. Herbicide efficacy was determined by measuring stand frequency of occurrence and biomass yield the year after establishment. The application of quinclorac plus atrazine resulted in acceptable stands and high biomass yields. Imazapic often reduced switchgrass stands in comparison to the nontreated control and is not recommended for switchgrass establishment. In the multi-state trials, the herbicide by cultivar interaction was not significant for stands or biomass yields, indicating that the effects of herbicides on switchgrass stands and biomass yields were consistent over the upland cultivars used in the trials. No differences were detected among switchgrass lowland and upland ecotypes for tolerance to atrazine and quinclorac. Quinclorac, which provides effective control of grassy weeds, and herbicides such as atrazine which provide good broadleaf weed control are an excellent herbicide combination for establishing switchgrass for biomass production in the Great Plains and the Midwest.

Dedicated Energy Crops and Crop Residues for Bioenergy Feedstocks in the Central and Eastern USA

“…An assessment of 10 managed farms produced switchgrass yields between 5.2 and 11.1 Mg ha −1 sustainably on marginal cropland in the upper Midwest with 94 % lower greenhouse gas emissions compared to gasoline [16]. Switchgrass has high biomass yields in most production systems receiving at least 600 mm of annual precipitation, east of the 100th Meridian, or anywhere rainfed corn can be grown reliably [17]. Although switchgrass and other native polycultures tolerate low fertility soils, optimizing biomass and maintaining quality stands requires nitrogen (N) fertilizer inputs and proper harvest management [17].…”

“…Switchgrass has high biomass yields in most production systems receiving at least 600 mm of annual precipitation, east of the 100th Meridian, or anywhere rainfed corn can be grown reliably [17]. Although switchgrass and other native polycultures tolerate low fertility soils, optimizing biomass and maintaining quality stands requires nitrogen (N) fertilizer inputs and proper harvest management [17]. Low input native polycultures have been evaluated in a limited number of sites and species mixes and are expected to reduce life-cycle greenhouse gas emissions and required inputs [18].…”

“…However, with increased inputs, production can sometimes be comparable to native monocultures. Both systems lack multi-location comparative evaluations against other high-yielding perennial monocultures [17].…”

“…The goal of perennial grass feedstock planting is to establish the feedstock as rapidly, completely, and inexpensively as possible [17]. There is substantial cost to establishing perennial biomass feedstocks, and the economic viability of the feedstock is impacted by the success of stand establishment in the seeding year, with stand failure costing farmers more than $300 ha −1 [40].…”

“…Perennial grass establishment is limited primarily by weed control, weather, and seed quality. For most perennial grass feedstocks, improved establishment techniques including improved minimum till grass drills, optimal seedbed preparation, seeding depth, planting date, and registered herbicides for weed control have resulted in reliable and rapid establishment [17,41,42]. Mitchell and Vogel [43] overcame seed quality issues by developing a seed lot establishment test which based switchgrass seeding rates on emerged seedlings per gram of seed with an associated stress test to reduce risk of seeding failure (Fig.…”