John H. Fike

The Biology and Agronomy of Switchgrass for Biofuels

Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plants biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plants growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears able to obtain N from sources that other crops cannot tap. The N removed in harvested biomass is often greater than the amount of N applied. In areas with sufficient rainfall, sustainable yields of ∼15 Mg ha−1 yr−1 may be achievable by applying ∼50 kg N ha−1 yr−1. Harvesting biomass once per season—after plants have senesced and translocated N into perennial tissues—appears to allow plants to maintain an internal N reserve. Two harvests yr−1 may increase yields in some cultivars, but a single annual harvest maximizes yields in many cases. If two harvests are taken, more N must be applied to compensate for the N removed in the midseason harvest. Taking more than two harvests yr−1 often adversely affects long-term productivity and persistence. Switchgrass has potential as a renewable fuel source, but such use will likely require large infrastructural changes; and, even at maximum output, such systems could not provide the energy currently being derived from fossil fuels.

Establishing and managing switchgrass as an energy crop.

When it was first adopted as a crop, switchgrass was evaluated and improved for forage uses; but it has more recently been extensively studied as an energy crop, where its biomass might be used as feedstock for bioenergy. Of the two morphological forms or cytotypes of switchgrass, the lowland cultivars tend to produce more biomass; but upland cultivars are generally of more northern origin and more cold tolerant and therefore are usually preferred in the North. Attention to weed control, planting date, planting depth, and seed dormancy can greatly increase establishment success with this species. Stands of switchgrass should be harvested no more than twice per year, and one cutting often provides as much biomass as two. Harvesting after aboveground biomass has senesced can aid persistence, facilitate harvest operations, conserve N, and improve feedstock quality; but other harvest patterns may provide a better fit in some situations. If its biology is properly taken into consideration, switchgrass can offer great potential as an energy crop. Reference: Parrish, D. J., Fike, J. H., Bransby, D. I., and Samson, R. 2008. Establishing and managing switchgrass as an energy crop. Online. Forage and Grazinglands doi:10.1094/FG-20080220-01-RV.

Forage systems for cow-calf production in the Appalachian region

Small cow-calf operations are common in the Appalachian region. Tall fescue [Lolium arundinaceum (Schreb.) S. J. Darbyshire] is the dominant forage in these systems for direct grazing as well as for stockpiling. The present study was conducted from 2001 to 2005. A total of 108 Angus and Angus crossbred cows were allotted randomly to 6 forage systems and then to 3 replicates within each system. In brief, system 1 had a stocking rate of 0.91 ha/cow in a Middleburg 3-paddock (A, B, and C) system. System 2 was similar to system 1 except for a stocking rate of 0.71 ha/cow. A stocking rate of 0.71 ha/cow also was used in systems 3 through 6. All A paddocks had tall fescue, whereas B paddocks had tall fescue/white clover (Trifolium repens L.) except in system 6, which had tall fescue/lespedeza [Lespedeza cuneata (Dum. Cours.) G. Don]. System 3 evaluated a 2-paddock (A and B) rotational grazing system, and system 4 evaluated a 3-paddock (A, B, and C) rotational grazing system, with paddock C containing orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.). Systems 5 and 6 differed from system 2 in the areas of paddocks B and C as well as in the forage mixtures used. In paddock C, system 5 had switchgrass (Panicum virgatum L.) and system 6 had tall fescue and birdsfoot trefoil (Lotus corniculatus L.). System 1 had the greatest average herbage availability from weaning until breeding (P < 0.05) with the least amount of hay fed (P = 0.03) when compared with the remainder of the systems. Differences (P > 0.05) in percentage of ground cover were not detected among systems. There was no year x system interaction effect on the cow or calf performance variables evaluated and no treatment effect on cow performance variables. There was a treatment effect on calf performance variables. System 2 produced the greatest adjusted weaning weight, kilograms of calf weaned per hectare, and kilograms of calf per kilograms of cow at weaning (P < 0.05). Numerical ranking for total calf production per hectare from the greatest to least was system 2, 6, 3, 5, 4, and 1. Systems evaluated did not affect cow performance although differences in calf performance and overall productivity of the systems were observed.

Effects of harvest frequency and biosolids application on switchgrass yield, feedstock quality, and theoretical ethanol yield.

Sustainable development of a bioenergy industry will require low‐cost, high‐yielding biomass feedstock of desirable quality. Switchgrass (Panicum virgatum L.) is one of the primary feedstock candidates in North America, but the potential to grow this biomass crop using fertility from biosolids has not been fully explored. The objective of this study was to examine the effects of harvest frequency and biosolids application on switchgrass in Virginia, USA. ‘Cave‐in‐Rock’ switchgrass from well‐established plots was cut once (November) or twice (July and November) per year between 2010 and 2012. Class A biosolids were applied once at rates of 0, 153, 306, and 459 kg N ha−1 in May 2010. Biomass yield, neutral and acid detergent fiber, cellulose, hemicellulose, lignin, and ash were determined. Theoretical ethanol potential (TEP, l ethanol Mg−1 biomass) and yield (TEY, l ethanol ha−1) were calculated based on cellulose and hemicellulose concentrations. Cutting twice per season produced greater biomass yields than one cutting (11.7 vs. 9.8 Mg ha−1) in 2011, but no differences were observed in other years. Cutting once produced feedstock with greater TEP (478 vs. 438 l Mg−1), but no differences in TEY between cutting frequencies. Biosolids applied at 153, 306, and 459 kg N ha−1 increased biomass yields by 25%, 37%, and 46%, and TEY by 25%, 34%, and 42%, respectively. Biosolids had inconsistent effects on feedstock quality and TEP. A single, end‐of‐season harvest likely will be preferred based on apparent advantages in feedstock quality. Biosolids can serve as an effective alternative to N fertilizer in switchgrass‐to‐energy systems.

Considerations for Establishing and Managing Silvopastures

Silvopasture managers deliberately integrate trees, forages, and livestock to take advantage of their beneficial interactions. Correctly managed, production of each component can be greater than in traditional forestry and forage-livestock systems. Silvopasture systems also support greater biological and economic diversity and provide environmental benefits. In this review, the authors discuss establishment and management of trees in pastures and potential benefits to system productivity, primarily in relation to hardwood species.

Switchgrass nitrogen response and estimated production costs on diverse sites

Switchgrass (Panicum virgatum L.) has been the principal perennial herbaceous crop investigated for bioenergy production in North America given its high production potential, relatively low input requirements, and potential suitability for use on marginal lands. Few large trials have determined switchgrass yields at field scale on marginal lands, including analysis of production costs. Thus, a field‐scale study was conducted to develop realistic yield and cost estimates for diverse regions of the USA. Objectives included measuring switchgrass response to fertility treatments (0, 56, and 112 kg N ha−1) and generating corresponding estimates of production costs for sites with diverse soil and climatic conditions. Trials occurred in Iowa, New York, Oklahoma, South Dakota, and Virginia, USA. Cultivars and management practices were site specific, and field‐scale equipment was used for all management practices. Input costs were estimated using final harvest‐year (2015) prices, and equipment operation costs were estimated with the MachData model (

Industrial Hemp: Renewed Opportunities for an Ancient Crop

2015). Switchgrass yields generally were below those reported elsewhere, averaging 6.3 Mg ha−1 across sites and treatments. Establishment stand percent ranged from 28% to 76% and was linked to initial year production. No response to N was observed at any site in the first production year. In subsequent seasons, N generally increased yields on well‐drained soils; however, responses to N were nil or negative on less well‐drained soils. Greatest percent increases in response to 112 kg N ha−1 were 57% and 76% on well‐drained South Dakota and Virginia sites, where breakeven prices to justify N applications were over

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

70 and

Nitrogen Fertilization Rate and Application Timing Effects on the Nutritive Value and Digestibility of Crabgrass

63 Mg−1, respectively. For some sites, typically promoted N application rates may be economically unjustified; it remains unknown whether a bioenergy industry can support the breakeven prices estimated for sites where N inputs had positive effects on switchgrass yield.

Nitrogen Fertilization Rate and Application Timing Effects on the Yield of Crabgrass

ABSTRACT Hemp (Cannabis sativa L.) has been a species of value to humans for much of our history given its broad adaptation and multiple uses. The plant is thought to have originated in Eurasia but has been carried to much of the rest of the world, largely for use as a fiber crop. Declining needs for fiber and competition from other plant fiber sources began to reduce demands for hemp. In turn, concern over psychotropically potent forms of hemp (i.e., marijuana) would lead to the crops effective prohibition during much of the 20th century. Growing recognition of the many uses for hemp beyond the traditional rope, cordage, and canvas has helped revive interest in the crop, and a majority of US states have reduced restrictions to allow research with the plant. Although hemp now appears on the verge of returning to favor in the United States, there will be much to learn to make it a viable crop competitive with other commodities. Variety and photoperiodicity, site suitability, end use (grain, fiber, or dual purposes) and management, and the interactions of these factors will have a strong impact on crop productivity and suitability for post-harvest use. In addition, the harvest and processing technologies (particularly for fibers and essential oils) that are needed to optimize the plants value are limited or lacking in the United States. Disease and pest issues are often considered of little concern for hemp, but these likely will grow as the plants range expands. Opportunities for hemp have increased with the recognition that the crop offers growing and diverse uses for not only its fibers, but for its seed grain and essential oils as well. Several studies indicate that hemp grains are nutritious as feed and food additives and its essential oils are of interest given a number of pharmacologically beneficial properties. Although full of promise given its numerous potential benefits and uses, building markets for these products will be a critical (and likely slow) part of hemps development into a useful agronomic species for US growers.