Commercially available harvesting technologies are in use on farms to harvest and package forages for livestock and, in most cases, can be used on high-yielding (> 12 Mg ha-1) switchgrass fields (Mitchell and Schmer 2012). Harvest machines with rotary heads are superior to those with sicklebars. Use of the latter likely will be limited to low-yield or small farm operations where harvesting switchgrass can take advantage of existing hay-making equipment but where energy cropping is not the primary enterprise.

With large-scale commercial bioenergy production, rotary mowers will be required to efficiently handle the volume and coarse stems typical of bioenergy switchgrass production fields and will be facilitated by self- propelled harvesters (Mitchell and Schmer 2012). For independent mowing and baling operations, a cutting height of 10 to 15 cm will keep the windrows elevated above the soil surface; this facilitates air movement under the swath and speeds drying to less than 20% moisture prior to baling (Vogel et al.

2011) . However, senesced switchgrass often can be dry enough for one-pass (i. e., essentially simultaneous) cutting and baling operations in which the baler is pulled behind the swather (Fig. 4). Such operating systems likely will be commonplace in well-developed harvest systems.

While it is often assumed that switchgrass will be packaged for storage and transportation in large round or rectangular bales (Mitchell et al. 2010; Vogel et al. 2011), there is some question about the best methods of switchgrass collection. Chopping with direct hauling or chopping and pressing into modules has been suggested as an alternative to baling (Popp and Hogan Jr. 2007; Bransby et al. 2008; Sokhansanj et al. 2009) and some analyses suggest this will be the preferred method of harvest (Larson et al.

2010) . Advantages and disadvantages are evident for each system, and we discuss these briefly below.

In bale-based systems, the baling step densities and bundles switchgrass or other biomass; this eases handling, transport and storage needs, in part because baling breaks the link between in-field harvest and hauling. Because bales can be dropped on the ground and recovered later, this provides an important advantage over a chopping-based system, which will require at least two laborers at any time—one to harvest and one to haul away the material. Bales also are easy to handle with front end loaders or forklifts and require less storage infrastructure.

When comparing bale types, large round bales have a storage advantage in that they have fewer losses than large rectangular bales when stored outside (Cundiff and Marsh 1996); this may have greater importance in the humid east. In contrast, large rectangular bales will be the bundling method of choice in regions with larger field sizes and lower amounts of precipitation. This is because large square balers can achieve higher bale density and the bales tend to be easier to handle and to load on a truck for transport without road width restrictions (Mitchell et al. 2010).

While baling can reduce labor needs on the harvest-end of a biomass system, moving bales from fields to storage locations (and at any other stage in the process) can significantly increase the harvest system’s labor and equipment costs. Bales also will need to be size reduced (for flowability and improved conversion) at a satellite storage or process site. Thus, although the added labor and infrastructure of chopping at harvest has been noted, there is significant interest in using in-field chopping to eliminate a downstream process step. Some analyses suggests these systems are most cost effective (Larson et al. 2010) but actual head-to-head comparisons are few and the outcomes depend on several assumptions about equipment costs (e. g., new vs. existing), use (hours/day) and field site accessibility among others.