Single-pass harvest of corn grain and stover: performance of three harvester configurations.

Corn stover was harvested with a modified combine that simultaneously harvested grain and stover in separate streams. The harvester was used to collect the following stover fractions using three different heads: cob and husk (ear-snapper head); stalk and leaves (stalk-gathering head); and stalks, leaves, husk, and cob (whole-plant head). Cob and husk were also collected when using the stalk-gathering head, but in a separate stream from the stalks and leaves. Material harvested with the ear-snapper, whole-plant, or stalk-gathering head had average moisture of 38.2%, 45.0%, and 46.7% (w.b.); particle size of 14, 22, and 90 mm; and density in the transport container of 98, 64, and 40 kg DM m-3, respectively. Area productivity was 3.4, 1.5, and 1.9 ha h-1; fraction of available stover DM actually harvested was 18%, 64%, and 49%; and total harvester specific fuel use was 1.46, 2.07, and 1.83 L Mg-1 DM or 17.0, 33.4, and 27.4 L ha-1 for the ear-snapper, whole-plant, and stalk-gathering head configurations, respectively. The untilled ground cover in the fall and spring was greater than the minimum requirement of 30% when using any of the three heads. Chisel plowing in the fall with twisted shovels buried too much residue no matter which harvester configuration was used. Chisel plowing in the spring with sweeps left sufficient residue when stover was harvested with either the ear-snapper or stalk-gathering heads. Material harvested with the ear-snapper, stalk-gathering, and whole-plant heads had an average density in a bag silo of 261, 111, and 160 kg DM m-3, respectively. Average loss in a bag silo was less than 4.3% of total stover DM after nine months of storage. Based on estimated cellulose and hemicellulose content, ethanol yield was 868, 1474, and 2804 L ha-1 from materials harvested with the ear-snapper, stalk-gathering, and whole-plant heads, respectively.