News & Articles

New Seed Harvester Eases Collection of Difficult-to-Harvest Native Grass and Forb Seed

Ecological Restoration
June 2006

One of the principal means of restoring native plant communities is planting of grass, forb, and shrub species—an effort that is often restricted by the high cost of seeds and limited availability of many desirable species. In August 2000, for example, a single seed procurement order from the U.S. Bureau of Land Management required 5 million pounds of primarily native species (USGPO 2000). However, most of the seed was unavailable in the amounts requested. Superior seed harvesting methods are needed to expand the species used in restoration of native plant communities and to cover the cost of seed through increased harvest volumes (Lochner 1997).

One of us (Arbuckle) is a rancher in Montana who recently discovered a harvester technology that we specifically developed for difficult-to-harvest native grass and forb species, including open-panicle, indeterminate, and shatter-prone grasses. The parented “Arbuckle Native Seedster” features counter-rotating brush and combs that dislodge seed and minimal chaff, while simultaneously generating airflow to transport the seed to a pneumatic conveyance system. Speeds of the electric motor-powered brush and combing drum are independently controlled for optimum harvest efficiency. The Seedster is constructed in 40-inch (101.6-cm) modules that allow configuration of a lightweight machine in widths from 4 ft (1.2 m) up to 10 ft (3 m) or more. The machine will first be offered for loader mounting on a tractor. A pull-type Seedster will be available in 2007.

Unlike current harvesters, the fully adjustable comb/brush action 1) increases the percentage of available seed recovered, 2) provides precision calibration to dislodge ripe seeds and leave immature seeds, and 3) can adapt to harvest a wide range of native species, including grass, forbs, and shrubs in difficult terrain. The pneumatic conveyance system deposits chaff-free seed directly into a standard seed bag to facilitate rapid unloading of seed, unlike other commercial harvesters that use a single rotating brush to propel seed directly into a container behind the brush, which slows unloading.

The Arbuckle design ream includes the authors, mechanical engineers, and the fabricators. Arbuckle has received several U.S. Department of Agriculture Small Business Innovative Research grants that have funded extensive field and laboratory research in development of the concept. Using high-speed video photography, we have recorded seed dislodgement at 1,000 frames/sec in laboratory and field studies. This has helped us both confirm and further improve a design.

During field trials in Montana, North Dakota and Minnesota, the Native Seedster successfully harvested warm and cool-season grasses, including green needlegrass (Nassella viridula), needle-and-thread (Hesperostipa comata), Indiangrass (Sorghastrum nutans), big bluestem (Andropogon gerardii), and switchgrass (Panicum virgatum). In 2005, research trials in Montana resulted in the harvest of up to 358 lbs of green needlegrass seed per acre (400 kg/ha) in one machine pass of the 10-ft wide Seedster. Hand harvest showed that the field contained an average 390 lbs of seed per acre (437 kg/ha). Foreign material in the harvested seed averaged less than 2 percent by weight. All research was carried out in replicated plots using experimental designs we developed with a statistician from Montana State University (MSU). Samples were cleaned and weighed by the MSU Seed Lab. Trials also confirmed that ground speeds of up to 5 mph minimally reduced seed recovery rates not significantly different from those achieved at 1 mph.

Under the direction of Dr. Sindelar, a graduate student is developing a morphological key to the native grass seeds of western United States with assistance from Dr. Matt Lavin, an agrostologist/taxonomist at MSU. The key will eventually be completed for economically important grass species of the continental United States and will be instrumental in identifying native grass seeds that are potentially harvestable with the Arbuckle Native Seedster.

The Seedster is currently being readied for commercial release with the first model available in the front loader mount configuration in fall 2006. By late July 2007, we will activate a web site featuring comprehensive product information, including pricing.