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Pneumatic harvester plucks tiny seed

Louisville, Ky. – The lure of lucrative transactions, with native grass species selling for $20 per pound and higher, is enough to make most seed growers take notice.

Supply and demand is at work in the native seed niche market. Demand for native species continues to rise because of reclamation activities of pipeline, mining and road construction companies.

In addition, native species are increasingly used in cropland conversion and grassland restoration and by private and public wildlife conservation groups for habitat plantings.

Unfortunately, the combines most farmers use for small grains are capable of harvesting only 18 percent of the native grass species. These are the seeds with a spike inflorescence – those that have a head similar to a wheat plant.

A stripper header, rotary or conventional straw walker combine is capable of collecting most of the seeds from these spike inflorescence species.

But with the other 82 percent of native grass species with panicle inflorescence, similar to a seed configuration on oats, stripper headers and small grain combines can’t do the job.

These panicle inflorescence species are often hand harvested, which increases harvest cost per pound, results in a low yield and drives the market price up beyond the range where the seeds can be economically viable.

Montana rancher Lee Arbuckle studied this situation and concluded it was more of an opportunity than a problem.

With decades of ranching and native grass experience, Arbuckle developed his innovative pneumatic harvester, a machine he calls the Native Seedster.

“Whenever the design team got together for a conference call, I represented the grass plants,” said Arbuckle. “I explained to the rest of them how the plant lives and what it does.”

The Native Seedster project drew the attention of the American Society of Agricultural and Biological Engineers and the society invited him to make a presentation to its International Conference on Crop Harvesting and Processing, held in Louisville, Kentucky.

In his presentation, titled Plucking Difficult to Harvest Native Grass Seed, Arbuckle said that land reclamation has become reliant on only18 percent of the total number of native species.

“These agencies are all using the same short list of native grass species regardless of what the land requires. They’re not necessarily the best species for each site. They’re just the easiest to harvest and get seed, that’s all,” said Arbuckle.

“People talk about sustainable native grass plantings or sustainable ecosystems, but it’s not true. If you want a native replanted site to actually be sustainable, you’ve got to use the species that nature intended for that land.

“The other 82 percent of species are the panicle inflorescence types. These are the ones that need a special machine if we want to pluck their seeds.”

Arbuckle said he has tested his prototype Native Seedster harvest machine on every native grass species he knows of. In the 17 western states, that’s a total of 206 species made up of 37 spike inflorescence and 169 panicle inflorescence species.

“To date, we have been able to successfully collect seed from every one of those native grass species. We have not yet found a native species we can’t harvest.”

From the start, Arbuckle realized that a modified combine would not do the trick. He needed to start from the drawing board.

His Seedster has no beaters, rotors, straw walkers, sieves or any of the other devices found in a normal combine. But there are fans for the air flow. Plus there are the carefully engineered, relatively soft surfaces that dislodge the seed.

To be as gentle as possible on the fragile seeds, his dislodgement system uses a combination of counter-rotating combs and brushes. The grooves of the combs hold the stem, while the soft brush sweeps the seed away. As the seed is loosened from the stem, a stream of air directs it toward the waiting bag. Arbuckle said little chaff goes into the air stream.

One of the most important factors is getting the speeds and forces adjusted just right for each species.

“Everything is adjustable. We can adjust the comb shape and rpm independent of the brush rpm. We can change the brush filament from something as soft as a shaving brush all the way to nearly as hard as a street cleaner brush. Plus we can adjust the brush rpm and the clearance between the comb and brush. You need to have that whole range of adjustment if you expect to harvest every type of seed.”

The 10-foot wide harvest head mounts on the front of an 80 horsepower tractor with loader arms and independent power take-off. Variable speed hydraulic motors run the combs, brushes and fans.

The exact operating height and angle of the plucking unit can be adjusted with the tractor’s regular bucket controls.

In 120 trial plots harvested in 2006, the Seedster successfully plucked seeds at ground speeds up to five mph.

Once the air flow captures the seeds, they fly through a big pneumatic tube over the top of the tractor into a standard-sized bulk seed tote bag mounted at the back of the tractor. As each bulk bag is filled with the cargo, it is manually removed and another bag is strapped into place.

In his earliest Seedster experimental machines, Arbuckle was able to collect seeds with a bottom-dump harvester, but he had no way to handle it or move it around. It was just a huge pile of fluffy stuff lying on the ground, waiting for a strong wind to blow it away.

In the end, it was a strong wind that did sweep the seed away.

“It’s damned near impossible to use an auger or conveyor to move native grass seed. That’s why we use an air system to move the seed. There’s really no alternative. This way, the air flow brings the seed to the bag immediately and it’s ready to transport,” said Arbuckle.

The Seedster will be on the market in May and will cost $50,000 U.S.

For more information, contact Lee Arbuckle at 406-294-2995 or visit

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