Chestnut Harvest Burr Management

Final Report for FNC14-946

Project Type: Farmer/Rancher
Funds awarded in 2014: $7,390.00
Projected End Date: 12/31/2015
Region: North Central
State: Michigan
Project Coordinator:
Carl DeKleine
Dekleine Orchards, LLC
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Project Information


  • Project Duration: 2 years
  • Date of Report: December 28, 2015

DeKleine Orchards is a 48-acre, family-owned farm, in operation since 1948. Today the farm consists of 2 acres of tart cherries, 4 acres of sweet cherries and 25 acres of chestnuts. Seven acres are in rotational soil enhancement after cherries and 8 newly purchased acres are being prepared for additional chestnuts.

During the last 75 years, DeKleine Orchards has hired local high school students for summer work. Education is an important objective.

All cherries and 20% of the chestnuts are sold u-pick. Eighty percent of the chestnuts are sold through Chestnut Growers Inc., a growers’ cooperative of which DeKleine Orchards is a charter member.

DeKleine Orchards has continuously strived to use environmentally friendly practices. One example is our non-traditional control of bird damage to the cherry crop. We mechanically remove pits from cherries as a service to customers. The pits are spread throughout the cherry orchard in locations convenient for small rodents. Young trees are carefully protected year around. As the rodent population grows, hawks will nest in large nearby trees. Kestrel houses are also provided. Most years hawks will nest and feed on the rodents. Where hawks are present, there are no small birds. The natural cycle is complete with little effort and a wonderful benefit to crop yield.


GOALS: The project is to identify new systems for economical harvest of chestnuts through efficient handling of burrs. Goals are to modify an older walnut harvester for burr/nut pickup, separation of the burrs and nuts during harvest, remove burrs from the orchard and communicate our findings to other chestnut growers.  

Armed with 20 years of chestnut experience, and an older used Weiss McNair 936 walnut harvester, the task of redesigning and modifying the harvester began with a trial run without changes. Limitations and needed improvements were recorded. The first test was made in the fall of 2013.

This machine, as well as all other nut harvesters, was not built to deal with the chestnut burrs. The 936 did not separate burrs from nuts or provide a method of collecting burrs for removal from the orchard.

During the winter of 2014, two meetings were held with engineering staff at the Weiss McNair office in Chico, CA. Changes decided upon included shortening of the exit conveyor and channeling air from the cleaning fan to a trailer for burr transport and collection. Additionally a new wider bar spaced conveyor belt increased speed of the cleaning air fan, and rerouting cleaning air within the machine were decided upon.

Early tasks also included determining the required air speed needed to elevate nuts (19 meters/sec ) and burrs (13 m/s ). Several observations were made to determine the relative volume of nuts compared to burrs. Open burrs and the nuts dropped were compared in a bucket. The determined volume ratio of nuts to burrs is 1:6. The box to collect burrs was designed to be 6 times larger than the bin to hold nuts.

Finally a PERT chart plan covering 18 months was constructed detailing the project tasks.

From past experience, chestnut burrs do not flow and in fact form a single solid mass when accumulated. This makes emptying a trailer of burrs very difficult. A burr box was designed made of angle iron and wire mesh. The box has a drop bottom for easy emptying. A trailer was purchased, modified, and fitted to hold the burr box. It is pulled behind the harvester with burrs blown into it.

An angle iron frame was welded to the back of the harvester to collect nuts dropped from the harvester belt. The frame was welded to the frame of the harvester.

After a new belt was installed, internal chambers were modified to concentrate the air flow of the two fans. The first fan creates a vacuum above the picked up burrs and nuts. This removes light weight debris. The second fan blows air through the conveying belt lifting heavier debris (burrs) from the top of the belt. As the changes were made, the second fan air speed was doubled to create a possible speed of 19 m/s. The speed could be achieved below the belt but was marginal above it.

Finally, air ducts were fabricated to convey debris and burrs to the towed burr box. This was completed just prior to the 2014 chestnut harvest season. Also a meeting of the Michigan Nut Grower Assoc. was scheduled at DeKleine Orchards to demonstrate the harvester in operation.

In addition to the core team named in the project proposal, a great deal of advice was obtained from four other sources. First is Richard Winkel, a professional aerospace engineer and chestnut grower. His input covered the entire project but focused on air flow and burr/chestnut relative volumes. Another contributor was Dr. Mark DeKleine, an agriculture engineer specializing in fruit harvesters. His contributions were air fan requirements, ground mechanical pick up, and burr handling. Additionally, Mr. Joe Riggs of Weiss McNair shared company experiences and aided in design of machine modifications. Finally, many neighbors and friends with varied experience contributed valuable advice.


OBJECTIVE: The project objective of identifying new systems for economical harvest of chestnuts through efficient handling of burrs was a huge success.

Of the four goals, three were successes and one did not work as intended.


1. Modify a Weiss McNair 936 Harvester for Mechanical Burr and Nut Pickup

The ground pickup method of a revolving brush and opposing revolving wire finger belt, proved 99% effective. Less than 1% of burrs or nuts were left on the ground after one pass of the harvester. Uneven ground did not significantly change the result. Mechanical method of pickup is most cost efficient and has been shown to work.

2. Separation of Burrs and Nuts during Field Harvest

The Weiss McNair 936 walnut harvester modified for separation of burrs from nuts did not work as intended. Pre-harvest testing showed that the second fan produced an air speed sufficient to lift burrs off the belt. During actual harvest usage in the fall of 2014, separation was not being achieved. Separation was only 25% to 40% due to some burrs still containing nuts and the variation in relative weight due to early morning moisture and after rain. The burrs became heavier.

Rather than make further and more expensive changes to the model 936, it is clear that a new harvester needs to be designed specifically for chestnuts and their burrs. This new concept would incorporate an additional operation to remove nuts from unopened burrs and presort burrs over 2.5” in size by sifting smaller burr pieces and nuts through 2.5” openings. The new design harvester must be no more than 5 ft. high and 7 ft. wide.

3. Remove Burrs and Nuts from the Orchard

Modification of the 936 harvester provided for a platform to hold a 40”x 48” bin to collect nuts and burrs picked up by the machine. Although separation was ineffective, removal of burrs was an operational success. One week prior to the 2015 chestnut harvest, all empty burrs and trash were picked up and removed to a compost pile. Starting with a perfectly clean orchard floor, harvest costs went from $.40 per pound to $.30. Much of this efficiency is attributed to a reduction of the under tree clutter of burrs.

4. Communication of Findings

On October 4, 2014, DeKleine Orchards hosted the annual meeting of Michigan Nut Growers Assoc. It was a daylong event including the formal meeting, a potluck lunch, farm tour and presentation of the chestnut harvester. Carl DeKleine gave a presentation of the SARE project from conception to current pre-harvest testing. Although it was a bitter cold rainy day, approximately 45 members attended. Arthur DeKleine led the physical demonstration showing actual pickup, separation of nuts and burrs, and deposit into the nut bin and burr box.

Over the last year we’ve had many calls asking for additional information. Plans call for two presentations, one to Chestnut Growers of America and another to Chestnut Growers Inc.

This SARE project made some huge steps forward in understanding the equipment necessary to manage burrs during harvest of chestnuts. Lessons learned will provide a clear path to design and use of a future inexpensive harvester. The modified Weiss McNair 936 will continue to be used each year just prior to harvest to pick up un-pollinated burrs and clean the orchard floor. This step is necessary for economical harvest of chestnuts.



Click linked name(s) to expand/collapse or show everyone's info
  • Art DeKleine
  • Mark DeKleine
  • Earl Mast
  • Rodney Poortenga
  • Donald Smallegan


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.