Growing Organic Sorghum for Syrup

Growing organic sorghum for syrup

Sweet sorghum is a high-value crop that grows well in Kentucky and has very few pest problems. During 2005-07 we included sweet sorghum as part of the crop rotation in organic demonstration plots at the Kentucky State University Research Farm. We found that sweet sorghum is easily compatible with organic production systems.

Some photographs and notes from our growing seasons are posted below. More detailed information about growing and processing sorghum is available at the National Sweet Sorghum Producers and Processors Association website.

Earthway seeder
Sweet sorghum in July
June July-August
In 2005 and 2006 we seeded sorghum on June 6th, using an Earthway row seeder fitted with a 'radish' seed plate. Rows were spaced 30" apart to allow space for a roto-tiller. We planted a half acre of 'Dale' in 2005 and a quarter acre of 'Della' in 2006. 
The crop grew well without irrigation, even in the unusually dry summer of 2005. Sorghum out-competes most weeds by growing rapidly and exuding toxic chemicals from its roots (allelopathy). We used a single pass with a roto-tiller to control weeds between rows.
Johnsongrass root
Sorghum beside high tunnel
August September
Our biggest weed problem was Johnsongrass, which is closely related to sorghum. Like sorghum, it grows quickly and uses toxic chemicals to weaken competitors. The weed was difficult to distinguish from the crop when it was small enough to hoe, so we hand-pulled any Johnsongrass plants still in the sorghum rows in August, removing as much of the rhizomous root as possible. By September the crop was more than 10 feet tall and formed a dense canopy that shaded out remaining weeds (shown here beside our 12-foot high tunnel).

Lodged sorghum
Sorghum juice extraction
September-October Juice extraction (October 19, 2006)
We experienced severe lodging of our crop during the late summer storms of 2006. In 2005 one person was able to cut half an acre of sorghum in a single September afternoon with a sicklebar mower. The lodging in 2006 made it necessary to cut individual stalks by hand with tobacco knives, taking about 20 man-hours to harvest a quarter acre of sorghum.
Lawrence Jenkins brought his mule-driven extractor to the KSU farm in 2005. Dr. Morris Bitzer brought his portable PTO-driven extractor in 2006 (above). We extracted juice from stalks that had been stripped of leaves (left) or had not been stripped (right).
Juice from stripped and unstripped sorghum
Cooking the juice
To strip or not to strip? Cooking the juice
Stripping the leaves had no effect on the amount of juice extracted from the stalks: 100 stalks produced about 6.5 gallons (25 liters) of juice either way, with no obvious difference in quality or sugar content. The bucket in the foreground contains juce from 50 stripped stalks; the bucket in the background contains juice from 50 unstripped stalks. We cooked 50 gallons of juice over propane burners in a big stainless steel pan. We stirred constantly, removing the froth from the surface, and monitoring the temperature and sugar content. The syrup was ready when the temperature reached 230 ºF (110 ºC) and the sugar content was 80 ºBrix.
Sorghum syrup
Morris Bitzer draining sorghum syrup
Syrup! The final product
50 gallons of juice made about 5 gallons of syrup. Dr. Bitzer pronounced it excellent syrup. High praise indeed!

Thanks to:

College of Agriculture, Food Science and Sustainable Systems