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Garlic producer closes in on successful weeding strategies

March 27, 2010

Patty Fluegel holds some beautiful Georgian Crystal garlic
harvested from the weed research trials.

Project title: Effectiveness and economic impact of weed control systems in organic garlic production

Investigator: Susan Fluegel, Grey Duck Garlic, Moscow, ID

Organic gourmet hardneck garlic is an excellent niche market, high value crop that can be profitably grown on a few acres. Demand for organic gourmet garlic is growing and the supply cannot keep up with the demand.  As a result, interest in garlic production is increasing.

Organic hardneck garlic is extremely labor intensive, and the most labor intensive aspect of organic garlic growing is weeding. Even moderate weed coverage can severely reduce garlic yield and bulb size. Since garlic is a nine month crop the organic farmer must combat multiple flushes of weeds.

To help organic farmers choose suitable weed control, Susan Fluegel and her partners at Grey Duck Garlic Farm evaluated the effectiveness of four different weeding methods on two varieties of organic hardneck garlic, German Red and Georgian Crystal.

Pre-planting weed control included solarization or stale seedbed technique. Solarization used plastic placed over the crop bed to heat up the soil and kill weed seedlings and seeds. Stale seedbed technique used repeated shallow cultivation before planting to destroy emerging weeds.

Post-planting weed control compared hand weeding with flame weeding.

The two main treatments were pre-planting solarization and stale seedbed. The subplots were garlic variety, German Red (GR) or Georgian Crystal (GC)  and weeding method (flame or hand).  Each of the larger main plots contained four randomized subplots: GR flame weeded, GR hand weeded, GC flame weeded or GC hand weeded.

To determine the effectiveness of each combination of pre- and post-planting weeding methods, Susan evaluated weeding time, weed coverage, garlic bulb weight (total yield), garlic bulb size, and the economic feasibility for all weed control methods.

At the end of the study, Susan’s results showed that the most economically effective weed control method, as measured by cost of weed control per pound of garlic, was stale seedbed followed by hand weeding.

Her results also showed that while solarization had significantly reduced weed coverage by 1% compared to stale seedbed, it also decreased total garlic yield by 10% and bulb size by 5.5% compared to stale seedbed–an economically significant loss.

This is not the result that Susan had expected.

“It really surprised me that solarization decreased yields. I’d expected yields to increase based on what I’d read about solarization in other crops,” says Susan.

Other studies report that solarization reduces weed coverage and increases yields in horticultural crops when compared to conventional tillage. At the start of the experiment, Susan had expected to see a decrease in weeds and no change or a slight increase in yield in the solarized plots when compared to stale tillage technique.  She also expected flame weeding to be a faster method of weed control when compared to hand weeding.

“I really enjoyed doing this study and getting an unexpected outcome was interesting to me. Now I’m in a position where I can repeat it and see if I get the same result,” she says.

In the study, flame weeding was slightly faster than hand weeding during the first month, but at week five hand weeding became less time consuming than flame weeding, and there was no difference in weeding time between the two methods over the entire weeding season.  Too, flame weeding was approximately a third more costly than hand weeding. One interesting outcome was that German Red weeded by hand was 11% heavier than flame weeded German Red, although there was no difference in garlic weight between hand or flame weeded Georgian Crystal. German Red is an heirloom garlic and is more sensitive to environmental variations than Georgian Crystal.

Susan noted that in her farming practice, based on these results she would consider a combination of stale seedbed, followed by flaming and then hand weeding.“We still think that a combination of flame weeding and hand weeding is probably a really good idea. Flaming just didn’t work as well on those larger weeds later in the season.”

Susan also says she is already starting to think about other weeding strategies, such as acetic acid, in particular for broadleaf weeds, and work with different types of mulches. She adds that the most challenging part of doing this study was weighing all the cloves prior to planting. “I weighed every single clove, and we had almost 5,000 bulbs in the experiment. But it was good that we had that many because it really helped with the significance of the results. And then we weighed and measured all the bulbs again post-harvest–this is where my sister Patty really helped.”

A final report describing the results of this project was submitted in December 2009.

Susan Fluegel
Grey Duck Garlic, LLC
510 N. Washington
Moscow, ID 38343
(208) 882-6284

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