Molasses won’t work as a fertilizer

Published 4:34 pm Friday, December 23, 2022

Sometimes I get the most interesting calls! Questions from plant, weed, and insect identification to various products to be used in helping us grow our plants. This week I got an “Ask an Expert” question about using molasses as fertilizer. First, let me tell you about the “Ask an Expert” (https://ask.extension.org/ask) program. This is a National Extension service that allows folks to ask questions completely anonymously. Sometimes we don’t like to ask questions because they may be silly or perhaps, we are embarrassed but we still want to know the answer. In my opinion there is no silly question. I learned more about molasses than I ever thought I would know this week.

I learned about how molasses is made. Did you know it is a byproduct of processing sugarcane or sugar beets? Sugarcane molasses is the major food molasses today, processed especially for that industry. Both sugarcane and sugar beet molasses are used in the animal feed industry and as fermentation sources for various alcohols. What about sorghum molasses? Sorghum syrup was known colloquially all over the South as “sorghum molasses” or just “molasses”. In the 1800’s into the middle part of the 20th century, molasses was used in place of much more expensive sugar. It was used on many products such as collards, grits, corn bread, pie, and even popcorn. Then, just like today, it was used around the world to distill into Rum. If you are ever over at the Outer Banks, check out Outer Banks Distilling, makers of Kill Devil Hills Rum. They offer tours of the distillery and tastings where you can learn all about the process and history of molasses and rum.

There are different grades of molasses depending upon how refined it is as well. Blackstrap molasses is the byproduct from the sugar factory or raw sugar refinery. This isn’t your grandma’s molasses! It is a very dark, highly viscous liquid that remains after no more sugar can economically be extracted. This is the product we are concerned with in our venture to use molasses as fertilizer. There is “Sulfured Molasses” and “Unsulfured Molasses”. The sulfured molasses has had sulfur dioxide added during the refining process. Unsulfured molasses is much more common and contains less sulfur.

As important of an agricultural product as molasses has been to the history, economy, and taste buds of North Carolina, this question covered another possible use of this product, fertilizer. There are a multitude of ways this product is being marketed. There is a liquid “recipe” that consists of molasses and organic fertilizers. Key words – organic fertilizers. This same concoction is marketed for use as a foliar fertilizer. The way that foliar fertilizer work is that they are taken into the leaf through tiny openings called Stomata. Stomata are the plant’s mechanism for gas exchange, water, carbon dioxide, and oxygen to move into and out of the leaf. The other means to enter the plant is across the protective cuticle. This is not going to happen. There is no research-based information, that I can find, which supports the use of molasses, in any formulation, as a fertilizer.

Molasses is also being touted as a soil amendment. “Dry Molasses” is what is being used in this one. This product is made by spraying molasses onto corn meal or soybean meal, it is then dried and pelletized. While there are some benefits of supporting microbial activity with molasses based products, there is still no research based information that supports this claim.

Lastly, molasses is being touted as a fire ant killer or insecticide replacement. Linda Chalker-Scott of the University of Washington is the author of a blog called “The Garden Professors” in which she debunks horticultural myths. She has a great 3-part piece titled “Molasses Malarkey” where she discusses the insecticidal claims of one marketing advertisement. This is a great piece of reading that has practical information and a bit of horticultural humor.

If you are having trouble with growing in your home landscape, call the Extension office at (252)946-0111 or email me at gene_fox@ncsu.edu. If you have a plant that you are unable to identify or would like to know more about the plants in your landscape, let’s talk! Like an old family doctor, I do house calls if we can’t figure out your problem!