This is a hot gardening topic these days and many of organic gardeners are promoting the idea that you should add molasses to your compost pile, to compost rea or even spray plants with it. In tea and on soil it makes microbes grow and on plants it can prevent pests.
Molasses; should you eat it, or use it in the garden?
Molasses, What is it?
Molasses is a by-product produced during the manufacture of sugar. Sugar cane or sugar beets are processed so that the sugar can be extracted. The material that is left after most of the sugar is removed is a black sticky material called molasses. It contains sugar, some other carbohydrates, vitamins and a number of minerals like calcium and iron. It may or may not contain sulfur.
Is Molasses Good for Microbes?
Microbes are opportunistic in that their populations will increase and decrease as the conditions change. Let’s assume you have not been doing too much in the garden so conditions are not changing. In that case the microbe populations remain steady. Things are chugging along at a normal pace and everybody is happy.
Now you dump a lot of molasses on the garden. Instantly, microbes sense the extra food and they start to multiply. Bacteria in a lab can divide (ie double the population) every 20 minutes. The population explodes very quickly. All those bacteria need to eat and they quickly consume the molasses you added. As the food source runs out there is massive famine and most of the bacteria die.
What has the molasses accomplished?
Not much. It is true that all of the dead bacteria go on to feed other microbes, and they help build soil structure. The minerals in the molasses stay in the soil and plants can use them, but your soil probably had enough calcium and iron before you added the molasses. The vitamins in molasses are of no value to plants.
The burst of microbe growth is short lived and adds very little value to the garden and it won’t increase the microbe population except for a very short period of time.
You might be thinking that molasses is organic and therefore it must be good for the garden. Organic fertilizers are good for the garden because they decompose slowly, feeding both microbes and plants over a long period of tine. Adding sugar does not do this.
Should Molasses Be Added to a Compost Pile?
It does not add much in terms of nutrients but people like adding it to grow microbes. As noted above, it does not really work since the sugar is used up too quickly. Sugar is also easily washed out of the pile with the first rain.
Will Molasses Keep Pests Away From Plants?
There might some benefit here if the molasses contains sulfur. Sulfur compounds are known to repel insects.
One problem with this solution is that sugar attracts insects who use it as a food source. Sugar can also lead to black mold growing on leaves which can harm the plant and attract insects.
Even if the sulfur repels insects, there are better options. Sprays of garlic or onion juice would be much more effective and they don’t contain as much sugar.
Molasses in Compost Tea
Molasses is a common additive when making compost tea. Gardeners believe that it results in higher microbe numbers and they are right. The sugar in molasses is candy for microbes and they gorge on it. I don’t think molasses is any better for this job than white sugar, but maybe?
There have however been some interesting studies that show molasses does grow more pathogens, especially in compost tea. “Salmonella populations increased from 1 to over 1000 CFU ml−1 in dairy manure compost tea with 1% molasses, and from 1 to over 350,000 CFU ml−1 in chicken manure compost tea by 72 h. E. coli populations increased from 1 to approximately 1000 CFU ml−1 in both types of tea by 72 h. Pathogen regrowth did not occur when molasses was eliminated or kept below 0.2%.”
Do You Need to Feed the Microbes?
The main reason for adding molasses is to feed the microbes, so it is important to ask, “is it important to feed the microbes?” The answer is a resounding YES! However, there are many ways to do this. Adding compost, wood chips or other organic matter as a mulch is the best way. This provides a slow, steady release of food for the microbes.
You also don’t need to add purchased microbes.
Molasses is a product that we can use to feed people and animals. I’d rather eat gingerbread cookies than compost and wood chips. From an environmental point of view it makes more sense to put non-edible organic matter in the garden and keep the food in the fridge.
There is no “magic” in molasses. It’s just another source of organic matter that will be decomposed very quickly. All organic matter contains carbohydrates, sugars, minerals and vitamins, just like molasses. Don’t believe me …… consider the fact that molasses is made from plants; sugar cane or sugar beets.
I came here as I’ve inherited a gallon of open mollases on my allotment and couldn’t imagine it doing anything positive. I’ve long been interested in micobial ecology and macro effects and how much of a continuum soil ecology has with human microbiomes.
Human microbiomes and human sugar consomption have been well studied in recent years especially, although the former is very cutting edge. Anyway- refined sugar tends to disturb our microbiota with various negative effects- such as candidiasis, etc. I’d expect something similar in soils.
I can see though that there are two viewpoints at odds in much of what has been said: one is ‘what is good for the soil’s health’ and the other: ‘what gives me fast growth- and who cares about the soil?’.
If long term soil health is the concern- as it should be in our current ecological crisis and anyway for long term productivity, etc. Then there’s no need to buy plastic coated products shipped in. Just retain organic material on site and bring in waste from home- food, paper, wood, urine, ashes, etc. If you’ve got all that in good balance, there’s no more additives needed it seems to me.
Importing organic matter from material harvested elsewhere creates an unbalanced carbon cycle in both locations. Ie: large soil carbon and thus carbon respiration on the plot, with low plant carbon fixation and therefore a net greenhouse gas source. Whilst the land where the, eg: peat/mollasses/coir, etc is sourced from is deleted of soil carbon to support it’s potential productivity and fixation! Result: net overall soil carbon loss and atmospheric carbon gain. Plus all the energy used to grow, process, pack, transport and sell the products.
You should read about what Dr. Elaine Ingham has to say about soil. I love that woman.
I have and I have commented about her teachings in several posts. Some of her idea are sound – many are not and are not, as she claims, based on science.
Teaming with Microbes – In-depth Book Review
I understand you are looking for peer reviewed research to unequivocally support molasses. The problem is most organic people are not scientists who have the time, money, and expertise necessary to pass peer reviewed science. That said, molasses has enough anecdotal testimony to validate actual scientific evaluation. Will that occur? Absolutely not because there’s more money in high end synthetic NPK fertilizers.
Do the research and you will find the vast majority of data on molasses come from actual organic growers who aren’t hawking product or looking for accolades. In my opinion, these people are only reporting their experiences and I’m certain if molasses sucked it would be in every organic growers post. So, there must be more proponents than non-believers.
I use MicroLife organic fertilizers out of Texas and I know for a fact they include molasses in my products. Can I attribute the success of their product to molasses? I doubt it.
If you want to end the debate on additives like molasses have the Scott’s company dish out some bucks to thoroughly compare anything they produce to what organic people are doing. I’ll supply the popcorn
“enough anecdotal testimony to validate actual scientific evaluation” – it does not work that way. No amount of anecdotal testimony validates science.
“If you want to end the debate on additives like molasses” – the debate is ended – there is no scientific support. That does not mean everyone believes the findings – but that is true in many areas of knowledge. Until some real science exists – there really is no debate. We only have the public guessing and believing one side or the other.
I believe you misinterpreted what the previous commenter was saying. They weren’t saying anecdotal evidence “validates science”. They were saying that, when there is sufficient anecdotal evidence, it would be smart to do some actual science to genuinely test whether or not the results can be reproduced under controlled conditions.
Can you cite studies which demonstrate conclusively that it does *not* work? Or is it actually the case that no studies have been done which either prove or disprove the effect?
Because without conclusive studies, all either side has is a hypothesis, perhaps one based on solid scientific foundations, but still just a hypothesis.
What is ” when there is sufficient anecdotal evidence”? When is it sufficient?
Have a look at my latest post about organic food. A large % of the population believes in its benefits – lots of anecdotal evidence – but it is all wrong.
https://www.gardenmyths.com/anecdotal-evidence-not-worth-the-screen-its-displayed-on/
Hey, you might be right about adding Molasses to a stable garden or compost won’t do much work. But how about when you are just beginning to build your garden? It is true that too much of everything can be bad, but when you are still starting and moderate the use of molasses to grow your organic garden plants, then you should be on the right track.
New garden – old garden – does not change the facts. molasses does not build long term benefits.
I have grapes vine garden
i have plan to use
20.kg sulpar
10 kg lime
15 kg molasses
cook for 2 hours in 200 kg water
after two hour
pick up clear liquid water
mix one kg of liqud to 20 kg fresh water
spary on grape vine woody area 500 grams fluid to vine for decompost alkaline soil and fungas
Sounds like the person that wrote this article doesn’t know what they’re talking about. 20 year gardener here and I know for a fact that molasses benefits your plants so much, it’s stupid not to use it. Especially since most microbe food is $30-$50 a bottle and molasses is like $4 a bottle….
You are the typical gardener who thinks they know something. You claim molasses benefits the plants and yet – not one reference to support that claim.
Lets see your proof!
Why compare molasses to buying microbes in a bottle? Your soil is already full of microbes – buying more makes no sense.
Make certain to take your depop shots, science says!
In other news, I’ll take empirical data and personal experience over what some study paid for by the chemical industrial complex presents as “science” and “facts”. Follow the shekels is the order of the day when it comes to revealing the true nature of scientific bias.
Find out who funds it and the agenda becomes perfectly clear.
What? No company is going to fund research on using molasses in gardens.
Yeah and it attracts snails!!!
Would it be of use in a scenario where there is an excess of N and shortage of P?
I understand Kelp meal adds K slowly, will it hasten that process if I top dress with Kelp meal before watering with molasses solution?
If you have a shortage of P – as some. Molasses is expensive phosphorus.
But I do appreciate you challenging the concept of using molasses it made me look more into the fact and I know not to believe the first thing google throws up when I ask questions and yours was the first lol all other info supports use .
Molasses works thats all there is to
If that were true you would be able to prove it by posting a link to a scientific article that supports your claim.