A while ago I wrote about Milk As Fertilizer and concluded that although milk would add organic matter to a garden, it was no ‘magic bullet’. Since that report I have spent more time looking at the subject of milk fertilizer and tracked down how this myth was born. It a thriller full of deception and lies. Today I will dig deep into this myth and uncover some surprising facts. Then I will review the latest research on the subject.
Milk Fertilizer – a Glimmer of Hope
Around the year 2000 a steel industry executive turned dairyman by the name of Dave Wetzel started spreading his excess milk on agricultural land. It did not take long for Mr. Wetzel to convince himself, and a local Knox County Extension Educator, Terry Gompert, that the milk fertilizer was producing superior production yields. Not only were pasture fields much more productive but soil core sampling displayed increased ‘ground porosity’, ie less compaction. Milk was having a very positive affect on soil structure.
With Terry’s connection to the University of Nebraska, they were able to convince a research team to do some scientific studies to prove what ‘they already knew’.
A number of test cases were designed that used milk and/or milk+cod liver oil. I don’t know why cod liver oil was added ?
What were the results?
- Nothing short of amazing:
- Two gallons of milk increased yield by 26%
- A few ounces of cod liver oil per acre increased yield by 20%
- Milk + cod liver oil increased yield by 31%
- The porosity of soil treated with milk increased by 19%
Note: the above results are the ones that Mr. Wetzel has been promoting. This is his interpretation of the research study.
There are now numerous reports on the internet that report these findings. Mr. Wetzel has been very good at getting his message out.
Milk Fertilizer – Real Data
I could not find the published research on this study, so I decided to contact the original researchers. A Dr. Charles Shapiro, Professor of Agronomy and Horticulture, Soil Scientist – Crop Nutrition, Haskell Ag Lab was generous with his time, and provided me with a summary of the research project, the data from the project as well as background about the relationship with Mr. Wetzel. He has asked that the full report not be made public since the data has not been officially published. He has given me permission to write a summary of the data.
The original milk fertilizer study was planned for several years, but after seeing no positive results after one year, the research project was discontinued.
At the end of the experiment the data, with statistics, were presented to Terry and Mr. Wetzel, who used it as “they saw fit”. The researchers made their findings clear, but David Wetzel decided to ignore the real data and the researchers conclusions.
What were the ‘real’ results?
“There is no statistical evidence that the milk and oil affected any of the parameters measured. It is true that the no milk, no oil treatment had the lowest yield (4454 lbs/acre), but another no milk treatment, the one with 4 oz of cod liver oil had (5314 lbs/acre). The LSD which indicates the difference needed to be significant was almost a ton (1980 lbs/acre) indicating a large amount of variability at this site. The coefficient of variation (CV) which is a measure of variability was almost 25% for dry matter. This is about twice the level we usually find for yields.”
They measured productivity, individual nutrients, as well as soil compaction. Milk or Milk + cod liver oil, had no effect on the outcome. Milk fertilizer did not improve yields, nor did it improve soil structure.
The Value of Statistics
I am not a big fan of statistics – they can be manipulated to prove almost anything. But when it comes to horticultural studies statistics are vital, and here is why. Plants are living things, and each plant will behave differently. Some grow faster and better than the one next to it. One acre of land is quite different than a neighboring acre. To get any meaningful data you need to do lots of replicates and comparisons.
The above study is a good example of this. Even if NO milk was added, the variability of production between acres was huge – 2000lb/acre. In order to prove milk had an effect, they would need to see the treated fields produce much more than this.
Mr. Wetzel was not happy with the results – they did not prove him right! So he cherry picked a few numbers in the study, and used them to talk to reporters. He selected the data that proved his anecdotal observations and convinced himself he was right. He then proceeded to convince a lot of writers that he had found the magic milk elixir.
Lets be clear. The study did not say that milk has no effect. What it shows is that in this study, done on certain fields and with certain crops, there was no real value in adding milk.
I have now found a second study, Raw Waste Milk as a Pasture Amendment, done by Dr. Sid Bosworth of the University of Vermont. They studied the impact of raw milk on pasture yield, forage quality and soil fertility on two farms in Vermont.
They concluded that “the application of raw milk onto pasture is not an economical means enhancing forage production or forage and soil quality. The meager gains recorded are neither great enough to influence milk production nor consistent enough to be a reliable solution. ”
In other words, the benefits of adding milk, if there are any, are not worth the effort of spreading it.
Is Milk Good For the Garden?
Milk is an organic product, and any organic material added to your garden will help – so yes, it is good for the garden.
But keep in mind that milk is mostly water – around 90% water. A gallon of milk contains very little organic matter. A handful of compost would be just as good as a gallon of milk.
There is NO scientific evidence that milk has any special powers, or that it does anything different to soil than any other organic material.