Spaying dilute raw milk onto pastures is a novel, untested practice that has recently gained widespread prominence as a potential means of increasing forage production and quality. This partnership project investigated if foliar applications of dilute raw milk on pasture would improve the productivity, palatability and quality of pasture using an on-farm testing method on two organic dairy farms. In 2012, two Vermont organic dairy farms, Choiniere Family Farm and Applecheck Family Farm, partnered with University of Vermont researchers to examine the impact of raw milk on pasture yield, forage quality and soil fertility. Each of the farms followed a similar research protocol. Dilute raw milk (2X) applied at a rate of 20 gallons active ingredient per acre was compared to a non-treated control, replicated in six paddocks on each farm. We found no significant difference in forage quality, soil quality, and forage production between areas sprayed with milk and non-treated control areas. In a concurrent greenhouse study using perennial ryegrass seedlings, the only growth parameter that showed a significant increase to raw milk was tillering rate during the initial growth but not in the subsequent regrowth. To follow up on the 2012 year, a replicated field trial comparing raw milk applied at two rates, 5 and 10 gallons/acre, was conducted at the Larson Farm in Wells, VT. As in 2012, we found no difference in pre or post grazing yield during the subsequent grazing period. It may be that there are too many environmental variables in the field for the slight benefits we found in the controlled environment of the greenhouse to be expressed and be biologically or economically significant. Results of the 2012 year were reported at the Vermont Grazing and Livestock Conference in January and at the Northeast Pasture Consortium meeting in February. A newsletter article was published on the study in the Solar Dollar as well as the Northeast Organic Dairy Producers Association News in June 2013. A final report has been posted on the Vermont Crops and Soils webpage.
The cost to renovate poor quality, low productive pastures can be very expensive especially for organic farmers. To manage this problem, some graziers are experimenting with highly active biological compounds known as positive plant growth regulators, metabolic enhancers, and biostimulants. These compounds, which are neither fertilizers nor pesticides, promote efficient plant nutrient uptake and enhance plant growth and development through a wide variety of mechanisms. They are typically applied in very small amounts to the soil or sprayed directly onto the plant. Humic acids and seaweed extracts are well known examples.
Raw cow milk has been suggested as an effective pasture biostimulant. Raw milk has been used as a crop amendment for centuries. It contains proteins and other compounds which have been observed to suppress plant disease and enhance plant tolerance to heat stress and nutrient uptake capabilities. Furthermore, many of the bacteria ubiquitous in raw milk are established beneficial, plant growth promoting, soil microbes. In recent years, there have been anecdotal reports and claims from field observations in the Midwest that raw milk applied to pasture at rates up to 20 lbs. per acre (too low to provide a significant amount of nutrients) boosts yields, forage quality, soil porosity and grass brix measurements. However, none of these claims have been thoroughly investigated in replicated trials and there have been no studies report in the Northeast.
Our aim was to verify these reported observations in Vermont by assessing the effect of diluted raw milk on pasture production, quality, botanical composition, and soil health. It is our intent that this project will provide additional information to help farmers make informed decisions before investing their time and/or money into implementing this novel practice.
Objective 1: Assess changes in pasture soil health, and forage production, quality, and palatability that occur as a result of a dilute foliar application of waste (or raw) milk.
Objective 2: Provide graziers with a prototype On-Farm Testing (OFT) methodology that can be replicated on other farms in order to test other products and practices.
In order to test the efficacy of raw milk applied to pasture, two greenhouse studies and three field experiments were conducted between 2012 and 2013.
Two separate preliminary greenhouse experiments were conducted in 2012. The first aimed to measure the effect of milk on forage growth parameters. Perennial ryegrass was grown from seed in 12 pots. After 21 days, milk, diluted 50 fold with water, was applied to the surface of half of the pots at rate comparable to 20 gal/acre. The forage above and below ground mass, tiller elongation rate, tillering rate, and other characteristics of the forage above ground and below ground biomass was monitored for 43 days over two cuttings.
In a second greenhouse experiment, the impact of raw milk on soil nitrogen dynamics and organic matter decomposition was investigated by destructively sampling soil microcosms. Fresh, sieved, pasture soils were packed into small pots. Mesh bags containing dry, ground grass were buried 1 cm beneath the soil surface. Diluted raw milk was applied to the surface of half of the pots at the rate of 20 gal/acre. After periods of 1, 7, 14, 21, and 28 days, pots were destructively sampled to determine litter decomposition rates and soil mineral nitrate and ammonium concentrations.
In 2012, field trials were conducted on two Vermont dairy farms – Applecheek Farm, a diversified organic farm located in Hyde Park, Vermont and the Choiniere Family Farm, a family run organic dairy located in Highgate, Vermont. At both locations, existing pastures were used to test the application of raw milk compared to an untreated control. The dominate grass species were orchardgrass and Kentucky bluegrass at Hyde Park and Highgate, respectively. At both farms, the pastures had been subject to managed intensive grazing (MIG) methods for many years. Cows are usually moved between each milking and rest periods vary from two weeks to a month depending on growing conditions.
Treatments consisted of raw milk applied just after grazing compared to an untreated control. All other management practices were keep consistent and the same. Treatments were replicated at each farm using a paired-comparison design with each pair of treatments (milk supplement verses a no milk control) replicated six times for a total of 12 plots. Plot sizes were ranged from a quarter to half acre each. Within each grazing paddock, treatments were assigned to one side of the paddock or the other. In the first paddock, the treatments were randomly assigned and treatments alternated in the subsequent paddocks.
The milk treatment was applied only once at a rate of 20 gallons of milk per acre to each of the six appropriate plots in early June of 2012. Raw milk was collected from each respective farm, diluted 1:1 with tap water, and sprayed at the rate of 40 gallons of milk solution/acre using a tractor mounted boom sprayer. Treatment application occurred within five days of the pasture being grazed. Our intent was for the pasture to be relatively short to help facilitate some of the solution reaching the soil and to have at least 30 days of pasture growth between application and next grazing. However, since these were dairy cow pastures, the residual sward height at time of application was not as low as you would expect with a dry cow or beef pasture.
Plots were sampled twice during 2012, approximately 30 and 60 days post milk application immediately before the next two or three grazing periods.Pasture pre-grazing mass was measured just prior to grazing by collecting cut samples from 30 randomly placed 1.5 ft2 quadrates within each plot. Each sample was placed in marked cloth bags and put in a forced air drying room located at the University of Vermont Horticultural Research and Education Center where once dried, they were weighed. Post-grazing yields were collected immediate after the animals grazed the plots using a calibrated rising plate meter. Soil samples were collected from each plot taking a 20 subsample composite and analyzed at the UVM Agricultural and Environmental Testing Lab to measure organic matter, nutrient content and moisture content. Forage grass samples were separated from the mixture and sent to Dairy One (Ithaca, NY) to be tested for ADF, NDF, and crude protein in a analysis. Forage botanical composition was determined by collecting a composite of 20 subsamples across each plot and hand separating grass, legume and weeds. BRIX measurements were determined by taking random grab samples of 6-10 leaves were collected from 30 locations in each plot. Each sample was vigorously rolled between researchers’ hands for 15 seconds to form a tight ball; the sap was then extracted used a garlic press. Brix values for each batch were measured immediately using a Vee Gee Scientific STX-3 Handheld Refractometer.
In 2013, a field trial was conducted at the Larson Farm in Wells, VT. Like the two previous farms, the Larsons practice MIG and a soil test of the study site showed high organic matter and good soil pH and nutrient levels. Dominate species included tall fescue, orchardgrass, reed canarygrass and white clover. One concern from the 2012 studies was that the 20 gallon per acre rate would be too expensive even if there was a positive response. In addition, some of the previous observations stated responses at lower rates. Therefore, we imposed two lower rates of milk in this study, 5 gallons and 10 gallons per acre. In addition, the Larsons were interested in also testing whey that they received from the cheese plant were they sold their milk.
Since there were four treatments – two milk rates, whey applied at a rate typical of the farm, and the untreated control – the study was set up as a randomized block design with six replications and the plots were small (12’ x 25’) all contained in one grazing paddock. The treatments were applied July 17 after the third grazing. The raw milk was collected from the farm and diluted 1:1 with the farm’s tap water and applied with the same boom sprayer used in 2012 except it was calibrated for the two rates of application. The whey was applied at a rate that the farm had been using. We estimated the whey was applied at a rate of approximately 40 gallons per acre.
Pre-grazing mass was measured on all treatment plots on August 14 just before the cows were turned out on the pasture. Ten falling plate heights were collected from each plot. Hand samples were collected from each plot to determine forage quality evaluation. On August 16, post-grazing mass was measured in the same manner taking 10 falling plate heights per plot.
To calibrate the falling plate, 12 samples ranging in mass from low to high were collected across the study area. At each site, the rising plate height was documented and a quadrat of the same dimensions as the falling plate was used to collect all the forage down to the ground surface. The material was placed in a cloth bag, dried and weighed to determine dry matter yield. Regression analysis showed that a quadratic equation was the best fit to develop a prediction equation. The model used was y = -4.5508x2 + 290.62x, where y is yield in lbs dm per acre and x is height in centimeters.
In preliminary greenhouse studies we conducted at the University of Vermont, perennial ryegrass treated with dilute raw milk tillered more rapidly than those that did not receive the treatment (Figure 2). This resulted in significantly greater above ground biomass in pots treated with milk. This only occurred in the initial growth period and the affect did not have any long lasting influence since there was no difference in tillering rate nor yield in the next growth period. Other forage growth parameters including root density, shoot elongation, and forage Brix Content, were not affected by the application of raw milk. With some positive effects, our next goal was to test milk treatments in real world situations on farms in Vermont.
In the second greenhouse experiment, soil ammonium-N concentrations spiked 1 day after milk application in pots treated with milk. However, ammonium concentration on other days as well as nitrate concentrations and litter decomposition rates were not affected by the milk treatment.
In the 2012 field trials, we generally found little to no effect of the raw milk on pasture growth or productivity at either farm (Table 1). Participating farms were not able to distinguish the areas that had been treated with milk from the controls.
There were no statistical differences in pre-grazing or post-grazing yields at either farm for either growth period. We were unable to collect post-grazing for the first sampling at Applecheeck, therefore, we could not calculate consumed forage. There was a statistical difference between the milk treatment and the control for consumed forage during the second sampling at Applecheek Farm, but the numerical differences were not great. Also, there were no consumed forage differences at Choiniere farm. Since these are calculations using both pre and post grazing yields, there is more likelihood of variation.
Legume content was consistent between treatments across farms and sampling times and tended to be low at all sites. The percent of weeds in the pastures were also relatively low. The milk treatment in the second sampling at the Choiniere farm had statistically greater weed content than the control but the numerical differences were not very large (9% verses 6%). ,
There were no consistent differences in forage quality nor soil quality measurements (data not shown). Calcium content was slightly higher than the control in the first sampling at Applecheek. Since the interval between application and sampling was only 20 days and it was dry during that time period, it may be likely that the milk residue contributed to this slight increase in calcium content. There were no differences by the second sampling.
In the 2013 field trial comparing two lower rates of milk and whey, we found no significant differences in pre-grazing or post-grazing yields or forage consumption for any of the treatments (Table 2). At the time of collecting pre-grazing pasture mass, there were no observable differences as well (Figure 7). Forage quality was also not different amongst treatments. The pasture residue at time of application was relatively high and this may have interfered with any movement of the milk to the soil. However, the residue was not atypical of dairy pasture managed for high milk production. The soil quality of this site, like the other two farms, was quite good, having high organic matter, soil pH at about 7.0, and soil nutrient levels adequate to high. Therefore, growth rate was already good and could mask any subtle benefits from a biostimulant.
Even though an application of raw milk had a positive effect on initial grass tiller production and yield in the greenhouse study, we found no effect of milk on pasture growth or yield within the first 60 days of application in three different on-farm trials. There are several possible explanations. First, the dry conditions present during the summer of 2012 may have inhibited any stimulatory effect milk might otherwise have had. During the summer of 2012, the experimental sites received less than 3.5 centimeters of rain. As a result, very little of milk sprayed onto plant leaves was likely not washed into the soil via a natural precipitation event. In addition, under the droughty summer conditions soil microbial activity and nutrient cycling would process slowly. The dry conditions may have inhibited the movement of the beneficial bacterial into the soil thereby negating the potential for milk to positively influence soil and forage parameters. The other condition that may make this difficult for dairy grazers is the level of residue at time of application. In all three farm studies, the pasture residue at time of treatment was at least at four inches. This could have interfered with any milk getting to the soil while still biologically active. Or, it may also be that there are too many environmental variables in the field for the slight benefits we found in the controlled environment of the greenhouse to be expressed and be biologically or economically significant.
The results of this experiment indicate that the application of raw milk onto pasture is not an economical means of enhancing forage production or forage and soil quality. The meager gains recorded are neither great enough to influence pasture production nor consistent enough to be a reliable solution.
Education & Outreach Activities and Participation Summary
The following are publications as a result of this project:
Hilshey, B. (2013, April). Raw Milk to Help Grass Grow. On Pasture. April 3, 2013. Retrieved from http://onpasture.com/2013/04/30/raw-milk-to-help-grass-grow/
Hilshey, Bridgett. and Sid Bosworth (2013, June). Raw Milk as a Pasture Biostimulant. Northeast Organic Dairy Producers Alliance. Retrieved from http://www.nodpa.com/research_ed_milk_as_biostimulant_060313.shtml
Hilshey, Bridgett and Sid Bosworth (May 2014). The Evaluation of Raw Milk as a Biostimulant, Research Report. Vermont Crops and Soils Homepage, UVM Extension.
Hilshey, Bridgett, Sid Bosworth and Rachel Gilker (January 2014). A Practical Guide to On-Farm Pasture Research. UVM Extension and USDA-SARE. http://pss.uvm.edu/vtcrops/research/Conducting_On-Farm_Pasture_Research_Guide2.pdf
Results of this project were presented at the following events:
- Initial results were presented at a University of Vermont Plant and Soil Science Seminar in 2012 (approximately 20 attendees).
- A brief article outlining the study was also submitted to The Solar Dollar, the Vermont Grass Farmer’s Association Newsletter in 2012.
- A presentation on the raw milk studies was given at the Vermont Grazing and Livestock Conference at Lake Morey Inn in January 2013 (30 farmers)
- A presentation on conducting on-farm pasture research was made at the same Vermont Grazing and Livestock Conference (15 attended)
- A poster presentation was given at the Northeast Pasture Consortium in Manchester, NH in Feb. 2013
- A discussion of the trials was made on site at the Larson Field Day August 2013
- A presentation on conducting on-farm pasture research was made at the 2014 Vermont Grazing and Livestock Conference in January 2014 (6 attended)
If the field trials had shown significant results, it was our intent to conduct a cost benefit analysis for the application of the milk as a cost and changes in pasture productivity and quality as benefits. However, since we did not get significant nor consistent reponsese, there was no need to conduct an analysis.
For Objective 1, we demonstrated that the practice of applying raw milk on pastures did not work; therefore, we would not expect farmers to adopt or to do more study before adopting this practice.
Pertaining to Objective 2, we did not followup on the few who attended our training session at the 2013 VT Grazing Conferrence. It is my intention to provide our booklet to the Vermont Grass Farmers Association for their grant program for farmers doing their own research. I will also be using this publication during the up coming PDP on Forage and Weed Management.
Areas needing additional study
There are opportunities to utilize many biostimulants for pasture improvements and there are many products on the market with many claims. These need field testing to provide farmers with the knowledge to make informed decisions.