Soil Testing

is a valuable process for long term soil treatment but it’s very limited in terms of helping to determine what to feed and supplement to correct imbalances/ deficiencies and excesses in a horse’s intake.

Balanced Equine is all about calculating as accurately as possible the amounts of nutrients a horse receives when eating grass or hay. Soil tests are not a tool for this. Soil tests will only indicate what is in the soil, not in the pasture. Plants differ from uptake of minerals based on species, growth stage, soil pH, moisture, oxygen and nitrogen levels. Plants regulate uptake of many minerals.

Even if your soil test results say your soils are excellent, this does not mean that the grass will be providing a balanced intake. Of course, these soils will be better than highly acidic or alkaline soils. It’s always interesting to compare the results of a soil test to the results of a pasture test and it’s nice to know the soil pH, as it can be very helpful to explain pasture test results. Levels of minerals in soil can be to a degree fairly insoluble or unavailable for uptake in plant roots, depending on soil pH and other factors.

Emil Truog did some outstanding work over 60 years ago and his conclusions on how pH affects the availability of nutrients are still widely used today. For most plants, the ideal pH is slightly acidic, neutral or slightly alkaline. Links are at the bottom of the page.

First let’s look closer at the pH range
The lower the number the higher the acid and the higher the number more alkaline, also known as basic.

Soil Testing

Image sourced from http://www.edu.pe.ca/gulfshore/Archives/ACIDSBAS/scipage.htm

Soil testing and pH

Nutrient availability and microbial activity as affected by soil pH; the wider the band, the greater the availability or activity.
Adapted from Truog, USDA Yearbook of Agriculture 1943-1947 – https://commons.wikimedia.org/wiki/File:Truog_1947_pH_and_nutrient_availability.jpg

Plants can and do regulate uptake of many minerals from the soil. For example, it’s normal for plants to have much higher potassium levels than sodium. Too much sodium in the soil can kill plants unless the plants have adaptations to deal with the high sodium (halophytic species like mangroves). Potassium is essential for growth, can be around 25:1 K:Na depending on the plant portion tested and stage of growth (higher in young, growing grass or during regrowth).

Hair and blood testing

Unfortunately hair testing for working what nutrients are deficient or in excess or balance has been shown to be unreliable. Read about hair testing and what the research shows. Blood testing is for non-nutritional wellness states, it’s extremely limited for nutritional analysis.

Pasture or hay testing

The best way to find out what your horse needs is to find out what nutrients he is getting already from the main source of fibre, also known as roughage. Pasture or chaff/hay is the foundation of the diet. The horse’s digestive system evolved over a very long time to a design that is geared to extract available calories from high fibre foods by hindgut fermentation. The base of the diet for EVERY class of horse should be pasture or chaff/hay.

Grass or hay (preferably grass unless the horse is insulin resistant) is the best food for horses as this is what their digestive systems evolved to eat. Grass contains so many nutrients that horses need and is very high in fibre. This includes protein, carbohydrates, fat, minerals and vitamins. You may be surprised to read that there is fat in grass. In fact, if your horse did not have access to grass and was mostly on hay instead then the horse would need supplementing with omega-3 fatty acids essential for the immune system. These cannot be manufactured by the horse, they have to come from the diet. Read more about the best source of omega-3 fatty acids: linseeds.

Many pastures contain grasses, especially pasture improved species like Kikuyu that are high in protein and energy. Some may think you always need to supplement protein for horses, but the pasture may be supplying 2-3 times their protein requirements or even higher. To be able to know for sure what amounts of each nutrient/mineral your horse is getting it is best to have a sample of your pasture tested in a laboratory. If only a small amount of hay is in the diet then Balanced Equine can use average figures for your preferred type of hay but the most accurate way is to test a representative sample. Of course, some horse owners buy small amounts of hay from different sources so testing in this situation is not realistic.

Testing is not costly, especially if viewed as a way to find out what just how nutritious your forage is rather than guessing. Looking at photos of pasture cannot tell us what the nutrient levels are. The reason is that nutrient levels can vary so much. An explanation of what a test provides is in the Understanding test results article. I have chosen a laboratory that provides a most comprehensive test for nutrients and will also measure the energy in terms of a horse (rather than cattle which have a rumen) and is the cheapest. A pasture test costs about $39USD, a hay test can cost as little as $35USD plus postage.

You can learn how to do this yourself by enrolling in NRCPlus presented by Dr Eleanor Kellon VMD. All links are at the bottom of the page.

Frequently Asked Questions (FAQ)

Q. My pasture is diverse with different species of grass. It isn’t one grass that never changes.
A. This doesn’t take anything away from the value of a pasture test. It’s not an exact science but it’s the best we have. By sampling your pasture the way it is most of the time, we not only learn what the nutrient levels can be but also the mineral ratios.  This example may help; at my last property, my neighbour also got his pasture tested. If you can imagine 2x 25 acre properties, side by side. On his property, a variety of pasture improved species like rye, cocksfoot, fescue and others. On my side, mostly Kikuyu with other species. It was amazing to compare the two pasture tests, pretty much exactly the same in mineral ratios, the exception of course being that my grasses were mainly oxalate type. What makes this even more interesting is that the copper to zinc ratios for both properties were around 1:10, way out of balance and very unusual. Way back, both had been (50 years or so) free range chook farms. The extremely high differences and diversity of grass species didn’t change this. 

Q. If I test my pasture now won’t it change by summer and then in winter? Wouldn’t you have to keep testing many times a year?
A. Trace minerals and especially the ratios do not change much over the seasons but digestible energy and protein will. Potassium can be a bit higher and magnesium lower in new shoots of grass. A pasture test will indicate the amounts of minerals that need to be supplemented to make up deficiencies and correct imbalances and this can be used year round. As the seasons change, the digestible energy will go up and down and that is where the art of feeding comes in. If there is less energy value in the grass then you will need to feed more so that your horse can maintain a good body condition score. On the other hand, with the flush of feed in spring you will need to feed less but the mineral mix can stay the same.

Q. I use my horse for eventing and I was told to use a high protein feed. Is that the right thing to do?
A. If your horse needs the additional protein then yes but you may be surprised to find that the pasture or hay that your horse has for forage is already very high in protein and therefore it would be totally unnecessary to add more to his diet. If the protein is excess to his needs then your horse will have to excrete the excess protein.

Further reading

Links may change over time. If a link doesn’t work, search the title in your search engine.

Dr Eleanor Kellon VMD offers equine nutrition courses, start with NRCPlus
http://drkellon.com

Agriculture of Victoria The Effect of Soil pH on Supply of Nutrients 
http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/soilhealth_ph_nutrients

WA DPIRD (2018) Developing a Liming Program 
https://www.agric.wa.gov.au/managing-soils/developing-liming-program

Dairy Australia Chapter 7: Managing limiting soil factors – website currently suspended, may be retrieved in the future
http://fertsmart.dairyingfortomorrow.com.au/dairy-soils-and-fertiliser-manual/chapter-7-managing-limiting-soil-factors/7-6-soil-ph/

Lake B (2000) 2. Understanding Soil pH. NSW DPI 
http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0003/167187/soil-ph.pdf

Thumbnail from https://www.smart-fertilizer.com/articles/soil-acidity