Soil Sampling and Fertility

When was the last time you took a soil sample in your pasture?  If you can’t remember, then it is probably time to sample again.  It is recommended to sample every 2-3 years on a sandy soil, and every 4 on a clay soil.  As of today, sample results will be returned about 2 weeks after arriving at the lab.  Remember, there is a $4.00 per sample fee right now.  Samples will be free again after April 1^st, and will remain free through the end of November.

Why is soil sampling so important, and why do it every few years?  Without soil test reports, you cannot accurately provide the nutrients that your pastures need.  Any time an application is made without a soil test, there is a potential that you are throwing money away and potentially even doing harm to your pastures.  Remember, the essential nutrients your horse needs are provided through healthy forage, so if the plants don’t have the nutrients they need, your horse won’t have them either.  Over time nutrients are removed through grazing or leach through the soil profile, and soils will return to lower pH and nutrient levels.  This happens in all soils, more rapidly on sandy soils, and is why nutrient levels and pH should be monitored through regular soils testing.

Be sure to lime your pastures at the recommended rate.  While lime may seem like a large and expensive input up front, especially if it has been a long time since your last application, it is actually one of the cheapest ways to improve your pasture health.  Did you know that when soil pH is not in the proper range that many nutrients are not plant available?  This means without proper liming, your pasture may not have the nutrients that the plants or your horses need, in spite of proper fertilizer applications.  Just check out the chart below to see what I mean:

Nutrients are most available at the pH recommended by your soil test

Source: Crouse, D.A. 2016. Soils and Plant Nutrients, Chpt 1. In: K.A. Moore, and. L.K. Bradley (eds). Extension Gardener Handbook. NC State Extension, Raleigh, NC. <https://content.ces.ncsu.edu/extension-gardener-handbook/1-soils-and-plant-nutrients>

Right now is a great time to apply lime since it does take time and moisture to activate in the soil.  Lime can be applied while horses are grazing with no rest period. 

The time to apply nutrients is fast approaching as well, since they need to be applied when the forage is actively growing.  Nitrogen will always be recommended on a grass pasture, and should be applied when grasses are actively growing.  Phosphorus and potassium have the potential to build up in soils depending on soil type, so an application may or may not be needed.  Remember to rotate horses to another pasture when applying fertilizer, and keep them off fertilized pastures until adequate rainfall has washed the fertilizer into the soil.  Micronutrients are supplied in many blends, so if they are recommended, be sure to check the label of the product you buy and supply them appropriately.  Never use a fertilizer intended for a home lawn on pastures.  Homeowner fertilizers often contain herbicides which may not be safe on pastures, and may use slow release nitrogen sources which will persist after rainfall and can be harmful to horses.

When you take a soil sample, once your results return, you have in your hands powerful information which will help you build a healthy pasture and a healthy horse.  Be sure to follow recommendations and make applications at the right time.  Contact your local extension agent if you have questions soil testing, reading the report, or choosing which fertilizer source is right for you.