Soil is the foundation of a healthy pasture. It is essential to know the prior crops, herbicides and current condition of your soil before planting - nutrient deficiency or pH imbalance could prevent your pastures from producing high quality, highly nutritious forage.

Conducting a soil test is the best and most effective way of understanding your land. The best time to test is in the fall and early spring before your last year's crop residue starts to break down. If fertilization has already taken place, wait at least 12 weeks before testing in order to get an accurate reading.

When taking samples or if you have a professional take them for you make sure you are using clean tools. Pesticide or fertilizer residues on the tools or in the container will affect the results. Take 15 to 20 cores from each field where the soil type and topography are uniform, and the field has been uniformly managed. Limit the maximum area of each sample to no more than 20 acres. Collect the samples by making a zig-zag pattern over the entire field. Mix the cores thoroughly and then submit about a pint of soil to the lab.

Rule of thumb:

• Soil test every 2 to 3 years
• Take soil cores from the top 3 to 6 inches

Fertilization

 Fertilization enables the plant to develop denser and deeper roots which allow the plant to:

• Absorb more nutrients and moisture
• Develop denser foliage to increase the absorption of sunlight Increases the plant's ground cover which inhibits the growth of weeds
• Good vegetative cover slows water runoff and enables plants to soak up water
• Develop a deeper, thicker root system to take up more moisture and nutrients

So what are the primary nutients (building blocks) that you should be thinking about?

When you purchase a bag of fertilizer there are typically 3 number on the bag such as 18-24-10 which stands for N-P-K. Let's discuss what each letter means and what it does for the plant. 

Photo taken at Michigan State University - Dr. Richard Leep N study. From left to right - first plot received 0 units of N, 100 units of N , 200 units of N, 300 units of N

Nitrogen (N)

Nitrogen is critical for the maximum growth of cool season grasses. An adequate supply of N is associated with vigorous vegetative growth and a plant's dark green color. Nitrogen is very mobile in the soil. It moves from the soil into the plant as part of the growth process and seeping water can leach it out of the soil over time. So it must be continually replenished. Other benefits on N include:

• Assists plants in producing more vegetative growth even during hot, dry periods when none fertilized plant stop growing
• Assists plants in growing through times when leaf diseases like rust may be present
• Helps create denser foliage

There are several sources on Nitrogen available for hay or pasture, but the most common ones will be: Urea or Ammonium Sulphate. Heavily grazed pastures with high yielding forages require 390 to 650 lbs of Urea or 850 to 1,400 lbs of Ammonium Sulphate per acre for season long production. These amounts should NOT be applied in one application, however should be applied in at least 3 applications. These applications will vary depending on the part of the United States you are in, but a general rule of thumb would be Early Spring, Early Summer, and Fall.

Phosphorus (P)

Phosphorus require phosphorus for steady, strong growth. As growth occurs, phophorus is used to efficiently use sugars, starches and maximize photosynthesis in the young roots, stems and leaves. When adequate phosphorus is in the soil you will generally see rapid growth, earlier maturity, and frequently raise the forage quality of the plant for the animal. As a general rule your pasture will require 100-150 lbs of phosphorus per acre per year.

Potassium (K)

Potassium is required for overall strong plant growth, increased disease resistance, increased resistance to drought stress and increased winter hardiness. As a general rule of thumb your food plot will require 250-300 lbs of potassium per acre per year.

Now that we have discussed the building blocks and their importance, let's review those numbers on a bag of fertilizer one more time. On a bag of fertilizer that has an analysis of 18-24-10 means for every 100 lbs of fertilizer you will receive 18 lbs of N, 24 lbs of P and 10 lbs of K. So for an example, in a 36 lb bag of fertilizer you will receive 6.48 lbs of N, 8.64 lbs of P and 3.6 lbs of K. So if your goal is to apply 50 lbs of N per acre you will need to purchase 8 - 36 lb bags of 18-24-10 to achieve your goal.