As we enter the fall of the year, it is a perfect time to address soil acidity.
While we can apply limestone to raise pH anytime, fall months are ideal for most. During the fall, most warm season forages begin going dormant. Fall months are typically when we receive adequate rainfall and moisture that is important to the reaction of limestone.
Plants need 16 elements to grow normally. Carbon (C), Hydrogen (H), and Oxygen (O) are found in air and water. Nitrogen (N), Phosphorus (P), Potassium (K), Magnesium (Mg), Calcium (Ca), and Sulfur (S) are found in the soil. Important for plant growth and development; however, not needed in large amounts are Zinc (Zn), Iron (Fe), Molybdenum (Mo), Boron (B), Copper (Cu), Manganese (Mn), and Chlorine (Cl).
Soil pH is a measure of the hydrogen ion (H+) activity in the soil solution. A soil pH ranges from 0 to 14 with 7 being neutral. Anything below 6.5 on the pH scale is considered on the acid side. Anything above 7.4 on the pH scale is considered on the alkaline side. Most grass species for forage production prefers a pH of 6.0 to 7.0 to perform at the optimum level. This is a great time to perform a soil test on your property. Soil testing laboratories base the rates of limestone recommended on the use of 100 percent effective limestone material on a dry weight basis.
Limestone particle size is important as well. The speed at which limestone reacts in a soil can also be largely determined by the particle size. Crushed limestone is screened through a series of sieves to determine particle size. Smaller particles have more surface area to contact soil therefore a more rapid change in soil pH.
The Effective Calcium Carbonate Equivalence (ECCE) value is a combination of fineness efficiency rating (ER) and the calcium carbonate equivalence (CCE) to estimate the percentage of effective limestone in a given product. The ECCE is calculated by multiplying the CCE times the ER. For example, if the CCE is 95 percent and the ER is 65 percent then the ECCE would be 62 percent. This means the material would be only 62 percent as effective as finely ground, pure calcium carbonate.
So how do I figure how much limestone is needed? If the soil test limestone recommendation calls for 2 tons of 100 percent ECCE limestone per acre and the 62 percent material is used, it would require 3.23 tons per acre of the 62 percent material applied. To calculate application rate in tons per acre, divide soil test lime rate (tons/acre) by the ECCE/100 to get the actual tons per acre of the desired material.
Nitrogen, phosphorus, and potassium are all needed by the plants and a soil test will determine at what levels these nutrients are present or lacking. The lower the acidity, the less percentage of nutrient recovery of nitrogen, phosphorus, and potassium is available. For example, if your pH is 4.5, there is 21 percent nitrogen, 8 percent phosphorus, and 21 percent potassium available to the plant. If the pH is 7.0, there is 70 percent nitrogen, 30 percent phosphorus, and 60 percent potassium available to the plant.
So with soil acidity, do not wait until you are ready to plant to start trying to manage this. Begin now by performing a soil test and following the recommendations to prepare your soil for the desired grass species. There are a number of sources around the area that can be of service to you when you decide to apply limestone to your property.
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