Ag Notes

Published 9:46 am Friday, October 14, 2016

Fall fertilizer applications to hay fields and pastures

As you’re probably aware, the price for agricultural inputs has dramatically increased, and fertilizer is no exception. In fact, the price of fertilizer is so high cattle producers are asking if it’s economical to apply fertilizer to pasture and hay ground this fall.

The answer to that question is difficult because it depends on your specific situation. When considering the answer for your operation, the first thing you should do is examine your soil test levels. If you have not taken soil samples within the past three years, you would be wise to collect new ons before making a decision. From the soil test results, determine what, if anything, is most limiting. In terms of soil pH, the minimum value depends on the type of forage you’re producing. If it’s alfalfa and the pH is below 6.0, you could apply lime. A grass-legume mixture probably can tolerate soil pH down to about 5.8 and a pure grass system probably can go down to pH 5.5 before yields are affected. Similar statements could also be made for phosphorus (P) and potassium (K) nutrition, with alfalfa requiring the most and pure grass, fescue, requiring the least.

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The University of Kentucky College of Agriculture recommends P applications starting when the soil test P level drops below 60 pounds per acre and K when soil test K drops below 300 pounds per acre. If soil test levels are above 60 pounds per acre and or 300 pounds of K per acre, the likelihood of a yield response to additional P and/or K fertilizer is extremely low.  But if you want to be sure that P and K are not limiting, apply fertilizers as recommended. If you are conservative and assume some risk that P and K might reduce yield, you might allow soil test levels to decline further. From small plot research, we know that once soil test P drops below 30 pounds per acre and/or soil test K drops below 200 pounds per acre, a yield response to added fertilizer is likely, therefore; these would be the minimum tolerable levels.

For more information on soil sampling and fall fertilizer recommendations, contact the Boyle County Cooperative Extension Service.

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