Ag Notes, Sept. 12

Published 8:38 am Tuesday, September 12, 2017

Fall fertilizer applications to hay field and pastures

You may be wondering if it’s necessary and economical to apply fertilizer to your pastures and hay grounds this fall.

The answer depends on your specific situation. When considering the options for your operation, the first thing you need to do is examine your soil test. If you have not taken soil samples within the past three years, you need to collect new ones before making a decision. From the soil test results, determine what, if anything, is 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 should apply lime. A grass-legume mixture usually 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 can be made for phosphorus (P) and potassium (K) nutrition, with alfalfa requiring the most and pure grass, specifically fescue, requiring the least.

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The University of Kentucky College of Agriculture, Food and Environment 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 for grasses and legumes. If you are growing alfalfa, we recommend applications for K levels below 450 pounds per acre.

If soil test levels are above these numbers, 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, contact the Boyle County Extension office.

Educational programs of the Cooperative Extension Service serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expressions, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability.

Jerry Little, County Extension Agent for Agriculture/Natural Resources