Due to high fertilizer prices in the spring, many farmers reduced or omitted fertilizer applications early this season. As fertilizer prices have somewhat fallen, you may be considering to apply fertilizer to your pastures and hay grounds this fall.
When considering fertilizer applications, 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 its 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.
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.
Farmers who are running short on pasture should consider nitrogen applications on pastures in mid-August to stockpile tall fescue. Nitrogen and moisture are critical to successfully stockpiling tall fescue. Apply nitrogen in mid-August. Topdress at the rate of 40 to 100 pounds of actual nitrogen per acre on tall fescue.
Numerous studies have shown that wise fertilizer use and timing produces high production during fall and early winter. In fact, tall fescue crude protein and digestibility are better during fall and early winter than any other time of the year.
Yields can be very good when water is available during the stockpiling period. Tall fescue can produce two tons of dry matter up to late November. With adequate water, producers can achieve 25 pounds of dry matter for each pound of nitrogen used.
For more information, contact the Adair County Cooperative Extension Service at 270-384-2317.
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