Foliar potassium application an alfalfa enhancement

Ray Mueller, Correspondent


Visitors are welcome at the corn, soybean and alfalfa plots sponsored by Poplar Farms Sales & Service along Middle Road in Manitowoc County.

Is there a way to improve both alfalfa yields and quality without relying mainly on genetic advances, ideal growing conditions, or standard fertilization practices?

That this is a possibility is shown by the results of a project carried out on seven acres in 2015 involving eight alfalfa varieties from Dairyland Seed, DuPont Pioneer, Legacy, Croplan, WL, and Dekalb. It was conducted with a third cutting taken on Aug. 6 on a research plot sponsored by Poplar Farms Sales & Service on leased land along Middle Road.

Liquid vs. dry potassium

The only difference in the management of the field which was divided into east and west halves was the form in which potassium was applied shortly after the second cutting last year. Those treatments were the foliar application of Agro-Liquid's liquid Sure K at a rate of 6 gallons per acre and the surface application of 150 pounds of dry potassium per acre.

An application of Baythroid XL insecticide was included in both treatments. It provides control of such typical alfalfa pests as potato leaf hopper, grasshoppers, plant bugs, weevils, meadow spittlebugs, loopers, stinkbugs, bud worms and armyworms.

A report on the 2015 project was reviewed by Agro-Liquid's field agronomy manager Daniel Peterson of West Bend at a recent Poplar Farms field day at the plot. He told attendees that the favorable differences attributed to the application method and product are most evident in the latter three cuttings of the season.

Daniel Peterson

Multiple locations

Peterson is very confident in the findings in the Poplar Farms because similar results have been documented in plots near Waupun and Lena in Wisconsin along with four in Minnesota and one in Upper Michigan. He said the best time for the liquid application is early in the alfalfa's regrowth stage — at a height of no more than a soda can.

Based on testing by representatives of Dairyland Seed, the August 2015 results at the Poplar Farms plot showed differences between the individual alfalfa varieties but the averages were greatly in favor of the foliar application with the liquid product, Peterson pointed out.

Dairy interests

Of particular interest to dairy farmers was the calculation for milk per ton and milk per acre from the alfalfa forage, Peterson said. Per ton of alfalfa dry matter, the average milk potential per acre from the foliar application was 2,704 pounds — a 12.6 percent or 302 pound advantage which could convert into 1 or 2 pounds of milk per cow per day depending on portion of the alfalfa forage in the ration.

With the average dry matter yield of .94 ton per acre for the foliar application being only .07 ton more than with the dry application, the milk per ton advantage for the foliar application was limited to 3.5 percent or 97 pounds. The greater advantage in the milk per acre tabulation was due to 4.5 to 8.1 percent advantages in relative feed value; rumen digestibility of both neutral detergent fiber and total fiber content; and relative feed quality, Peterson explained.

Variety differences

The differences in dry matter yield and milk production potential per acre were significant between the alfalfa varieties in both application methods, Peterson noted. What also stood out was that the rankings of the varieties on those points were not consistent between the liquid and dry treatment portions of the field.

For the foliar application, the 3rd cutting yields ranged from 1.17 to .71 tons per acre but the milk per ton range was only 2,722 to 2,910 pounds. For the dry application, the per acre dry matter yield range was 1.13 to .63 tons while the milk per ton spread was from 2,434 to 2,952 pounds.

In both settings, one of the varieties posted the highest yields in all but one of the strips, one had the same yield from both applications and minimal differences on the other traits, and others shifted positions for having either the lowest yield per acre or lowest potential milk production per acre.

Another phenomenon in the testing of the forage was the smaller difference between the alfalfa varieties in the spread on milk per ton with the foliar application of the potassium — a consistency that impresses Peterson. The range was 240 pounds in the foliar application group compared to 603 pounds in the dry application category. Countering the trend was the calculation that the highest milk per ton of 3,047 pounds — at least 95 pounds more than all the others — was credited to a variety getting the dry treatment.

Growing timetable

An overall major difference between the foliar and dry potassium applications was a 4 to 5 day faster maturity with the foliar treatment on the harvest time for the desirable feed quality traits, Peterson said. Without an awareness on that point, there could be a risk of allowing the alfalfa to become too mature before cutting, thereby reducing the fiber digestibility.

Asked how a more rapid growth cycle with the foliar application could mesh with the new low-lignin alfalfa which provides a harvest extension of about 6 to 8 days without sacrificing fiber digestibility or other desirable forage traits, Peterson suggested that this shouldn't be a problem. No such research has been done but both of the claimed benefits could apply.

At one of Agro-Liquid's plots on the potassium comparisons, Peterson said the top documented difference has been a 24 percent increase in alfalfa yield. With the addition of sulfur as a fertilizer, a trial in Minnesota supported a potential 5 pound daily increase in milk per cow, he reported.

Peterson is also enthusiastic about the potential of foliar applications of potassium, combined with smaller portions of nitrogen and phosphorus, at tassel emergence in corn intended for silage in order to deter the development of toxins. The foliar application is also suitable for a great variety of fruits and vegetables. Unlike dry products, he emphasized that the Agro-Liquid foliar product is free of the chloride and hyroxide that can burn foliage on plants.