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This article in AJ

  1. Vol. 58 No. 5, p. 545-549
    Received: Mar 16, 1966

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Response of Two Alfalfas (Medicago sativa L. and M. falcata L.) to Time and Rate of Potassium Application in the Subarctic1

  1. L. J. Klebesadel and
  2. J. C. Brinsmade2



Annual topdressings of K at 0, 42, and 166 pounds per acre, applied either in spring or mid-summer, were compared with 2 alfalfas—Medicago sativa (var. ‘Vernal’) and M. falcata—for 3 seasons in Alaska's Tanana Valley.

Stands of both alfalfas thinned rapidly during the study but stands and stand losses showed virtually no relationship to K treatments. Winterkill accounted for most of the reduction of stands and Vernal winterkilled more than M. falcata.

K treatments resulted in large differences in yield. Both rates of K topdressing resulted in higher alfalfa yields than no topdressing; and 166 pounds of K per acre were superior to 42 pounds per acre.

Crude protein content of forage was seldom influenced to a significant extent by K applications. Where differences existed, crude protein content was lowest with the highest rate of K application. M. falcata contained higher levels of crude protein than Vernal.

K content of forage, virtually always lowest where no K was topdressed, was usually higher in alfalfa topdressed with 166 pounds of K per acre than at the lower rate. K content was lower in Vernal than in M. falcata.

Highest percentage recovery in forage of applied K occurred with no topdressing. There, recovery exceeded the amount of K applied at planting. K recovery with the higher rate of topdressing was poorer than with the lower rate. M. falcata was superior to Vernal in K recovery.

Amounts of available K in the soil did not differ among treatments until the third harvest season, when K levels were higher in most plots that had received the higher rate of K topdressing.

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