EFFECT OF COLD TREATMENT ON ALFALFA AS INFLUENCED BY HARVESTING SYSTEM AND RATE OF POTASSIUM APPLICATION

Abstract

Alfalfa plants were grown in the greenhouse and harvested by three systems: (1) as one hay crop, (2) as two hay crops, and (3) as a hay crop followed by two pasture cuts. The cutting systems were arranged factorially with three levels of potassium fertilization: no potassium, 200 lb K per acre, and 300 lb K per acre. After hardening and freezing in an environmental control chamber, plants which were harvested only once had the best recovery, the most etiolated regrowth, and the highest percent of total available carbohydrates (TAG) in the roots. Plants harvested only once also had the largest root weight but the lowest yield of harvested herbage. One crop harvested at early bloom followed by two pasture cuts produced the second highest herbage yield, the lowest root yield, the lowest percentage of total available carbohydrates in roots, the highest percent K and P in the tissue, the lowest yield of etiolated regrowth, and the poorest recovery after freezing.Plants which received 200 and 300 lb K per acre were not significantly different in most criteria measured but gave higher yields than the plants which did not receive additional K. Etiolated regrowth, percent TAG in the roots, and recovery rating were better for plants fertilized with K. The plants which recovered best after the cold treatment were those fertilized with K and allowed to reach full bloom following the first hay-cut.