Root reserves of alfalfa with special reference to time of cutting and yield

1. Any extensive reduction of root reserves of alfalfa as measured by total weight of roots per acre consistently resulted in a reduction in yield and vigor of growth. Severe winterkilling from heaving followed extreme reduction in reserves, but the loss in vigor occurred without this. 2. Up to the first cutting for hay, young alfalfa gained in root reserves regularly and consistently, both in the fall of the seeding year and in late April, May, and early June of the next year. 3. Under Columbus conditions, alfalfa did not in four years show a gain in root reserves in August when the second cutting was allowed to stand from full bloom to seed stage. During the same period in June, gains took place in some years and not in others. This failure to store root reserves after full bloom was associated with yellowed and diseased leaves and does not indicate that gains during this stage would not take place in a region where the leaves remained healthy. 4. The loss in root reserves in recovery after cutting, as an average of 35 observations, was 177 pounds per acre. This was accompanied by an average loss in percentage of nitrogen (on an air-dry basis) of 0.17. 5. Recovery after cutting was almost uniformly accompanied by a decrease in the percentage of dry matter in the green roots, averaging 4.9% in 23 comparisons. 6. At Columbus the most uniformly important period of root storage is in October, when the last cutting of the season has been taken off early enough so that a considerable top growth has been produced by October 1. 7. The most favorable condition for storage of root reserves seems to be the combination of a large amount of healthy leaf area and drier weather than normal. 8. While Grimm and other variegated varieties of alfalfa are more winterhardy than common alfalfas under all cutting treatments, there is no evidence that this difference is due to or associated with differences in the amount of root reserves stored. 9. The effect of cutting on different dates at Columbus is determined nearly as much by the activities of the potato leafhopper as by root reserves, but at present the former are to a large extent unpredictable.