EFFECT OF FREQUENT CLIPPING ON THE DEVELOPMENT OF CERTAIN GRASS SEEDLINGS

Abstract

The study reported here deals with the effects of the removal of tops upon the development of various species of grass seedlings. Not only the establishment but also the yield and nutritive value of range and pasture grasses are dependent to a great extent upon the manner and frequency with which the tops are removed. Winter-killing and lowered vitality, with attendant decreased yield, result from improper utilization of the herbage. In native pastures and range lands, undesirable species increase when there is early grazing and overstocking (8). Although the relation of harvesting practices to the development of grassland is known in a general way from observation, and more definitely for a few species from experiment, there is still a definite need for further experimental work. Graber (7) has shown that frequent removal of tops limits root development. This in turn may lessen drought resistance and absorptive capacity, and result in increased injury from low temperature and insects. Since most of the foods used as reserves in roots are synthesized above ground, frequent harvesting necessarily limits these reserves. Internal food reserves as well as a supply of nutrients are factors in productivity. In addition, frequent removal of tops promotes a deficiency of nitrogen in the soil (7). Dicotyledonous plants are similarly weakened by too early or too frequent harvesting. Pruning reduces the root spread of almond trees (3). Cutting of immature alfalfa increases invasion of weeds and may cause winter-killing. The specific gravity of alfalfa roots decreases slightly after each cutting. Cutting when the plants are mature gives more reserve food and higher yield with less winter-killing and a longer life of crop, whether grass or alfalfa (1). Sampson and Malmsten (16) found that harvesting range grasses twice each season increased the yield with but slight injury to the roots. Yield tends to vary inversely with frequency of clipping in bluestem pastures of Kansas. Disappearance of valuable species is proportional to frequency of cutting. The higher nutritive value gained from frequent harvesting does not compensate for loss in yield (2). The deleterious effect of frequent cutting may be offset partially by cutting the plants at a greater height above the ground (2, 9, 18). Reseeding of western range land is successful only when grazing is delayed until late in the