RESPONSES OF KENTUCKY BLUEGRASS TO VARIATIONS IN TEMPERATURE, LIGHT, CUTTING, AND FERTILIZING

Abstract

Of primary importance among the several environmental factors which influence the production and maintenance of turf are seasonal variations in temperature, amount and intensity of sunlight, and cutting and fertilizing practices. It has long been observed that bluegrass grows best during the cooler seasons, although the reasons for such behavior have never been fully understood. When bluegrass is cut short and heavily watered or fertilized, especially during the hot summer months, undesirable results follow. The turf thins out, the production of new leaves ceases, and during the cooler, wetter period of fall large numbers of the plants fail to recover. In attempts to maintain a vigorous green growth, nitrogenous fertilizers are often added to such turf when actually such an addition may be harmful instead of beneficial, especially during the hot weather of summer. With a view to determining a possible cause for the widely differing results often obtained from apparently similar practice, the following experiments were conducted in sand culture. All cultures were obtained from the vegetative propagation of one original bluegrass plant. More particularly the experiments dealt with: (a) the effect of cutting to 0.5 inch, 1 inch, and 2 inches, plants which were supplied either with a solution high in ammonium nitrogen and low in nitrate nitrogen, or one high in nitrate and low in ammonium nitrogen; (b) the type of growth produced at different seasons of the year and the effect upon such growth of varying degrees and times of defoliation; (c) the effect of cutting plants grown with a continuous nitrogen supply as contrasted with some which had had no nitrogen during a period beginning 6 weeks prior to the initial cutting and extending to the close of the experiment; (d) the type of recovery growth produced when cultures were cut back to 1 inch in height every ten days, at 60°, 80°, and 100° F., with and without a nitrogenous fertilizer. The experiments were conducted in the University of Chicago greenhouse, from the fall of 1930 to the fall of 1932. Several recent papers contain literature reviews of some length on much the same subjects as taken up here. Graber, Nelson, Luekel, and Albert (2), Pierre and Bertram (7), Luekel and Coleman (6), and Graber (1) have published recent papers on the food reserves of grasses in relation to