Effect of Heavy and Late Applications of Nitrogenous Fertilizer on the Cold Resistance of Kentucky Bluegrass

Abstract

IntroductionThe conditions under which turf-forming grasses on lawns and recreational fields are maintained are highly exacting. This is due chiefly to frequent and often close defoliation. On golf courses and athletic fields the situation is further aggravated by much trampling. To maintain a good sward under such adverse conditions resort is often made to liberal use of fertilizer. In order to take full advantage of the cool growing weather of late autumn and early spring, top-dressings are often made in the fall.These applications are regarded as desirable where annual weeds such as crabgrass are a pest. Under such conditions spring and summer treatments may do inore harm than good through undue stimulation of the weeds. In the judgment of many practical turf growers, however, late fall applications are detrimental because, in their opinion, they interfere with the normal "hardening off" of grass with the coming of cold weather and thus render it less resistant to the low temperatures of winter.The purpose of the work reported in this paper was to determine whether or not the above assumption held by certain growers has any basis in fact. The PLANT PHYSIOLOGYIn each season the plots were mowed at frequent intervals to maintain good lawn conditions. On account of extreme drouth, especially in 1930, infrequent mowing in midsummer sufficed. In addition to each fertilized plot there was an unfertilized plot of the same size which served as a check.Supplemental material was obtained from a new seeding of Kentucky bluegrass made in August, 1936. A part of this area was fertilized with ammonium sulphate on September 10 and October 22. Both applications were made at the same rate as in the test already described. Samples from the unfertilized and fertilized areas were gathered from time to time during the late fall.To test the relative resistance of unfertilized and fertilized Kentucky bluegrass to low temperatures a quantity of each kind was grown in gallon jars in a greenhouse in the winter of 1932-1933. The grass was grown in jars so that it could be transferred without disturbance of the roots to an artificial refrigeration room and there exposed to low temperatures. The jars were seeded at the rate of 5 pounds per 1000 sq. ft. Subirrigation was provided by means of a 0.75-inch glass tube placed at one side of the jar. The lower end rested on a layer of sand which covered the bottom of the jar. Some were fertilized with ammonium sulphate applied at the same rate as in the field tests. The first application was made when the grass was approximately 0.5 inch high; second and third applications were made at intervals of 6 and 12 weeks, respectively. CARROLL AND WELTON: NITROGENOUS FERTILIZER EFFECT ON GRASSES 299-250 C. for at least 3 days and the technique followed was essentially the same as that described by SAYRE (13). The bound water was obtained by difference.Determinations of the sap expressible from fresh tissue were made on 100-gram duplicates. A hydraulic press and press cage of the type described by...

Effects of Drought, Temperature and Nitrogen on Turf Grasses

“…The grasses were permitted to hardeln naturally. Previous work (7) had shown that air temperatuires near the freezing point were necessary to harden turf grasses. That nlitrogen treatments may affect the degree of hardening of turf grasses to cold was showni by CARROLL and WELTON (7).…”

“…It should be noted that weather coniditions previous to these tests were not conducive to hardening to drought. In tests conducted on P. pratensis in 1930 and 1931, however, whenl weather conditions favorable to hardening to drought prevailed, CARROLL and AVELTON (7) founld a lack of correlation between bouncld w-ater content and drought hardiiness in low-and high-nitrogen grass.…”

“…From previous tests (7) it was known that with the approach of cold weather, there was an elaboration of hydrophilic colloids in P. pratensis and an increase in the total sugar content, accompanied by increased hardiness to cold, but at that time no comparisoni -was made among different species.…”

“…The technique employed to test the survival of species of turf grasses exposed to low temperature by artificial refrigeration was essentially the samiie as that described previously (7). Samples from the low-and highnitrogen sections of each grass were placed in the freezing chamber at -25°C., and as soil temperatures of -5°, -10°, -15°, and -20°C., were reached.…”

“…In a search for methods to eliminate quack grass, DEXTER (10) found that heavv fertilization with nitrogen lowered its resistance to drought. DEXTER (9) and CARROLL and WELTON (7) found that high-nitrogen plants failed to harden to cold as much as low-nitrogen plants. MAXIMOV (15) in his inivestigations came to the conclusion that the true measure of drought resistanee is the ability of the plant to survive exposure to drought without permanent injury.…”