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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...

\1 [HERE hot, dry winds blow frequently during the growmg IV season, many plants die even though soil moisture has not been reduced to the wilting point. Such desiccation of plants is called atmospheric drought and has not received as much attention as soil, or edaphic drought. Although atmospheric drought seldom affects growth and duration of grasses in the Great Lakes region, these data on atmospheric drought are submitted in the hope that they will be of interest to those concerned with the physiology and ecology of grasses. Schultz and Hayes (4) 3 in a study of atmospheric drought resistance of a number of pasture grasses and legumes by means of the artificial drought machine devised by Shirley (5) obtained results which agreed closely with field observations. Aamodt and Johnston (r) tested the effects of atmospheric drought on a number of spring wheat varieties. They found that the plants could be hardened to atmospheric drought by short exposures to either soil drought or atmospheric drought.Vassiliev (6) deems it possible to breed plants resistant to atmospheric drought but not to soil drought. MATERIALS AND METHODSGrasses included in this test were Kentucky bluegrass (Poa pratensis L.), wood meadow grass (P. nemoralis L.), Astoria bent (Agrostis tenuis L.), cocoos bent (A. tenuis L.), South German mixed bent (A. tenuis L., A. palustris L., and A. canina L.), highland bent (A. canina L.), Cliewings fescue (F. estuca rubra fallax L.), red fescue (F. rubra), sweet vernal (Anthoxanthum. odoratum L.), red top (A. alba L.), carpet grass (Axonopus compressus L.), and Bermuda grass (Cynodon dactylon L.). With the exception of Bermuda and carpet grass, all species were seeded in the fall of 1939 and had established a thick, heavy sod within a year. Bermuda and carpet grass were sown in the spring of 1941, and although good stands were secured, they did not produce as heavy sod as did the other species.One-half of each plot of the earlier seeded species was fertilized with ammonium sulfate at the rate of 5 pounds per 1,ooo square feet in April, July, and October·each year. The unfertilized and fertilized portions of the plots were designated as "lowand high-nitrogen sections", respectively. Bermuda and carpet grass remained unfertilized.The plots were located on Wooster silt loam which was in a high state of productivity.. Samples were taken the middle of September r941. A golf cup-hole cutter was used to lift plugs of sod 4?1 inches in diameter and approximately 3 inches thick 'Contribution from the Department of Agronomy, Ohio Agricultural Experiment Station, Wooster, Ohio.

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