d. Maintenance Fertilization 



It is evident at quite a number of locations that a fertilizer 

 program consisting of 100 to 150 pounds of Nitrogen and 30 to 50 pounds 

 P 2 5 /acre/year will develop "full cover" by the end of the third growing 

 season. The term "fuM cover" is used here to mean something approaching 

 the maximum amount of growth of these grasses that these areas seem to be 

 capable of supporting, i.e., of the order of 7h to 3^ tons/acre dry weight. 

 In a number of cases where vigorous nursery stock of American beachgrass 

 was used, something approaching full cover was attained with only two 

 growing seasons. 



It also appears that any attempt to push growth beyond this point may 

 have some detrimental effects. For example, in the trials reported in 

 Tables I and 2, and on several areas under the general Park Service fer- 

 tilizer program, some loss of plants has occurred. This loss has taken 

 place largely during the summer of 1965, a very wet summer, and in spots 

 where growth was unusually dense. The cause of death in several instances 

 is strongly suspected to be the common fungus, Rhizootonia solani. This 

 loss is not surprising, for this organism is a frequent source of damage 

 to a wide range of host plants, both grasses and legumes, during periods 

 of hot humid weather. Such damage is usually increased by heavy matted 

 growth which limits air circulation and normal drying, and is aggravated 

 on cool season grasses by nitrogen applications made during the hot weather 

 period. 



For this reason, and economy, it seems highly desirable to switch to 

 a program of reduced fertilization once full cover is attained. Presumably, 

 maintenance would require less frequent and smaller applications of fertilizer 

 than were required to bring the stand to the full cover stage. Under the 

 fairly complete canopy prevailing at this stage, there should be considerable 

 recycling of nutrients. Unfortunately, sufficient areas having growth of 

 this kind have not been available long enough to permit much experimentation 

 on this point. Beginning after the September application in 1964, some sub- 

 plots have been laid out from which fertilizer has been omitted. Growth 

 estimates taken at the end of August on three of these plots are shown in 

 Table 7. 



TABLE 7 



Effect of Reducing Fertilization on Growth of Beachgrasses 



Yields lb/acre 



Beachgrass Cordgrass 



Treatment Oregon Is . Hatteras Is . Ocracoke 



No ferti I izer I 171 301 671 



30-10-0 through 1965 (450 



lb/acre per year from 1963) 8400 6640 5315 



30-10-0 through September 1964 7608 6183 5141 



15 



