even the lowest application (60 pounds per acre of nitrogen) resulted in nearly twice the 

 yield. The difference in growth was even greater on the backslope of the dune-width 

 panicum, where sand accumulation was minimal (Fig. 41). Effects of phosphorus and 

 potassium were unclear from these data, but as a result of greenhouse trials, application of a 

 complete fertilizer with 120 to 180 pounds per acre of nitrogen is recommended. 



Sea oats showed no response to any of the treatments, in direct contrast to greenhouse 

 results, and to general observations from the fertilized nurseries and beach plantings. The 

 reason may be the age of the dune, in comparison with the recently planted greenhouse and 

 nursery transplants, which responded with a 2.5 times increased yield. 



Woodhouse and Hanes (1967) tested field fertilizer response of deteriorating stands of 

 both sea oats and bitter panicum in North Carolina. Unfertilized plots yielded 1,899 pounds 

 per acre for sea oats, and 1,136 pounds per acre for bitter panicum, a higher yield than sea 

 oats control but lower than bitter panicum control for this study. Response to 90-30-0 

 pounds per acre of nitrogen-phosphorus-potassium fertilizer was 9,854 pounds per acre for 

 sea oats (5 times the control) and 9,411 pounds per acre for bitter panicum (8 times the 

 control). 



d. Effect of Fertilizer Application on Dune Growth. The purpose of fertilizing a dune 

 planting is to improve its sand-trapping ability by increasing the mass of plant material per 

 unit area. The effect of different rates of fertilizer on trapped sand was tested on the 

 15-month-old dune-width panicum plots. Before and after cross-sectional profiles were 

 surveyed on each fertilizer plot (two sections per 50- by 50-foot plot at fixed locations); 

 resulting sand volumes are given in Table 50. The amount of sand trapped varied little 



Table 50. Effect of various fertilizer treatments on sand-trapping efficiency of a 

 bitter panicum dune. 1 



Treatment 

 (pounds per acre) 



Dry yield 2 

 (pounds per acre) 



Volume of sand trapped 

 (cubic yards per lineal feet of beach) 



Nitrogen 



Phosphorus 



Potassium 



1973 



1974 



Difference 





May 



Dec. 



Mar. 



Mar. -May 















1,952 



4.5 



10.8 



11.3 



6.8 



60 



120 



60 



3,025 



3.7 



8.1 



8.7 



5.0 



120 



60 



60 



3,729 



4.4 



9.8 



10.4 



6.0 



120 



120 



120 



5,009 



3.7 



8.2 



8.5 



4.8 



180 



60 



60 



6,130 



3.2 



7.9 



8.7 



5.5 



180 



120 



60 



6,996 



4.2 



8.7 



9.2 



5.0 



1. 0- to 600-foot dune-width panicum, north Padre Island. Fertilization was in May, June, and July 1973 

 (1/3 application each). Data are means of two cross sections in each of two 50- by 50-foot plots per 

 treatment. 



2. Yield is for dune-width panicum plots only. 



139 



