concentration in the plant tissue was a part of the regression equation 

 for height but not for yield. Perhaps nitrogen does not show up in the 

 equation because it is the limiting factor in growth. If the availability 

 of nitrogen was limiting growth, then growth would proceed whenever nitro- 

 gen became available. Consequently, the concentration of nitrogen in the 

 plant tissue would remain relatively constant due to the increase in 

 biomass. It is possible that if samples had been taken earlier in the 

 growing season, the nitrogen concentration in the plant tissue would have 

 been a better indicator of yield potential. 



It is interesting to note that there was no significant correlation 

 of yield with the soil properties measured (Tab. 27). There are two 

 factors which contribute to this: (1), the waterlogged conditions of these 

 soils tend to equalize chemical differences, and (2), the methods by which 

 these determinations were made. Standard soil testing procedures were 

 used which probably are not suitable for these soils. An important limita- 

 tion is that North Carolina soil test procedures and extracting solutions 

 are designed for acid soils. The pH (hydrogen-ion concentration) of the 

 soils in this study were between 7 and 8. Developing suitable techniques 

 for studying properties of marsh soils would be an extensive project. 



In conclusion, it is not within the scope of this study to explain 

 each observed effect, but several relationships were shown to exist between 

 variables which were measured and yield and height of S. altevniflova. 

 Several of these effects may warrant further investigation. 



2 . Effects of Fertilizer . 



In the natural marshes, fertilizer was used as an experimental tool to 

 determine if nutrients were limiting factors in growth. Marshes at 

 Ocracoke and Oak Island were selected because of differences in substrate, 

 tide range, and age. On seedlings and transplants, the objective of the 

 fertilizer studies was to determine if adding nutrients would enhance 

 growth to produce cover more rapidly. 



a. Fertilizer Experiments in Natural Stands - 



(1) Ocracoke Island . Fertilizer , plots were located on the north 

 end of the island near Hatteras Inlet. This is a relatively young S. 

 altevniflora marsh on a sandy substrate with little development of tidal 

 creeks. There is some difference in growth between the different areas 

 within the marsh, which is apparently due to environmental factors. 

 However, zonation of height forms is not as obvious as in many older marshes. 

 The regular lunar tide range at this location is about 30 centimeters, but 

 the added wind effect may extend the range to 1 meter. 



A fertilizer experiment of factorial design with two rates of phosphorus 

 and four rates of nitrogen was started in 1971. It consisted of three ran- 

 domized complete blocks with 1.22- by 7.62-meter plots and 1.22-meter borders 

 between plots. Phosphorus was supplied by concentrated superphosphate at 



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