producing increases in growth; consequently there was an increase in the 

 cover produced by seedlings on dredged material during the first growing 

 season. 



Table 42. The Standing Crop of Seedlings at 

 Beaufort to which Nitrogen and 

 Phos^norus Fertilizers were Applied* 



Replicate 



Aerial Dry Weight (kg/ha) 





Fertilizer Treatmentt 





Check 



N 



NP 



1 



2 

 3 



4,450 

 2,860 

 3,100 



11,100 

 9,430 

 7,480 



14,180 



10,200 



8,010 



x$ 



3,470 



9,340 



10,800 



*Plots seeded 4 April 1972; harvested 

 5 October 1972. 



tN rate = 224 kg/ha N; P rate - 49 kg/ha P; 

 half the fertilizer was applied on 26 June 1972 

 and half on 26 July 1972. 



$X = main effects 



A fertilizer experiment on seedlings was begun on an island near Drum 

 Inlet in 1973. The fertilizer was applied in a randomized complete block 

 design with three blocks and was superimposed on a part of the large-scale 

 seeding experiment planted 18 April 1973. The fertilizer treatments were 

 two rates of phosphorus as concentrated superphosphate (0 and 49 kilograms 

 per hectare of phosphorus) and four rates of nitrogen as ammonium sulfate 

 (0, 112, 224, 448 kilograms per hectare of nitrogen) in a factorial 

 arrangement. Fertilizer was applied in split applications 11 July and 

 16 August. Plots were 1.22 meters by 7.62 meters with 1.22-meter borders 

 between plots. Samples were harvested 8 November by clipping 1 square 

 meter from each plot. Roots were also sampled by taking two cores 8.5 

 centimeters in diameter and 30-centimeters deep from each square meter 

 which was clipped. 



Growth measurements indicate significant responses to both nitrogen 

 and phosphorus fertilization (Tab. 43). Unlike fertilizer experiments in 

 the natural marsh at Ocracoke, the nitrogen-phosphorus interaction was 

 not statistically significant. The dry weights of shoots and roots were 

 doubled by both additions of nitrogen and additions of phosphorus. 



In another experiment, fertilizer was applied before planting at Drum 

 Inlet. The fertilizer treatments were a 2 by 4 factorial design 

 (nitrogen = 0, 56, 112, 224 kilograms per hectare and phosphorus = and 

 25 kilograms per hectare). Plots consisted of three rows 0.91 meters 



142 



