Nitrogen content of the plant tissue was closely related to the rate 

 of nitrogen applied as fertilizer (Fig. 58). During both growing seasons 

 the R 2 (multiple correlation coefficient, a measure of the percentage 

 variation in the dependent variable which is explained by independent 

 variables in the equation), values were higher where no phosphorus was 

 applied, indicating that a greater proportion of the variation in nitrogen 

 content is accounted for by nitrogen rate when nitrogen alone is applied. 

 Where phosphorus was applied, both the R 2 and the actual concentration 

 of nitrogen in the tissue decreased. This decrease was probably due to 

 dilution of nitrogen in a greater amount of dry matter as yield increased 

 when the phosphorus became adequate. 



The apparent recovery of fertilizer-nitrogen by the aboveground part 

 of the grass and the roots and rhizomes may be calculated by subtracting 

 the uptake of the check plots from that of the treated plots. The calcu- 

 lations reveal a surprisingly high recovery of nitrogen considering the 

 flooding which occurs (Tab. 34) . 



Table 34. Apparent Recovery of Fertilizer Nitrogen in the Shoots 

 at Harvest 



N Rate 



Apparent Recovery (Percent of 



Total N 



Applied) 







1971 



1972 



kg/ha 



0* 



74 



0* 



74 





Shoots 



Shoots 



Roots 



and 



Rhizomes 



Total 



Shoots 



Roots 



and 



Rhizomes 



Total 







































168 



15.2 



24.3 



20.2 



33.3 



53.5 



30.3 



31.5 



61.8 



336 



12.2 



33.0 



11.9 



22.9 



34.8 



28.0 



16.7 



44.7 



672 



9.6 



19.9 



9.7 



14.7 



24.4 



26.3 



16.7 



43.0 



*Rate 



of P 



(kg/h; 

















Concentration of phosphorus in the plant tissue was not significantly 

 affected by nitrogen rate; however, the increase in phosphorus concentra- 

 tion due to phosphorus fertilization was highly significant (0.01 level). 

 In 1971 the mean concentration of phosphorus in the shoots was increased 

 from 0.084 to 0.150 percent, where 74 kilograms per hectare of phosphorus 

 were applied. In 1972 there was a similar increase due to phosphorus 

 fertilization from 0.087 to 0.147 percent in the shoots, and concentration 

 in the roots increased from 0.052 to 0.091 percent. The amount of 

 fertilizer-phosphorus recovered by the shoots for treatments receiving the 

 maximum rate of nitrogen was 15.0 and 26.1 percent of that applied during 

 1971 and 1972, respectively. Apparent recovery of phosphorus by the roots 

 in 1972 was 12.4 percent. The calculations of recovery of both nitrogen 

 and phosphorus in 1972 may include some carryover from 1971 through storage 

 in the roots and rhizomes or residual in the soil. It is more likely that 

 phosphorus would be retained by the soil than nitrogen. 



127 



