25 



jftor© abundant in th« surface foot than below. While the 



minimum is not as low as in the Norfolk eandy soil, 



diffueion would seem to be ieee effective, which gives 



rise to the suspicion that HPO may have been equally as 



4 

 difficult for the plant to seeure as was NO3, As in the 



Norfolk sandy soil, the lowest proportion HPO4. in each of 



the four feet occurs on one date, which in this case is 



May 23. 



The above series of data indieates the general 

 variability of NO3 and of H?04. ^he HPO_^, .while doubtless 

 deficient in some cases, does not generally seem to show 

 the variability which NO3 does. It would be expected, 

 therefore, that any plant growth which made large demands 

 on these substances, would make rapid and large changes 

 upon the soil content of these radicles. 



The effect of weeds growing alone upon the acid 

 radicles as compared with those where crops were cultivated 

 is shown b|i King (Bu. Soils 26, 44). The results which 

 fellow are given for the surface four feet s 



