8 



N. H. Agr. Experiment Station 



[Bulletin 306 



The honu' mixed 8-6-6 in this test was made up of soluble materials. 

 Ammo Phos A, 11 X-48 P.O.-., nitrate of potash. 13 X-44 K2O, and Cal 

 Nitro. 20.5% N. This was contrasted with an 8-6-6 of commercial 

 origin. Tlie 10-20-20 as listed was used the tirst two years of the test, 

 but during the last two years an 8-16-16 was employed. The content 

 of nitrogen of the mixed fertilizers applied was 32 pounds per acre or 

 400 pounds of the 8-6-6 formulas. 320 of the 10-20-20 and 400 of the 

 8-16-16. 



Table III. Four-year average of yields of Mathes farm plots which were 



treated with complete fertilizers. 



It will be observed that the increased production due to the use of 

 these complete fertilizers is in two cases more than double the increase 

 recorded for the nitrogen carriers alone ; and in the other case, the in- 

 crease is appi'oximatel}^ doul)le that of all the nitrogen carriers, with the 

 exception of Cal Nitro, while in the results reported for another test 

 (Table I), the increase for the complete fertilizer is approximately 50% 

 greater than that for nitrogen alone. 



The explanation for this is undoubtedly associated with the previous 

 history of the fields in question, the one at Greenland having been more 

 generously treated with mineral fertilizers than this one. while in the 

 Mathes plots the content of available phosphoric acid and potash may 

 have been so low as to permit of oidy a low rate of nitrogen recovery 

 at least when nitrogen alone was applied. 



In order to emphasize this point more fully, per cent nitrogen recovery 

 has been calculated for the treatments thus far discussed in this test. 

 The calcuhition used is as follows: 



Increase of protein over check v 100 

 6.25 X 32 (pounds of niti'ogen api)lied') 



The result is the percentage of nitrogen recovered in the hay and these 

 percentages are here listed : 



Tahle IV. f'l r(<')if(if/<s of Nifro(/eii Rcrovcri/ at ^[athrfl Farm. 



