66 



The Action of Manure vs. that of Commercial Fertilizers. — 



The above facts, taken in connection with those shown in the two 

 earHer experiments, indicate that the plant-food action of manure is 

 practically identical with that of a commercial fertilizer rich in 

 nitrogen and phosphates. It also apparently indicates that the pot- 

 ash in the manure may be less readily available than that carried in 

 commercial forms. The old controversy over the relative value of 

 manure and commercial fertilizers, therefore, is without any par- 

 ticular significance so far as plant food is concerned. Either type 

 of fertilizer may be successful or either may be a failure depending 

 upon the particular conditions involved. 



The manure, however, often has some additional value, due to 

 its mulching effect. This, of course, can not be duplicated by com- 

 mercial fertilizers alone though it may be duplicated by any other 

 kind of a mulch, as has been shown especially in our experiment 339 

 in Bradford County. The matter of availability also must be often 

 considered and it is for this reason that the relation between manure 

 and nitrogenous fertilizers should be well understood. Besides this, 

 it sometimes happens that large and regular applications of manure 

 result in a distinct increase in the amount of blight, and also in an 

 undue increase in the size of the fruit and in the amount of punky 

 pitting in the latter. In such cases, a reduction in the applications or 

 the partial or complete substitution of a proper commercial fer- 

 tilizer is desirable. 



A Summary of Fertilizer Influences on Apples. 



It is impossible in the present space to consider all our experi- 

 ments singly, to the extent done with the three just considered. 

 Before passing to the last stage of our discussion, however, it 

 seems desirable to present a very brief summary of the fertilizer 

 influences shown in six of our experiments, including the three just 

 considered. This summary shows the calculated influences of the 

 various fertilizer elements on the four important characteristics of 

 apples, viz : their yield, color, average size and the amount of wood- 

 growth. The relative values of the different elements during a five- 

 year period, in terms of per cents, of benefit over the normal results 

 obtained without fertilization, are shown in Table V. 



Table V. — Influence of Fertilizer Elements on Apples. 



(Average Benefits over Normals, 1908-1912.) 



(a) Expts. 215, 216, and 220 Yield Color Size Growth 



per cent, per cent, per cent, per cent. 



1907-12 



Nitrates in Combin. 62.7 ii.o 0.7 10.43 



Nitrates alone, 32.5 12.7 4.3 15.51 



Phos. in Combin., 20.2 2.1 0.3 2.28 



