70 FEKTILIZEBS. 



in trying all kinds of fertilizing mixtures, before they can 

 succeed in ascertaining the states of combinations, and 

 the relative proportions in which these shall be combined, 

 in order to produce the best practical results." 



The original formulas published by Professor Stock- 

 bridge, in which his plant-food was determined solely by 

 analyzing the plant, as further experience has thrown 

 light on the subject, the feeding-power of the plant hav- 

 ing been found to be a factor of importance, have been 

 considerably modified. He has increased his phosphoric 

 acid for potatoes and grass about thirty-three per cent, for 

 corn fifty per cent, and in the two latter has decreased the 

 nitrogen about twenty-five per cent. In pease and beans 

 he has increased the phosphoric acid about fifty per cent, and 

 has decreased the nitrogen : and, further, some of the finer 

 distinctions have been dropped ; and the formulas are now 

 generalized so far as to have in several instances the same 

 formula for several different crops, in this respect approach- 

 ing to the " Ville " theory of plant-feeding. The objec- 

 tion that the wide latitude shown in the extremes in the 

 nitrogen, potash, and phosphoric acid in the corn, potato, 

 and onion formulas, elevates them in real value at pres- 

 ent but little above a good superphosphate, has a degree 

 of weight. To my mind, it arises from the fact that 

 formulas, being for general use, can be compounded only 

 in a general way, by reason of the many differences in 

 the natural condition of various soils, the additional vari- 

 ations in the manurial elements which they may have 

 acquired through years of manuring, and the difference 

 between crops in their feeding capacity. Here, I think, 

 we have the weakness of the Stockbridge or any other 

 formulas. They do not take cognizance of the state of 

 the soil to which they are to be applied ; neither can they 

 do so, except in a general way, for otherwise they would 



