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the yield was between 4i> and 50 bushels of shelled coin to the acre. Another 

 plat to whieh we have applied nitrate of soda annually at the rate of IGO 

 pounds per acre gave us a yield of corn scarcely more than the nothing plats. 



Potash alone, or in any of the combinations — and we iised it in the same com- 

 binations as Doctor Hopkins — increased the crop in a marked degree every time. 



One of the tirst points I want to make is to support Doctor Hopkins in his 

 position that in the case of general farm crops the farmer need not purchase 

 nitrogen. In proof of that I point to the result on the plat which every year 

 during the seventeen years has had muriate of potash and dissolved bon*'- 

 black — that being the phosphate we have used. The last time that plat was in 

 corn it gave a yield at the rate of ;")<» bushels of shelled corn to the acre, while 

 the other plat which had received the same quantities of potash and j)hosphorus, 

 and in addition nitrate of soda, every year at the rate of 1(>(> i)ounds to the 

 acre, gave a yield of only a small fraction of a bushel more. The crops were 

 practically identical, after sixteen years. It was one year ago when the laud 

 was in corn last. Now, in all that time we have not cultivated a legume by 

 Itself. We have not green-manured the land. Whenever it was in grass, it 

 was cut twice annually, and the product all carried away; and still the nitrogen 

 c(mtent of the soil has been so kept up that we get this yield of corn, which is 

 very good from our point of view, where for seventeen years we have been 

 using only i)hosphoric acid and i)otash. 



I would say that the character of the herbage on the i)lats was as different 

 as it ccmld be. Clover would come up on all the plats, but it would die in a 

 short time where nitrogen and where nitrogen and i)hosphorus were applied, 

 and would live only where thei'e was potash; and where there had been used 

 constantly phosphorus and potassium only, the product was almost wholly 

 clover. On some soils, of which we have very many, withoiit doubt, in New 

 England, the different elements seem to be so evenly balanced that we can not 

 consider the question of what is retpiired apart from the croj). For it makes 

 all the difference in the world what the crop is. On this very field that I have 

 been talking about potash controls the crop absolutely when it is corn or clover, 

 as you would expect ; but when we seed to mixed grasses and clovers, we get 

 an excellent crop of hay on the plat where we use nitrate of soda only, for 

 nitrogen is the controlling element for the hay crop with us, and may very 

 profitably be used for that crop. 



If into the rotation a crop like cabbages or turnips is introduced, phosphoric 

 acid is invariably the controlling element. In Massachusetts, therefore, we are 

 not justified in talking about what our soils require apart from the crop ; with 

 us it is what the crop I'equires. 



We have raised rye in rotation, and there the nitrate of soda was the con- 

 trolling element, although the response of the rye was not quite as decisive in 

 favor of any one element as was the response of some of the other crops. 



H. J. Wheeler, of Rhode Island. We have many soils in our State where, 

 if we would advise our farmers to use fine phosphate rock on certain classes of 

 crops, ^they would find themselves in bankruptcy before long, simply because 

 those plants, as Professor Brooks pointed out, can not use phosphorvis in that 

 particular material readily if the land is in a very exhausted condition. Doctor 

 Hopkins's work, as I understand, applies to the cereals exclusively. But, being 

 a body here representing the whole country, we ought to remember that his 

 discussion is confined to the cereals. I can emphasize what Professor Brooks 

 says. We find that while we have applied no potash to the soil for years, we 

 can nevertheless get a very good crop of redtop, a suiprisingly good crop, but 

 you can not get a single plat of clover to grow unless lime and potash are added. 



2133(>-No. 104 — U(J M 10 



