8 



manure, while the latter had only $21 (this is at the compara- 

 tively low price of $3 per cord) ; the investment of $21 gave a 

 gain over no manure (plot 9) of 11.44 tons of ensilage, or the 

 cost of manure per ton of ensilage for the first 20 loads was 

 $1.83. Now when we apply an additional 20 loads to the 

 same land, we get as the increase due to the last amount of 

 manure, the difference between the yield of plot 6 (23.17) and 

 plot 8 (16.13), which is almost exactly 7 tons, or a ton for $3 

 -worth of manure. Now, so far as this evidence goes, it is 

 plain that 3o loads was profitable, while the additional 20 was 

 not. 



But the question comes up, How about the residue left in 

 the soil in these two plots.'' This question cannot be answered, 

 for many reasons. First, we know very little of the availability 

 of the plant food in the manure ; second, we know next to 

 nothing of the amount lost in the drainage water ; third, we 

 have no knowledge as to the condition of the plant food that 

 is thus left in the soil. Without doubt some portion of it is 

 rendered insoluble by the action of the soil, thus making it of 

 no more value than the unavailable plant food which most 

 soils contain in considerable quantities. 



In general, I do not believe that more than from 15 to 20 

 loads (5 to 7 cords) of manure can be advantageously used on 

 our field crops, like corn, oats, barley, and grass ; and I do 

 not believe that 40 loads of manure (14 cords) can be applied 

 to two acres with more profit than to one acre. 



SUBSTITUTES FOR FARM-YARD MANURE. 



The subject of chemical fertilizers has been carefully studied 

 by this station, and the results can be found in Bulletins 5, 6, 

 10, and 12 ; but as new results are year by year being added, a 

 short statement will not be out of place in this bulletin. 



The results of all our work show, without exception, that 

 New Hampshire soils are more in need of potash than any 

 other element of plant food, and consequently, that we may so 

 compound our fertilizers that better results shall follow their 

 use than is possible with the average fertilizer found in our 

 markets, and this the farmer is enabled to do by buying his 



