1903.] PUBLIC DOCUMENT — No. 33. 131 



be worth this sum there is a decrease iu the amount of 

 stover, which brings the net increased value below the cost 

 of the nitrate. 



The Effect of the Phoq^horic Acid. — Dissolved bone- 

 black (phosphoric acid) used alone produced an insignifi- 

 cant increase. In the difterent combinations the results of 

 its use indicate it to be moderately beneficial. The best 

 result is secured where it is employed in connection with 

 potash. The cost of the dissolved bone-black Avherever 

 employed was at the rate of about $3.20 per acre. The 

 average increase in crop is suflicient to barely cover this 

 amount. Particular attention is called to the splendid crop 

 produced Avhere dissolved bone-black and muriate of potash 

 are used together. The combination of these two fertilizers 

 without nitrogen apparently suffices, under the system of 

 rotation which has been followed, to fully maintain the 

 productiveness of this plot. Last year its yield was at the 

 rate of 1,900 pounds of hay to the acre in the first crop and 

 1,500 pounds of rowen in the second crop. As was pointed 

 out last year, this splendid product is undoubtedly due to 

 the capacity which clover grown in mixture with the grasses 

 possesses to draw the needed nitrogen from the air. The 

 advantage obtained by this system of manuring is, however, 

 not exhausted when we have taken the hay crops ; for, as 

 shown by the yield of corn this year of almost 56 bushels 

 of sound grain to the acre, the corn crop which requires a 

 large amount of nitrogen (which, so far as we know, must 

 be taken from the soil) , is able to derive the needed quantity 

 of this element from the products of the decay of the clover 

 roots and stubble. The expenditure for fertilizers applied 

 to this plot has been at the rate of about $6.40 per acre, and 

 for this sum we have this year nearly 56 bushels of corn 

 and more than 21/2 tons of stover. Moreover, the beneficial 

 effects of this system of manuring appear to be cumulative. 

 The productivity of this plot shows not the slightest signs 

 of decrease after fourteen years, during which time neither 

 manure nor fertilizer furnishing a single ounce of nitrogen 

 has been applied. In view of the results upon other plots, 

 it cannot be doubted that the increased yield on this plot is 



