1908.] PUBLIC DOCUMENT — No. 33. 47 



combination of a lesser quantity of manure and the potash. On 

 the other hand, the average yield of soft corn and of stover is 

 greater on the combination of manure and potash. This result 

 is in some respects analogous to that obtained with fertilizers 

 on the north corn acre. In a more favorable season, the com- 

 bination of manure and potash is likely to make a better relative 

 showing. In estimating the significance of the results actually 

 obtained, however, it should be kept in mind that, assuming 

 the farmyard manure to cost $5 per cord applied to the field, 

 the annual difference in cost of materials applied under the two 

 systems of manuring has amounted to about $6 per acre, the 

 application of the lesser amount of manure and the potash cost- 

 ing about that amount less than the larger application of manure. 



VI. — Comparison of Phosphates on the Basis of Equal 

 Application of Phosphoric Acid. 

 This experiment, comparing different phosphates, has been 

 in progress eleven years. The phosphates under comparison 

 are as follows : apatite (fine ground 1 ) , South Carolina rock phos- 

 phate (fine ground), Florida soft phosphate, basic slag meal, 

 Tennessee rock phosphate (fine ground), dissolved bone black, 

 raw bone meal, dissolved bone meal, steamed bone meal and 

 acid phosphate. Each is applied in such quantities as to fur- 

 nish phosphoric acid at the rate of 9(3 pounds per acre. Three 

 plots have received no phosphoric acid during the entire period 

 of the experiment. All plots have annually received an appli- 

 cation of materials furnishing nitrogen and potash and in equal 

 amounts, nitrogen being furnished at the rate of 52 pounds and 

 potash at the rate of 152 pounds per acre. In the case of a few 

 crops requiring especially high manuring (onions and cabbages) , 

 a supplementary application of quick-acting nitrogen fertilizers 

 has been made to all plots alike. The crops grown in this field 

 in the order of succession have been as follows : corn, cabbages, 

 corn, — in 1900 two crops, — oats and Hungarian grass (both 

 for hay) , onions, onions, cabbages, and mixed grass and clover 

 for two years. The plots were seeded to mixed grass and 

 clover in the spring of 1905 ; the present is therefore the third 

 year that they have been in grass. The yields and the gain or 



i Not used either in 1906 or 1907, as it is not offered by dealers. 



