1903.] 



PUBLIC DOCUMENT — No. 33. 



125 



Clover Roiven. — Average Yield jyer Acre (Pounds). 



The figures call for little comment. They strikingly show 

 the marked inferiority of the product on the plot receiving 

 kainite. Not only is the average product on this plot lower 

 than the yield on any of the other potash salts, — but it is 

 lower in every series except one than the yield on the plot 

 receiving no potash. The potash salt giving the highest 

 average total Afield is the silicate, — almost as good is the 

 high-grade sulfate, — while the vield on the nitrate muriate 

 and carbonate is not far behind. 



VI. — Comparison of Phosphates on the Basis of Equal 

 Application of Phosphoric Acid. 

 In this experiment, which has been in progress six years, 

 we have under comparison the following phosphates : apatite, 

 South Carolina rock phosphate, Florida soft phosphate, phos- 

 phatic slag, Tennessee phosphate, dissolved bone-black, 

 raw bone, dissolved bone, steamed bone, and acid phosphate. 

 The phosphates are all applied in the finely ground form, 

 being carefully spread broadcast after ploughing in the 

 spring, and harrowed in. Three plots in the field have re- 

 ceived no phosphoric acid in any form since the beginning 

 of the experiment. The plots are one-eighth of an acre 

 each in area. The phosphates yearly applied are used in 

 (quantities sufficient to furnish actual phosphoric acid at the 

 rate of 96 pounds to the acre. All plots are manured alike, 

 with materials furnishing nitrogen and potash in available 

 forms and in equal amounts to each. The materials regu- 

 larly used furnish nitrogen at the rate of 52 pounds and 

 potash at the rate of 152 pounds per acre. During the past 



