EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. ~— 85 
It is evident from the figures given in Table LI that the more finely 
raw rock phosphate is ground the more effective it becomes. The 
floats in almost every instance produced appreciably greater yields 
than the coarser phosphatic material. The same is true, though to 
a less extent, of bone meal. 
-» In the first experiment (1899-1900) where no organic matter was 
applied, the pots treated with acid phosphate showed greater yields 
than those treated with the less soluble phosphates, but in the second 
experiment where organic matter was added the very finely ground 
raw rock and floats gave as good and better yields than the acid phos- 
phate, although it was supplied in quantities far less than phos- 
phates occur in most soils. 
One other pot experiment to test the fertilizer value of several 
relatively insoluble phosphates on barley was conducted by the 
Geneva? station in 1912. 
The same artificial soil employed in the previous experiments was 
used in this test, but the quantity of phosphoric acid added to each 
pot in the various forms was from two to four times as great. Ade- 
quate amounts of potash and nitrogen were added to each pot, but 
no organic matter was employed. Each treatment was run in dupli- 
cate. 
The average results of this experiment are given in Table LII. 
TasLE LII.—Yields of barley obtained in a pot experiment (58.9 pounds of 
soil) with various phosphatic fertilizers; potash and nitrogen supplied to all 
pots. 
Amount Off saeldjot 
Form of phosphates. Bnaed barley per 
t 
per pot. ete 
Grams Grams. 
MOWOCAICIO INE DNOSPNALC sess cree Re cee eens on ae hack cae Soe eae eee 5. 82 71.0 
PEOMPORCIW ASLO se ee ete ey eth anys Soe e ad 8 Ac ee ek ce bela cte cee concent s 5. 82 - 44.2 
IASICIS | ACen eee ee ener eee en Men a. SER Ree UR Pe ee ey 5. 82 68.7 
CROMER nieSSCC ROC Kap oa Fae em Se = ein os Oe Sas eae aS Se ee sene ob Sesh e Ee 5. 82 55.7 
IB OMNES Ssh SCRE Se DEAS A EE aR ee ae ate ee tae gel ea 5. 82 74.7 
TET ATDURS 25 oo Se SSS SS eR a Se ee ea ree SO ot oy en ey (rt a eS 38.2 
The monocalcium phosphate, bone, and basic-slag treatments all 
gave yields of barley greater than the ground Tennessee rock, but 
apparently this crop was able to utilize to a certain extent the phos- 
phoric acid of this latter material. 
In view of the fact that barley in previous experiments has not 
responded readily to the less soluble forms of phosphoric acid when 
they were present in small quantities, the results of this experiment 
are not surprising, for while greater amounts of phosphoric acid 
1N. Y. Agr. Expt. Sta. (Geneva). Fertilizer Value of An Iron Ore Waste. Bul. No. 
358, pp. 252-253 (1918). 
BL 
