16 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE VII.—Phosphoric acid (P20s) voided in dung of animals fed with phos- 
phated and unphosphated ensilage. 
Phosphoric acid found. 
Material. Soluble in 
Total. 0.1 per cent¢ 
citric acid. 
Per cent. | Per cent. 
Dimngstromcow NOs 10) (untreatedsensilave) sass eee ee eee ee eee eee i barlyy 0. 
Dung from cow No. 10 (untreated ensilage) plus a quantity of floats equal to that 
in the dung from cow No. 30 fed with treated ensilage...............---------- 5. 95 . 88 
Dung from/‘cow:No:30 (phosphatediensilage)=: 2.222. ses ce sete cone se eee 5.95 1.05 
Dung from tawntheiter (intreated ensilage)=o se cn see elec eee ee eee sf 1.38 
Dung from fawn heifer (untreated ensilage) plus a quantity of floats equal to that 
in the dung from the blue heifer fed with phosphated ensilage...........-....- 9. 34 1.47 
Dung from blue heifer (phosphated ensilage) ............02cecececccccccccccccces 9.34 1.86 
Apparently the combined processes of fermentation and subse- 
quent digestion of the phosphated ensilage produced small increases 
in the citric solubility of the rock phosphate, but in view of the 
fact that the animals would eat but limited quantities of the treated” 
ensilage, and that it was doubtful whether the increase in solubility 
was due to the ensilage process or to animal digestion, he concluded 
that this method did not offer a practical means of rendering the 
phosphoric acid of raw rock phosphate available for agricultural 
purposes. 
In a laboratory investigation on the effect of phosphates and 
sulphates on soil bacteria Fred and Hart? found that the addition 
of such materials to a soil in soluble form increased the ammonifi- 
cation, carbon dioxide evolution, and total number of bacteria. 
While these effects were much less marked in the case of a rela- 
tively insoluble phosphate (bone ash), the suggestion that the in- 
crease in yield resulting from phosphate applications is due in part 
to the promotion of bacterial activity, which in turn increases ammo- 
nification (or the supply of available nitrogen) and also the carbon 
dioxide content of the soil, seems reasonable. The latter compound 
is effective in bringing about the solution of a further quantity of 
phosphate mineral. 
Hopkins and Whiting,? in an article entitled “Soil Bacteria and 
Phosphates,” showed that nitrous acid produced by the action of 
nitrate bacteria upon ammonium salts dissolved phosphate of lime, 
the amounts of lime and phosphoric acid in solution increasing as 
the quantity of oxidized nitrogen increased. These same authors 
also point out that if all the nitrogen required by standard crops 
were obtained from the oxidation of ammonia or ammonium salts 
and the acid thus produced made to act upon rock phosphate the 
1 Wis. Agr. Expt. Sta. Research Bul. No. 35, pp. 35-66 (1915). 
Ill]. Agr. Expt. Sta., Bul 190, pp. 395-406 (1916). 
