g04 ANNUAL, REPORT OF THE Off. Doc. 



that an increase in the content of lime carbonate will give still 

 better results, and the experiments are under way, but there is en- 

 couragement in the fact that any increase in the lime content is 

 attended by an improvement iu soil conditions. The clover problem 

 has been solved for this Wooster station soil. 



There has been discussion concerning the form of lime that should 

 be used. Beyond doubt finely pulverized limestone is superior to 

 caustic lime, because it can be used without auy danger of harm to 

 the land. It does not liberate the soil nitrogen in the form of am- 

 monia, as does caustic lime, but assists in its retention. We have 

 three scientists whose work is pre-eminent in calling public atten- 

 tion to the wide need of soil acidity correction. I refer to Dr. Hil- 

 gard, to Dr. Hopkins, who is demonstrating the way to restore the 

 infertile lands of Southern Illinois by correction of its acidity and 

 restoration of the supply of phosphoric acid, and to Director Thorne, 

 of Ohio, who is doing a great work for Ohio, and these three gentle- 

 men believe that the carbonate of lime — pulverized limestone — is 

 preferable to caustic lime. It is true, however, that caustic lime, 

 in moderation, is used with admirable results, and is to be advised 

 when this form of lime is cheaper, or for other reasons more avail- 

 able, than the pulverized carbonate. 



^Vhile lime is a dominant factor in soil i)roductiveness, it is evi- 

 dent from such data that crop yields throughout our country are 

 limited by the deficiency of phosphoric acid in the land. It is a 

 condition so nearly universal with us that the purchase of this plant 

 food for our fields rarely is unwise. Desirable as steamed animal 

 bone and basic slag are known to be as carriers of phosphoi'ic acid, 

 it is idle to recommend their sole use, because they are in insufficient 

 supply upon the market. The chief source of phosphoric acid for 

 land must be the phosphatic rock. This is our great storehouse of 

 this plant food, and the use is imperative. There is objection to 

 the use of acid phosphate on lands having a low lime content, and ' 

 this objection is w-ell based upon the experience of many farmers and 

 the careful experiments of the Ohio station. Where the content of 

 carbonate of lime in the Wooster soil naturally was only four and a 

 half tons in the surface foot of an acre of land, the continued use 

 of acid phosphates increased the difticulty of getting growths of 

 clover. This objection is not vital, however, since we know the prac- 

 ticability of correcting this condition by supplying lime. 



Another objection to the use of acid phosphates is the addition to 

 the cost of the plant food due to the treatment of the rock with sul- 

 phuric acid. At the Wooster station a pound of pho.splioric acid in 

 an acid phosphate — the rock treated with sulphuric acid — costs three 

 times as much as a pound of acid })hosphate in the raw, or untreated 

 rook. The desirnbility of full supplies of ])lu)sphnri(' acid in all fiirni 

 land rend< j's this dilTerence in price a very iuipoi-laiit point. If the 

 acids resulting from the decay of organic matter could be made to 

 take the place of the sulphuric acid, there would be an immense 

 saving in money to the farmers, a saving from injury to soils that 

 are naturally not rich in lime, and there would be a resulting impetus 

 given to the free use of phosphoric aciTl upon land that would be 

 reflected in larger crop yields. 



Important work along this line is being done by Director Thorne, 

 of the Ohio station, and Dr. Hopkins, of the Illinois station. The 

 experiments at the Ohio station were begun ten years ago, and are 



