No. 6. DEPARTMENT OF AGRICULTURE. 205 



concerned with the effectiveness of the plant food in the raw phos- 

 phatic rock when mixed with stable manure. As measured in crop 

 yields, the phosphoric acid in the raw rock has brought returns show- 

 ing about the same net ^)rolit from the application as is shown from 

 the application of acid phospltate by its side, and the ill result from 

 use of acid phosphate on this acid soil is escaped. An increase in 

 net profit from the crops, due to the smaller cost of the phosphoric 

 acid in the raw rock, has uot appeared in this experiment. Some 

 data from experiTiients elsewhere are more favorable to the raw 

 rock phosphates. 



In Illinois the effects of the applications of the raw rock are so 

 marked that Dr. Hopkins urges its use to the exclusion of acid phos- 

 phates. He is using it freely upon his own farm, purchased a few 

 years ago in Southern Illinois, where land prices are very low on 

 account of the low state of productivity to which that whole section 

 has fallen, and he is using it on many test farms over the state. His 

 results with raw phosphatic rock and ground limestone lead him to 

 believe that the infertile southern third of his state will be brought 

 back to a high state of production through their use, and the clover 

 that follows their use. The rock is broadcasted on a sod or other 

 green crop, and is plowed down, it being important that the raw rock 

 be intimately mixed with the decaying vegetation. 



AYhere organic matter is lacking, and where phosphoric acid is 

 wanted in an immediately available form for a crop, it is advisable 

 to continue our present use of acid phosphates, steamed bone or 

 basic slag. The essential thing is that phosphoric acid be given to 

 our hungry soils, and any carrier is good that brings results. 



Our country has a wide variety of soils, but, exclusive of the 

 leachy sands that are deficient in all elements of plant food, and the 

 limited muck area, the great areas of farm lands east of the Missis- 

 sippi, whose productiveness is distinctly unsatisfactory, should be 

 subjected by their owners to tests with lime and phosphoric acid 

 used with a free hand. Our calcareous soils, except where they have 

 been subjected to a skinning process, are not within these disappoint- 

 ing areas. It is, as a rule, the land with low lime content that has 

 presented the puzzling problem. When this dominant factor in soil 

 productiveness has been supplied, then should the deficiency in phos- 

 phoric acid be made good, and that deficiency exists inside of most 

 limestone areas as well as outside, if cropping has been hard. With 

 a full supply of carbonate of lime and phosphate of lime, the cloveio 

 usually are assured, and they furnish both the nitrogen and the 

 organic matter that is essential to continued crop productiveness. 

 The supplies of inert potash in most clay soils is so large that they 

 may be largely depended upon wherever the supply of rotting or- 

 ganic matter is abundant, as it should become after the applica- 

 tions of lime and phosphoric acid. Sands and muck soils are less 

 rich in potash. 



Full practical recognition of the possibility of giving land out- 

 side of the limestone areas some of the advantages of a calcareous 

 soil by applications of ground limestone, and full practical recogni- 

 tion of the deficiency of phosphoric acid in most old farm lands, 

 would restore heavy clover growths to the farms, rich humus to the 

 soils and new heart to the owners. It is the biggest consideration 

 today in eastern agriculture. 



