Peoceedings of Seventeenth !N^oemal Institute 1"1 



slag and ground bone superior to dissolved bone black and dissolved 

 bone on unlimed plats, the reverse being true on limed plats ; acid 

 phosphate ranked fifth on both limed and unlimed soils, being 

 markedly superior to the raw rock phosphate or floats. 



At the end of ten years, when the applications had supplied 

 equal amounts of phosphorus on all plats, the phosphorus in 

 Thomas slag, ground bone and dissolved bone seemed of the 

 greatest, and nearly equal, availability on both limed and un- 

 limed soils, though the acidity-correcting power of the Thomas 

 slag was partly responsible for its favorable action on the un- 

 limed plats, and the nitrogen in the bone may also have been a 

 factor. Dissolved bone black and dissolved rock followed the 

 three materials just mentioned and were again considerably su- 

 perior to the raw ground rock. 



At the end of the twenty years, the effect of the applications 

 of phosphorus made more than ten years before were still evi- 

 dent on all plats except those of raw Redonda phosphate, par- 

 ticularly on the limed soil. The figure at this time left the 

 rank of the sources practically unchanged on the unlimed plats, 

 but on the limed plats the dissolved bone black had shown equal 

 efiiciency with the Thomas slag, ground bone and dissolved bone. 

 The acid phosphate (dissolved rock) holds an intermediate place 

 on both limed and unlimed soils, being decidely superior to raw 

 rock, double superphosphate, or roasted or raw Eedonda phos- 

 phate. The double superphosphate requires lime to be effective, 

 ranking next to acid phosphate on limed soils, but below raw 

 rock on the unlimed plats. The roasted Eedonda phosphate be- 

 haved similarly to the double phosphate but was not of as great 

 value, and the raw Redonda phosphate was valueless, or even 

 deleterious on limed soil. 



Because of its relative cheapness, raw rock, an cost basis only, 

 ranks with the Thomas slag and bone; but owing to the smaller 

 crops produced it suffers in comparison with the better phosphates 

 when all cost factors are considered. 



Where no phosphorus was used, nine tons of slaked lime per 

 acre in three applications, eight or nine years apart, resulted in 

 crop increases during twenty years valued at $400 per acre; 

 with insoluble phosphates, ground bone, Thomas slag, raw rock 



