SOILS FERTILIZERS. 723 



sium of the guanos being matched by using nitrate of soda and muriate of 

 potash to supplement the bone and dissolved phosphate rock. The soil was 

 acid. It was found under these conditions that the phosphorus of ground bone 

 was the most available, followed in order by that of guanos and the dissolved 

 phosphate rock. In the second experiment the results of a seven-year com- 

 parison of Thomas slag phosphate, Lobos guano, ground bone, and dissolved 

 phosphate rock on an equal phosphorus basis in the presence of liberal amounts 

 of nitrogen and potassium M-ere inconclusive. 



The third experiment covered twenty years, the purpose being to determine 

 the relative availability of the phosphorus in dissolved boneblack, dissolved 

 bone, dissolved phosphate rock, fine ground bone, Thomas slag phosphate, raw 

 rock phosphate, raw Redonda phosphate, roasted Redonda phosphate, and 

 double superphosphate applied during the first half of the experiment, with 

 liberal amounts of nitrate of soda and muriate of potash, to limed and unlimed 

 land. In the first five years of the experiment, during which the phosphates 

 were added on the basis of equal cost, it was found that Thomas slag phosphate 

 and ground bone were superior even to dissolved boneblack and dissolved bone 

 on unlimed soil, the reverse being true on limed soil. Dissolved phosphate rock 

 ranked fifth in both the limed and unlimed soil, being markedly superior to 

 the raw phosphate rock. In the following ten years, during which the combined 

 phosphatic applications were adjusted to an equal phosphorus basis, it was 

 found that the most available phosphorus for both limed and unlimed soils 

 was apparently that in Thomas slag phosphate, ground bone, and dissolved 

 bone. The dissolved boneblack and dissolved phosphate rock ranked next and 

 were considerably superior to raw rock phosphate. 



The final summary of the entire 20 years' work shows that the after effects 

 of the phosphates were very marked and indicate the importance of continued 

 tenure of the land. The rank of the different phosphates was left practically 

 unchanged with the unlimed plats. With the limed plats the main change was 

 that the dissolved boneblack was placed among those of first rank. Dissolved 

 phosphate rock held an intermediate place, being decidedly superior to double 

 superphosphate, raw rock phosphate, and Redonda phosphate on both limed and 

 unlimed soil. The double superphosphate needed considerable lime for its 

 greatest efliciency, for only on the limed soil did it rank next to the dissolved 

 phosphate rock, being decidedly inferior even to the raw phosphate rock in 

 case of the unlimed soil. With the limed soil roasted Redonda phosphate was 

 somewhat superior to the raw phosphate rock, although decidedly inferior 

 with the unlimed soil. The raw Redonda phosphate was practically valueless. 



In connection with this experiment a comparison of the effect of 3 tons 

 of slaked lime per acre applied to the limed phosphate plats with the effect on 

 limed plats receiving no phosphorus showed that in the latter case the increase 

 in the value of the crop during the twenty years, due to the lime, was about 

 $400 per acre. With the insoluble phosphates, ground bone, Thomas slag phos- 

 phate, raw phosphate rock, and raw Redonda phosphate it was $330 and less, 

 and with the other phosphates the increase ranged from $442 with the dis- 

 solved phosphate rock to $590 with the double superphosphate. 



Use of lime on the farm, C. B. Williams (North Carolina Sta. Circ. 28 

 (1915), pp. 7). — This circular gives instructions as to the proper use of lime on 

 North Carolina soils and a brief resume of results securetl with lime when used 

 on various crops at the different experimental farms in the State. 



Fertilizing materials, F. T. Shutt (CavMda Expt. Farms Rpts. 1914, PP- 

 96-104). — Chemical analyses of 25 samples of marl and limestone, super- 

 phosphate of lime, w^ood ashes, sewage sludge, flue ashes, and pulp mill refuse 

 are reported. 



12146°— No. S—1 5 3 



