86 BULLETIN 699, U. S. DEPARTMENT OF AGEICULTURE. 



were added than in the previous experiments with the artificial soil, 

 the total quantity present in each pot was still considerably below 

 that present in a soil of low phosphate content. 



While only one field experiment (of two years' duration) with raw 

 rock phosphate has been reported by the New York stations, the six 

 pot experiments warranting consideration in detail indicate that this 

 material increases the yield of a number of crops even when applied 

 in very small quantities. The data also seem to show that the pres- 

 ence of organic matter renders the raw phosphate more effective. A 

 comparison of the relative merits of the different phosphates used in 

 these experiments, however, is hardly admissible. 



NORTH CAROLINA. 



The work with raw rock phosphate reported by this State consists 

 of three field experiments ^ conducted for periods of one to three 

 years. Owing to the short duration of these experiments and also to 

 the fact that the data presented in two of them are very limited, one 

 is hardly justified in considering the results even indicative of the 

 relative merits of the phosphates used. 



OHIO. 



Probably the most valuable experiment with raw rock phosphate 

 yet reported is one undertaken by the Ohio station in 1897.^ Not 

 only has this experiment been conducted over a considerable period of 

 time (18 years), but the raw rock phosphate has been applied in a 

 manner generally thought to render it most effective under soil condi- 

 tions. Moreover, a direct comparison is made between this form and 

 the more soluble form of phosphoric acid in superphosphate. 



The field selected for this experiment was rather below the average 

 m fertility, but no data are available showing the relative natural 

 productivity of the treated plots. The yields of most of the check 

 plots, however, with the exception of No. 1, section A, No. 7, section 

 B, and No. 1, section C, have agreed fairly well throughout the ex- 

 periment, indicating that the field is comparatively uniform. The 

 joil is a sandy clay of glacial drift origin. In 1892 it grew a crop 

 of oats and in 1893 it was plotted, drained, and sown to wheat. 

 Clover and timothy were grown in 1895 and 1896. 



Up to the time of the experiment herein described, no manure 

 whatever had bfoen applied to the field since it came into the posses- 

 sion of the State. 



IN. C. State Board of Agr., Bui. No. 128 (1907) ; N. C. Dept. Agr., Bui. No. 151, pp. 

 31-34 (1911) ; N. C. Agr. Expt. Sta., Bui. No. 227 (1914). 



a Ohio Agr. Expt. Sda., Buls. Nos. 110, 134, 183, 184, 246, 305; Circulars Nos. 54, 83, 

 92, 104, 114, 120, 131^ 144. 



