86 BULLETIN 699, U. S.. DEPARTMENT OF AGRICULTURE. 
* 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 thist 
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 1897.2 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 
in 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 1s comparatively uniform. The 
soil 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 been applied to the field since it came into the posses- 
sion of the State. 
1N. C. State Board of Agr., Bul. No. 128 (1907) ; N. C. Dept. Agr., Bul. No. 151, pp. 
31-34 (1911) ; N. C. Agr. Expt. Sta., Bul. No. 227 (1914). 
2Ohio Agr. Expt. Sta., Buls. Nos. 110, 134, 183, 184, 246, 305; Circulars Nos. 54, 83, 
92, 104, 114, 120, 131, 144. 
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