156 



Ineulentally it is to be noted in oonnoctlon with those analyses that one of 

 them shows the hijihest percent aj^e of phosjiliorus tiiat the writer lias ever ob- 

 served or seen rei)orted in any soil — anionntiiijjc to If per cent of phosphorus 

 pentoxid. The very larjje amount of available phosphorus compomids ij» these 

 samples renders the differences noted in available phosphorus of no significance. 



C. G. Hopkins, of Illinois. I would like to say a word about the amount of 

 ])hosphorus reported in this paper. I have made a computation from the 

 figures given, and I find from 12,(KX) to 1.").000 pounds of the element phosphorus 

 to the acre, which is aboiit ten times the amount we have in our Illinois soil. 

 It is, of course, quite generally known that many of the soils in the region of 

 Tennessee and Kentucky, and even in the Piedmont section in other States, 

 run very high in phosphorus. 



M. A. ScovELL. of Kentucky. Our bluegrass lands are very full of lime, and 

 streaks and nodules of i)hosphate of lime occur in many places in the soil, 

 but even the virgin soils are lacking in potash, and we must supply it by arti- 

 ficial means. 



W. J. Spillman, of the Bureau of Plant Industry. It seems to me that in this 

 case it is clear that the limiting factor is potash, and the result given by the 

 methods of analysis agree with the results of the crop. Now. immediately the 

 Question arises that where potash is the limiting factor and the result agrees 

 with field tests, we should like to see it tried on a soil where phosphoric acid 

 is the limiting factor. 



We must not confuse the available amount with the amount the plant uses. 

 It does not use, and could not very well use. all the phosphoric acid available 

 in this soil. 



Soil Investigation. 



A paper upon this subject was read by C. E. Thorne, of Ohio, as follows : 



The dream of the earlier chemists, that chemical analysis would ])rove to be 

 the magic key which would unlock all the mysteries of plant growth and soil 

 fertility, has proven to be only a dream ; for. while chemistry has made and is 

 still making contril»utions of priceless value to our knowledge of the soil on the 

 one hand and of plant nutrition on the other, we have come to realize that our 

 study of these problems must be directed along several lines of inquiry, no one 

 of which may be neglected. 



It is a well-known fact that soils derived from limestones are, as a rule, 

 much more productive than those originating in uoncalcareous rocks; while 

 these rocks again produce soils differing widely in character The geological 

 origin of a soil is therefore a matter of prime importance in determining its 

 value ; Imt this origin is not always revealed by analysis, either chemical or 

 mechanical, hence no classification of soils c;ui be accepted as satisfactory which 

 does not take this factor into consideration. 



It is very true that our information respecting the relationship between geo- 

 logical origin and practical adaptation is, as yet, very imperfect, and the exten- 

 sion of the Iioundaries of knowledge on this sul»ject is. in my judgment, one of 

 the most ini])ortant ()l)jects toward which soil study should l>e directed. There 

 is in existing agricultural and scientific literature a very considerable accumu- 

 lation of data ui)on this (inestion, which if collated by an exjiert soil geologist, 

 might be made very useful as the point of departure for further studies along 

 this line. 



Within very recent years we have learned that l)iological factors play a very 

 imi)ortant role in the soil, but as yet we stand only at the threshold of knowledge 

 on this snliject. The discoveries made in this direction have thrown a new light 

 upon the function of lime in the soil, suggesting that in some cases this func- 

 tion may l>e chiefiy to furnish a l>ase tiy which the nitric acid, resulting from the 

 growth of the soil organisms, may be neutralized. 



EXPERIMENTS WITH LIME AND FERTILIZERS ON AN ACID SOIL. 



At the Ohio station, the soil of which is chiefly derived from sandstones and 

 shales, we have had some very interesting exjieriences in the culture of clover. 

 lor a number of years it has been increasingly ditficult to secure a satisfactory 



