143 



iniily low in tli.it clciiiciil. m111ii)U,l,'1i tlit-y -aw llir liclicsi soils in nitroirtMi Mnd 

 phospliorus. 



Some of our soutlicrn Illinois soils wbii-h are low in avjiilai>le potassium, also 

 .trive us a marked increase in corn and cowpeas. and also in clover, with i)otas- 

 siuni. and heavy jipplications of it. 



In all our experiments calcium carbonate is used. We .assure ourselves that 

 we have it in the soil. We always add lime, if necessary, to correct the acidity 

 of the soil. 



B. V. Kl'ffu.m. of Wyomin.i,'. I think the Wyominji st.ition threw some li,i,'lit 

 on the reason for the reduction of the crop by the addition of the potassium 

 salt by its work with alkali soil. I was very nnich interested in Dr. Wheeler's 

 late bulletin on the use of sodium salts, but I think ho would have f(mnd a 

 f,'reat deal of difference if he had used the sulphate instead of the chlorid in 

 those experiments. We have found that the reduction of the germinating,' power 

 of the seetls and the growth of plants seem to be proiK)rtional to the osmotic 

 pressure of the solution when these salts are added, and the cblorid always 

 produced more effect than the sulphate. I have always obtained uegative 

 results in fertilizer tests on Wyoming soils with potassium chlorid, and some 

 reduction with sulphate. There seems to be plenty of the chlorid associated 

 with the alkali in those soils, and if we add the potassium in this foru\ it 

 reduces the yield. 



H. P. AR.MSitv. Doctor Hopkins's jiaper was on the very important question of 

 the maintenance of the fertility of the soil on a large scale. I do not rise to dis- 

 cuss the question or to criticise what has been said, but to suggest that this seems 

 to me to be the very kernel of his paper, and personally I would be glad to hear 

 discussed the <iuestion of the maintenance, on a large scale, of soil fertility. 



R. J. Redding. Several days ago I was asked by a farmer what was the value 

 of the phosphoric acid. i)otash, and nitrogen in an acre of average Georgia soil. 

 1 happened to have at hand an analysis of such a soil and I made a calculation 

 of the amounts of the different ingredients in available form at the market prices. 

 The result was over .$1,000 an acre. I think it nught lielp us to impress on the 

 farmers the importance of developing the amount of plant food in the soil to 

 know that $1,800 or $2,000 worth of it is within easy reach of the farmers and 

 what are the methods and w^hat are the tools and implements which may be 

 used to develop it. 



W. M. Hays, Assistant Secretary of the U. S. Department of Agriculture. I 

 am very much interested in the discussion. I want to especially call attention 

 to one or two relations of this paper to the work that Doctor Hopkins is doing 

 in Illinois. One is the division of the State into these soil and agricultural 

 areas and the following out of the detailed study of chemical facts and rela- 

 tions with schemes of organizing farms on a system of rotation. I think his 

 scheme of analyzing the general situation of the whole State and working up 

 schemes of farm management that will enable the farmer to see best how to 

 keep up the fertility of his land and increase the yield of his crops so that he 

 will have the maximum crops, and yet retain the fertility of the land, should 

 be studied by all. 



C. E. Thorxe, of Ohio. The experience of the Ohio station would seem to me 

 to bear strictly upon this paper. The station purchased three adjoining farms 

 lying on the same general geological formation. The soil, so far as superficial 

 examination would indicate, originally was practically, if not identically, the 

 same. On one of these farms, for the last seven years, one-half of the soil hav- 

 ing been cleared from the original forest for this work, we have maintained an 

 average yield of wheat, without any fertilizer whatever, of .35 bushels to the 

 acre. We have been able to increase that yield by the addition of acid phosphate 



