147 



crop? It seems to me that the (luestion is not so much with regard to the soil 

 or the chemistry of the soil, as it is with regard to the plants themselves, and 

 liow we can hest stimulate these to Itring us ijrotitahlc <n)ps. 



V. (J. Hopkins. There are two different points that have been raised which 

 I would like to refer to for a moment. One of them 1 might spealc of as price, 

 and the other as percentage. 



Whether the use of any given material upon our soils for growing crops is 

 economical or profitable depends more largely, than many of us stop to think 

 of. upon the price we allow for that material when it is produced. Even in 

 raising a crop of hay, near some eastern market where that hay crop brings 

 .$1.") to .$20 a ton to the farmer, you can pay anything, almost, for the materials 

 you use to gn)w that crop; but when you get out into the agricultural regions 

 of the West, where the farmer gets a net return of only .^fS a ton for his hay. 

 of course he can not pay much for such materials. 



T.ake the work Director Thorne has spoken of in Ohio : when we tigure on the 

 prici's tli.it he mentions, using nitrogen and potassium, it paid very well, figuring 

 wheat at a dollar a bushel, corn at 50 cents a bushel, and oats at 33J cents a 

 bushel. lUit when I have taken the most recent figures from the Ohio experi- 

 ment stations and applied them to Illinois conditions and considered them in 

 relation to the last tyn years, neither nitrogen nor potassium has paid for itself 

 upon the basis of the Illinois yield. It makes all the difference in the world 

 what i)rices we allow for our produce. 



The other point which I wish to mention was raised by Director Kedding. of 

 Georgia, regarding the large (piantities of plant food in our soils. Even in our 

 soils in Illinois we have 600 pounds of phosphorus per acre. We are cOming to 

 look upon the phosphorus in the soil as being available by some sort of per- 

 centage : that is. we do not look upon that (iOO pounds as being so much that we 

 can slice off at will. We are limited i)artly by the .amount of decaying organic 

 matter, and also l»y the seasonal conditions, and we are also limited by the root 

 development. Some plants have more extensive root systems which may touch 

 more of the soil particles than others, and if an estimate of the plant food 

 which we can get may be made by calculating the percentage of the surface of 

 the soil particles touched by the surfaces of the roots there would be some per- 

 centage relation there. If we can get 1 per cent of the phosphorus from the 

 soil with the ordinary cereal crop, such as clover ; if we can get out 1 per cent 

 of the phosphorus in the soil in a normal season, when we have present 600 

 pounds, we get. of course. 6 pounds of the phosphorus out in the season. If we 

 can get out 2 per cent of the phosphorus in the soil, we would get 12 pounds out. 

 If we had 2.0(10 pounds of phosphorus in the soil, on the percentage basis of 1 

 per cent we would get 20 i)ounds, and with 2 per cent of the phosphorus made 

 available to the root system we would get out 40 pounds. It means a great 

 deal more to us to put it directly upon some percentage liasis. What that per- 

 centage basis is, actually, we do not know. We must make it as large as we 

 can. profitably. 



W. .J. Spillman. of the V. S. Department of Agriculture. Unfortunately for 

 myself I did not hear all of Doctor Hopkins's paper, but as the general subject 

 is the maintenance of permanent soil fertility, I want to call attention to the 

 importance, from my point of view, of one class of investigations which have 

 not been carried on as extensively as I should like to see them carried on in 

 our experiment stations. Of course I realize very fully that each of us gets a 

 different point of view from the field of agriculture, and I may have miscon- 

 ceived the importance of a certain line of work. I think we will all agree, 

 however, that where it is possible to do so the use of barnyard manure is 

 [•erhaps the most legitimate means of maintaining permanent fertility, but it 



