126 BOARD OF AGRICULTURE. [Pub. Doc. 



gression of the other is to be found in the maintenance of, 

 or faihu'e to maintain, certain soil conditions, rather than 

 in an inspection of the debit and credit account with certain 

 soil elements. This picture is a true representation of con- 

 ditions frequently seen. 



There is other knowledge of more or less recent develop- 

 ment which cannot be ignored in reaching the best understand- 

 ing now possible concerning soil economics. Generalizations 

 so common in the past regarding plant nutrition and soil 

 exhaustion have, in my opinion, too fully ignored the wide 

 variations in the compositions of plants. Recent experi- 

 ments at the NeAv York Agricultural Experiment Station, 

 not yet published, ap})ear to me to place renewed emphasis 

 upon the fact that there are not yet ascertained fixed amounts 

 of the essential constituents of plants which constitute the 

 mininmm rec^uirement. I have found that, when the supply 

 of potash varies in the soil, one plant may attain what is 

 apparentl}^ a maximum development with 100 to 200 per 

 cent less content of potash than is found in another plant 

 of no larger groAvth. This has proved true in the case of 

 tomatoes, tobacco, peas, rape, and to a less degree with 

 barley. Similar results, though not so emphatic, were 

 secured touching the relations of phosphoric acid to the dry 

 matter produced. 



As an illustration of the wide variation in the figures 

 given for the quantities of ingredients withdrawn from the 

 soil b}^ crops may be mentioned the large differences between 

 the Geniian and American tallies. According to the aver- 

 ages Avhich represent the composition of American-grown 

 ])otatoes, a crop of 300 bushels would withdraw from the 

 soil 12i pounds of phosphoric acid and 52 pounds of potash. 

 Similar calculations based upon the averages of German 

 tables would show a use of 25 pounds of phosphoric acid 

 and 81 pounds of potash. The German figures call for twice 

 as much phosphoric acid and approximately 5G per cent 

 more potash than the American. On the other hand, figures 

 for sugar beets show exactly opposite relations. From 

 estimations by the American tables we learn that 15 tons of 

 sugar beets will utilize in growth 30 pounds of })hosphoric 



