Decembeb 18, 1908] 



SCIENCE 



863 



nent agriculture— for the wheat belt, and 

 for the corn belt, and for the cotton belt; 

 but we believe the problem is being solved 

 for the state of Illinois — not by theories or 

 hypothesis, but by mathematical and chem- 

 ical facts, supported by actual demonstra- 

 tions in the field and on the farm in all 

 parts of the state. So far as I have been 

 able to learn, the oldest soil experiment 

 fields in the United States are in Illinois, 

 with an authentic record and history of 

 nearly a third of a century ; and extensive 

 investigations are in progress on subse- 

 quently established fields. Lands that 

 were once poor are becoming rich— rich in 

 materials absolutely required to make 

 crops. "Where 12 bushels of wheat were 

 commonly grown, 30 bushels are now pro- 

 duced, and in both eases the same crop 

 rotation is practised, wheat being grown 

 but once in four years on the same field. 

 "Where without soil treatment, in the best 

 rotation, corn yields but 50 or 60 bushels, 

 the present average yield on treated land 

 is from 90 to 100 bushels, under the same 

 crop rotation. "Where clover commonly 

 fails or yields less than a ton of hay to the 

 acre, two to three tons are now produced 

 on properly treated land. 



How is this accomplished? Simply by 

 knowing the chemistry of the air and of 

 the soil and by applying that knowledge 

 mathematically to agriculture, by drawing 

 upon these natural sources for every ele- 

 ment of plant food which they contain in 

 inexhaustible amount, and by supplying 

 from other sources such elements as it is 

 mathematically impossible for the air or 

 soil to furnish indefinitely. "Where the soil 

 contains a very limited amount of any ele- 

 ment of plant food not present in the 

 atmosphere, that element is supplied not 

 in small quantities of high-priced soil stim- 

 ulants as in the so-called "complete fertil- 

 izers" that have helped to ruin much of 

 the lands of the eastern and southern 



states, but in the positive addition of plant 

 food in larger amounts' than are required 

 for the largest crops, so that the soil be- 

 comes richer, actually and mathematically, 

 even though large crops are removed from 

 the land. The fertilizers thus used are not 

 artificial, but natural, and chiefly in the 

 same form as existed originally in our 

 naturally rich virgin soil. 



Chief among the materials that we have 

 found it necessary to use are fine-ground 

 phosphate rock and natural limestone, 

 together with abundance of legume crops, 

 which must be returned to the land either 

 directly or in manure. 



"We have absolutely permanent supplies 

 of nitrogen in the air, to be secured as 

 needed by means of clover and other 

 legume crops, and for our system of farm- 

 ing we have in our common soils almost un- 

 limited supplies of potassium and of the 

 other less important essential mineral ele- 

 ments, which may be liberated as needed 

 by means of decaying organic matter; so 

 that with these, as with our inexhaustible 

 limestone deposits, we are agriculturally 

 independent. But, as the result of hun- 

 dreds of analyses'^ of soils and crops, we 

 know that the average common prairie and 

 upland timber soils of Illinois contain 

 about 2,000 pounds of total phosphorus 

 per acre-foot, and with equal chemical and 

 mathematical accuracy we know that a 

 hundred such crops as we are now growing 

 on our richest and best fertilized lands re- 

 move from the soil about 2,000 pounds of 

 phosphorus. A thousand years of such 

 cropping would require every pound of 

 phosphorus contained in our average soil to 

 a depth of ten feet. 



"Whatever we might vdsh to believe, we 

 can not alter these absolute facts. "We 

 need to conserve our supplies of phos- 

 phorus, whether in the deposits of natural 

 phosphate rock or in our farm lands or in 



" Illinois Experiment Station Bulletin 123. 



