446 ANNUAL REPORT OF THE Off. Doc. 



LAND KUIN COMPARED WITH SOIL IMPROVEMENT. 



By Pbof. Ci'RIL U. HOPKIXS, UnireisUy of Illinois, Urba)ia, III. 



To permanently maintain profitable systems of agriculture is the 

 most important material problem of the United States, not only be- 

 cause agriculture must be self-supporting, but because every other 

 important industry in America depends upon agriculture for sup- 

 port. Every form of agriculture rests, first of all, upon the fertil- 

 ity of the soil, whether it be grain farming, fruit growing, market 

 gardening or live stock husbandry. 



In our present prosperity and abundance we almost forget the 

 latest famine in Kussia; can scarcely realize that much of the time 

 more people are hungry in India than live in the United States; and 

 will not remember tomorrow President's call of today for help to 

 relieve the widespread famine now existing in China. Meanwhile 

 we go on, as a people, ignorantly, carelessly or wantonly robbing 

 the soil of its fertility and American posterity and our children of a 

 rightful heritage. 



Among all the nations of the earth the United States stands 

 first in the rapidity of soil exhaustion. The improvement of seed, 

 the use of tile drainage, the invention and immediate adoption of 

 labor saving agricultural machinery, the wonderful development 

 of cheap and rapid means of transportation, and the opening of the 

 world's markets to the American farmer have all combined to make 

 possible and to encourage the rapid depletion of American soils, 

 until practical agricultural ruin already exists over vast areas in 

 the older parts of this new country — the United States of Amer- 

 ica; while it is common knowledge even in new rich states of the 

 Central West that the lands that have been under cultivation tor 

 half or three-quarters of a century are much less productive now 

 than they once were. 



The almost universal practice of the civilized world to this date 

 has been to ruin laud and then to seek out newer lands on which to 

 repeat the process even more quickly. 



\Vhat have been the common systems of land ruin? First, begin- 

 ning with the virgin soil, we crop continuously with corn and small 

 grains till the reduced yields render the system unprofitable. Next 

 we introduce clover into the rotation and thus secure from the air 

 not sufficient nitrogen to meet the needs of the crops grown in the 

 rotation, but only sufficient to supplement what can still be taken 

 from the soil by succeeding crops. 



But the fixation of nitrogen is not the only function of clover, 

 nor indeed its most effective function on many soils. Clover is a 

 gross feeder on phosphorus and potassium, and on soils deficient in 

 one or both of these elements clover serves as a most powerful ele- 

 ment to deplete the soil of mineral plant food, not only by remov- 

 ing what it needs for its own f':rowth, but also by its powers, as its 

 residues decay, to liberate additional amounts of mineral plant food 



