112 Missouri Agricultural Report. 



of maintaining our soil fertility has recently become, and is today, 

 the paramount problem of American agriculture; for if we can 

 not keep up the fertility of our soil, our days as a nation of agri- 

 culture are numbered; not that the total amount of plant food in 

 our soil can be cropped away in a few years, but that reduction 

 in fertility is followed by such rapid reduction in crop yields that 

 the element of profit disappears long before the soil is completely 

 exhausted. So that, to make agriculture permanent, the fertility 

 must be maintained. 



Now as to the manner of keeping up fertility, there are some 

 very vague and erroneous ideas. The popular idea is that rest 

 restores land. When we crop a piece of land pretty hard, and it 

 becomes unable to produce a satisfactory crop, we say that it is 

 tired, and needs a rest; but recent research has shown that it is 

 not only tired, but hungry. When we work a horse hard all day 

 we say that he is tired, but we have learned by experience that it is 

 a pretty good idea to give him some corn and hay to help him rest 

 up on; and we have also learned that if we rest him every night 

 and give him plenty of feed, we can work him right along the year 

 round. And so it is with our land — it does need rest, but it needs 

 feed as well, and it takes both to keep up its ability to produce. 



The next step of progress in our idea of maintaining soil 

 fertility is the idea of rotation of crops. The reduced yield on 

 land continuously cultivated to one crop, was explained by saying 

 that the land was "sick" toward that crop, and that a rotation with 

 other crops would make it well again. This idea is, in substance, 

 like that of the man who takes his horse out of the plow at night, 

 and drives him to town, without feed, to rest him up. What the 

 horse needed most was not so much a change of work as a change 

 of diet. A horse was never made fat, nor a field fertile, on a diet 

 of aqua pura and atmosphere. 



Another important step of progress was the idea not only 

 of rotating the crops, but of including in the rotation a crop like 

 clover or cowpeas, that has the power of taking nitrogen from the 

 air and adding it to the soil. It has been observed after a crop 

 of clover or of cowpeas has been grown on land, that its productive 

 capacity is greatly increased. This discovery was hailed as the 

 final solution of the problem, but recent investigations have shown 

 that even this will not suffice for, although clover may add nitro- 

 gen to the soil, it takes away potash and phosphoric acid the same 

 as other crops do, and the seemingly good effects of its gro\vth 

 may be misleading on this point. Professor Hopkins, of Illinois, 



