89 



The exchange of 1 ton of corn for 1 ton of wheat bran, for instance, 

 with result in a gain of 16 pounds of nitrogen, 43 of phospheric acid, 

 and 21 of potash. With an exchange of milk or potatoes for the con- 

 centrated feeding stuffs the gain is still more striking. 



A careful study of the present condition of farming in the United 

 States indicates, however, that as a rule the manure produced on the 

 farm is not sufficient to maintain its fertility and that the need for arti- 

 ficial supplies is real, though the amount required may be considerably 

 reduced by careful management. 



In the system of so-called " grain-farming" which has obtained over 

 large areas of this country for a long time, and is still practiced in the 

 Eastern, Middle, and Central Western States, the live stock ktpt is often 

 limited to a number sufficient only to the needs of the farm for labour 

 and food ; the grain is sold, and the manure is make up chiefly of the 

 natural wastes, or unsalable material, such as straw, stalks, etc. The 

 grain contains proportionately greater amounts of nitrogen and mineral 

 constituents than these wastes ; hence the practice continued for a long 

 time results not only in a deficiency in the soil of organic substances 

 containing nitrogen, but also in an exhaustion of the mineral substances. 

 The original character of the soil and its treatment measure the rate of 

 exhaustion. The less fertile soils of the East and South are rapidly de- 

 pleted, while the rich prairie and river bottoms maintain their fertility 

 for a longer period. 



Special crop farming, as for example the continuous cotton and 

 tobacco growing of the South and the wheat growing of the West, i- 

 even more exhaustive, since here the demands upon the soil are not 

 changed — year after year the same crop is grown and the same kind 

 and proportion of constituents are required, while even less returns are 

 made in the way of manure than in the system of farming above de- 

 scribed. Moreover, the|land is left bare for a large part of the year and 

 loss of fertility from this cause is very large. The crops are less abun- 

 dant each year, not because the soil is entirely exhausted, but because 

 it is so far exhausted of those constituents essential to the special crop 

 grown that its production is no longer profitable. 



Changed conditions of farming, which have an important bearing, on 

 this point, may be observed in two directions — (1) in the increased cost 

 of labour and in the lower prices of grain, cotton, and tobacco ; and (2) 

 in the increasing demand for market garden products and fruit. For 

 example, in growing wheat, the labour of preparing the soil, of cultiva- 

 tion, and of harvesting is practically the same whether the yield is 10 

 bushels per acre or 30 bushels. The same is true of a number of other 

 crops ; hence in the larger yield the cost of labour per bushel is mate- 

 rially reduced ; meagre crops of a relatively low value can not be pro- 

 duced profitably with high-priced labour. Soils of a high degree of 

 fertility are required in order to produce large yields of these crops. 

 The return to the soil of only the wastes of the farm results sooner or 

 later in a decrease in fertility, however good the management may be ; 

 hence the need of supplies of plant food from sources outside the farm 

 in order that maximum crops may be produced. 



In the case of market garden crops, it has been proven that even very 

 fertile soils contain too little available food to insure a maximum pro- 

 duction ; this is especially true where rapidity of growth, earlmess, and 



