66 MAINE AGRICULTURAL EXPERIMENT STATION. I907. 



invited to write the Dean of the College of Agriculture, Uni- 

 versity of Maine, Orono, Maine, who will gladly send a list of 

 suitable books and give full information relative to corespond- 

 ence courses on this subject. 



Soils vary greatly in their capabilities of supplying food to 

 crops. Different ingredients are deficient in different soils. 

 The way to learn what materials are proper in a given case is by 

 observation and experiment. The rational method for deter- 

 mining what ingredients of plant-food a soil fails to furnish in 

 abundance, and how these lacking materials can be most eco- 

 nomically supplied, is to put the questions to the soil with differ- 

 ent fertilizing materials and get the reply in the crops pro- 

 duced. How to make these experiments is explained in Cir- 

 cular No. 8 of the Office of Experiment Stations of the U. S. 

 Department of Agriculture. A copy of this circular can be 

 had by applying to the Secretary of Agriculture, Washington, 

 D. C. 



The chief use of fertilizers is to supply plant-food. It is good 

 farming to make the most of the natural resources of the soil 

 and of the manures produced on the farm, and to depend upon 

 artificial fertilizers only to furnish what more is needed. It is 

 not good economy to pay high prices for materials which the 

 soil may itself yield, but it is good economy to supply the lack- 

 ing ones in the cheapest way. The rule in the purchase of costly 

 commercial fertilizers should be to select those that supply, in 

 the best forms and at the lowest cost, the plant-food which the 

 crop needs and the soil fails to furnish. 



Plants differ widely with respect to their capacities for gath- 

 ering their food from soil and air; hence the proper fertilizer 

 in a given case depends upon the crop as well as upon the soil. 

 The fertility of the soil would remain practically unchanged if 

 all the ingredients removed in the various farm products were 

 restored to the land. This may be accomplished by feeding the 

 crops grown on the farm to animals, carefully saving the 

 manure and returning it to the soil. If it is practicable to 

 pursue a system of stock feeding in which those products of the 

 farm which are comparatively poor in fertilizing constituents are 

 exchanged in the market for feeding stuffs of high fertilizing 

 value, the loss of soil fertility may be reduced to a minimum, or 

 there may be an actual gain in fertility. 



