26 MAINE AGRICULTURAL EXPERIMENT STATION. I9O3. 



will on application, send a list of suitable books. Experience in 

 the field, explained by experiments in the laboratory, has clearly 

 demonstrated a few jirinciplcs which underlie the successful and 

 economical use of fertilizers. 



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 econom- 

 ically supplied, is to put the questions to the soil with different 

 fertilizing materials and get the reply in the crops produced. 

 How to make these experiments is explained in Circular 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, or to the 

 Maine Agricultural Experiment Station. 



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

 fanning to make the most of tlie 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 gather- 

 ing 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 w^ould remain practicallv 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. 



