148 Appendix. 



PLANT-FOOD AND USE OF FERTILIZERS. 



By A. L. Kniseia', Chemist Oregon Agricultural Experiment Station. 



Judging from the correspondence received by the Station Chemist, there 

 is a great desire on the part of the people throughout the state to know about 

 soils, plant-foods and fertilizers, which goes to show that the farmer is seeking- 

 information along these lines. Many of the letters ask straightforward questions, 

 but it is impossible to answer them satisfactorily. The following extract is a fair 

 sample of many letters received : 



Oregon Experiment Station. CorvalUs, Oregon : 



Dear Sirs : — I send you this day, under separate cover, a sample of soil. 

 Will you please analyze and tell me what it will produce in paying quantities 

 in this climate, or if there is any chemical lacking which could be supplied at 

 a reasonable cost to make it first-class land, etc 



The object of this bulletin is to furnish popular information concerning 

 such questions as those asked in the foregoing letter. 



Questions relating to the fertility of the soil are very hard to answer and 

 many times definite satisfactory answers cannot be given. 



Soils are Very Complex. — The soils of no two farms are alike — neither are 

 the soils of two fields on the same farm exactly alike. The total plant-food 

 in one field differs from that of the adjoining field ; the amount of decaying 

 organic matter (humus) differs in different fields; the degree of coarseness or 

 fineness of the soil particles varies greatly : the moisture conditions of no two 

 fields are identical ; neither are other physical conditions, nor texture of the 

 soil exactly alike in two different fields — and so on with an almost infinite num- 

 ber of conditions, each having more or less infiuence upon the fertility or pro- 

 ductivity of the soil, each having its infiuence upon plant growth. 



Law of the Minimum. — Since so many conditions surround and influence the 

 growth of a plant it is important to find out which ones affect the growth of 

 the plant most. It has been found by experimentation that it is not the most 

 favorable conditions but the most tinfarorable ones which have the greatest influ- 

 ence upon the growth of a plant. There may be one hundred conditions favorable 

 for plant growth, and five or even one. only, which is unfavorable. It is not 

 the many favorable conditions but the few unfavorable ones which influence the 

 growth of the plant, or crop. 



If a field is unproductive on account of poor drainage or because of a 

 lack of humus, it would not be made more productive by adding commercial 

 fertilizer. On the other hand, if a field is unproductive, due to a lack of avail- 

 able plant-food, then the addition of fertilizers will Increase its productivity. 



The essential conditions of a field uhich are the poorest or at the lowest 

 ebb must be sought out and improved before the fertility of the field is increased^ 



It happens many times that poor yields are not due at all to a lack of 

 plant-food, but are due to essential conditions other than those of plant-food. 



Plant-food. — There are known to exist and the scientist recognizes about 

 seventy-seven or seventy-eight different elements or simple substances. These 

 elements are not all necessary, but a certain few are indispensable to plant growth. 

 The elements which are necessary and without which plants cannot flourish are 

 known as the plant-food elements. Authorities differ as to the number of ele- 

 ments which are essential for plant growth — some give nine or ten, others- 



