140 STATE BOARD OF HORTICULTURE. 



by fertilization. 1 am this year using the Bradley Orange 

 Tree Fertilizer at the rate of thirty pounds per tree, or twenty- 

 four hundred pounds per acre, making two applications in the 

 year, say one in January and one in July. 



ECONOMY IN FERTILIZATION.* 



Numerous inquiries regarding the necessity or expediency of 

 potash fertilization in this State, and the fact that active mis- 

 representation of my views and teaching in the premises has 

 been made by interested parties, render it expedient that these 

 views should be briefly formulated in print for the benefit of 

 persons interested. 



What the Plant Needs. — It is an elementary fact, pretty 

 generally understood, that, strictly speaking, all substances 

 used by plants for building up their tissues are of equal impor- 

 tance; in so far as in the entire absence of any one of them, plant 

 development cannot occur at all. But it is universally known 

 and admitted that all but three or four of these are present in 

 ordinary soils in sufficient amounts and in an available con- 

 dition for the purposes of plant growth. The only ingredients 

 usually required to be replaced by the use of fertilizers are 

 potash, phosphoric acid, nitrogen, and lime. Any fertilizer 

 containing all of these may be considered " complete," and 

 when supplied after each crop in the same amount and in the 

 same proportion as has been finally withdrawn by the sale of 

 the crop, soil exhaustion can be indefinitely prevented and 

 fertility perpetuated. The only question, then, about which 

 there can be any discussion is: whether in every case the use of 

 all the four substances is really necessary, or whether one or more 

 can, for the time at least, be omitted. This question arises 

 most obviously with reference to the great difierences existing 

 in the kind and amount of draft made by different crops on 

 the soil. Thus, root crops withdraw very large amounts of 

 potash from the soil, while drawing but lightly upon phos- 

 phoric acid and nitrogen; on the other hand, cereal crops are 

 known to bear very heavily on phosphoric acid and nitrogen, 

 while taking up a comparatively small amount of potash only. 

 These facts form the main basis of the utility of rotation of 



*By Prof. E. W. Hilgard, Director of Agricultural Experiment Station, 

 University of California. In "Pacific Rural Press," November 4, 1896. 



