148 STATE BOARD OF HORTICXTLTrRE. 



outset, these soils being as poor in potash as Eastern lands. 

 The same is true of some of the sandy lands of the interior. 



My advice to the farmers of California is and has been simply 

 that, in order not to waste their money for the purchase of 

 ingredients probably not necessarj^, they should begin by sup- 

 plying those most likely to be required at the time, and to turn 

 to the use of potash fertilizers only after they have found the 

 effect of phosphatic and nitrogenous ones to be unsatisfactory. 



The etibrts of those interested in selling as much as possible 

 of their manufactured products are, quite naturally, in opposi- 

 tion to this policy, but the advice of the interested party is not 

 usually the one most likely to benefit the taker. 



Hoiv to Make Experiments. — Plot experiments made with dif- 

 ferent fertilizers must, in order to be of definite value, be made 

 on a sufficiently large scale to eliminate the source of error 

 arising from local differences in soil and subsoil, and must be 

 checked by several check plots so interposed between the others 

 as to not only check them by direct comparison, and to prevent 

 the washing of fertilizers from one fertilized plot to another, 

 but must also be compared, first of all, among themselves, so 

 as to determine what is the normal product of the unfertilized 

 land. It will frei^uently be found that these unfertilized check 

 plots differ more widely between themselves than do the 

 fertilized ones from them or from each other. It usually takes 

 several seasons to come to definite results. 



A question wholly aside from those discussed above is that 

 of the special modification of crops by the use of a surplus of 

 certain substances known to produce a specific effect. Thus, 

 common salt is known to make asparagus and some other 

 vegetables more succulent and tender; nitrogenous matter 

 increases the size and succulence of fruits, and some experi- 

 ments made with potash fertilizers on oranges point to an 

 increase of sweetness thereby. It is then simply a question 

 whether or not purchasers appreciate such modifications suffi- 

 ciently to render their attainment a profitable undertaking, 

 apart from any increase of the crop or the maintenance of soil 

 fertility. 



