FERTILIZATION EXPERIMENTS NECESSARY l$\ 



essential mineral elements discussed above. An experiment in fer- 

 tilization or any other which is carried out on a few trees or vines, 

 therefore, may give results which have little application to a whole 

 orchard or vineyard. Much fruitless work on fertilization and soil 

 management generally, as well as laboratory studies, have been 

 carried out all over the world because of ignorance of this funda- 

 mental fact and it behooves us to take cognizance of it in the work 

 of the future. This is particularly true in its application to orchard 

 and vineyard problems, because of the relatively small number of 

 plants used per acre and hence because according to the laws of 

 chance, we have no opportunity of averaging the effects of the soil's 

 variability. 



LONG-TERM FERTILIZER EXPERIMENTS 



One would naturally expect that the results of experiments on 

 the fertilization of soils which have been in progress for long periods 

 uninterruptedly like the celebrated ones at Rothamsted, England, 

 at Wooster and Strongsville in Ohio, and at State College in Penn- 

 sylvania, can be reckoned on as reliable guides for fertilizer practice. 

 Unfortunately, however, these experiments were planned, and have 

 been carried on without reference to the important principles of soil 

 chemistry, plant physiology, and the variability of soils which are 

 discussed above. Their results may, and may not, possess, therefore, 

 the requisite cogency and utility for the average orchardist and 

 particularly as regards California conditions. In none of these ex- 

 periments, moreover, has there been ascertained the magnitude of 

 the errors attaching to the work, and hence increases in crop sup- 

 posedly due to fertilization may, and may not, be significant. Then, 

 too, when the errors are properly allowed for as has been done in a 

 series of studies carried on at the California Agricultural Experiment 

 Station and which will soon be published, the question as to whether 

 or not the increases are sufficiently great to pay for the cost of fer- 

 tilization and allow a good profit, still remains to be settled. This is 

 all true in addition to the conclusion, which follows from the dis- 

 cussion above, that any results obtained in such an experiment have 

 no necessary application on any other tract of land than that on 

 which the experiment is conducted. 



LEARNING TO USE FERTILIZERS 



It follows from what has been said above that the best method 

 available to us now of determining the fertilizer needs of an orchard 

 or a vineyard soil is to try fertilization wherever the question arises. 

 It is important, moreover, that the fertilizer be tried on a large tract, 

 preferably no less than three to five acres in size, and that a control 

 or check lot of trees or vines of the same number as in the treated 

 plot be left untreated as a means of determining the effects exerted 

 by the fertilizer. It is the writer's judgment that this is the only 

 rational method yet discovered of determining the fertilizer needs 

 of a given orchard or vineyard. The fruit produced on the fertilized 



