162 



THIRTY-FOURTH FRUIT-GROWERS ' C0N\T:XTI0N. 



may have been applied; and this because of the fact that the free 

 roots can not take up fertilizers in the forms in which we apply them. 

 Almost all the fertilizin^i' elements that we use have first to be eon- 

 verted, by the action of the soil bacteria, into other forms that are 

 available to the tree. 



Tv hat are the conditions here in Southern California ? We have a 

 semi -arid region. Our soils contain, as a rule, plenty of lime and 

 potash, but are very deficient in humus and nitrogen. It thus becomes 

 of vital importance that we conserve our humus supply, and add to 

 it in every feasible way. I consider that for our arid region the basis 

 and foundation for all successful fertilization is the maintenance of a 

 supply of humus. 



How is this to be done ? I know of only two ways. One is by liberal 

 applications of stable manure, or straw, alfalfa hay, or other mulch, 

 and the other is by the growing and plowing under of cover crops. 



STABLE MANURE. 



The fertilizing effect of stable manure is far in excess of what we 

 would expect from simply studying the amount of plant food contained 

 in the manure. Dr. Wiley of the Agricultural Department has this 

 to say on that point : 



Th;' nctioii of stable manure is another instance of the great benefit which is 

 diMi\i I iioi.ii i,iaii niinii- a field with nitrifying organisms. It is well known that the 

 uiirityin^ t'ermeiiis uf decomposing stable manure are particularly numerous and 

 vigorous It has long been a matter of wonder among agronomists to find stall 

 manure, when scattered over a field, producing fertilizing results far in excess of 

 what could bo ex , r; i rmin the quantity of plant food contained therein. In the 

 light oi" 111 ' r;i( - U ;il)()\r. however, these results are no longer surprising. 



In the (iisii ihut ; iii;i,nin' large numbers of a particularly vigorous species 



of nitrityini; ui j r.S-i i- ,,f incorporated with the soil, and these and their progeny 

 coutimie to ( :;i i ( is>> ilioir :icvi\ ity upon the inert nitrogen of the soil when the more 

 easily nitritiable ponious of the stall manure are exhausted. 



Let us, then, use stable manure, and accord to it the high apprecia- 

 tion that it deserves. It is a most valuable fertilizer, particularly 

 for use in old orchards, where, owing to the size of the trees, it is 

 difficult to grow cover-crops successfully. Before leaving the subject 

 I desire to add. however, that I do not regard the exclusive use of stable 

 manure as desirable. It is a one-sided, unbalanced fertilizer; being 

 rich in nitrogen as compared with phosphoric acid and potash. In 

 its action it will combine with its nitrogen the available potash and 

 phosphoric acid already in the soil, and year after year the available 

 supply of these two constituents will become less. A bulletin of the 

 New York Station cites the fact that the soil of many farms in that 

 State has actually become exhausted by this process, where the exclu- 

 sive use of stable manure has continued for long periods of years. 

 Therefore, when using stable manure continuously, it seems to be 

 evident that we should use some form of potash with it, and possibly 

 both phosphate and potash. 



CO^^R CROPS. 



I mentioned the use of stable manure and the growing of cover-crops 

 as the two best methods for maintaining the requisite supply of humus 

 in the soil. Cover-crops easily rank first in this particular ; and. besides 



