WHEN TO USE FERTILIZERS 141 



properties, as is shown in the chapter on the fruit soils of California. 

 But certain of these soils are already showing the need of refreshment, 

 and intelligent growers are quick to minister to the lands which are 

 giving them such generous returns, as they can well afford to do. 



WHEN IS FERTILIZATION NECESSARY? 



Though the use of fertilizers by our fruit growers is beginning, it 

 should be plainly stated that at present, except perhaps with citrus 

 fruit trees, or the oldest orchards of other fruits, it is not yet the rule 

 that such applications are necessary. There are some soils which are 

 really too rich for fruit. There is sometimes an over-rank growth of 

 wood, which delays or prevents the formation of fruit buds, and there 

 is a marvelous development of fruit which is inconsistent with the high- 

 est quality. For this reason the grower should not conclude, from the 

 foregoing general remarks concerning the need of fertilization in Cali- 

 fornia, that he must manure his soil whether it needs it or not. Espe- 

 cially is this the case with young trees, in which the wood growth is 

 easily over-stimulated. As with irrigation, so in fertilization; the tree 

 or vine itself will give the observing grower hints as to its needs, and if 

 the growth of wood and color of foliage are such as obviously indicate 

 health and vigor, it may be concluded that the plant needs nothing but 

 good cultivation and intelligent pruning. 



Usually cases of over-rich ground will cure themselves as the trees 

 attain size and full bearing, and it is then that fertilization may be 

 necessary. When the tree or vine which has been properly pruned and 

 cultivated is not able to mature a good weight of well-developed fruit, 

 and make a satisfactory wood growth, usually at the same time showing 

 some degree of distress by the color of its foliage, it needs help ; and 

 if the grower is sure that the trouble is not from lack of moisture in 

 the soil, he should bestir himself in the manuring of his orchard or 

 vineyard. In examining the soil for moisture, one should dig deeply, for 

 there have been cases of moisture near the surface, and drouth below. 



WHAT FERTILIZERS APPLY TO FRUIT TREES AND VINES 



A discussion of this subject from a chemist's point of view is 

 beyond the scope of this volume. The results of research at the Uni- 

 versity Experiment Station at Berkeley are summarized in the treatise 

 on soils by Dr. E. W. Hilgard, who maintains the position that the 

 most intelligent and economical choice of fertilizers is to be made 

 after ascertaining by analysis in what constituents the soil is deficient 

 and in what it is well supplied. Some applications made in conformity 

 with suggestions based upon analysis have proved very satisfactory. 

 But as soils vary within narrow limits of area, there must be analysis 

 for each soil in question. 



Approaching the matter of choosing fertilizers without soil analysis, 

 the method by local trial is open. In this recourse there is danger 

 of error, as pointed out by Dr. Hilgard, 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 com- 



