CULTIVATION OF CITRUS GROVES. 279 



the Glendora grove had been cultivated to a uniform depth 

 a few more seasons, deeper plowing and the destruction 

 of the surface roots would have become inevitable there 

 also. The breaking up of all hard layers of soil caused 

 by improper cultivation or careless use of water is of the 

 first importance to the health and profit of an orchard. 



"After Mrs. McKenzie's experience at Kiverside, pre- 

 viously mentioned, sub-soilers of different forms were 

 used, and the idea soon became common among growers 

 that the deeper a plow could be run, the better would be 

 the results that would follow. The injurious results of 

 such practice cannot be estimated without careful study 

 of the root systems of orange trees on various stocks and 

 soils. A number of bearing citrus groves were so much 

 injured by the reckless use of sub-soil plows, that the 

 leaves of the trees actually wilted down immediately after 

 the operation. In these cases, the sharp-cutting plow 

 was run close to and on all sides of the trees. When trees 

 over ten years of age, which have been subjected to uni- 

 form shallow plowing and irrigation, are submitted to 

 such treatment, they probably lose at one blow not less 

 than seventy-five per cent of their active roots. The shock 

 is such that it would take several years of careful treat- 

 ment to restore the trees. 



"It is almost always more economical to use a sub- 

 soiler or plow where 'irrigation hard-pan' has been formed 

 than it is to use the large amount of water necessary to 

 soften it; but according to the best practice the deepen- 

 ing of cultivation should be gradual, and the implement 

 should never run deeper than fifteen inches. One must 

 remember that the really serious loss in sudden deep culti- 

 vation comes from the destruction of thousands of fibrous 



