278 CITRUS FRUITS AND THEIR CULTURE. 



forming in a part of his orange grove. He irrigated a 

 few trees that were within reach of the domestic water 

 supply, and followed this up at the proper time with thor- 

 ough cultivation. After each irrigation he cultivated a 

 little deeper. As a result of deep irrigation and cultiva- 

 tion, the soil took in water as readily as ever and the 

 trees regained their vigorous appearance. He simply 

 used a chisel-tooth cultivator and plenty of water. 



"A somewhat different case was that of Mrs. McKen- 

 zie, of Riverside, whose orange grove failed to be profit- 

 able, though apparently well irrigated. This orchard 

 had been cultivated to the same depth until a hard, clay 

 'plow-sole' had been formed. The stratum of hard sub-soil 

 was several inches thick and contained a number of large 

 surface roots. She wrote to the California Experiment 

 Station, sending samples of soil for examination. It was 

 found that the plow-sole prevented the irrigation water 

 from reaching the deeper roots, and she was advised to 

 plow the entire orchard, roots and all, as deep as the 

 plow would go. This was done, much to the alarm of 

 many growers, and great numbers of orange roots of all 

 sizes were turned to the surface. Following further ad- 

 vice, she irrigated and cultivated the ground deeply, and 

 the following season she harvested the largest crop ever 

 taken from this grove. 



"The Glendora grove, to which allusion has been 

 made, had had deep cultivation from the beginning, and 

 the roots were mainly below the so-called hard-pan. The 

 McKenzie grove had many roots in the hard 'plow-sole,' 

 so that the only remedy was to destroy these useless roots 

 and force the growth of new and deeper ones, at the same 

 time giving the irrigation water a chance to penetrate. 

 This rather drastic root-pruning was necessary, and if 



