THE ORANGE IN CALIFORNIA CULTIVATION. Ill 



prevailing ten years ago. But in spite of the much we have 

 learned, new problems arise continually, which require new 

 study. Just now one that is attracting considerable attention 

 is the difficulty found, especially in some of our older orchards, 

 of getting the soil to take irrigating water as readily as is desir- 

 able. The cause is found in a hard stratum of earth just under 

 the cultivated portion, varying in thickness from a few inches 

 to a foot or more, which is sometimes almost impervious to 

 water. The result is, difficulty in keeping the root stratum 

 underneath sufficiently moist. This hard layer is doubtless 

 caused by frequent wetting and drying out. Not being dis- 

 turbed, it becomes harder after each irrigation, the same as the 

 surface would if not carefully stirred, only to a lesser degree. 

 The cultivator shovels constantly running over this layer also 

 has a firming effect on it. The first question is, how best to 

 get rid of this objectionable stratum of earth. In the East, we 

 remember, that it is very desirable to break up the subsoil 

 without bringing it to the surface. This their modern subsoil 

 plow does effectually. The plow is now being introduced here 

 for the purpose of breaking up this hard layer. And those who 

 have tried it, so far as I can ascertain, seem favorably impressed 

 with the results. The plow is usually run in the center of the 

 spaces between the trees once each way from twelve to sixteen 

 inches deep. It does not disturb the surface further than the 

 mark left by the thin standard, but lifts the subsoil sufficiently 

 to break it up to the width of twelve to twenty inches on each 

 side. The draught, where the ground has become hard, is 

 necessarily heavy, even with the small shoe and thin standard, 

 requiring from six to eight good horses. These narrow broken 

 spaces take in the water very rapidly. How long it will take 

 it to work out under the unbroken squares till the entire root- 

 bed is wetted, and how permanent may be the results, are ques- 

 tions yet to be determined. If the same general treatment of 

 the orchard is followed, the hard layer will doubtless gradually 

 re-form, and this special process need to be repeated. 



An important consideration is the effect of the disturbance 

 of the roots necessarily made by this deep plow. I have not 

 been able to see its workings in an old orchard. In orchards 

 seven to ten years old the leaders at that distance from the 

 trees have not become large. But the root stratum commenc- 

 ing immediately below the cultivated portion, to an indefinite 



