Four or five feet of good soil over a hardpan, which was somewhat porous, is likely to be satisfactory for orange planting. There has been trouble from hardpan too near the surface and from the occurrence of a hardpan too rich in lime, which has resulted in yellow leaf and other manifestations of unthrift in the tree. Discussion of this subject is given on page 434 of the fifth edition of our book on "California Fruits," where we especially commend a good depth of "strong, free loam." This does not mean necessarily deep. The orange likes rather a heavier soil, while a deep sandy loam is preferred by some other fruits. If you keep the moisture supply regular and right and feed the plant with fertilizers, as may be required, the soil you mention is of sufficient depth - if it is otherwise satisfactory.
Oranges Over High Ground Water.
Does California experience show that citrus trees can be grown upon land successfully where the water-level is 6 feet from the surface; that is, where water is found at that level at all seasons and does not appear to rise higher during the rainy season?
We do not know of citrus trees in California with ground-water permanently at six feet below the surface. If the soil should be a free loam and the capillarity therefore somewhat reduced, orange trees would probably be permanently productive. If the soil were very heavy, capillary rise might be too energetic and saturate the soil for some distance above the water-level. In a free soil without this danger the roots could approach the water as they find it desirable and be permanently supplied. Orange trees are largely dependent upon a shallow root system, the chief roots generally occupying the first four feet below the surface. From this fact we conclude that deep rooting is not necessary to the orange, although unquestionably deep rooting and deep penetration for water are desirable as allowing the tree to draw upon a much greater soil mass and therefore be less dependent upon frequent irrigations and fertilizations.
Depth of Ground-Water.
Is there probable harm from water standing 12 feet from the surface in an orchard? Also probable age of trees before any effect of said water would be felt by them? The soil is almost entirely chocolate dry bog. - W. E. Wahtoke.
Water at twelve feet from the surface is desirable, and water at that point will be indefinitely desirable for the growing of fruit trees. Of course, conditions would change rapidly as standing water might approach more nearly to the surface, a condition which has to be carefully guarded against in irrigation. But it can come nearer than twelve feet without danger.
Summer Fallow and Summer Cropping.
I own some hill land which has been run down by continuous hay cropping. I am told that a portion must be summer-fallowed each year, but I wish to grow some summer crop on this fallow ground that will both enrich the soil and at the same time furnish good milk-producing feed for cows - thoroughly cultivating it between the rows. What crop would be best? I am told the common Kaffir or Egyptian corn are both soil enriching and milk producing.
If you grow a summer crop on the summer-fallowed upland, you lose the chief advantage of summer fallowing, which is the storing of moisture for the following year's crop. A cultivated crop would waste less moisture than a broadcast crop, surely, but on uplands without irrigation it would take out all the moisture available and not act in the line of a summer fallow.