The Almond in California

by R. H. Taylor

CULTURE

Soil Handling.—The almond is one of the most exacting of fruits as regards its cultivation. The assumption is very often made by growers that because the tree will live through periods of prolonged drouth, it will also thrive under careless or poor methods of cultivation. That this is entirely erroneous may be inferred from the fact previously referred to that the almond draws more heavily upon the plant food of the soil for the ripening of its crop than any of the common orchard fruits. Experience has abundantly proved that many almond orchards are not bearing profitable crops because the requisite soil constituents are not available in sufficient quantities during the long growing season. The reasons for this condition may be one or several. First, there may not be sufficient moisture available throughout the season, or it may not be distributed evenly or in sufficient amounts throughout the entire soil area. Second, there may be insufficient aeration of the soil; and third, there may not be sufficient humus to fix the soluble plant food in the soil and render it readily available as needed by the roots.

Proper distribution of moisture in sufficient quantities is essential to secure adequate solution of the mineral elements needed by the roots for the use of the tree in all its parts. Sufficient aeration is needed to provide for the normal oxidation and weathering of the soil particles, and also for the respiration of the roots themselves.

There seems to be no question about the value of spring plowing and cultivation to put the soil in good physical condition, but many growers apparently question the value of summer cultivation. Though the surface of the soil appears to be unchanged after a period of several months, the fact is entirely overlooked that the structure of the mulch has been gradually changed and capillarity to the surface has been restored. The result is that evaporation takes place so rapidly from soils in such a condition, as well as from the leaves of the trees, that long before the end of the season the moisture is practically gone.

The methods and tools used are much the same as for other orchard trees and it is only necessary to call attention to items likely to be neglected. Spring plowing should vary in depth from year to year to avoid the formation of an impervious plow-sole. The depth to plow ranges from a minimum of six inches to ten or twelve inches or more as desirable. Summer cultivation should be kept up at least once a month, and preferably oftener, throughout the summer months and the soil should be stirred to a depth of four inches to provide a mulch sufficient to hold the moisture effectively in the hot, dry climates where almonds are grown. The actual number of cultivations necessary will depend on the types of soil. Harness with projecting hames or broad singletrees or with projections of any kind to catch on the branches or bark of the trees should never be used in an orchard.

Cover Crops.—Constant cultivation throughout the summer allows the humus to be burned out of the surface soil and, by hindering the growth of vegetation, prevents the addition of a natural supply of humus to replace that which has been lost. It is necessary, therefore, that some artificial means be used to supply the deficiency. The annual growth of winter cover crops to be plowed in during the spring, while not entirely replacing the humus burned out in the summer, serves to reduce the annual loss and at the same time assists materially in improving the texture of the soil.

A shade crop, such as alfalfa, may be grown successfully in mature orchards where irrigation water is available, and where perfect drainage of surface and subsoil can be maintained. During the first four or five years or more such a crop is generally a detriment to the almond trees, but after the trees reach maturity it may be beneficial in securing better drainage and aeration of the soil by the penetration of the numerous roots to considerable depths and their consequent decay when it is plowed in. Alfalfa also supplies nitrogen to the soil and thus gradually increases the fertility. The great danger with such a crop is that the orchardist is apt to irrigate for the alfalfa at the expense of the trees because of the quicker returns from the former. In deep, rich soils the cuttings of alfalfa may be removed from the land, though the last cutting in the fall should be allowed to remain on the land. Where this is done, a natural mulch is obtained which helps to increase the supply of humus. If the soil is poor and lacking in humus it is better to leave more cuttings of the alfalfa on the ground to decay. As this continues the soil becomes, through the increased accumulations of humus, more permeable and yet more retentive of moisture, and less irrigation will serve the trees more effectively.

During the early spring a well-established stand of alfalfa may assist so materially in getting rid of the excess water in the soil that sour-sap, fruit drop and kindred ills resulting from the unseasonable warm weather while the ground is filled with water and the trees are starting into growth, may be greatly reduced or avoided entirely.

Irrigation.—Water for irrigating almonds must always be used with great care whether it be in summer or winter. All water should be so applied that it will readily spread through the soil and not remain in excessive quantities for any length of time. Water should not be applied during blossoming or setting of the fruit in the spring or within a week or more of harvest. On the other hand, water applied just before the hulls commence to open, where the soil has become too dry, greatly reduces the number of sticktights, or almonds in which the hulls stick to the ripening nuts without opening.

Fertilization.—Little or no systematic work has been done up to the present time in the use of commercial fertilizers on almonds. The use of barnyard manure is desirable wherever obtainable. The value of almond hulls as fertilizers is doubtful because of the difficulty of bringing about their thorough decay when applied in sufficient quantities to be worth while. The use of lime to correct soil acidity and for improving the texture of heavy soils will be found desirable where this is obtainable at reasonable rates.