The Almond in California

by R. H. Taylor

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.

PRUNING

The almond trees normally set a larger number of fruit buds than they are capable of maturing. The number of blossoms set on a healthy tree to produce a full crop will be generally not more than 20 per cent of the total number which opened in the spring, and oftentimes much less. It has frequently been noted that trees which are somewhat lacking in vigor are inclined to set a larger number of fruit buds than those that are strong and vigorous. The normal set of blossoms on a young, vigorous tree is shown in [figure 2]. The result is that with the sub-normal strength of such trees being distributed among the extra number of fruit buds, the latter are not able to develop into the strong, healthy buds they should. The results of such conditions have been discussed on [pages 23, bottom, and 24, top]. One of the best means of securing and keeping healthy, productive trees is by careful, thoughtful and systematic pruning. The treatment given most of the almond orchards would indicate that the growers consider pruning to be one of the least important of the cultural practices.

Fig. 8.—Typical Drake almond tree in University Farm orchard; nine years old.