One Thousand Questions in California Agriculture Answered Part 58

We have just put out 50 acres to walnuts. The party who put them out wants me to have some boxes or troughs made 15 inches long with a 3-inch opening, and put in on the slant so as to have the water hit the roots.

Many such arrangements of boxes, perforated cans, pieces of tile, etc., have been proposed during the last fifty years in California for accomplis.h.i.+ng the purposes which are mentioned in your letter, and all such devices have been abandoned as undesirable. They may bring the water to bear upon a lower level as intended, but the free access of air and the fact that, with their use, proper stirring of the soil is neglected renders them undesirable. The best way to water young trees singly is to make a trench around tree, but not allowing the water to touch the bark, applying the water and then thoroughly hoe when the surface soil comes into proper condition. Young trees treated in this way, with the surface always in good condition, do not require much water. The amount depends, of course, upon whether the soil is naturally porous or retentive.

Underground Irrigation.

How extensively used and with what results is the underground tile system for irrigation used, and what especial character of soil is it best suited for?

Not extensively at all; in fact, if there is an acre of it which has been for three years in continuous and successful operation, it has escaped us. After forty years of trial of different systems, none has demonstrated value enough to warrant its use. Theoretically, they are excellent; in practice they are defective. Surface application in different ways, according to the nature of the soil, accompanied with thorough cultivation, is the only thing that at the present time promises satisfactory results, except that where the land suits it, irrigation by underflow from ditches on higher elevations is being successfully used on small areas in the foothills. For gardens the most promising arrangement seems to be a laying of drain tiles rather near the surface, which shall be taken up each year, cleaned of silt and plant roots, and relaid along the rows before planting; but this calls for too much labor, except perhaps for amateur gardeners. The kind of soil best suited to such a system is a medium loam which will distribute water sufficiently to avoid saturation and air-exclusion. Both a heavy soil which does this, and a coa.r.s.e sandy loam which takes water down out of reach of shallow-rooting plants too rapidly and lacks capillarity to draw it up again, are ill adapted to underground distribution.

Irrigation of Potatoes.

Will you kindly tell me when is the proper time to irrigate potatoes, before they bloom or after they bloom, and do they require much water?

It should seldom be necessary to irrigate potatoes after the bloom appears. Potatoes do not need much water, and there is danger of giving them too much. It is absolutely essential to see that there is no check in the growth of the plant, for once the growth is at all checked by drought, and irrigation is done, a new lot of potatoes start and new and old growth of tubers are worthless. Give what irrigation is needed and make cultivation do the rest. The secret of success is keeping the soil continually at the right moisture, so that the first growth of the plant may continue regularly until the tubers are brought to maturity.

Irrigated or Non-Irrigated Apples.

Where soil and climatic conditions are favorable to the raising of apples, what effect has irrigation an them?

The commercial product of California apples is chiefly made upon deep soils in districts of ample rainfall so that the fruit can be perfected and the trees maintained in thrift by thorough cultivation and without irrigation. In the foothill and mountain regions, however, apple trees are irrigated and first-cla.s.s fruit produced by the process. There is no particular virtue in the absence of irrigation nor in the presence of it. All that the tree requires is that the moisture supply should be adequate and timely. There are undoubtedly many apple orchards grown without irrigation where a little water during the latter part of the summer would be a great advantage for the perfection of winter varieties.

Irrigating Walnuts-Checks or Furrows.

Which is the best method to irrigate a tract of 25 acres of sandy sediment sail, nearly level, preparatory to planting walnuts?

By all means use the furrow system of irrigation unless your land should be so light that the water would sink in the furrows and distribution would be very unequal without covering the whole surface as is done by filling checks. When the land cannot be covered well by the furrow system, checking is resorted to, but not otherwise.

Summer and Fall Irrigation.

Is it desirable to irrigate peach trees in the fall after the crop is gathered?

The popularity of autumn irrigation for peaches in the San Joaquin valley is based upon the experience of the last few years where trees that have been allowed to become dormant too early in the season and have been weakened by a long period of soil-drought during the autumn, have cast their blossoms or manifested other indications of weakness during the following year. It is thoroughly rational to apply irrigation to hold the leaves and secure their service in the strengthening of bloom buds for the following year by irrigation. Such irrigation should be applied immediately after the fruit is gathered or even before that, if the yellowing of the leaves indicates lack of strength in the tree and the frequency and amount of irrigation during the autumn depends upon whether the soil will hold moisture enough to carry the tree to its proper period of dormancy. This may be determined by the aspect of the trees and by digging down two or three feet to see whether the soil carries moisture which is likely to be sufficient until the coming of the rains. Whether late irrigation will be necessary is also determinable by the character of the soil; on close retentive soil it may not be necessary, while on loose, sandy or gravelly soil it may be essential to the life of the tree. One has to settle all these matters by judgment and not by recipe.

Fertilizers in Irrigation Water.

Do you recommend putting fertilizers in irrigating water? I am about to water the orchard and am thinking of putting some nitrate in the water.

You can distribute any soluble fertilizer by dissolving it in irrigation water, but few have ever done it because of the difficulties of getting equal strength in running water. It is much easier to distribute on land before irrigation.

Irrigating Alfalfa on Heavy Soils.

How does alfalfa succeed on adobe and soils slightly modified from it?

Does irrigation work well an adobe planted to alfalfa?

If you get the irrigation adjusted so that the soil shall not be water-logged and so that the water does not stand on the surface when the sun is hot, you can get plenty of good alfalfa on a heavy soil.

Irrigation on adobe soils must be done more frequently and a less amount at each application to guard against the dangers named above.

How Much Water for Crops?

Same of my land is heavy but the most of it is light soil. I want alfalfa mostly, same potatoes and grain, and later oranges, olives and other fruit. How much water in inches or acre feet is required per acre per year far the irrigation of it?

The amount of water required to grow different crops depends upon the crop itself, upon the time of the year in which it grows, the character of the soil, etc. There is no such thing as stating how much water would be used for all crops on all soils, and at all times of the year. The range would be from, say, ten acre inches for irrigation of deciduous fruits, which need moisture supplementary to rainfall; twice or thrice as much for citrus fruit trees; four or five times as much for alfalfa where a full number of cuttings are required. These are, of course, only rough estimates which would have to be modified according to local rainfall and soil character. Water should be applied frequently enough to keep the lower soil amply moist. A color of moisture is not enough and a muddy condition results from too much water. One has to learn to judge when there is moisture enough, and a good test of this to take up a handful of soil, squeeze it and open the hand. If the ball retains its shape it is probably moist enough. If it has a tendency to crack upon opening the hand, it is too dry. This test, of course, is somewhat affected by the character of the soil, but one has to form the best judgment possible how far allowance has to be made for that.

Sewage Irrigation.

What is the usefulness or harmfulness of the outflow from septic tanks for use an fruits and vegetables?

There is no question as to the suitability of the affluent from a septic tank for irrigation purposes. Waste waters are sometimes injurious when they are loaded with antiseptics, but the septic tank will not work unless it has a chance for free fermentation in the absence of antiseptics, therefore, this objection against waste water does not hold with the out-flow from septic tanks. It has the advantage over straight sewage irrigation because fermentation in the septic tank is believed to free the water from many dangerous germs, though not all of them.