This section is from the book "The Potato: A Compilation of Information from Every Available Source", by Eugene H. Grubb, W. S. Guilford. Also available from Amazon: The Potato: A Compilation Of Information From Every Available Source.
The Sacramento Valley is watered and has been made by the Sacramento River and its tributaries. It is a vast, alluvial plain, comprising over 2,500,000 acres of land.
The annual rainfall in the valley is about eighteen inches, and it comes entirely during the winter months.
Without irrigation the principal crop has been grain - wheat and barley. This is sown in the fall, gets the benefit of the winter rains, and is ripened in early summer. From June until the rains come in October the country is dry and brown.
With irrigation, every crop of the temperate or semitropical zones can be grown.
The Sacramento Valley Irrigation Project of 150,000 acres is the most important undertaking in the valley. Water is taken from the Sacramento River under an Act of Congress.
There are wonderful possibilities for early potate growing on some of the lands in this valley.
The potato being a cool weather crop, in hot countries it is grown to the best advantage during the cooler parts of the growing season. For instance - in the Sacramento Valley there are two growing seasons each year: Potatoes planted in February or early in March are dug in July or August and those planted in August are dug late in November. Many failures are recorded when the crop is planted in May or June because of the too intense heat of atmosphere and soil during the period that the tuber should be forming and developing.
This climatic situation makes two crops of potatoes possible where soil conditions are right and cultural conditions are properly managed.
The potato-growing business is a very profitable one now on the bottom lands along the Sacramento and San Joaquin rivers and on the islands and deltas.
The easiest kind of soil in which to grow potatoes is a sandy loam, or one well filled with humus or decayed vegetable matter.
The reason for this is that such a soil is easies4; to work; it does not bake when it becomes dry, it takes water from irrigation in sufficient quantity but does not water-log, it drains readily, and is a mellow, friable medium in which the tubers can develop symmetrically and quickly without too great resistance in order to grow potatoes on heavy clay and clay loam soils, in which the percentage of sand or vegetable matter is very small, it is necessary to do such preparatory work as is necessary to make them open and friable; in other words, to better the mechanical condition.
These heavy clay loam soils are among the richest known in agriculture. This is because they have been made of the finer particles that have been washed out of hills and mountains over a large area. The valleys in which such soils are usually found are really the cream of an entire watershed. A soil that is easier to handle may be very much less rich, because the finer soil particles are held apart by coarse sand of little or no fertility, or by large quantities of decayed vegetable matter.
For this reason about the only problem connected with potato growing on the heavier lands in the Sacramento Valley, is to add sufficient vegetable matter to the soil to hold apart the fine soil particles and make it more loose, open, friable and easily worked.
This can be done by growing alfalfa for several years, filling the soil and subsoil with roots and when it is plowed up turn under a big crop of the green alfalfa to further add to the vegetable content.
Another way would be to grow and turn under successive crops of peas, vetch, or other cover crops.
The addition of large quantities of animal manures is another way to loosen up heavy lands.
In Scotland, one large potato farmer has hauled sand onto heavy clay land to a depth of five inches, incorporating this and large quantities of stable manure into the soil.
On a small, intensely cultivated farm in the Sacramento Valley, where large quantities of animal manures are returned to the soil, and alfalfa and other deep rooted crops grown, it will be easy to have a plot in fine condition for growing potatoes each year.
The Burbank is the most popular variety of the potato in California. For early planting it would be well to try Bliss Triumph and Early Rose. New early varieties should be experimented with. Only by trial can the most profitable varieties be determined. In a warm climate the best seed is generally that imported from colder or high altitude districts.
Preparation for the early crop of potatoes should begin the year previous to that in which the crop is grown. If stable manure is to be applied this should be done the first or second year prior to the raising of the crop. The presence of too much manure before it is thoroughly decomposed or rotted makes a favorable condition for the development of diseases, like scab.
If the land to be cropped in potatoes has been in alfalfa, it is a good plan to first plow it shallow, with a sharp plow, to cut all the crowns, then plow it ten to fourteen inches deep. Land for early potatoes should be fall plowed.
As soon as the ground is in condition in the early spring, it should be disked and harrowed, to make a good seed bed and to "warm it up" as much as possible in preparation for the seed about to be planted.
A practice not now followed, but one that could be used to advantage, would be to plant nothing but whole seed, and start the sprouts in a greenhouse or sheltered spot, so that there is a sturdy sprout developed on each tuber before it is put in the ground. This will advance the maturity of the crop from twenty to twenty-five days.
The furrows may be opened up a few days in advance of the planting, so that warm soil will surround the seed when it is dropped. The seed should be dropped by hand and carefully covered with a shovel plow or ridger.
As soon as the first crop is out of the ground, the ground should be thoroughly worked in preparation for the second crop, if another crop of potatoes is to follow. If potatoes are to follow grain or some other crop the ground should be deeply plowed and a good seed bed made. The ground is warm at this time, so that no sprouting of seed is necessary before planting. Seed from the preceding crop, or northern-grown seed that has been kept dormant in storage may be used.
Cultivation should begin soon after the seed is planted. The first cultivation should be deep, to thoroughly open up a deep root nest in which the tubers are to form. On irrigated land the high ridge system of growing potatoes is usually used, because it makes it possible for the potatoes to develop in a loose, open, well-aired soil, the moisture supply coming through the bottom of a fairly deep furrow into the base of the ridge and being drawn up by capillarity.
The number of irrigations, and the number of cultivations, must be determined by the needs of the soil and the growing plant. No fixed rule can be set, because conditions may change daily. Irrigation water must be used with sufficient frequency to furnish all the moisture the crop needs. Too much is as bad or worse than too little. A shortage of moisture makes a short crop. Cultivation is required as often as is necessary to keep the soil open and mellow.
In the Sacramento Valley the first crop starts out with a sufficiency of moisture in the soil from the winter rains. Late in the spring one - or perhaps two, irrigations might be required while the potatoes are making the greatest growth. After the tubers are full size they are dug.
After the first crop is taken from the ground (whether this be potatoes, another root crop, or grain) the ground should be thoroughly irrigated before a seed bed is made in which to plant the second crop of potatoes. The irrigation of the second crop, during its early growth, will be more important than the early irrigation of the first crop, because the weather is hot and plenty of moisture must be provided for greater evaporation at this season. Irrigation of the second crop must be discontinued in time to permit the ripening of the tubers in dry ground.
The moisture supply to a potato crop must be constant. If the ground is allowed to become too dry, the tubers begin to mature, and when another supply of moisture is provided, a new growth is started, making little wart-like growths on the already formed tubers.
Practically all of the crop in the Sacramento Valley would probably be sold almost direct from the field, making storage unnecessary. If it was desired to store potatoes, a cool, underground cel-car, or a regular cold storage room, should be provided. Heat, rather than cold, is the factor to guard against here.
The potato crop requires deep, thorough preparation and cultivation of the soil; consequently, is a good crop in a rotation. After a crop of potatoes has been grown the soil is in fine mellow condition for a succeeding crop, for in addition to the fine mechanical condition produced, much fer-tility has been made available.
On heavy soil, small "patches" of potatoes are sometimes grown under straw, or some similar material used as a mulch. By this method the seed bed is prepared (mellow and moist), the seed planted very close to, or just at the top of, the ground, then the whole area is covered with straw to a depth of six to ten inches. This settles down, the plants come through it, and the tubers develop beneath.
When planted this way the crop is not touched from the time the straw is placed until the tubers are dug.