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Auction will often require it to facilitate spading and working the soil. a. Sprinkle the garden area long enough to moisten the soil to a depth of 12 inches. b. Do not work the soil too soon after irrigating or a rain. It is too wet if it clings to a clean spade or other tool. Sandy soil can usually be worked 1 to 2 days after water* ing; loam 3 to 4; and clay 5 to 7. 2. Irrigating for Germination during the D ry Season a. Sprinkle immediately after seeding, Wetting the soil to a depth of about 3 inches. Sprinkling with a fine spray from an ordinary hose nozzle or lawn sprinkler (fig. 1) will be the most practical and economical method. b. Repeat the procedure often enough to maintain moisture around the seed and to prevent crusting. This will mean sprinkling every day or two. During high temperature or strong wind, Sprinkle oftener than when it is cool or calm. c. Continue frequent sprinklings until the plants appear. d. To reduce the rate of evaporation and, therefore, the number of sprinklings, a mulch over the ridge may be used. Materials that will serve for this mulch are grass clippings, straw, newspaper, boards, or gunny sacks. If the mulching material will interfere with growth, it should be removed as soon as the plants have emerged. 3. Irrigating for Germination in the W et Season a. Do not plant when the soil is too wet. b. Sprinkle between rains when the soil dries out to a depth of % inch. 4. Irrigating at Tim e o f Transplanting a. Set the plants in holes in moist soil, and press the soil firmly around the roots. b. Apply % pint of water to each plant. c. Cover the wetted ground with dry soil. d. Irrigate in a few days if necessary. Young plants may wilt after transplanting, in which case, they should be irrigated. 5. Irrigating Y ou ng Plants With summer and fall planting such irrigation is necessary in all districts. With winter and spring planting it will seldom be necessary in northern California until the root system be­comes established, except in years of low rainfall; hut it will usually be necessary in southern California and in the southern San Joaquin Valley. a. After the plants are up, gradually lengthen the interval between irrigations and increase the quantity of water. Continue to use the sprinklers. b. The root system will be fairly well 'established 3 to 6 weeks after plant emergence. Then develop the irrigation practice as suggested in section 6. Quick-maturing crops will establish their root systems sooner than slow-matur­ing crops. 6. Irrigating Older Plants during the Main Period o f Growth The general principles of irrigation will apply to all gardens. For effective and economical irrigation the home gardener should also consider the soil type, the depth of rooting of various crops, and the.climate during the growing period. a. Irrigation may be accomplished by the use of sprinklers, furrows, or basins. b. A continuous and adequate moisture supply must be maintained throughout the growing season. The soil acts as a reservoir of water for plant use, and the purpose of irrigation is to replenish this supply. c. Clays hold more water than sandy soils, and loamy soiJi are intermediate between sands and clays (table 1 ). More water, accordingly, can be added to a clay soil than to a sandy soil without penetrating blow the root zone; and so less frequent and heavier irrigation can be applied on a clay soil (figs. 5 and 6)'. d. Crops vary in the development of their root systems; that is, some root to relatively shallow depths, whereas others penetrate deeply (table 2 ). At each irrigation, moisten the soil to the rooting depth of the particular crop. For deeper-rooted plants more water should be applied at each irrigation, and the interval between irrigations may be longer than for shallow-rooted crops. e. The depth of water penetration can be tested with a sharp­ened stick or a probe which will penetrate the wet soil easily, but will stop or require force when dry soil is reached. Other methods for estimating the penetration of water may be used. /. Plants require more water in warm, dry weather than during cool, humid periods. Likewise, more frequent irri­gations will be necessary during the summer in the hot interior valleys than in the cooler coastal areas. SOIL TYPES Ordinarily, soils are classified broadly as. sands, loams, • and clays. Table 1 compares the relation of the physical and water properties of these three soil types. TABLE 1 Comparison of the P hysical and W ater Properties of Three Soil Types* Soil and texture Hate of water penetration • Amount of water usable in soil when wet General frequency • of irrigation Depth of soil wetted .by water 1 inch deepf Sandy g coarse-grained. Rapid Small days 4-10 inches 12 Loams, intermediate texture.................. Intermediate Intermediate 8-15 6-10 Clay, fine-grained....... Slow Large 15-30 4-5 * See figures 5 and 6. t Water “ 1 inch deep” is equivalent to an inch of rainfall. D EPTH OF R O O T IN G OF VEGETABLE CROPS In table 2 the depths of rooting f o r :various vegetable crops are expressed as shallow, moderately deep, and deep. Shallow-rooted plants may root to 2 feet in depth, moderately deep-rooted ones to about 4 feet, and deep-rooted ones to 6 feet or moreTTo group the' Crops in the garden according to their rooting depths will simplify the irrigation procedure. TABLE 2 R oot Depths of Vegetable P lants Shallow-rooted Moderately Deep-rooted (down to 2 feet) deep-rooted (down to 4 feet) (down to 6 feet) Broccoli, sprouting Beans; bush I Artichoke Brussel sprquts Beans, pole - Asparagus Cabbage Beets Beans,, lima Cauliflower Carrots. Cantaloupes Celery Chard Parsnips Corn, sweet I Cucumbers Pumpkins Lettuce Eggplant Squash, winter Onions Mustard Sweet .potatoes Potatoes, Irish 'Peas Tomatoes Radish Spinach Peppers Squash, summer Turnips Watermelons % TABLE 3 Suggested Frequencies of Irrigation for V egetables w ith Different R oot Depths on the T hree Main Soil T ypes Soil type Shallow-rooted ' .crops • (down to 2 feet . Moderately deep-rooted (down to 4 feet Deep-rooted (down to 6 feet) days days day s ' Sandy............................. 4-6 . 7-10 . 10-12 Loam.............................. 7-10 10-15 15-20 Clay....... .................... 15-20 20-30 30 or more Hard pan, bedrock, or a high water table close to the sur­face will limit the penetration of plant roots. In irrigating under such conditions take special care to avoid waterlogging the soil. Of necessity, light applications of water should be made. Under this condition all crops will be treated as though they were shallow-rooted, and the frequency of irrigation sug­gested for shallow-rooted crops in table 3 should be followed. Fig. 4.—Preirrigation of a small garden area by the basin method. Small levees 5 inches high form the basin, which is 6 feet long and 5 feet wide. This method also may be used in irrigating small blocks of plants. FREQUENCY OF IR R IG A T IO N A satisfactory irrigation program can be devised by reference to the information in table 3. Factors to be considered are the crop, the soil type, and the temperature. Onions or potatoes on a loamy soil, for example, should be irrigated every 7 days when the temperature is high or every 10 days during cooler Weather. Other methods of determining when to irrigate include ex­amining the soil and the plants. Soils change from a dark to, a lighter color as they dry out. When the soil appears dry at, a depth of 6 to 12 inches, an irrigation should be given. To detect symptoms of water shortage by examining the plants requires considerable experience and is therefore not a reliable guide for most home gardeners. Plants receiving in­sufficient Water differ in appearance. Corn leaves, for example, curl; beets, radishes, peppers, spinach, wilt; the older leaves at the center of the cucumber, cantaloupe, bean, pumpkin, and watermelon plants, die; carrots, potatoes, and tomatoes may change color slightly, usually becoming a darker green, often bordering on bluish or grayish, instead of the light green of new growth. Most of these indications result from a check­ing of the growth, which may reduce the yield. When these symptoms appear, irrigate immediately. M ETHODS OF IR R IG A T IO N After plants are established, sprinkler, furrow, or basin irri-S gation may be used. Sprinkler Irrigation The application of water by sprinklers (fig. 1) requires little labor and usually results in fairly uniform coverage and pene­tration (fig. 5 ). This method may be used for all flat plantings on either level or slightly sloping land and also for row plant­ings on raised beds. There is one disadvantage: it is difficult to wet the soil in small gardens to different depths, in accord­ance with the rooting depth of the various plants, unless the crops are grouped according to their rooting habits. In gardens where the crops have not been so grouped, sprin­kling will be fairly satisfactory if the entire soil is moistened to 2 feet, the depth suggested for shallow-rooted crops. In this case one will treat all the crops as shallow-rooted and should follow the approximate frequencies of irrigation presented in the left-hand column of table 3. The common sprinkler used for small home gardens and lawns will cover a circle of varying diameter according to the water pressure and the type of sprinkler. The amount of water thrown to the outside of the circle is usually small. For uni­form application, accordingly, set the sprinkler so that the area covered by each new setting overlaps "the wetted area of the previous setting (fig. 5 ). If the diameter of the circle cov­ered by the sprinkler is, for example, 20 feet, one can dis­tribute the water satisfactorily by spacing the settings of the sprinkler 10 feet apart in the planted row, then moving to the row 10 feet distant from the first, and repeating the 10-foot settings. Be careful to run the water long enough for the de­sired penetration, testing this with a sharp stick or iron rod. Where the soil takes water slowly and runoff results after short periods of sprinkling, it may be well to employ other methods of irrigation. Furrow Irrigation The furrow method may be used for flat plantings when small ditches have been constructed between the rows and for plantings on raised beds. The length of furrows will be deter­mined by the size and shape of the garden plot. Short furrows 10 to 40 feet long should be level—that is, with little or no grade. In a hillside garden, the furrows should be constructed at right angles to the general slope. Longer furrows should