As the onion is a shallow-rooted plant, care must be taken not to injure the roots by deep tillage. When hard rains incrust the soil before seeds have germinated, light raking or rolling will be an advantage. Horse cultivators are sometimes employed, especially in the heavier soils, which are difficult to work by hand. However, the additional spacing between rows, required for horse tillage, necessarily limits the yield. If ground has been properly prepared, there will be few instances when the rows should be more than 1 foot apart. Hand wheel hoes must then be employed in cultivating. Both single and double wheel types are in common use, but it is more economical to use double than single wheel hoes when the plants are small. Many growers prefer the single wheels at all stages of growth. Straight rows and uniform spacing are a great advantage in the operation of wheel hoes. The vertical shovels or teeth are most useful in heavy soils, while the horizontal sweeps are most serviceable in light soils. The latter attachments may be used without danger of covering the small plants. It is necessary to cultivate from 8 to 15 times during the season.
Hand weeding and thinning are required. This work is often done by boys and girls. The thinning is usually performed at the first weeding, when 8 or 10 plants are allowed to the linear foot of row, but in very good soils and when large bulbs are desired, the plants should stand about 2 inches apart. Special hand weeders (Figure 7) are in common use. Both weeding and thinning should be avoided as much as possible by the proper preparation of the soil and the adjustment of drills. Figure 92 shows a well-managed onion field on Long Island.
Fig. 92. Field Of Onions On Long Island.
In many sections of the West and the Southwest onions cannot be grown without irrigation, the ground being too dry to supply the moisture necessary. AH of the Bermuda onions of the Southwest are grown under irrigation. The land is flooded before planting and afterwards at intervals of a week or 10 days until the bulbs are full sized, when water is withheld to induce ripening. An increasing number of growers in various parts of the country are employing the overhead system of irrigation, which is ideal when applied to this crop. Sprinkling; before or after planting prevents the blowing of muck and sandy soils and the accompanying disastrous results in young plantations. Irrigation increases yields and insures the crop against loss from drouth.
When the bulbs are to be stored they will keep better if allowed to become fully ripe before pulling. Figure 93 illustrates a field of onions in ideal condition for harvesting; the tops are dead and shriveled and the outer skin of the bulbs dry. While full ripeness is highly desirable, other factors should be considered: There is danger of second growth, especially if there is much rain: better prices for the early crop may be an inducement to gather part or all of the crop sooner than if the bulbs are to be stored; when there are large areas to harvest it is necessary to start in ample time in order to complete the work while weather conditions are favorable and before there is loss from rain. Harvesting is often begun when most of the tops have merely turned yellow. Early pulling in the North is especially important for bulbs of foreign types. August and September are the busy harvesting months in the North, and March and April for the Bermuda crop in the South.
Fig. 93. Field Of Onions At Harvest.
It is the universal custom to partially dry or cure the crop in the field. After removing the bulbs by hand or with a plow, if they are covered with soil, 8 or 10 rows of onions are thrown together into windrows, allowed to remain undisturbed for a few days and then stirred occasionally with a wooden rake to facilitate drying. White bulbs are quickly injured by exposure to sun and rain, so that these must be cured under some kind of cover. Topping is usually done in the field after the bulbs are ready for storage, the tops being twisted off by hand or cut with sheep shears. Extensive growers sometimes use topping machines, which also grade and deliver the bulbs in bags or crates. The curing process is continued in sheds, cribs or other suitable houses until the bulbs are ready for permanent storage.
Onions should not be stored until thoroughly cured. Soft and immature bulbs and bulbs with thick necks should be sold when gathered, because they will not keep well. A bright appearance is an important characteristic of the most salable bulbs. To secure this the crop should not be exposed to the weather longer than absolutely necessary. The onions are usually kept in crates or bags, in sheds, or covered in the field, for several weeks, and then screened to remove loose skins before placing in permanent storage. At this time they are also sorted to remove soft or decaying onions.
The United States Department of Agriculture (U. S. D. A. Farmers' Bulletin 354, p. 25) gives the following information in regard to storing this crop: "The essentials for the successful storage of onions are plenty of ventilation, storing in small quantities, a comparatively low temperature, dryness, and safety from actual freezing. Any building wherein the above conditions may be secured will answer, but houses of the type shown in Figure 94, which are built especially for the purpose, are most satisfactory.
"The construction of the storage house should be double throughout, with plenty of felt or paper lining. Both top and bottom ventilation should be provided, and the ventilator openings should have windows that may be closed to control the temperature. The floors are constructed of narrow planks with «-inch spaces between the planks for the passage of air. Bottom ventilation is frequently secured by means of drain pipes built into the foundation at the surface of the ground. These pipes are carried some distance toward the center of the house. They discharge the cool air at a point where it is most needed.