by W.R. Beattie, USDA Bulletin 1909
As with so much of the older reprint material we offer, you are encouraged to do your homework and make sure that the practices are suitable for your region and farm, as well as meeting whatever standards you have chosen to adhere to. SFJ
The onion is one of the important market-garden and truck crops in the United States and is very generally grown in home gardens. It thrives best on alluvial and drained muck soils under a temperate climate, but may be grown under a very wide range of soil and climate conditions. Onions are grown to perfection on the alluvial soils of the Nile River Valley in Egypt, under the sea breezes of the South Sea Islands, on the delta lands along the sea coast, on sandy uplands, in the arid regions under irrigation, and on reclaimed swamp lands. There is perhaps no extensive area in the United States or its possessions where the onion, in one or more of its forms cannot be successfully grown, at least for home and local use.
The onion is of Old World origin and has been used as a food plant from the earliest historic times. It was an important article of diet in Egypt at the time of the building of the pyramids, and Moses, in his account of the exodus of the children of Israel from Egypt, mentions it as one of the articles of food for which the Israelites longed for during their sojourn in the wilderness.
Onions were brought to North America by the early discovers and became one of the common crops of colonial gardens. Commercial onion culture in its present form has developed mainly during the last 40 or 50 years. Formerly the production of onions for sale was confined principally to the New England States, but the industry soon spread to other sections, and when the vast muck areas of the Great Lakes and other regions were drained and brought under cultivation the onion soon became one of the most important crops on these soils.
At present the principal commercial onion-growing centers are located in New England, especially in the Connecticut River Valley, in northern New Jersey, southeastern New York, the entire Great Lakes region, and as far west as Minnesota. The production of Creole onions centers around New Orleans, La, and the greater part of the Bermuda-onion crop is grown in southwestern Texas and in California. Within the last few years the production of the Sweet Spanish onion has developed in several of the Western States, including New Mexico, California, Arizona, Utah, Nevada, Washington, and Oregon. In addition there are many local areas in the United States where onions are being grown in considerable quantities for the market.
The production of several crops closely related to the onion, such as chives, shallot, leek, and garlic, has been developed around local centers, especially in connection with market gardening near the large cities. Garlic might be mentioned as an exception, because it is produced mainly in a few localities where soil and climate are especially suitable for its growth.
For best results a temperate climate without great extremes of heat and should be selected. Onion culture is rarely profitable in regions where the climate does not change or has no definite seasons of heat and cold or moisture and drought. The onion does best under rather cool conditions, with plenty of moisture during its early stages, but requires a reasonable degree of heat, together with dryness of both soil and atmosphere, for its proper ripening. Where the onion industry has become established in the extreme southern part of the United States, the growing season is during the late autumn and winter, the crop maturing during the spring and early summer. If the crop matures at a time when there is considerable rainfall, it will be impossible to cure the bulbs without artificial means and they will be lacking in keeping qualities.
Certain types and varieties of onions, including the top onions and the multipliers or potato onions, are extremely hardy and may remain in the open ground throughout the winters of our Northern States, especially if given slight protection. These types are, however, not adapted to growing for market, except as green onions, “peelers”, or “bunchers” to be sold during the early springtime. In certain sections of the South Atlantic coast region large areas of the top multiplier onions are grown for this purpose. There is also a marked difference in the day-length requirements of the standard commercial sorts, some being adapted to growing far northward, while others, like the Bermuda and Creole types, do best in restricted southern localities.
The period required for the production of a crop of onions will depend upon the season, the methods employed in growing, and in the variety. If grown from seed, a period of from 130 to 150 days will be required. If from sets, the crop often may be matured in 100 days. If grown in the extreme northern part of the United States, where seasons are short, the crop will mature more rapidly to the southward. In the case of the Bermuda onion, as grown in Texas, the growing season extends from October to the following March or April.
Onions require an abundance of moisture during the early stages of their growth, but should be ripened under comparatively dry conditions. In most sections the seed is sown at a time of year when frequent spring rains occur. Their period of greatest growth is during the early part of the summer, and the crop is ripened late in the summer when drying conditions may be expected. In irrigated regions the application of water is almost entirely under the control of the grower. During the active period of growth the water is applied about once a week, the soil being thoroughly soaked and the surplus water drawn off.
The amount of rainfall or irrigation required for the production of a crop of onions will depend largely upon the character of the soil and its drainage. Many of the peat or muck soils in which the soil water remains near the surface will require very little rainfall; in fact, the best crops of onions are produced on these soils during seasons of comparatively light, but evenly distributed rainfall. Sandy and loose soils generally require a greater amount of water, especially during the early part of the season.
SOILS ADAPTED TO ONION CULTURE
The essential requirements of a soil upon which to grow onions profitably are a high state of fertility, good mechanical condition, properties – that is, if it contains sufficient sand and humus to be easily worked, is retentive of moisture and fertilizers, and is capable of drainage – all other requirements can be met. At least three types of soil are being extensively planted to onions in this country, the one common essential being proper mechanical condition.
Clay and alluvial soils abound in the river valley and delta regions near the coast. These soils are generally very fertile, but may require the addition of humus or stable manure in order to lighten them. The greatest difficulty encountered in growing onions upon land of this character is the tendency of the soil to run together and bake after hard rains. This is especially injurious after the seed has been sown and before the small plants have attained sufficient size to permit of stirring the soil about them. Where those soils contain considerable sand they are ideal for onion culture. Soils of this type are easily injured by plowing or working while wet.
Sandy soils, especially where underlaid by a well-drained clay subsoil are often well adapted to onions. Soils of this character generally require heavy applications of fertilizers before they will produce a paying crop, but the quality of the product is excellent. Onions grown on sandy loams are generally solid, heavy, and of excellent keeping quality. Where sandy soils are lacking in humus this may often be applied by means of crops of legumes grown upon the land and plowed under.
Throughout the north-central part of the United States and the delta region of California there are vast tracks of peat and muck soils that are being utilized for the production of the commercial onion crop. Before planting to onions, however, these soils must be cleared, drained, and brought to a suitable state of cultivation. In many cases this process will require two or three years’ time, but sometimes the soil can be broken during the early winter, allowed to lie exposed to the action of frost, then worked down and planted to onions the following spring. The store of plant food in muck soil is usually large, but often it is not in available condition, and heavy applications of manure (and/or commercial fertilizers, especially super-phosphate and potash), are essential to profitable crops.
The onion belongs to that class of crops that gives best results under very intensive culture, and the greatest yield are secured where a moderate acreage is planted and the work conducted in a most thorough manner. There is nothing technical about the growing of onions, but close attention and frequent cultivations are essential. Once the weeds get a start, the cost of production will be greatly increased, or the crop may be lost altogether.
PREPARATION OF NEW LAND
As a general rule new land is not adapted to onion growing until it has been worked one or two years with other crops. Onions should follow some row crop that has been kept free of weeds the previous season. Corn, beans, and potatoes are suitable crops with which to precede onions. Muck and sandy soils may in some cases be brought to a suitable condition for onions the first season, but the fitting will have to be thoroughly performed. The land should be plowed in the spring, after which numerous harrowings and doubtless some hand work will be required to get the soil in suitable shape.
If necessary to manure the land heavily before planting to onions, it will be desirable to plant to some farm crop one season, then apply the manure during the autumn in order to give it time to become incorporated with the soil. Owing to the value of good onion land it would be advisable to devote it to general farm crops for any extended period, although corn is frequently planted and oats or rye are sometimes used in the North. Cowpeas may be of great service in bringing new land into shape for planting onions.
Onions should not be planted on the same piece of land year after year, but some system of crop rotation should be maintained. Care should be taken, however, to use crops in rotation that will not be exhaustive of the high fertility necessary in the onion land. During the years when the land is not devoted to onions it can be planted to some truck crop that will give a return that will justify the applications of large quantities of fertilizers, or, better, to a leguminous crop to be turned under as green manure. Continuous cropping with onions will cause the land to become infested with both disease and insect enemies that will sooner or later injure the crop to such and extent as to render it unprofitable.
PREPARATION OF THE SOIL
Assuming that the land intended for planting to onions is capable of being brought to a good mechanical condition, is fertile, well drained, and reasonably free from weed seeds, the first step in the production of the crop will be to plow moderately deep, then harrow, disk, roll, and drag until the soil is smooth and mellow to a depth of 5 to 7 inches. The method of preparing the soil will depend some what on the character, the manner of planting to be followed, and the requirements for irrigation. There are few truck or other crops that require so careful fitting of the soil as do onions, and it is essential that the fertilizers be well mixed with the soil.
On soils that are naturally well drained and where surface water can not accumulate, the plowing may be done in large blocks, but where the opposite conditions are found or irrigation is practiced it may be necessary to plow the land in narrow beds. In the case of insufficient drainage it will be desirable to throw the soil into beds, leaving double furrows between the beds to carry off surplus water. Where the flooding system of irrigation is practiced the beds must be leveled and a system of ditches and ridges provided for distributing and controlling the water. Where it is merely desired to secure surface drainage the beds may be from 75 to 150 feet in width, but for irrigation purposes the beds are generally but 12 or 15 feet in width. If spring plowing is practiced the soil should be harrowed closely behind the plow in order to prevent drying out.
For cutting and pulverizing the soil there is perhaps no tool as serviceable as the disc harrow. There is a type of disc having four gangs, in two sets, one combination in front of the other and so arranged that the soil is first turned to the center and then turned outward again by means of rear combination. This tool turns the soil twice and leaves it in level condition. For smoothing and leveling the soil behind the plow a harrow of the type shown in figure 1 is very desirable; this tool not only levels but turns and crushed the soil at the same time.
For imparting the final smoothing touch to the soil before planting there is a device consisting of a large number of small disc set in a wooden frame, which does about the same work as a steel rake but in a rapid manner. A drag or float made from several pieces of scantling nailed together, may be used for this purpose, or if the soil is very loose a roller should be run over it. The final leveling should be performed with a tool that will fill and obliterate all tracks or other depressions in the soil, leaving a smooth, even seedbed for either seed sowing or transplanting.
As the onion is an intensive crop and should yield great quantities of marketable bulbs for the area planted, the grower is justified in fertilizing heavily. It would be difficult indeed to make the soil too rich for onions, provided the manures are thoroughly incorporated with the soil. A heavy application of fresh raw manure just before planting would have an injurious effect, but where the manure is well rotted and uniformly applied there is nothing to be feared.
There is perhaps no fertilizer so well adapted to the production of onions as plenty of disease-free, well-composted stable manure, and the quantity and frequency of application will depend upon the nature of the land under cultivation. The Bermuda-onion growers of southwestern Texas apply as high as 20 tons of sheep and goat manure to an acre every three years.
In addition to the manure, there is used 1,000 to 2,000 pounds of cottonseed meal or commercial fertilizer, and sometimes a top-dressing of nitrate of soda. This sheep and goat manure, from animals that are fed largely on cottonseed meal, is saved in the corrals in a climate where there is very little rain, and contains the essential fertilizing ingredients in very high percentages. The manure is first piled where little water can be thrown over it, and it is composted for several months before spreading on the land. The best results from this manure are not realized until the second or even the third year after its application.
All stable manure used on onion land should be well composted before use and then spread upon the land several months before planting to onions. In the Northern States the manure may be applied during the autumn and well disced into the soil. The land can then be allowed to lie in the rough state and exposed to the action of frost during the winter, or it can be smoothed and seeded to rye, in which case it will be necessary to replow early in spring. In the Bermuda district the manure should be applied during spring and the land kept frequently stirred during the summer, with occasional irrigations in order to incorporate the manure and destroy weeds; the planting is not done until the autumn. Another practice in the Bermuda district is to apply fresh manure broadcast at the rate of 10 to 12 tons to the acre during the spring, then plant to corn and cultivate through the early summer, and add a top-dressing of well-rotted manure after plowing the land for onions in the autumn. This top-dressing should be well worked into the soil by means of disk harrows. Large quantities of fresh manure applied on onion land just before planting will have a tendency to produce an overgrowth of tops at the expense of the bulbs. This is especially true on irrigated lands and soils that are naturally moist.
A fertilizer that is suited to the growing of potatoes will serve quite well for onions, but the potash should be supplied in the form of muriate rather than sulphate. A fertilizer adapted to the growing of onions should contain 4 to 5 percent of nitrogen, 8 to 10 percent phosphoric acid, and 8 to 10 percent of potash. A fertilizer of this character can be profitably applied at the rate of 1,000 pounds to the acre on most soils. Where very intensive cultivation is practiced it may be profitable to apply as much as a ton to the acre in addition to stable manure.
Commercial fertilizers should be applied shortly before sowing the seed and should be uniformly distributed and thoroughly worked into the soil. There are fertilizer distributors that scatter the fertilizer broadcast, but where an amount not exceeding 1,000 pounds of fertilizer to the acre is being used the work of distribution may be preformed by means of a common grain drill having a fertilizer attachment. On a small scale the work is generally performed by hand.
Many growers follow the practice of applying only a part of the fertilizer at planting time, reserving the balance to be put on as a top-dressing at some time during the period of cultivation. This plan is especially desirable where onions are grown during the winter, as the application of highly nitrogenous fertilizers in the autumn is liable to promote a soft growth that will be injured by cold. If the fertilizer is not put on until cold weather is over, the crop may be forced without danger of injury. For this purpose only those fertilizers of a very available form will answer. Nitrate of soda* is frequently used as a top-dressing during the height of the growing period.
- The National Organic Program stipulates that the nitrogen obtained from sodium nitrate must account for no more than 20 percent of the crop’s total nitrogen requirement. This can be used cautiously when rapidly available nitrogen is needed. It is prohibited by the Farm Verified Organic and Organic Crop Improvement Association-International Federation of the Organic Agriculture Movements accredited levels of certification. European organic standards consider it to be the equivalent of a synthetic fertilizer because it is highly soluble and leaches readily from the soil. Check with your (organic) certifier before using.
Most of the onions grown in the United States are started from seed. Propagation from seed is conducted by three more or less distinct methods: (1) By sowing the seed in rows where the crop is to grow and mature; (2) by sowing the seed in specially prepared beds and transplanting the seedlings to the open ground; and (3) by first growing sets from the seed and then, after keeping them through the winter, planting them in the field to produce the crop of mature bulbs. Of these three methods the one first mentioned of seeding the rows where the crop is to mature is the one most used on a very large scale.
SEEDING IN ROWS
In the Northern onion-growing districts the seed is sown as early in the spring as the soil can be brought to the proper condition. While it is desirable to plant quite early, it never pays to sow the seed before the land is in the best possible condition. When the soil has been brought to a smooth, even surface and is fine and mellow, the seed is sown by means of a common seed drill, of which there are several makes on the market. The hand drills which sow one row at a time are extensively employed, but many of the larger growers employ a gang of drills hitched together and plant form five to seven rows at once. In heavy or moist soils the depth to cover the seed should not be more than one-half to three-fourths inch, while on loose and sandy soils the seed may be covered about an inch.
Where hand cultivation is practiced throughout, the usual distance between rows is 12 to 18 inches. Where horse culture is employed the distance between rows varies between 24 and 36 inches. The quantity of seed required to plant an acre will depend both upon the distance between rows and the purpose for which the onions are being grown. For the growing of standard market onions in rows 14 inches apart, about 4 ½ pounds of first-class seed will be required. With the rows 3 feet apart, but 1 ¼ to 1 ½ pounds will be necessary. Where it is desired to produce onions for pickling purposes, the amount of seed may be as great as 25 pounds to an acre. Good seed is essential, and if there is any doubt regarding the vitality of the seed it should be tested before planting by counting and planting 400 or 500 seeds in a window box and then determining the germination by counting the seedlings after 10 days; or 2 weeks time. First-class seed is seldom sold at a low price. Old and inferior seeds are not only low in percentage of germination but lack the vitality necessary to produce strong healthy plants. There are dealers who make a specialty of securing and furnishing extra-quality onion seed, and while their prices are often somewhat above the general market the seed furnished by them is preferable to ordinary seed.
TRANSPLANTING METHOD OF GROWING ONIONS
The transplanting process is merely a modification of the regular seeding method. The objects gained by transplanting are an earlier crop, a uniform stand, and bulbs of more regular size. Practically the entire crop of Bermuda- and Creole-type onions grown in the United States is handled in this manner. Where a small area is to be grown, the transplanting process is the ideal method, but for large acreages where labor is difficult to obtain this would not be practicable. After transplanting, the seedlings will require rain or watering, and for this reason the transplanting process is practically limited to areas where some form of irrigations is available.
In growing onions by the transplanting method the seed is sown in greenhouses, hotbeds, cold frames, or specifically prepared beds at the rate of 2 to 3 pounds for each acre to be planted. When the seedlings are grown under cover, they are given the necessary attention regarding watering and ventilation and kept growing quite rapidly until near the time for setting them in the open ground. As planting time approaches, the seedlings are “hardened” or prepared for transplanting by increased ventilation and exposure and by withholding water. When ready to transplant the seedlings should be somewhat smaller than a lead pencil and rather stocky. The plants are lifted from the seedbed and the roots and tops both trimmed somewhat, as shown in figure 4. They are then packed neatly in shallow boxes for removal to the field where they are to be planted. Various methods are employed for handling the plants in setting. As a rule, a line is used and the land marked to indicate the location of rows. Several methods are employed for marking the distance between plants in the rows. A marking device much used by the Bermuda-onion growers in Texas consists of a sectional roller with the sections the same distance apart as the distance between the rows and each section provided with conical pins to form holes in which the plants are set. The objection to the sectional roller-marker is that it cannot easily be drawn in a straight line and straight rows are essential for good cultivation.
After marking the land, the plants are dropped ahead of the planters, or they may be kept in trays and simply removed as planted. The transplanting process consists mainly in pushing the root end of the seedling into the soil with one finger and then firming the soil around the plant. This work is very laborious and can only be preformed economically by very cheap labor. A small plow, such as is generally included with the attachments of the wheel hoe (fig 5), is often employed for opening a furrow in which to set the small onion plants. As the plants are set the soil is either drawn about by hand, or the plow may again be used for this purpose. In the Bermuda-onion district the work of transplanting is as a rule done by contract. In transplanting, all inferior plants should be rejected, thus ensuring a more nearly perfect stand and development.
PROPAGATION BY SETS
The use of sets is still another modification of the regular seeding method, in which the seed is planted one year to form the sets form which to grow a crop of mature onions the following year. Like the transplanting process the use of sets is limited in its application. Onions grown from sets will ripen earlier than those from seed sown in the field and often make a good crop of bulbs when the crop grown from seed will not. In planting onion sets a furrow about 2 inches deep is opened, the sets being dropped about 3 inches apart and firmly covered. The quantity of the sets required to plant an acre will depend upon their individual size and planting distances, but is generally between 12 and 22 bushels.
The cultivation requirements of the onion are frequent shallow stirring of the soil and freedom from weeds. The feeding roots of the onion run close to the surface of the soil and should not be disturbed by deep cultivation. Sometimes a heavy rain immediately after seeding will so pack the surface that the seedlings cannot break through. Under such circumstances it will be necessary to slightly break the surface by means of a steel rake or a rake-like attachment on a cultivator. As soon as the plants are up and the rows can be followed the cultivator should be started to loosen the soil, which is always more or less compacted during seeding.
Where the rows are 14 inches or less apart, the work of caring for the crop is usually done by hand. For this purpose the wheel-hoe tools of various types are essential. These implements are provided with several kinds of hoes, cutters, and sweeps designed to work the soil away from the plants, to shave the surface and destroy weeds, and to stir the soil and work it back around the plants. Onions grown on much and alluvial soils will require from 8 to 14 working with the wheel-hoe implements; on sandy soils it will not be necessary to cultivate so frequently.
Several types of wheel hoe are in use, but those having a single wheel and passing between the rows are most desirable. Those of the type shown in figure 5 are good. Many growers have designed special implements to suit the requirements of their soils; two of these are shown in figure 6, the one designed to cut the soil away form the row and the other to stir and work the soil back to the row. Some of the growers in the onion fields near Chicago have adapted a hoe stock consisting of a pair of light plow handles, an iron stock, and the front wheel of a bicycle. To the stock of this device may be attached almost any form of sweep or cutter, and the implement is exceptionally easy to propel. The wide distance between the handles places the implement well under the general appearance of this implement.
In sections where onions are grown on a soil that is not well adapted to hand culture the rows are placed 30 to 36 inches apart and the cultivation is performed by means of horse-drawn and tractor tools. This is particularly true where onions are grown on the black waxy soils of Texas and other soils of the prairie type. As with hand culture, frequent shallow stirring of the soil is essential, the work generally being performed with one of the harrow-tooth cultivators. Those of the type shown in figure 8 are well adapted to this work. An implement known as a weeder can be used for breaking the surface before the seedlings appear; also for general cultivation by removing a tooth at the point where the rows are located.
It is well-nigh impossible to produce a crop of onions without some hand weeding. During favorable seasons the strictly handwork may be reduced to but one or two weedings, but a greater number will be necessary during rainy seasons. The work of hand weeding may be facilitated by the use of some of the small hand tools designed for the purpose. Among these tools might be mentioned the onion hoe (fig. 9), the hand weeder (fig. 10), and the thinning or weeding hook (fig. 11). Girls and boys of advanced school age are frequently employed to do the hand weeding, especially during the early summer vacation period.
Outside the areas where irrigation methods are depended upon for the production of general crops it is not customary to use artificial watering in the growing of onions. In a few cases the land has been equipped with overhead sprinkling systems which are employed to moisten the soil after the seed is planted and also during extremely dry weather. On peat and muck soils the young seedlings are frequently lost by the dry muck blowing with the high winds of early spring. In this way a part of the field may have the soil blown off to such an extent that the plants will be left without soil about them, while other portions of the field will be covered by 1 or 2 inches of loose muck. The use of a small quantity of water sprayed over the field will sometimes prevent this shifting of the soil during a windstorm but will not prevent the accumulation of muck blown on to the plants from adjacent non-irrigated areas. Sandy soils are also subject to the action of winds to a greater or less extent, and losses may be prevented by the timely application of water over the surface. In a few instances sub-irrigation is employed in the growing of onions.
Throughout the Southwest surface irrigation is almost universally employed. The Bermuda onions in Texas are planted mostly in comparatively level beds with dividing ridges and are flooded once each week or 10 days during the growing period. About a week before the plants are set the soil is flooded and then worked over with disk and smoothing harrows just ahead of the planters. Within a day or two after planting the land is again flooded and the surface water drawn off; this process is repeated, with alternate cultivations, as often as required. Toward the end of the growing season the water is withheld to allow the bulbs to ripen. As a rule about 10 waterings in all are required.
In the principal Bermuda-onion growing districts the water for irrigation purposes is obtained only after the expenditure of thousands of dollars for pipe lines and pumping machinery. The cost of watering as given above does not include any share of the original cost for installation or water charges, but covers only the labor. In the upper San Joaquin and Coachella Valleys of California the Bermuda and Sweet Spanish onions are grown on raised beds usually holding two rows of onions and with water furrows between the beds.
HARVESTING AND CURING
In the northern onion districts the crop ripens and is harvested during the latter part of the summer and early autumn. As a rule the work of harvesting onions begins late in July and is practically completed and the crop housed before October. In the Southern States, where the crop is grown during the winter, the harvesting and marketing period is during the spring and is practically ended before the northern product comes upon the market.
In the North the bulbs are allowed to become as ripe as possible before they are removed from the soil. Growers prefer that the tops ripen down and shrivel and that the outer skin of the bulbs be dry before they are pulled. To the southward, where the onions are not cured so thoroughly, they are often pulled about the time that the tops begin to break and fall. The ripening process often may be hastened by rolling a very light roller or a barrel over the tops to break them down. This process is frequently spoken of as “barreling.”
Where the bulbs are practically upon the surface they may be pulled by hand and thrown in windrows consisting of 8 or 10 onion rows. If the onion bulbs are considerably covered with soil it will be necessary to employ a 1-horse plow or a cultivator with a sweep attached for lifting them. In any case it will be necessary to gather them from the soil by hand. After lying in the windrows for several days and being stirred occasionally with wooden rakes, the tops are removed by cutting with ordinary sheep shears. In cases where very bright color is important, as with fancy White Globe onions, and this would be injured by exposure to the sun and rain, the bulbs are cured in long, narrow, low ricks formed by placing several rows of onions laid with the bulbs to the center of the tops to the outside to protect the bulbs. As the tops are removed the bulbs are generally placed in crates for drying. Onion-topping machines frequently are employed, the bulbs being hauled from the field to a central location and run through the topper. These machines remove the tops, grade the bulbs, and deliver them into the crates or bags. If crates are not employed for curing, the bulbs are allowed to lie in the windrows for some time, and are then either put into sacks or hauled to slat cribs, where the curing process is completed. Too long exposure to hot sunshine will injure the bulbs.
After gathering into crates, the crates are either stacked in the field, hauled to a central stacking yard where they are covered with boards or canvas, or hauled to open sheds and there piled one upon the other with numerous air spaces until the onions are thoroughly cured.
Where the bulbs are extremely dry at the time of their removal from the soil, they may be allowed to lie in the windrows for a few days only, and then sorted and cleaned in the field ready for packing and marketing. Where onions are put into sacks and afterward allowed to remain in the field, the sacks should be supported on poles laid on the ground. In the irrigated districts of the West, where the soil can be kept dry, this precaution is not necessary.
In the Bermuda-onion districts, where only a short curing process is given to the crop, it is the practice to pack and load into the cars as soon as possible after pulling and topping. When the shipping is at its height, it is not uncommon for onions that are pulled from the soil in the morning to be in the cars and on their way to market by evening; however, a portion of the crop is given a more thorough curing process, and the entire crop would be benefited by at least two days of curing before shipment.
To keep well when stored, onions must be well ripened and thoroughly cured. “Thick necks” or those that are immature, or soft, should never be placed in storage but should be sold as soon as gathered for whatever price they will bring. Good storage onions will rattle almost like blocks of wood when poured from one crate to another. In order that the bulbs may remain bright and of attractive appearance they should not be allowed to lie exposed to the weather, but should be hauled and stored in open sheds just as soon as they may safely be placed in 1-bushel crates.
After the bulbs have remained in drying sheds or cribs for 4 or 5 weeks they will be ready for screening and removal to the storehouse. In handling onions it is the rule to pass them over a screen each time they are moved, as in this way the loose skins are removed and any soft or decaying bulbs may be sorted out. When bags are used for drying in the field, the onions are screened, and the bags refilled for hauling to the storage house.
The essentials for the successful storage of onions are suitable containers, plenty of ventilation, a comparatively low temperature, dryness, and safety from actual freezing. Any building wherein the above conditions may be secured will answer, but houses 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 doors that may be closed to control the temperature. The floors are constructed of narrow planks with half-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 and discharge the cool air at a point where it is most needed.
The temperature of the storage house should be carried as low as possible without actual freezing. During extremely cold weather the ventilator openings and doors should be kept closed to keep out cold air, and after the onions have become thoroughly chilled the house should be kept closed in order to hold the temperature down and prevent the entrance of moisture during warm or rainy periods. Damp, foggy weather is injurious to onions, especially if it follows a period of cold and will cause the bulbs to become covered with moisture if the outside air is admitted. A little artificial heat from a stove or radiator may be required during excessively cold weather, but so long as the temperature in the house does not fall below 32? F there will be no danger of injury. A temperature of 36? to 38? will give good results.
The best method of storing onions is in standard-size slat crates 20 inches long, 16 inches wide, and 14 inches deep, outside measurements. The material for the sides and bottom is about three-eighths inch think and 2 ½ inches wide, four pieces being used to form a side. The corners are reinforced on the inside by means of 3-cornered pieces of oak, to which the slats are nailed. These dimensions provide crates that are interchangeable, with width of five being equal to the length of four. The crates will also next together when empty, with one inside of two turned together. The full crates are stacked in the storehouse with 1 by 3 inch strips between them to allow for the circulation of air.
Onions are sometimes stored in slat bins holding 100 to 300 bushels each. Bags are also used to some extent, but neither bags nor bins are as satisfactory as the crates, on account of the difficulty in providing the necessary ventilation and change of air through the onions. Bulbs stored in bags or bins must be more thoroughly cured than those stored in crates. There are single large storehouses in use that will accommodate 50,000 to 60,000 bushels of onions when stored in crates.