Studies have found pungency reaches its peak when soil sulfur levels reach ppm and does not increase much above that. This is just a ballpark.

Some fertilizers come with sulfur, so read the ingredients list. You might be better off without it. Beyond cultivar choice, and soil and water sulfur levels, also consider that onion flavor changes with time, water content and environmental stress.

Older, matured plants that are dried down will always taste stronger. Younger, succulent plants will be milder.

Even sweet onions will get more pungent when fully dried down. However, they should not get more pungent than a dedicated storage type onion. An onion can have a stronger flavor when under stress as well. If the tops die down mid-season from environmental pressures like drought, insects or disease, the plant may divert its energy to plant defense.

Part of its defense is making that hot flavor. Keeping healthy tops will maintain milder bulbs in the middle of the season when plants should be at their sweetest. It is worth noting that the sweeter the onion, the poorer it will keep in storage into the winter. True storage onions have fewer sugars and more pyruvic acid, and that aids in its shelf life.

However, the same moisture stress and pest issues that may make a sweet onion hot will also reduce the yield and storage life of a storage onion.

Popular Long-Day storage onions include Blush red , Copra yellow , Redwing red , Red Zeppelin red and Sterling white. Once you have made your cultivar selection, time direct-seeding for late-March through early-April and transplanting for early April.

Keep bare-root transplants dry and cool until planting. The reason for early planting is because the larger the plant gets prior to bulbing, the larger the resulting bulb. Intermediate-Day onions should be planted earlier than Long-Day onions to give them more time.

Nitrogen recommendations on Coastal Plain soils range from to pounds of nitrogen per acre. On Piedmont, Mountain, and Limestone Valley soils apply 90 to pounds per acre. Table 1 indicates the phosphorus and potassium recommendations based on soil residual phosphorus and potassium levels.

In addition, boron should be applied at one 1 pound per acre. If zinc results are low, five 5 pounds per acre of zinc should be applied. Sulfur is critical for proper onion production.

This is particularly true on the Coastal Plain soils of South Georgia that are very low in sulfur. Sulfur at a rate of pounds per acre will be required to produce quality onion transplants on these sandy loam soils. This would supply pounds of N-P-K along with pounds of S. This would be followed by additional applications of P and K according to soil test recommendations.

Generally additional P will not be needed, while additional K can be supplied as potassium nitrate The additional N can be supplied in one to two applications of calcium nitrate It should be noted that any fertilizer that supplies the required nutrients as required by the soil test can be used to produce plant bed onions.

More recent work indicates that high P applications at plant bed seeding have no effect. It is critically important that seedbeds be irrigated regularly to develop a good plant stand. A tenth of an inch of water applied several times a day may be needed to insure consistent soil moisture.

See section on irrigation. Plants are ready for harvest in about eight to ten weeks. Good quality transplants will be about the diameter of a pencil when ready. Transplants are pulled and bundled in groups of plants and tied with a rubber band. Approximately one half of the tops are cut from the transplants, usually with a machete.

Harvested transplants are transported to the field in polyethylene net or burlap bags. Care should be taken with transplants so they are not stored for excessively long periods of time in these bags, nor should they be left in the sun for too long.

Planning is critical, harvest only enough plants that can be reasonably transplanted that day. Overnight storage in these bags should be avoided whenever possible, but if necessary they should be removed from the field to a cool dry location.

Alternatively, onions can be directly sown in the soil for production. This eliminates all of the fertilizer and other management requirements of transplant production. Timing and seedbed preparation are critical for successfully growing onions from direct seeding. For direct seeding, onion seed should be sown on October 15th plus or minus one week.

This is later than sowing for transplant production, but is required to avoid undue seed-stem formation flowering in the spring. The soil should be prepared so that it is free of clods and plant residue. The soil surface should be smooth with the proper amount of soil moisture. Soil that is too wet will clog the sowing equipment.

Soil that is too dry may result in the seeder riding up on the soil and not sowing the seed at the proper depth. The plant stand will be similar to transplanted onions with four rows on a slightly raised bed with inches between the rows. Direct sowing can save a tremendous amount on costs and labor; however, care must be exercised to correctly sow the seed since you will only have one chance to get it right.

Table 1. Recommendations for phosphorus and potassium based on soil test analysis for plant bed onion production. Although limited research has been done in this area, it may be possible to grow intermediate-day onions in North Georgia; however, they would not be as mild as the south Georgia Vidalia onions.

Figure 1. Bulb Shapes: 1. flattened globe; 2. globe; 3. high globe; 4. spindle; 5. Spanish; 6. flat; 7. thick flat; 8. Granex; 9. The Vidalia onion industry is controlled by a Federal marketing order that is administered by the Vidalia Onion Committee and the Georgia Department of Agriculture.

This market order defines what type of onions can be grown and be marketed as a Vidalia onion. A Vidalia onion must be a yellow Granex type.

These onions should be slightly flattened, broader at the distalend top and tapering to the proximal end bottom Figure 1. In addition, rules have given the Georgia Department of Agriculture the authority to determine acceptable varieties for the Vidalia industry.

Under these rules, the University of Georgia has been mandated to test all onion varieties for three 3 years before making recommendations to the Georgia Commissioner of Agriculture. Varieties that the Georgia Department of Agriculture have recommended to be grown as Vidalia onions are listed in Table 2.

Onion varieties grown in Southeast Georgia fall into three broad maturity categories; early, mid-season, or late. There can; however, be considerable overlap in these categories and not all varieties will perform the same as to their maturity from one year to the next.

Along with maturity, varieties will perform differently on a wide range of quality attributes, as well as yield. Varieties can differ for pungency, sugar content, disease resistance, seed stem formation, double centers, bulb shape, and bulb size.

Growers should consider all of these characteristics when making decisions on variety selection. Growers wishing to try new varieties should consult University of Georgia variety trial results.

Even after evaluating trial data, growers considering new varieties should grow them on limited acreage to get a feel for their performance potential under their growing conditions.

In addition, growers wishing to grow Vidalia onions should check with the Georgia Department of Agriculture for the current allowed varieties. Onions grow best on fertile, well-drained soils. Tifton series 1 and 2 soils are found in the Vidalia onion area and are well suited for onion production.

However, most sandy loam, loamy sand or sandy soils will be advantageous to sweet onion production. These soils are inherently low in sulfur, which allows greater flexibility in sulfur management to produce sweet onions. Avoid soils with heavy clay content and coarse sandy soils.

Clay soils tend to have a higher sulfur content, which can lead to pungent onions. Exceedingly sandy soils are more difficult to manage because they require more fertilizer and water.

Fertilizer and lime requirements should always be based on a recent, properly obtained soil sample. Check with your local county extension office or crop consultant regarding proper procedures for soil sampling and interpretation of results.

Obtain the soil sample a few months prior to crop establishment in order to determine lime requirements and make necessary lime applications in a timely manner.

If soil test results show a pH below 6. It is essential to apply sufficient lime to keep the soil pH above 6. Low pH can cause nutrient deficiencies during the growing season. Also, the high rates of fertilizer used in producing onions cause the pH to drop during the growing season.

If the pH is not corrected at the beginning of the onion season, nutrient deficiencies could occur during the year and reduce yield. Calcium and phosphorous deficiencies can often be linked to low pH, even though soil tests indicate adequate levels.

But phosphorus deficiencies due to low pH can be difficult to correct during the growing season. Onions require more fertilizer than are used in most vegetable crops because fertilization of both plantbeds and dry bulb onions must be considered.

They respond well to additional fertilizer applied 40 to 60 days after seeding or transplanting. The method of fertilizer application is very important in obtaining maximum yield with multiple applications insuring good yields.

This will increase the amount of fertilizer utilized by the plant and lessen the amount lost from leaching. More recent research; however, indicates that good results can be obtained with as few as three fertilizer applications.

Preplant fertilizer will vary with the natural fertility and cropping history. Proper application methods and function of various nutrients are outlined below. Table 3 shows a suggested fertilizer program for a soil testing medium in P and K. Nitrogen N , especially in nitrate NO3 form, is extremely leachable.

If too little nitrogen is available, onions can be severely stunted. High nitrogen rates are believed to produce succulent plants that are more susceptible to chilling or freezing injury, disease, and to production of flower stalks.

Onions, heavily fertilized with nitrogen, are believed to not store well. Finally, excess nitrogen late in the growing season is believed to delay maturity and causes double centers. Make the final nitrogen application at least four weeks prior to harvest.

Rates of nitrogen will vary depending on soil type, rainfall, irrigation, plant populations and method and timing of applications. Phosphorus P is essential for rapid root development. It is found in adequate levels in most soils but is not readily available at low soil temperatures.

Because of these factors, under most conditions all of the P should be applied preplant and incorporated before transplanting. This amount should be counted as part of the total seasonal fertilizer application. Table 4 shows the recommended phosphorous to be applied based on various soil test levels.

Potassium K , is an important factor in plant water relations, cell-wall formation and energy reactions in the plant. Potassium is also subject to leaching from heavy rainfall or irrigation. A low K level makes plants more susceptible to cold injury.

Table 4 lists recommended K applications based on soil test results. Sulfur S is an essential element for plant growth. Early applications of sulfur are advisable in both direct-seeded and transplanted onions. To minimize pungency, fertilizers that contain S should not be applied after the end of January.

Research conducted in Georgia on S and onion pungency has shown that pungency pyruvate analysis of mature onions increases with high rates of S or whenever S applications are made after late January. Therefore, S should not be applied to onions after late January unless the onions exhibit S deficiency.

Do not completely eliminate S from the fertility program. Apply 40 to 60 pounds of elemental S with half incorporated at transplanting or seeding and half applied at the first sidedress application. Boron B is required by direct-seeded or transplanted onions in the field.

If the soil test shows B levels are low, apply one pound of B per acre and incorporate prior to transplanting or seeding. Do not exceed the recommended amount since boron can be toxic to onions. Zinc Zn levels determined to be low by soil testing can be corrected by applying five pounds of Zn per acre.

Excessive amounts of Zn can be toxic, so apply only if needed. Zinc is usually added in the preplant fertilizer. Magnesium Mg levels in the soil must be adequate for good onion growth. If dolomitic limestone is used in the liming program it will usually supply some of the required Mg.

However, if soil pH is adequate and the soil-test Mg level is low, apply 25 pounds of Mg per acre in the preplant fertilizer. Slow release fertilizers have been introduced to the Vidalia growing region. These fertilizers have performed well and can be considered in a fertility program.

These fertilizers; however, have not proven satisfactory for single fertilizer application. Table 3. Sample fertilizer recommendations for transplanted onions with a plant population of 60, to 80, plants per acre.

Make adjustments for soil test levels other than medium P and medium K. A complete fertilizer with minor elements will provide most of the other required nutrients. Micronutrients can become toxic, if excessively applied so apply them only when needed and in precise amounts.

Routine visual inspection of onion fields to watch for nutrient deficiencies is always important. However, during periods of high rainfall or frequent irrigation, be particularly aware of the potential for nutrient deficiencies to occur.

Deficiencies of major nutrients cannot be feasibly corrected through foliar nutrient applications. Therefore, it is important to properly manage soil fertility to maintain optimum growth and development.

Some deficiencies of minor elements can be remedially corrected through foliar applications. However, it is always best to supply adequate amounts of these nutrients through your basic soil fertility program.

Plants utilize nutrients more efficiently when the nutrients are taken up from the soil. Also, by the time you visually see a deficiency symptoms, you have probably already lost some potential yield. Table 4. Recommended potassium and phosphorous applications based on soil test ratings of each nutrient.

Plant tissue analysis is an excellent tool to evaluate crop nutrient status. Periodic tissue analysis can be used to determine if fertility levels are adequate or if supplemental fertilizer applications are required.

Tissue analysis can often be used to detect nutrient deficiencies before they are visible. Plant tissue analysis is accomplished by sampling the most recently mature leaves of the plant. A sample of leaves should be taken from the field area s in question.

Check with your local county extension office or crop consultant on proper tissue analysis techniques. The University of Georgia through its Plant, Soil, and Water Testing Laboratory can analyze your samples.

Table 5 shows critical ranges for nutrient concentrations in onion tissue for the crop stage just prior to bulb initiation. Adapted from Vegetable Production Guide for Florida.

SP of Florida Cooperative Extension Service. Transplants see Transplant Production are generally set in November to December. They can, however, be successfully set in January. Plants set in February will generally be smaller at maturity. Consequently, they will have a smaller percent of jumbos.

Early varieties should be planted prior to the end of December. Transplants are field set on slightly raised beds approximately four feet wide. Beds are six feet center to center. These beds or panels, as they are sometimes called, will have four 4 rows of onions spaced inches apart and a spacing of 4.

The spacing is determined by peg spacing on a pegger used to place holes in the bed surface 1 to 2 inches deep Figure 3. Transplants are hand set in each hole. Onions grow slowly during the cool short days of winter. Because of this, fertilizer, pesticide, and irrigation practices must minimize disease while maintaining optimum growing conditions.

Figure 2. Typical onion field. In most seasons, onion neck tissue will break down when the plant is mature. Although this is a good rule-of-thumb for determining when onions mature, the tops may not go down as readily in some years or for some varieties.

In addition, early varieties are very day length sensitive and usually go down early and uniformly.

They can be allowed to stay in the field for a week after tops down and will continue to enlarge. This will increase yield as the bulbs continue to increase in size.

Knowing the variety and carefully inspecting the crop is the best method to determine maturity. Whether the tops go down or not, the neck tissue will become soft, pliable, and weak at maturity.

Onions harvested too early may be soft and not dry down sufficiently during curing. In addition, they may begin to grow because they are not completely dormant. If the onions are harvested too late, there may be an increase in post-harvest diseases and sunscald on the shoulder of the bulb.

Although F1 hybrids will have a narrow window of maturity, they will not all mature at once. Generally, a field of onions will be harvested before all the bulbs have their tops down. Onions are prone to physiological disorders that growers should try to minimize.

One such disorder is splits or doubles. This condition is caused by cultural and environmental factors as well as being influenced by genetics. Over-fertilization, uneven watering, and temperature fluctuations particularly below 20 °F are all believed to have an influence on double formation.

Some varieties are more prone to production of doubles than others. Varieties prone to doubling should be seeded a week or so later on the plant beds as well as transplanted a bit later to minimize this disorder.

Onions are biennials forming bulbs the first year, which will act as a food source the following year when the plant flowers. The process of flowering in onions is called bolting. A seedstalk or scape will form very quickly and appear to bolt up.

These flower stalks or seedstems can form in the first year if appropriate environmental conditions occur and plant size are favorable.

Cool temperatures during the latter part of the growing season March and April , when plants are relatively large, can result in a high percentage of seedstems. There also appears to be a variety component to seedstem formation.

Onions can generally withstand light to heavy frosts, but hard freezes can result in onion damage. Freeze injury may be readily detectable as translucent or water soaked outer scales of the bulbs. A day or two after the freeze event, onions should be cut transversely to see if translucent scales are present.

In some cases, freeze damage may not be readily detectable for several days. In these cases, the growing point may have been affected and subsequent growth will be abnormal, increasing the incidence of doubles. Apparently, the growing point is damaged to the extent that two growing points develop.

Under severe freeze conditions the plant may be killed. Control of freeze and frost injury is usually done by cultivating the fields, if such an event is anticipated. Cultivating fields results in a layer of moist soil at the surface which acts as insulation.

The downside to cultivating may increase the incidence of disease caused by throwing up contaminated soil on tender onion tissue. Onions may develop disorders that are not associated with insect, disease, or nutrient problems. Greening is one such occurrence.

This occurs when the bulb is exposed to sunlight for an extended period of time. Early fertilizer application is needed to develop a strong healthy top, which shade the bulb during development. Sunscald will occur at the shoulder of all onions that are exposed to sunlight for an extended period of time.

Bulb sunscalding can occur when maturity is reached and harvest is delayed. Harvest should occur as soon as possible after the crop has matured. Scales several layers deep will dry and turn brown. Under severe conditions the internal tissue may actually cook or, become soft and translucent.

Translucent scale is a physiological disorder similar in appearance to freeze injury. The big difference is, freeze injury will always affect the outer scales whereas translucent scale may first appear on scales several layers deep in the bulb.

Translucent scale is a postharvest phenomenon caused by high CO2 in storage facilities. This is most likely to occur in refrigerated storage without adequate ventilation. Growers and packers should carefully monitor storage facilities to prevent this.

Physical damage of onions may appear that may be confused with botrytis leaf blight see disease section. This damage is usually caused by wind-blown sand or hail.

Strong winds can cause flecking of leaves particularly in fields with dry sandy soils. Hail damage will usually be more severe with large 0.

The shoulders of the exposed bulbs will often have a dimpled feel. In severe cases, the crop can be defoliated and destroyed. Occasionally plants may exhibit a striped appearance. If this is widespread in a field, S deficiency is the probable cause see fertility section.

If it appears on an isolated plant, it is probably a chimera. Chimeras result when a mutation occurs in the meristematic tissue growing point resulting in a striped plant. This should not be a concern. Because of the importance of water management in onions, all commercially grown onions in Georgia are irrigated.

Research and extension trials in Georgia have indicated that properly irrigated onions will yield 25 to 50 percent more than dry land onions.

Irrigated fields typically yield a higher percentage of jumbo bulbs, which generally bring a higher price on the market. Irrigated onions are sweeter and less pungent than dryland onions, which is especially important for Vidalia onions.

Almost all onions in Georgia are sprinkler-irrigated. The two most commonly used systems are center pivots and traveling guns. Center pivot systems are generally one of the lowest cost systems per acre to install and require very little labor to operate.

If properly maintained, they apply water very uniformly, and because of the low pressure required to operate them, they are generally very energy efficient. They are not well adapted to small irregular shaped fields, and unless the system is towable, it is restricted to use in only one field.

If a farmer has a limited amount of irrigated land, this characteristic can be detrimental to desirable crop rotations. Traveling guns are mobile systems that can be moved from field to field or farm to farm. They can be used on almost any shaped field. They do require high water pressure to operate and consequently require more fuel per acre-inch of water than other options.

Traveling guns also require a considerable amount of labor to operate. These systems tend to increase soil compaction and are harsh on young plants.

Other irrigation systems can be used as long as they can supply the need water evenly over the entire field. Water use of onions varies considerably throughout the growing period and varies with weather conditions.

The peak water demand for onions can be as high as 1. Peak use generally occurs during the latter stages of bulb enlargement especially during periods of warm weather. However, there are other stages when supplemental water may be needed.

Transplanted onions should be watered very soon after setting. About one-half inch applied at this time will help establish good contact between the soil and roots and assure a good stand. During the next two or three months the plants will be small and have a relatively shallow root system.

The fall months also tend to be some of the driest months in Georgia. During this period, irrigation should be applied whenever the soil becomes dry in the top six inches. Irrigation amounts should be limited to about one-half inch per application during this stage. Irrigation applications are typically infrequent during this period, since the plants are small and water demand is relatively low.

When the bulbs begin to enlarge water demand will gradually increase as will the need to irrigate when the weather turns dry. Rooting depths at this stage are typically 12 inches or less.

Because of the shallow rooting depth, irrigation applications should not exceed 1. Typical applications should range between 0. During dry weather, irrigate two or three times per week, especially when the weather is warm.

Of course, when temperatures are cool, irrigations may be less frequent. Unlike most other crops, onions do not generally wilt when they experience moisture stress. Since moisture stress is difficult to detect by visual inspection, it is very helpful to monitor soil moisture.

This can be done by installing tensiometers or electric resistance blocks or any other moisture sensor in the soil. Install soil moisture sensors at two depths, one near the middle of the root zone and one near the bottom.

Common practice is to install one at four to six inches and one at 10 to 12 inches. The ideal range for soil moisture is between soil tension 5 and 20 centibars for most coastal plain soils. Readings of less than five indicates saturated conditions and above 20 indicates the soil is becoming dry.

If you use a center pivot or traveling gun, you should start early enough so that the last part of the field to get watered does not get too dry before the system gets there.

In general, if the system requires three days to water the entire field, then you should install at least three soil moisture stations, evenly spaced around the field.

Each station will consist of two sensors, one shallow and one deep. You should monitor the readings on the soil moisture sensors at least three times per week when the weather is dry. Two types of sprayers, boom and air-assisted, are used for applying insecticides, fungicides, herbicides, and foliar fertilizers.

Air-assisted sprayers Figure 4 utilize a conventional hydraulic nozzle, plus air to force the spray into the plant foliage. Boom sprayers Figure 5 get their name from the arrangement of the conduit that carries the spray liquid to the nozzles.

Booms or long arms on the sprayer extend across a given width to cover a swath as the sprayer passes over the field.

Figure 4. Air assisted sprayer. Figure 5. Boom sprayer. Three factors to consider in selecting the proper pump for a sprayer are capacity, pressure, and resistance to corrosion and wear. The pump should be of proper capacity or size to supply the boom output and to provide for agitation 5 to 7 gallons per minute gpm per gallon tank capacity.

Boom output will vary depending upon the number and size of nozzles. Also, 20 to 30 percent should be allowed for pump wear when determining pump capacity.

Pump capacities are given in gallons per minute. The pump must produce the desired operating pressure for the spraying job to be done. Pressures are indicated as pounds per square inch psi.

The pump must be able to withstand the chemical spray materials without excessive corrosion or wear. Use care in selecting a pump if wettable powders are to be used as these materials will increase pump wear.

Before selecting a pump, consider factors such as cost, service, operating speeds, flow rate, pressure and durability. For spraying vegetable crops, a diaphragm pump is preferred because of service ability and pressures required.

Nozzle selection is one of the most important decisions to be made related to pesticide applications. The type of nozzle determines not only the amount of spray applied, but also the uniformity of application, the coverage obtained on the sprayed surfaces, and the amount of drift that can occur.

Each nozzle type has specific characteristics and capabilities and is designed for use under certain application conditions. The types which are commonly used for ground application of agricultural chemicals for onions are the fan and cone nozzles. The type of nozzle used for applying herbicides is one that develops a large droplet and has no drift.

The nozzles used for broadcast applications include the extended range flat fan, drift reduction flat fan, turbo flat fan, flooding fan, turbo flooding fan, turbo drop flat fan, and wide angle cone nozzles. Operating pressures should be 20 to 30 psi for all except drift reduction and turbo drop flat fans, flooding and wide angle cones.

Spray pressure more than 40 psi will create significant drift with flat fan nozzles. Drift reduction and turbo drop nozzles should be operates at 40 psi. Flooding fan and wide angle cone nozzles should be operated at 15 to 18 psi.

These nozzles will achieve uniform application of the chemical if they are uniformly spaced along the boom. Flat fan nozzles should overlap 50 to 60 percent. Hollow cone nozzles are used primarily for plant foliage penetration for effective insect and disease control, when drift is not a major concern.

At pressures of 60 to psi, these nozzles produce small droplets that penetrate plant canopies and cover the underside of the leaves more effectively than any other nozzle type. The hollow cone nozzles produce a cone shaped pattern with the spray concentrated in a ring around the outer edge of the pattern.

Even fan and hollow cone nozzles can be used for banding insecticide or fungicides over the row. Various types of nozzle bodies and caps, including color-coded versions, and multiple nozzle bodies are available. Nozzle tips are interchangeable and are available in a wide variety of materials, including hardened stainless steel, stainless steel, brass, ceramic, and various types of plastic.

Hardened stainless steel and ceramic are the most wear-resistant materials. Stainless steel tips, even when used with corrosive or abrasive materials, have excellent wear resistance. Plastic tips are resistant to corrosion and abrasion and are proving to be very economical for applying pesticides.

Brass tips have been common, but wear rapidly when used to apply abrasive materials such as wettable powders. Brass tips are economical for limited use, but other types should be considered for more extensive use.

The grower who plans to use spray materials at the low water rate should follow all recommendations carefully. Use product label recommendations on water rates to achieve optimal performance.

Plant size and condition influence the water rate applied per acre. Examination of the crop behind the sprayer before the spray dries will give a good indication of coverage. Most materials applied by a sprayer are in a mixture or suspension. Uniform application requires a homogeneous solution provided by proper agitation mixing.

The agitation may be produced by jet agitators, volume boosters sometimes referred to as hydraulic agitators , and mechanical agitators.

These can be purchased separately and installed on sprayer tanks. Continuous agitation is needed when applying pesticides that tend to settle out, even when moving from field to field or when stopping for a few minutes. When applying insecticides and fungicides, use a broadcast boom arrangement.

Place nozzles on 10 to 12 inch centers for complete coverage of the plant. Because there are ounces of liquid in 1 gallon, this convenient relationship results in ounces of liquid collected being directly equal to the application rate in gallons per acre.

Calibrate with clean water when applying toxic pesticides mixed with large volumes of water. Check uniformity of nozzle output across the boom.

Collect from each for a known time period. Each nozzle should be within 10 percent of the average output. Replace with new nozzles if necessary.

When applying materials that are appreciably different from water in weight or flow characteristics, such as fertilizer solutions, etc. Exercise extreme care and use protective equipment when active ingredient is involved. Table 6. One ounce discharged equals one gallon per acre.

To determine a calibration distance for an unlisted spacing, divide the spacing expressed in feet into Onion diseases can cause severe losses by reducing yield and quality of marketable onions. These onion diseases can occur in seedbeds, production fields and in storage.

can provide good weed control in and between rows if applied in a thick mat before weeds emerge. There are also OMRI-approved organic herbicides that can assist in weed management in these operations. These organic herbicides are primarily contact herbicides and must be applied to the green tissue of the weeds.

Care must be taken when using these contact herbicides that the chemical does not get on the onion seedlings. Most organic herbicides have limited residual activity so weed control involves a combination of approaches like tillage, hoeing, and mulches, in addition to the herbicides.

Herbicide labels often change, so make sure to always consult the label to determine if onion is listed on the label, what precautions are required, and what rates and application methods are allowed.

It is critical to read and understand the label. Finally, herbicides are just one tool available for weed control and their use should supplement other good weed-management practices.