Sweet Corn Production & Guidelines

To supply our customers with some information HarvestMan Sweet Corn would like to give some guidelines to just how sweet corn can be successfully grown. There are many different methods of raising sweet corn and also many different purposes and reasons for growing sweet corn. Commercial production obviously produces the highest quantity of sweet corn to supply our grocery stores, processing plants, and fresh markets but many grow sweet corn just for a hobby, a garden crop, or just some for the grandkids. No matter how you grow sweet corn people usually carry a lot of pride in just how well it does each season. Although everyone has there own way and reason for growing sweet corn, I hope that this information helps you raise a very successful crop and as always help you (our customer) achieve just exactly what you want out of our seed. Sweet corn can be a challenging crop to raise but with the right techniques and a little bit of luck from mother nature you can raise a sweet patch yourself.

HarvestMan Sweet Corn
4149 Waterthrush Drive
Indianapolis, Indiana 46254
Office Phone: 317-503-6424
harvestmansweetcorn@gmail.com

Background | History | General Planting | Spacing | Weed Control | Fertilization | Irrigation | Common Issues | Harvest | Cooling | Seed Quantity

Background

Sweet corn (Zea mays var. rugosa), also called sweet corn, sugar corn, or simply corn, is a variety of maize with a high sugar content. Sweet corn is the result of a naturally-occurring recessive mutation in the genes which control conversion of sugar to starch inside the endosperm of the corn kernel. Unlike field corn varieties, which are harvested when the kernels are dry and fully mature, sweet corn is picked when immature and eaten as a vegetable, rather than a grain. Since the process of maturation involves converting sugar into starch, sweet corn stores poorly and must be eaten, canned, or frozen before the kernels become tough and starchy.

History

Field corn was grown in North America before 200 B.C. Field corn is produced primarily for animal feed and industrial uses. Sweet corn is produced for human consumption as either a fresh or processed product. The specific time when sweet corn originated cannot be pin-pointed, but sweet corn was grown by the American Indian and first collected by European settlers in the 1770's. The first variety of sweet corn, Papoon, was acquired from the Iroquois Indians in 1779.

Sweet corn is a form of maize that has been cultivated since the nineteenth century. Maize (known as corn in the USA and elsewhere) has been an important foodstuff for thousands of years. It was eaten by Mexican and central American cultures as early as 3,400 B.C. and fuelled the Aztec Empire as well as the Mayan and the Inca civilizations.

General Planting Recommendations

The first step to making sure you will receive the stand you have planted is to make sure the soil temperature is at the proper level. Soil temperatures should be about 60 degrees Fahrenheit and slightly warmer for super-sweet varieties.

The second is to make sure you have a well prepared seed bed. Although minimal tillage is an option a finely worked seed bed will produce very consistent results. Plant your seed in well drained soils. The seed will be vulnerable to disease and seed rot if left in wet soils for a prolonged period. Having a well maintained seed bed and the right drainage is key to stand establishment and plant health in sweet corn.

Test your soil for fertility and ph levels. The PH level should be around 6.0 to 6.5. You can add limestone to raise the pH if it is low. Apply the powdered limestone during fall so that your soil will be ready by next growing season. You can also do this with your fertilizer depending on what form you use. Using fertilizer in the spring and side dressing along rows ensures that the plant intakes as much fertilizer as possible, but seed bed nourishment can be maintained by fertilizing in the fall as well. This will ensure that your soils levels are at the proper levels for seed establishment and growth.

Spacing

Row spacing may range from 30 to 42 inches apart depending on equipment and soil type. One plant every 6 to 12 inches is a common spacing and is determined by soil type. The next thing to consider is row length. Planting seed in short rows as shown in figure 1, will allow for better pollination and ear fill. This is more common in the garden type situation where other corn may not be planted. If Planting along field longer rows can be used but also know that some of that sweet corn will be pollinated by the field corn standing next to it. Most Sweet corn is planted next to field corn and I have not had any complaints of quality in that scenario. Weed Control Select a field that does not contain noxious weeds. Crop rotation is important for limiting the build up of troublesome weeds. Shallow cultivation should be used along with chemicals for weed control. If you are a organic farmer cultivation is a must along with good stand establishment early in the growing season to help shade out the weeds. The crop should remain weed-free during the early stages of plant growth otherwise yields might be substantially reduced. Several herbicides are available for weed control. Identify the weeds in each field and select the herbicide which will control those weeds. If double cropping to another crop after using these herbicides be sure that crop is not sensitive to herbicide carryover, particularly atrazine or atrazine-containing products.

Above shows excellent spacing and stand establishment for a sweet corn crop

Fertilization

Apply fertilizer according to soil test results noted above. A general recommendation would be to apply a total of 150 to 180 lb of nitrogen, 50 to 60 lb of phosphate (P2O5), and 70 to 90 lb potash (K2O5 per acre). Each amount will very depending on soil test results but as a standard application follow the above rates. For early plantings, when cold conditions are often encountered (60°F), use a "starter" fertilizer (e.g., 10 gal of 11-37-0 or 75 lb of 18-46-0 per acre) for improving seedling vigor, stand establishment and early plant growth is recommended. Fertilizer should be applied in 1 or 2 bands approximately 3 inches to the side and 2 to 3 inches below the seed. Between 50 to 60 lb of actual nitrogen per acre should be applied pre-plant or at planting, while a side-dress application of 90 to 100 lb should be applied when the plants are 18 to 24 inches tall. The market demands sweet corn with long green leaves and dark green husks. To accomplish this, an adequate supply of nitrogen must be maintained in the soil and available for the plant to intake.

Irrigation

A field with good soil moisture will produce early, uniform emergence, increase yields and improve overall health of the young plant. Irrigation should be provided before the soil becomes dry. Young sweet corn plants have a rather coarse, shallow root system, but as the plant approaches maturity, the root system becomes more fibrous and penetrates to a depth of 3 ft or more. A grower should be prepared to irrigate at least 1 to 1½ inches a week in order to produce high quality sweet corn. The most critical time period to have adequate moisture is during tasselling and silking. Common Issues in Sweet Corn Root Rot: If you have cool, moist soil, watch out for this problem. Improve soil drainage with compost and wait for soil temperatures to get to the recommended soil temperature. Rust/Leaf Blight: Warmer, wetter parts of the country have problems with these diseases. There are many blight resistant varieties available. Wireworms/White Grubs: These pests are mostly from soils recently planted with sod or alfalfa, they are also found in regular soils as well. A quick fix to the pest is our Latitude product. Corn rootworm beetles: This pest goes after corn silk on maturing cornstalks. They can cause problems with pollination. The immature beetles can be found in old corn fields, and when mature, they migrate to feed on tender, new corn. Keep on the lookout as your corn first starts to produce silk. Corn Smut: This is a fungus that causes the kernels to swell and turn grey and black. In Mexico, it is called Huitlacoche and is consumed as a delicacy. Corn smut is more common on white varieties. You can remove the smut by hand and you should destroy it so that it won’t infect other corn plants. If you’re curious, you can actually harvest the smut before it turns black and dries out. Check out this article from the University of Illinois at Urbana-Champaign on the economic importance of Huitlacoche in Mexico: sweetcorn.uiuc.edu/Common-smut/Huitlacoche-WSMBMP.doc. Also see Aztec Gardens for more information on this unusual food.

In commercial production of sweet corn they use large pivot irrigation, but you can use a small scale system for a garden as well. Click on image to view product description of how latitude can prevent damage from these pests

European corn borers: These pests bore into the stalks and can weaken them to the point of breakage. The larva is cream colored and they are about 1" long. They may eventually work their way into the corn cob. Their eggs begin to hatch in June. Fall armyworms: This moth lays small pinkish eggs on corn leaves. Adult worms are less than two inches long. They have a Y shaped marking on the head. Late sweet corn is especially susceptible. You can plant early to help avoid this pest.

Flea beetles: These pests attack in the early spring and can carry Stewart's bacterial wilt disease. This disease will eventually stunt the growth of young corn. Latitude again is a quick fix to this pest and will protect up to the first true leaf.

Corn earworms: These are brownish, flying moths that will lay eggs in corn silk. The worms will feed on the tips of the ears. You'll usually not find more than one caterpillar per ear as they are known to devour each other when there is competition. Pheromone traps placed around the planting area is an effective control. You can also use mineral oil in the tip of the silk tube, or by sealing off the husk with a rubber band.

Birds: Birds such as crows and black birds are common pests for sweet corn farmers. You can use reflective bird tape throughout the rows to scare them off and confuse them. A good old fashion scare crow is also effective.

If a weed, insect or disease problem does occur, consult HarvestMan Sweet Corn for recommendations.

Harvest and Handling

Sweet corn loses sweetness and freshness rapidly after harvest, and the rate of loss increases with increasing temperature. Corn harvested early in the morning will be 10 to 20°F cooler than that harvested later in the day. The longer the delay, the greater the heating conversion of sugar to starch and the end result is quality loss. Sweet corn must be moved quickly from the field to market, cold storage or processing. If cooled and stored properly sweet corn will hold its quality for quite some time, heat is the enemy in this process so the cooler the better.

Cooling

Sweet corn should be pre-cooled to as close to 32°F as possible, although it is rarely cooled below 40°F in commercial practice. Several methods of cooling sweet corn are available:

Hydro-cooling

Hydro-cooling Consists of pre-cooling by either showering the corn or immersing it in cold water. It is the most popular method of pre-cooling. Immersing the corn in cold water is much more efficient than showering the corn.

Package Icing

This is an excellent method of pre-cooling sweet corn that is used for local use and direct shipments. In this method crushed ice is distributed throughout the during the packaging process. The amount of ice needed in a package depends on the temperatures of the corn at the time of packing and on the expected length of the marketing period. Typically about one lb of ice for 5 lbs of sweet corn is sufficient.

Cold Storage

To maintain best quality, place sweet corn in cold storage immediately after pre-cooling, storage can be in a refrigerated truck, room, or just the old refrigerator in the shed. Temperature is maintained as close to 32°F as possible without freezing the corn, and relative humidity of the air in the cold room at 95% or higher to keep the corn fresh. Market or process the corn as soon as possible since more than a few days in cold storage will decrease quality.

Cooling in Transit

Sweet corn must also be kept cold in transit. The best method consists of blowing finely crushed ice over the top and through the corn crates as trucks is loaded. This method of icing keeps temperatures low during transit but provides little or no additional cooling. The refrigerated truck only maintains the temperature of the already cooled corn. It is not meant to be used as a substitute for pre-cooling. It is key to remember that for maximum quality and value, sweet corn must be continuously and properly refrigerated from harvest until it reaches the consumer.

Determining how much seed you will need.

Supersweet sweet corn seed contains a large quantity of sugar which causes the seed to be crinkled and smaller. Therefore, supersweet sweet corn varieties have a higher seed count (2250 seed per lb) than other sweet corn types (1500 seed per lb) and will require less seed (5 to 6 lb) to plant an acre.

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