John Gerber, University of Illinois Darbie Granberry, University of Georgia Doug Sanders, North Carolina State University Don Bullock, University of Illinois
Maize or corn is thought to have evolved from its wild ancestors in Mexico and Central America and became a staple food for American Indians in pre-Columbian times. Ancient sweet corn types have been found in the Andean zone of Peru. The Iroquois in upper New York State also grew a variety of sweet corn whose kernels turned blue as they matured.
Maize was first classified according to the variation in the carbohydrate stored in the endosperm. In sweet corn, the sugary (su) or sweet gene on chromosome-4 prevents or retards the normal conversion of sugar into starch during endosperm development, resulting in a sweet taste. Sweet corn is considered a high-quality vegetable when used in the milk stage at 70-80% seed moisture, depending on the endosperm type.
Total U.S. sweet corn acreage has been relatively stable over the last 15 years, with 193,000 and 427,000 acres harvested annually for fresh market and processing, respectively. Since 1970, sweet corn yields for fresh market and processing have increased 17 and 31% to 81 cwt and 5.97 tons/acre, while the crop values have risen by more than 150% to $13.10/cwt and $63.70/ton. Per capita consumption of fresh corn has remained constant over the same time period, but the production of processed sweet corn has risen substantially due to greatly increased consumption of frozen cut and cob sweet corn.
Florida produces 80% of the winter (Jan.-June) U.S. fresh market sweet corn, and most of the summer/fall production for fresh market occurs in the northeast. Processing production is located primarily in the upper midwestern (Minnesota, Wisconsin) and northwestern (Oregon, Washington) states.
This publication presents an overview of commercial sweet corn production practices. Much of the information can, however, be useful for home gardeners. Discussed are the management considerations involved in growing, harvesting, and postharvest handling of the crop. The primary pests of sweet corn are also listed.
Virtually all sweet corn varieties used are hybrids. Modern hybrids tend to be of either two types: fresh market or processing, according to intended use. Generalized differences between the two are summarized in Table 1. Processing requirements exact more rigid hybrid specifications, compared to some of the fresh market outlets; hence hybrids intended for processing may also be used in the fresh market trade.
Both yellow and white hybrids for processing and for fresh market are available, although most of the sales volume comes from the yellow type. White types, however, are more popular in the south. In recent years, a third color form (bicolor) which produces segregating yellow and white kernels has become increasingly popular for the fresh market, especially in the East. Bicolor types now occupy a significant share of the fresh market.
Historically, standard sweet corn, as noted in an earlier section, has been based on the gene su. However, a number of other genes also are known to slow or retard the conversion of sugar to starch in the maturing endosperm. Some of these are being used, either singly or in combinations in the development of high sugar (supersweet) corns. The most widely used are sh2 (shrunken-2) and se (sugary enhancer). Some use has been made of the bt (brittle) and of the combination ae du wx (ADX).
The major advantage of the high sugar types, in addition to greater sweetness, is their longer harvest window and longer shelf life. Slower sugar loss and higher initial sugar levels at harvest provide greater flexibility of harvest timing and of handling conditions. The sh2 hybrids, in particular, continue to make rapid inroads on the standard su hybrids in the fresh market trade. During the past several years more than 90% of the Florida winter production has been converted to sh2. Foreign markets also are most often based on sh2 rather than on su. For example, in Japan virtually all fresh market sweet corn is of the sh2 type.
Processing Frozen corn Trait2 Fresh-market Whole-kernel Cream-style on cob ---------------------------------------------------------------------- Yield Green weight 1 3 3 2 Weight of cut corn 1 3 3 1 Usable ears/acre 3 2 2 3 Ear characteristics Husk cover 3 2 2 2 Flag leaves 3 2 2 2 Ear length 2 2 2 3 Light silk color 3 2 3 3 Tip fill 3 2 2 3 Ease of husk removal 1 3 3 3 Appearance of husked ear 3 2 2 3 Color of cob (light) 3 3 3 3 Kernel characteristics Size 2 3 1 2 Depth 1 3 2 2 Color 2 3 3 3 Tenderness 2 3 2 2 Flavor 3 3 2 3 Silk attachment color 2 2 2 2 Black layer 1 3 2 1 ------------------------------------------------------------------ 1 Rated 1, relatively unimportant; to 3, very important. 2 Seedling vigor, uniformity, resistance to insects and diseases, lodging resistance, and stress tolerance are examples of traits that are equally important in fresh-market and processing sweet corn. Adapted from Kaukis, K. and D. W. Davis. 1986. Sweet Corn Breeding. In: Basset, M. Breeding Vegetable Crops. AVI Publishing Co., Inc. Westport, CN.
Some of the high sugar types have other traits which may influence production, handling and use. These mutants, in general, have more shriveled, collapsed seed, and they contain less starch reserve. Therefore, precision seeding and stand establishment are more difficult. Seed should be planted in warmer soils, as compared to normal su hybrids, and at less depth. Planting delay of one to three weeks is common. Seedlings often are weak and slow growing. Warm, sandy, or noncrusting soils are preferred.
Secondly, high sugar hybrids differing in the gene responsible for sugar building need to be separated in production, especially sh, bt, ae du wx, and su types. If they interpollinate, the resulting ears will have starchy rather than sweet kernels. Separation, and reduction of interpollination can be made based on either distance or time of silking/tasseling. The sugary enhancer (se) types can be interpollinated with normal su sweet corn without starchy kernels resulting. Where isolation is necessary, several hundred feet should be adequate. However, the effective distance will depend to some extent on the relative field size of the two hybrids.
Optimum growth of sweet corn occurs when temperatures range from 75 to 86 F. High night temperatures are detrimental since they result in increased respiration rates and loss of photoassimilates. Growth will not occur when temperatures are below 50 F.
For satisfactory growth and high yields, sweet corn requires a continuous supply of moisture. In most oases this is the equivalent of 18 to 28 in. or water to produce a crop. Seed will germinate in soils with moisture ranging from slightly above the permanent wilting percentage to field capacity. The most critical growth periods that require adequate soil moisture are during germination and stand establishment, tasseling and silking, and ear fill. Depending upon local environmental conditions, a minimum of 1 to 1.5 in. of water per week is required to insure pollination and ear fill.
Sweet corn varieties are affected by the length of day. Early maturing varieties grown in the north are adapted to long, cool summer days and do not grow well in the south. Varieties adapted to the south respond to short days. If planted in the north, southern varieties will not flower (produce tassels and silk) until the shorter days in the fall. They may grow up to 10 ft. or more in height. but seldom produce satisfactory ears before they are killed by frost.
Sweet corn production is based on continuous harvest in both fresh market and processing areas. Since the time between planting and harvest depends primarily upon temperatures, preseason planting schedules are generally based on the use of heat units (degree days). The number of degree days required by different varieties to reach maturity is generally determined by the seed companies developing the seed. In production planning, planting schedules are developed by using historical daily heat unit values (using a base of 50 F). After planting begins, planting schedules are modified based on actual heat unit accumulation. Using this method, it is possible to schedule harvest throughout the harvest season and take into account differences in varieties, actual growing conditions, and variation in demand during the harvest season. Other considerations in establishing planting and harvesting schedules are cultivar differences, day length, cloudiness, rainfall, and the fact that ears on the stalk remain in good marketable condition somewhat longer during cool weather than during warm weather.
Precision seeding for the desired plant spacing can assure uniform stand establishment and plant growth as well as reduce the seed use per acre. Prior to seeding, fields should be leveled to eliminate low, wet areas that cause poor stands and plant growth. Treated seed should be used for protection from soil-borne diseases and insects during germination and seedling development. This measure is particularly important for seed with the sh2 gene (and all super sweet types) since they tend to germinate slower and produce weaker seedlings.
Seed should have high germination (90%) and vigor, and be separated by size (large and small) and shape flat or round). Uniform seed are especially useful with precision seeding equipment. Large seeds frequently produce more vigorous plants and uniform stands than small seeds. Seeds of the super sweet types, and particularly those with the sh2 gene, are very small, fragile (easily damaged in handling and planting), and germinate poorly in cold soils.
Highest yields result from rows 28 to 32 in. apart and seeds spaced 8 to 7 in. in the row to give a stand of about 24,000 plants per acre. For larger ears, wider rows (36 in.) with seeds spaced 7.5 to 6.5 in. (20,000 to 23,000 plants per acre) can be used. A minimum row spacing of 30 in. is recommended for mechanical harvesting.
Uniform seedling emergence and stalk growth are essential for ears of uniform maturity at a single harvest. If there is more than one ear per plant, the range in maturity and ear size requires extensive sorting before packing. A much smaller range in maturity and ear size results from cultivars and plant spacing that produce only one ear per stalk.
Sweet corn requires a well-drained soil with adequate water holding capacity for optimum growth. Light, sandy soils, will require irrigation to meet crop water demands and heavy, clay soils may need to be tiled to improve drainage conditions. Sweet corn grows best in a soil with a pH between 5.8 and 6.5. Lime should be applied according to soil test recommendations if the pH falls below 5.8.
Efficient fertilizer use for sweet corn should be based on a soil testing program and selection of realistic yield goals. Tissue analysis can also be used to provide supplemental information on the fertilizer program and the nutritional status of the plant.
Soil tests prior to planting provide the best information for determining whether sweet corn will respond to applied fertilizer. Instructions for taking a soil sample can be obtained through county Extension offices or soil testing laboratories. Because nitrogen can move rapidly and fluctuate widely in many soils, the nitrogen soil test is not usually reliable and is used in only a few areas of the country for determining crop nitrogen requirements. The nitrogen soil test can be used for predicting fertilizer needs in areas with low rainfall where nitrogen loss is not a problem. Soil test interpretations will vary with extractant used and region of the country. Contact your local county agent for soil test interpretations in your area.
Tissue analysis can be used during the growing season to monitor the nutrient status of the plant. Sufficiency levels in whole plant samples taken when plants are 12 in. high and ear leaf samples taken during silking are provided in Table 2.
Nitrogen fertilizer recommendations for sweet corn are based on yield goal and previous crop. Nitrogen management is not only important from a crop production standpoint, but also from an environmental standpoint. On sandy soils, nitrogen can be leached out of the root zone with heavy rainfall or excessive irrigation. As a consequence, the potential for nitrate contamination of the ground water increases and nitrogen deficiency may result. On sandy irrigated soils, nitrogen should be split applied: one third to one half the nitrogen requirement at planting, and the remainder applied as one or two sidedress applications at the 6 and/or 12 leaf stage. On relatively heavy soils or nonirrigated soils that do not receive leaching rains, nitrogen incorporated prior to planting is usually sufficient to meet sweet corn needs. Avoid excessive nitrogen applications as some of the nitrogen not taken up by the crop may contribute to ground water problems. Nitrogen rate can be lowered if the crop follows a legume or if manure is used. Although nitrogen content of manure varies, nitrogen fertilizer rates can be lowered by about 5 lb. N/a. for each ton of cow manure applied. Poultry manure supplies about twice this amount. Symptoms of nitrogen deficiency include stunted growth, yellowing of the older leaves and poor yields.
Soil tests should be used to determine whether phosphorus or potassium fertilizers are needed. If soil tests are in the high range, only banded applications at low rates (15 lb. P2O5 /a., 15 lb. K2O/a.) at planting would be required. Root growth of young sweet corn seedlings is enhanced in cool soils with banded phosphorus applications. As soil temperatures increase, phosphorus becomes more available and response is not as likely. Potassium can leach in sandy soils low in organic matter. Broadcast applications of phosphorus and potassium are necessary when soil test levels are in the low range. Symptoms of phosphorus deficiency are stunted growth and a dark green or purpling of the older leaves. Potassium deficiency symptoms include scorching of the margins of the older leaves.
Micronutrients which include boron, chlorine, copper, iron, manganese, molybdenum, and zinc are required in lower amounts than the other essential nutrients. Generally, soils contain sufficient levels of micronutrients to meet crop demands; however in some areas micronutrient shortages occur and may limit yields. Sweet corn has a relatively high demand for zinc. Deficiency of zinc may occur in high pH soils (greater than 7.0), sandy soils, and soils containing high phosphorus levels. If soil test zinc is low then banded applications at planting (2 to 3 lb. Zn/a.) should be applied. Zinc deficiency symptoms include striping of the younger leaves and shortened internodes. The need for other micronutrients should be confirmed by soil tests and/or tissue analysis.
Weeds reduce yield and quality of sweet corn by direct competition for light, water, and nutrients in the soil. Weeds may also harbor insect and disease pests that attack corn. During 1975 to 1979, the estimated average annual loss due to weeds in sweet corn in the United States was 1,460,000 cwt of fresh market sweet corn worth $13,165,000 and 185,000 cwt. of sweet corn for processing with a value of $49,155,000.
Historically, the major reason for corn being grown in wide rows was weed control. Row width was dictated by the size widths of horses needed to pass between the rows pulling a cultivator.
Mechanical cultivation of sweet corn is still widespread. The initiation of the use of selective herbicides some 40 years ago in corn has decreased the number of cultivations needed per season. This has substantially lowered the fossil fuel energy used in sweet corn production. Many sweet corn fields now receive one or no cultivations at all. Cultivation reduces surface crusting, and controls weeds resistant to the herbicide combinations selected.
At the present time, a wide selection of herbicides is available that effectively control most weeds. Herbicide treatments are primarily categorized on the basis of the time of application: pre- planting, preemergence, and postemergence. Preplanting treatments are applied either before the corn is planted and as a surface treatment or incorporated into the soil. Preemergence application takes place after the corn is seeded but before emergence of the corn or weeds. Preplant and preemergence herbicides, properly selected and applied, prevent weed competition during emergence and early seedling growth. Postemergence applications take place after the emergence of both the corn and weeds. These are most effective when weeds are small.
Stage of Plant Part Growth Sampled N P K Ca Mg S Fe B Cu Zn Mn Mo ------------------------------------------------------------------------------------- 12 in. height whole plant 3.50 0.40 3.0 0.3 0.30 0.2 50 7 7 20 50 0.3 Silking ear leaf 2.80 0.25 1.8 0.3 0.25 0.2 60 6 6 20 25 0.3 ------------------------------------------------------------------------------------- 1 Levels below these values are considered low or deficient. Levels above these values are considered high or excessive
Insects can severely damage all portions and ages of sweet corn plants. More than 50 insect species or groups of species are known to cause economic losses to sweet corn in the U.S. Soil insects have been considered the most important pest grouping which consistently causes damage to all types of corn. In the Southeast, foliar pests and earworms are the major concern to sweet corn growers.
Of the soil insects, corn rootworms are a major concern especially in the midwestern corn production areas. There are three species, the southern, the northern, and the western rootworm. The rootworms actively feed on small roots of corn and tunnel into larger roots. The adult beetle will feed on ears, pollen, and silk of the corn plants. Wireworm damage is usually noticed as wilted and dying plants although the larvae feed on all underground parts of the plant including the seed. The adult wireworm is the "click beetle" and is usually not injurious. There are several types of cutworms that cause isolated damage each year. Cutworms when disturbed will curl into a tight coil and can be identified easily by this habit. Cutworms do not feed voraciously but will cut off small plants less than 3 ft. in height. A number of plants may be cut off during the evening hours. The cutworm will hide under clods or in the soil during the daylight hours.
Several other soil inhabiting pests may cause damage to corn. Soil grubs and webworms are pests more often found when corn follows pasture or in a no-till situation. These pests feed on the roots and lower stem of the plants.
Corn earworm. The corn earworm is a voracious feeder in the whorl and in the ear of corn plants. The adult moth overwinters in the southern U.S., and the population migrates north during the year. The moth lays eggs on the plants and then young caterpillars feed on the plants any time during the season. In fresh market corn, these worms found in the ears are the biggest cause of loss in grade. Without control, 100% of the field may be infested.
Armyworms. Several species of armyworms (fall, southern, and beet) are important, especially in the Southeast. On occasion. the larvae migrate in mass, especially across a young field, hence the name "armyworm." These caterpillars feed primarily in the leaves and whorl of the plants, and are sometimes referred to as budworms. If populations are severe, complete loss of the bud can occur. Armyworms also attack the ear in the southern U.S., and can produce several generations. In most cases, the armyworm complex is much more difficult to control then earworms.
Aphids. Aphids, or plant lice, are frequent pests of sweet corn. Aphids suck sap from the plants. Heavy infestations may cause plants to wilt and fail to produce a marketable ear. Aphids transport virus diseases, which is probably more damaging than just their feeding alone.
Stem borers. Several species of stem borers can be found attacking sweet corn in the U.S. The European corn borer probably is the most widely distributed and probably causes the most damage. The larvae overwinters in field debris. In the spring, after pupation the adult moth lays eggs on leaf surfaces. The larvae feed first on the leaf surfaces and midribs. The larvae then bore into the stems. Larger larvae often tunnel and feed in the stem and the ear, which results in stem and ear breakage.
The lesser cornstalk borer is an important pest in the southeastern production areas. Dry weather seems to favor the development of this pest. The lesser cornstalk borer is a pest of many crops in this area. The feeding activity can produce "dead-heart" condition of young plants. One of the identifying features of this pest is a silken tube leading away from the infected plant.
Other foliar insects. In addition to the above insects, leaf and flea beetles attack sweet corn foliage. Economic damage is caused by thrips, chinch bugs, and the corn leaf miner. Although not an insect. the spider mites have been identified as causing serious problems in several areas of the U.S. Of these, the grass mite, the two spotted spider mite, and the red spider mite are important.
Sweet corn is susceptible to the parasitic diseases common to dent corn. All parts of the plant are susceptible to a number of diseases which may reduce yield and quality of the sweet corn. The extent and severity of a disease depend on the presence of a pathogen (disease causing organism), the susceptibility of the sweet corn cultivar, and the right environment (rain, temperature, etc.) for the pathogen to develop. Some diseases are not of widespread economic importance because they occur rarely or only in localized areas. Others can be widespread, and if conditions are favorable, may cause significant economic damage. A good reference for corn disease identification is A Compendium of Corn Diseases published by the American Phytopathological Society, Inc.
Damping off is a term referring to the infection of kernels by either seed-borne or soil-borne fungi. These diseases caused by Pythium sp., Fusarium monilitorm and Diplodia maydis, cause reduced stands, wilting and chlorosis of the leaves, and/or rotting of the stem tissue around the soil line. These diseases are favored by cool (50-55 F), wet soils. Weak seed or weak seedlings caused by mechanical injury to the seed coat, or excessive planting depth are more susceptible to infection. Super sweet cultivars, if not handled properly may be weaker and are prone to attack by seedling diseases. Use of proper planting techniques and labelled seed treatments along with properly handled high-quality sweet corn seed will eliminate many seedling problems.
These diseases can be very destructive to sweet corn. Several fungi and/or bacteria may infect the roots and stalks of sweet corn at various times. Most commonly, infections are noted when the plants near maturity, due to lodging of plants and poorly filled ears. Stalk rots are most common where unbalanced high N fertilization is used and excessive periods of wet weather occur after silking is experienced. The stalk rot organisms can overwinter on seed and plant debris in the field. The disease is more severe in dense plant populations. Insect injuries can also predispose plants to infection. The use of cultural practices and resistant varieties, when available, are the best control methods.
Many organisms have been identified as causing spots and blights of sweet corn. Of these, the most damaging are Northern and Southern leaf blight, yellow leaf blight and anthracnose. Northern leaf blight caused by the Organism Helminthosporium turcicum is favored by relatively cool temperatures ranging from 65 to 80 F and heavy dews. However, when the mean weekly temperature is below 60 F or when the mean relative humidity is lower than 60%, the disease is checked. Young plants can be infected at an age of 6 weeks. Losses may range from very light to as much as 80% of the yield, depending on the severity of the attack and the time when the disease appears. A disastrous epidemic of this disease appeared in the U.S. on hybrids using the Texas male-sterile cytoplasm starting in 1970.
Southern leaf blight. Helminthosporium maydis, occurs world wide but is generally not as severe as Northern leaf blight and is favored by warm rainy weather specifically in the southern U.S. Northern leaf blight can be distinguished from Southern leaf blight many times by the length of the lesion. Lesions of Northern leaf blight are much longer, from 112 in. to 6 in. in length. Single Southern leaf blight lesions are rarely longer than 3/4 of an inch and often coalesce.
Yellow leaf blight or phyllosticta leaf spot appeared in the late 1960's in the northern production areas of the U.S. It has since been found occasionally in the south. The development of the disease is favored by cool, wet weather and favored by young plants growing through plant debris in the field. Clean plowing and rotations greatly reduce early season development. Planting resistant varieties is the best means of control.
Anthracnose. Colletotricum graminicolum was seen in limited locations in 1971 and 72. Anthracnose is generally favored by high temperatures and develops best on older tissues. Free water from rain, fog or dew is necessary for spore dispersion and germination. Most of the leaf spots and leaf blight diseases may be controlled by the use of resistant varieties, cultural practices to reduce the chance of early infection and fungicide applications.
Rusts and smuts. Rust and smut diseases may be found wherever corn is grown, but only occasionally are they economically important. Rust, Puccinia sorghi, usually appears late in the season, at about tasseling in northern temperate zones. P. polysora, southern rust prefers warmer climates. Both need alternate hosts to overwinter, such as wood sorrel.
The common smut. Ustilago maydis, is easily recognized as enlarged swellings on the stem, developing ears or tassels. The fungus overwinters in the soil and infection may take place anytime during the growing period.
Rots of this nature are not as important in sweet corn as dried corn (field corn, popcorn etc.). Stalk rots may invade the ear if the infection is severe enough. Most ear rots are secondary to damage from insects, such as earworms. Ear and kernel rots may throw shipments out of grade if insect feeding on the lower ears have been heavy.
Identification of different virus diseases that attack sweet corn at present is more art than science. Field symptoms of many virus diseases are easily confused between nutritional disorders and herbicide toxicity. Laboratory identification is the only practical method of identification of a virus. Maize dwarf mosaic and the sugarcane mosaic virus group are the major virus diseases found in sweet corn. Both are transferred from Johnsongrass by leafhoppers.
Sweet corn can be severely injured by several kinds of nematodes. Unlike diseases and insects, nematodes usually do not cause easily recognized symptoms. Visual conservation of a plant and its roots can often indicate nematode problems, but it is necessary to have soil and root samples examined to be sure they are present. Nematode injury usually results in irregularly shaped areas of stunted plants in a field. Plants may be chlorotic ana may wilt during hot weather, even when soil moisture is adequate. Nematodes may cause short, stubby, or galled roots which may also have brown or colorless lesions. The sting, stubby-root, awl, rootknot, lesion. and lance nematodes are more common on mineral soils. The most severe in organic soils include stubby root, spiral, stunt, and root-knot nematodes.
When harvested at optimum maturity, the silks are brown and dry, the kernels are plump, sweet, milky, tender, and almost maximum size. Sweet corn has a short harvest period, and harvesting on the day of optimum maturity is very important for good quality and yield. Immature ears have smaller diameters and the kernels are less developed, watery, and less sweet. With very little change in husk appearance, kernels will pass the period of maximum sweetness and start to dent.
Single harvests by hand or machine are practiced by commercial growers. Trucks or tractor drawn wagons haul the ears to an assembly area in the field, packinghouse, or processing plant for grading, packing, or processing. Harvesting methods differ due to availability of suitable labor, equipment, and destination of the corn. Processing sweet corn is all mechanically harvested and hauled bulk to the processing plant.
Self-propelled packing houses (mule trains) with conveyers for hand-harvested ears are still used to a degree in corn for the fresh market. With hand harvesting, there is some selection for marketable ears. Machines harvest all ears, culls, and trash included. Recent improvements in harvesting machinery allow shank trimming and reduction in ear damage. Removal of long shanks and flags is important for fresh market sales to prevent water loss during transportation. Fresh market corn is usually packed in wire bound crates or corrugated cartons containing five dozen ears.
Commercial fresh market growers ship U.S. Fancy (or a percentage of U.S. Fancy grade) which require a minimum cob length of 6 in. and freedom from injury by worms or other causes. Wide ranges in ear length and diameter result from differences in production areas, season, and variety.
Retailers of fresh market corn object to a wide range in number of ears per crate. because they purchase by the crate and sell by ear count. A uniform number of ears per crate is highly desirable. Defects of most concern are worm and mechanical damage, or perhaps poor cob fill.
Sweet corn that is not consumed or processed within a few hours after harvest should be precooled without delay to reduce conversion of sugar to starch and loss of flavor and tenderness. Hydrocooling is the most common precooling method. Palletized corn, either loose or in crates, are conveyed through a shower of 31 F to 34 F water or placed in a batch hydrocooler for a sufficient time (approximately 45 minutes) to achieve cooling. In some cases corn is placed in a cold room beneath nozzles which spray cold water over the bins or crates. Hydrocooling can be effectively used to lower center cob temperatures to the desired 40 F, if water temperature is kept low, the water has maximum surface contact with the corn and sufficient time is allowed. Some shippers of fresh market corn also put ice in the carton after cooling and packing to insure that corn remains cold in transit.
Vacuum cooling can be more rapid, but if the ears are not kept wet, a 1% moisture loss for each 10-degree drop in corn temperature occurs. Following precooling, sweet corn should be refrigerated at 32 F and marketed or processed as rapidly as possible.
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to our programs and facilities.