Where to plant corn?

CORN FERTILIZER RECOMMENDATIONS

For profitable production, corn requires adequate fertilizer management. Applying the right fertilizers at the right rate and at the right time is crucial for a successful crop.

The three main factors you should consider when deciding on the best fertilizer plan for your corn crop are:

The potential yield of the variety you grow.

The fertility of your soil.

Fertilizing according to corn growth stages and GDD.

CORN YIELD POTENTIAL

The nutrient requirements of corn depend on the yield goal and potential. New hybrids and high-yielding corn varieties will have a higher nutrient demand.

For example, to produce 230 bushels per acre (approx. 14.5 ton/ha) of new hybrid corn, the crop requires the following nutrient rates in lbs/acre:

N

P2O5

K2O

CaO

MgO

S

Fe

Mn

Zn

Cu

B

SOIL FERTILITY

The most important management tool you have to determine which fertilizer is best for your corn field is testing your soil.

Testing your soil allows you to determine the level of nutrients already available in the soil and which nutrients have to be supplemented using fertilizers.

This way you can have a fertilizer recommendation calibrated to your specific field conditions.

Plant tissue analysis and water analysis are other important tools you can use to adjust the fertilizer recommendation.

CORN GROWTH STAGES

Corn requires different nutrient rates at different stages of its growth. The timing of nutrient application for corn is critical.

According to those factors, it is obvious that there is no “single” “generic” fertilizer for corn.

In order to maximize corn crop, you should consider all 3 main factors and “create” the right fertilizer rates, mixture, timing that will optimize your fertilizer use.

Author: Guy Sela, international expert in plant nutrition and irrigation.

From guesswork to precision

Optimize your fertilizer management – corn, soybeans and other crops

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Fertilizers for Corn

The guidelines of fertilizer rates given in the following Table are general guidelines for optimum economic corn production.

Click image to download PDF

These general fertilizer guidelines should only be used in limited circumstances when a complete soil test has not been taken as the tables in this section are condensed for simplicity. More information is incorporated into the computerized guideline system than is considered in the general tables here. For example, in the Table the recommended rates of fertilizer application are broken down into five general soil groupings. Within each group, the years since a sod was plowed and the legume content of the sod are used to generalize the nitrogen guidelines at two rates of dairy manure additions. When these guidelines are formulated from a complete soil (and manure) test, they are tailored to the grower’s soil resources. Equations are used to calculate the guidelines based on yield potential (soil type specific), previous cropping practices, and the type, and rate of previous and present manure applications. The possible combinations range in the thousands.
For CAFO planning, see the relevant documents on the Cornell guidelines for field crops page accessible via the Cornell Nutrient Management Spear Program website: http://nmsp.cals.cornell.edu/guidelines/nutrientguide.html.

When fertilizer and manure rates are applied as suggested for agronomic response, nutrient losses into the environment are relatively small and optimum economic production can be achieved.

As mentioned, for nitrogen, guidelines are based on crop history and manure use. Work on the Illinois Soil N Test (ISNT) as a tool for assessment of soil N supply from organic matter for corn over the past six years has shown the test to be 84% accurate in identifying sites that do not need extra fertilizer N due to the soil’s N supply capacity (see http://nmsp.cals.cornell.edu/projects/NitrogenforCorn.html). These are sites where fertilizer savings can be made beyond what is recommended in the tables or soil test report based recommendation (i.e. where no N is needed due to high soil N supply even though the Cornell guidelines in the tables in this section state additional N could be needed). This test is most relevant in combination with the late season Corn Stalk Nitrate Test (CSNT) and for 2nd or higher year corn fields with a manure history where sidedressing of fertilizer N might not be needed. For more detailed nitrogen guidelines (Cornell guidelines for CAFO planning) see http://nmsp.cals.cornell.edu/guidelines/nutrientguide.html and the Nitrogen for Corn website of the Cornell Nutrient Management Spear Program: http://nmsp.cals.cornell.edu/projects/NitrogenforCorn.html. See also Agronomy Fact Sheet #63, #77 and #78 for more information on the use of the ISNT and CSNT for fine-tuning of nitrogen management for corn in New York State (nmsp.cals.cornell.edu/guidelines/factsheets.html).

Note: if soil test results are not available and previous crops do not have a history of adequate fertilization, use the fertilizer rates for medium soil test results. If the site does not have a history of fertilizer or manure, use the fertilizer rates given for the low soil test results.

BAND RATES
The fertilizer used as a starter should contain a small amount of nitrogen; most, if not all, of the recommended phosphorus; and possibly some potassium. Thus, a good starter fertilizer might range from a ratio of 1-4-0, 1-3-1, 1-3-3, to 1-1-1, depending on the rate of fertilizer required. Do not apply more than 80 to 100 pounds per acre of N + K2O in the starter band. For example, 350 pounds per acre more of 10-20-20 can result in seedling injury. Urea and diammonium phosphate (DAP) can also cause seedling injury and should not be used in the starter band to eliminate this risk (see “Fertilizer Injury”).

EFFICIENT NITROGEN USE
It is important to determine as accurately as possible the quantity of nitrogen necessary for optimum economical corn production and to apply only this quantity of nitrogen to prevent over-fertilization.

To determine the quantity of nitrogen that should be furnished by commercial fertilizer, all the nitrogen sources must be considered.

Soil organic matter supplies 40 to 80 pounds of nitrogen per acre per year. A good legume or legume-grass sod will supply 100 to 150 pounds per acre, or more, and a good grass or grass-legume sod will supply 75 to 100 pounds per acre in the first year after application. Thus, a legume sod and the soil itself will supply approximately 200 pounds per acre of nitrogen; hence, only a starter is needed to satisfy nitrogen requirements. Recent research in New York confirmed that for both optimum yield and quality a small starter N application (30 lbs N or less per acre) is needed for first year corn following sods in the rotation, independent of timing of sod kill (late fall or spring) or percentage legume in the sod (see Agronomy Fact Sheet #21 at nmsp.cals.cornell.edu/publications/factsheets/ factsheet21. pdf). Trials were conducted in 2010 and 2011 to determine if manure can replace the need for starter N fertilizer too. The findings were: (1) fields with low or marginal ISNT needed starter N unless manure was applied at the full N rate; and (2) if no manure was applied to the field the current crop year, starter N use increased yield UNLESS the field had an optimal ISNT result (fields with optimal ISNT did not respond to starter N fertilizer). In all scenarios, the CSNT could be used to check on appropriateness of the manure and N fertilizer rates at the end of the season: optimally fertilized fields will have a CSNT between 750 and 2000 ppm. In order to identify sites where a starter N application can be omitted, we recommend producers sample the soil (0-8 inches depth) after harvest of 1st year corn and analyze for ISNT-N (and other soil fertility indicators), and follow up with a CSNT sample for the 2nd+ years. Note that ISNT and soil fertility data are valid for 2-3 growing seasons.For more information, see Agronomy Fact Sheet #67 (nmsp.cals.cornell.edu/publications/factsheets/factsheet67.pdf).

Since first year corn does not need additional N beyond a small starter application, no soil (e.g. PSNT or ISNT) or plant analysis (CSNT) tools are needed to determine N rates.Crediting manuire nutrients should be based on a representative manure sample. For further information on deriving N credits from manure, see Agronomy Fact Sheet #4 and #61 at nmsp.cals.cornell.edu/guidelines/factsheets.html.

The optimum economic N rate for corn after soybean can be reduced by 20-30 lbs N/acre for the first year of corn following soybean. See Agronomy Fact Sheet #30 for more information (nmsp.cals.cornell.edu/publications/ factsheets/factsheet30.pdf).

The optimum economic N rate for first year corn after clover, interseeded into a small grain, can be reduced by 70-120 lbs N/acre. See Agronomy Fact Sheet #60 for more details (nmsp.cals.cornell.edu/publications/factsheets/factsheet60.pdf).

When needed, rates of nitrogen up to about 40 to 50 pounds per acre can be applied in the fertilizer band provided the N + K2O application does not exceed 80 to 100 pounds per acre. When rates above 40 pounds per acre of nitrogen are recommended, greatest nitrogen use efficiency can be obtained when a small starter rate (10 to 30 pounds per acre) is used in the fertilizer band, and the remaining nitrogen is applied at sidedress time just prior to the most rapid growth phase of the crop.

Enhanced efficiency fertilizers have been developed to minimize the potential for N loss to the environment. This includes technologies that delay nitrification (nitrification inhibitors), delay conversion of urea to ammonium (urease inhibitors), and/or use of sulfur or polymer coatings to allow release of N over a longer time period (slow or controlled release).

Nitrification inhibitors are substances that inhibit conversion of ammonium to nitrate. Nitrification inhibitors work by keeping N in ammonium form, which is done by inhibiting Nitrosomonas bacteria, commonly delaying conversion for four to ten weeks depending on the product, soil temperature and pH. These inhibitors can reduce N loss from leaching and denitrification but are only effective on fertilizers that either contain or are converted to ammonium, including anhydrous ammonia, urea, and ammonium sulfate. Nitrification inhibitors are effective for inhibition of the urea and ammonium in the fertilizer but not for nitrogen already in nitrate form (25% of the N in UAN).

In the humid conditions of New York State, nitrification inhibitors have the highest likelihood for a yield response when used on N applied at planting, in poorly drained soils (where denitrification losses might occur) or in sandy soils (where the leaching potential is high). They are less likely to be needed when N is sidedressed as conversion and rapid uptake is expected to be very rapid at that point. Proven chemistries include the use of dicyandiamide (DCD) and nitrapyrin.

Urease inhibitors are substances that inhibit conversion of urea to ammonia and carbon dioxide, reducing ammonia volatilization losses. Urease inhibitors can reduce or delay formation of ammonia for up to ten to fourteen days. Urease inhibitors are especially useful with N sources that have a high volatilization potential (e.g. urea) in situations in which tillage incorporation is not possible (e.g., no-till, pasture, and grass hay production). Treating with a urease inhibitor allows more time for rain to incorporate the N fertilizer. Ammonium sulfate is much less prone to volatilization and is hence a good alternative to the use of urease inhibitors. Documented chemistries that inhibit urease include N-(n-butyl) thiophosphoric triamide NBPT), phenylphosphorodiamidate, thiophosphoryl triamide, and ammonium thiosulfate.

Slow-release fertilizers minimize the potential of nutrient losses to the environment by slowly converting to ammonium and/or nitrate over time. These N sources can reduce N losses, especially in sandy soils more prone to N loss, and help extend N availability over a full growing season. Slow-release fertilizers release more slowly than soluble N sources. Their release is limited mostly by temperature and/or moisture.

Controlled-release fertilizers are usually common fertilizers such as urea coated with a polymer or with sulfur. The coating delays the availability of the nutrients for plant uptake after application and controls nutrient release over time. These products are not desirable when a quick release of available N is needed, for example, when sidedressing corn at the 6-leaf stage. In addition, some controlled release products, if applied on bare soil, should be incorporated to prevent runoff (particles may float) of the polymer coated fertilizers with heavy rains.

NITROGEN STATUS OF THE CORN CROP
One can determine whether the proper rate of nitrogen was used by examining the crop. This hindsight evaluation helps refine nitrogen management. Nitrogen sufficiency in one year does not necessarily imply that N rates should be decreased in the next year, and vice versa. Examine the lower leaves of the cornstalks. If three to five of the lower leaves are dead (or nearly so) by the early dent stage and the upper leaves on the plant remain medium to dark green, the proper rate of nitrogen fertilizer was used. If fewer than three leaves die by early dent and the top leaves remain moderately dark to dark green, too much nitrogen was used and the rate could have been decreased by 20 to 40 pounds per acre. If the leaves die up to or above the ear leaf or the entire plant has a light to very light green color and the leaves near the ear leaf are yellow, too little nitrogen fertilizer was used and the optimal rate was 20 to 40 pounds per acre higher than what was applied (in this evaluation, consider only leaves lost because of nitrogen deficiency and not losses caused by leaf blight or drought). Nitrogen deficiency starts as a V-shaped yellowing of the leaf tip, which proceeds toward the stalk, followed by gradual leaf death. Drought symptoms are almost the same as those of nitrogen deficiency, and drought will make nitrogen deficiency appear to be worse.

If a severe drought occurs late in the season (tasseling to early dent), the above descriptions are not valid. Instead, nitrogen rates even below those recommended would have been adequate because over fertilization does not compensate for lack of water.

The large quantities of N needed for optimal corn production can be supplied by soil organic matter, crop residues, manure, and/or commercial fertilizer. The pre-sidedress soil nitrogen test (PSNT) provides a way to determine if there will be sufficient nitrogen in the soil for maximum economic yields corn. PSNT determines the nitrate content of the top 12 inches of soil when the corn is 6 to 12 inches tall. The soil nitrate content at that time is an indication of the total nitrogen available to the plants for the remainder of the growing season.

If PSNT nitrate results are 25 ppm or above, there is sufficient N in the soil for maximum economic corn yields. If there is less than 21 ppm of soil nitrate, additional sidedress N is needed. When the results are between 21 and 25 ppm N, there is about a 10 percent probability that a yield response would be obtained from additional N. The quantity of N that is needed when the nitrate results are below 25 ppm is determined by computing the N requirements considering the soil, crop, rotation, and manure histories as described for corn, but subtracting any fertilizer N applied preplant or at planting.

For additional information on PSNT, instructions on sampling, soil testing kits, or interpretation of results, see or contact your local Cornell Cooperative Extension office.

A new tool released for use in New York in 2007 is the Late Season Stalk Nitrate Test (Agronomy Fact Sheet #31 at http://nmsp.cals.cornell.edu/guidelines/factsheets.html). This end-of-season test can be used to evaluate the N supply during the growing season. It is useful as a management tool as it helps identify if adjustments in N management are needed in future years.

For corn silage, samples should be collected from one week prior to harvest until one day after harvest (if stubble height is ≥ 14 inches).

The portion of the stalk used for the test is important as the test is calibrated for the nitrates that accumulate in this part of the stalk. First measure up 6 inches from the soil surface and cut the plant. Then measure 8 inches up from this first cut, and make a 2nd cut. These cuts result in an 8 inch sample of stalk taken from between 6 & 14 inches above the ground. Make sure not to touch the soil with the corn stalk segment; contamination with soil will greatly impact test results.

Sample an 8-inch segment of the corn stalk between 6 and 14 inches above the ground.

In a uniform field (≤15 acres in size) fifteen 8-inch segments should be randomly cut and combined to make one sample to be submitted for analysis. Areas differing in management or soil type should be sampled separately. Similarly, fields that are more than 15 acres large should be subdivided into smaller sampling units. Split each stalk into four parts by cutting it lengthwise using a clean kitchen knife and toss out three of the four quarters. This will quicken the drying process and reduce the volume to be submitted to the laboratory.

Samples can be taken within 5 days after corn silage harvest as long as there is no major rainfall between harvest and sampling. If the silage cutting height in the field exceeds 14 inches, it is recommended to sample the standard 8-inch section of stalk from the 6-14 inch height as described above. When stubble height is less than 14 inches but greater than 8 inches, stalk samples can be taken between 2 and 8 inches off the ground. This alternative cutting height should be reported to the laboratory when submitting CSNT samples so the laboratory staff can properly adjust the results. More information on this alternative sampling protocol can be found in Agronomy Fact Sheet #72 (nmsp.cals.cornell.edu/publications/factsheets/factsheet72. pdf).

Samples should be submitted as soon after collection as possible but can be stored in a refrigerator for up to 6 days. Samples should be placed in a paper bag (not plastic). This allows for some drying to occur and minimizes growth of mold. Samples can be submitted to several different laboratories. Contact Quirine Ketterings at 607-225-3061 or [email protected] for further information.

Based on research conducted in New York, current interpretations are:

  • Low = less than 250 ppm N
  • Marginal = 250-750 ppm N
  • Optimal = 750 to 2000 ppm N
  • Excess = greater than 2000 ppm N

Low (deficient)- Plants had difficulty accessing enough nitrogen in these fields. Nitrogen access was hindered by inadequate supply, root restrictions, lack of moisture, or nutrient deficiency interactions. At harvest time, leaves are dead to or above the ear leaf and/or the entire plant has a light to very light green color.

Marginal- In some years, yields could have been increased with some additional N. In those years, plants look like described as above. In other years, the N supply was sufficient. Since it is difficult to predict what kind of growing conditions a season will bring, farmers are advised to target CSNTs in the optimal range.

Optimal (sufficient)- Nitrogen availability was within the range needed for optimum economic production of corn. In this range, three of the five lower leaves will be dead by harvest time while the top leaves remain medium to dark green.

Excess – If the sample has more than 2000 ppm N, the corn had access to more N than it needed for optimum yield. Most likely, fewer than three leaves from the bottom will have died; the top leaves remain medium to dark green. If manure and/or N fertilizer was applied, the application(s) supplied more N than the crop needed that growing season.

This test is not meant as a one time measurement; it is most effective when used for multiple years on the same field (or fields with similar histories) in order to determine how the fields respond to the way N is being managed. Crop history, manure history, other N inputs, soil type, and growing conditions all impact whether the stalk nitrate test will show that the crop is deficient, sufficient or excessive in N.

The greatest benefit of this test is that it allows evaluation and fine-tuning of N management for each specific field. It does, however, require multiple years of testing to gain experience with on-farm interpretation. Stalk nitrate tests of 2000 ppm or greater indicate excessive levels of available N during the growing season and if corn stalks test above 2000 ppm for two years or more, consider analyzing a soil sample for the Illinois Soil Nitrogen Test to determine soil N supply potential and evaluate the risk of a yield decline if fertilizer and/or manure application rates are lowered. See Agronomy Fact Sheet #63 (nmsp.cals.cornell.edu/ publications/factsheets/factsheet63.pdf) for more information on use of the CSNT and ISNT for fine-tuning nitrogen management for corn.

ADAPT-N – INCORPORATING WEATHER INFORMATION TO ADJUST CORN N RATES IN SEASON

Appropriate nitrogen rates for corn vary greatly among locations and growing seasons. In some years corn is nitrogen deficient, while in others the same amount of fertilizer appears to be adequate. This happens because the appropriate N fertilizer rate is highly influenced by weather, soil, and management factors. Notably, early season precipitation has been shown to significantly affect corn fertilizer response. Much of the plant-available N is lost in years with wet springs, which then require more supplemental nitrogen fertilizer at sidedress time; lower. fertilizer rates are needed in dryer years. Soil type differences and management practices interact with weather and also affect the optimum N rate.

Adapt-N is a computational tool that incorporates the complex interactions among these factors to provide a field-specific, weather-adjusted N rate recommendation. It can be accessed from any computer or mobile device with Web access. Adapt-N simulates important processes day by day, incorporating high-resolution (3 x 3 mile) information on precipitation and temperatures, as well as soil type, organic matter content, previous crops, organic inputs (manure, etc.), tillage, planting date and population, cultivars, and yield potential. It can therefore provide a locally and seasonally adaptive N recommendation. At the same time, N losses – and therefore pollution of water and greenhouse gas emissions – are minimized. For more information on Adapt-N and sign-up instructions, visit adapt-n.cals. cornell.edu.

Recommended What’s Cropping Up? Articles

  • Nitrogen- vs. phosphorus-based manure and compost management of corn – January 2016 Agronomy Journal
  • Integrating Cover Crops for Nitrogen Management in Corn Systems on Northeastern Dairies – September 2015 (PDF)
  • Stalk nitrate test results for New York corn fields from 2007 through 2014 – January 2015 (PDF)
  • Adapt-N Boosts Profits and Cuts N Losses in Three Years of On-Farm Trials in New York and Iowa
  • Adapt-N Responds to Weather, Increases Grower Profits in 2013 Strip Trials
  • Effect of Sampling Height and Length on Corn Stalk Nitrate Test Results – March 2010 (PDF)
  • Impact of N Fertilizer Sources on Corn Silage Yield and Quality – February 2010 (PDF)
  • Evaluation of ISNT-Based Nitrogen Management for Multi-Year Corn Sites – June 2009 (PDF)
  • N Sidedress Rates on Corn Following Soybeans – April 2009 (PDF)
  • Nitrogen Savings for First Year Corn – February 2007 (PDF)

All About Growing Sweet Corn

For more information on types of sweet corn and our recommended varieties, see our Sweet Corn at a Glance chart.

When to Plant Sweet Corn

In late spring or early summer, sow seeds in warm, fertile and well-worked soil that contains plenty of nitrogen. Sow early sweet corn varieties one to two weeks before main season varieties for a longer harvest season. Many gardeners sow their early sweet corn when apple trees are in full bloom.

How to Plant Sweet Corn

Thoroughly mix in a 1-inch layer of fresh grass clippings, compost or well-rotted manure along with alfalfa meal, soybean meal or another high-nitrogen organic fertilizer (follow label directions). Sow seeds 1 inch deep and 4 inches apart, in blocks of at least three rows spaced about 24 inches apart. Thin early varieties to 8 inches apart; thin taller midseason and late varieties to 12 inches apart.

Harvesting and Storage

Once an ear feels plump and full when you squeeze it, pull back the shuck near the tip and pierce a kernel with your fingernail; it’s ready to harvest if the juice is milky.

Try to harvest sweet corn in the morning, when the ears are cool. Refrigerate them immediately or put the corn in a cooler and layer it with ice. Sweet corn can be canned in a pressure canner, but most people prefer the speed and convenience of freezing. Blanched corn off the cob takes up much less freezer space compared to whole ears.

Saving Seeds

Most sweet corn varieties are complex hybrids, so don’t expect good results from saving and replanting the seeds. To save seeds from open-pollinated varieties, allow perfect ears to dry on the plants until the husks turn tan. Continue to dry them indoors until a few kernels fall away when you twist the ear between your hands. Store seeds in a cool, dry place for up to two years. (To find the varieties you want, use our nifty new seed search.)

Pest and Disease Prevention Tips

  • Grublike gray to brown corn earworms feed on corn silks and kernels. They are larvae of moths that lay eggs in the tips of immature ears. To limit damage, use a squirt bottle to place five to six drops of vegetable oil in the tip of each new ear. For nearly worm-free harvests, add Bacillus thuringiensis (also known as Bt) organic insecticide to the oil. If earworms are minimal, simply break off the blemished tips as you shuck. Varieties with tight husk tips (such as ‘Argent’) often show only modest earworm damage.
  • A fungal disease called “corn smut” causes kernels to become black, swollen and distorted. You can limit its spread by removing infected ears. Revered in Mexico as a delicacy, blobs of corn smut actually are edible, and resemble mushrooms when cooked.
  • Inch-long striped army worms are common pests of late corn varieties, but early maturing varieties rarely are damaged. Tachinid flies and other beneficials kill large numbers of fall army worms, or you can use a spinosad-based pesticide.
  • Raccoons closely monitor sweet corn’s progress and stage nighttime raids just as it reaches perfection. To protect nearly ripe ears, tape the ears to the stalk with packing tape, or try some of the other deterrents suggested by the Internet Center for Wildlife Damage Management.

Growing Sweet Corn Tips

  • Precede sweet corn with a cover crop of hairy vetch or another legume to boost the soil’s nitrogen supply. In warm weather, sweet corn can be sown one to two weeks after a cover crop is cut down or turned under.
  • Sweet corn seed must germinate rapidly or it will rot. For best germination, soak seeds in clean water overnight before sowing in warm soil (65 degrees).
  • Hybrid sweet corn is bred to grow at close spacing with heavy fertilization. To keep plants supplied with nitrogen, fertilize before planting, then side dress them with a high nitrogen fertilizer such as cottonseed or blood meal when the plants are 1 foot tall, and again when tassels appear.
  • If plants are blown over by gusty summer thunderstorms, give them a few sunny days to right themselves. It won’t hurt nearly mature plants to grow crooked, but you may need to prop up young plants that don’t get back up by themselves. To prevent this problem, called “lodging,” hill up soil over the base of the plants as you hoe out weeds.
  • The best way to fit sweet corn into a small garden is to grow early varieties in hills comprising six to eight plants. Corn is pollinated when wind carries pollen onto emerging strands of silk. To assure big, well-filled ears in a small planting, gather pinches of dusty pollen from corn tassels and sprinkle it onto the silks once or twice a day.

In the Kitchen

Immediately refrigerate sweet corn to preserve its flavor. You can boil, steam or grill full ears, cut off whole kernels or make creamed corn. To get kernels like those found in canned and frozen corn, blanch ears in boiling water for a few minutes, then cut off the kernels. For creamy corn kernels, cut the kernels from raw ears, and use a spoon to scrape the remaining milky juice off the cobs.

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Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.

Sweet Corn

Overview

The total value of the 2016 sweet corn crop was nearly $9 million. Of that amount, 74 percent was produced for the fresh market and 26 percent for the processing market. Processing sweet corn production (both frozen and canned) in 2015 totaled 2.5 million tons with a crop value of $255.5 million (NASS 2017).

History

Sweet corn is a genetic mutation of field corn and was reportedly first grown in Pennsylvania in the mid-1700s. The naturally-occurring genetic mutation causes kernels to store more sugar than field corn. The first commercial variety was introduced in 1779. To capture maximum sweetness, sweet corn is harvested before it fully matures while sugar content is still high. (ERS 2007)

“Supersweet” hybrid varieties have been developed over the past 25 years. These genetic advances have improved the quality of both fresh and processed products. Supersweet varieties offer longer shelf life, extended marketing windows and the delivery of higher-quality products throughout the year. (ERS 2007)

Production

Sweet corn is produced for the fresh, frozen and canned markets. The fresh market accounts for nearly 74 percent of the value of the sweet corn crop.

In terms of production and value, sweet corn is the second largest processing crop, surpassed only by tomatoes. Processing sweet corn production (both frozen and canned) in 2015 totaled 2.5 million tons with a crop value of $255.5 million. (NASS 2017)

Sweet corn is harvested on over 28,000 farms and in all 50 states. Florida, California, Washington, New York and Georigia are the largest producers of sweet corn. The production of sweet corn for processing is heavily concentrated in the upper Midwest and the Pacific Northwest. Minnesota, Washington and Wisconsin are the leading producers.

Fresh sweet corn is typically sold in daily spot markets and is highly seasonal. However, processing sweet corn is often marketed through the use of contracts that are generally offered through a variety of brokers. Processing plants often produce both branded and private-labeled products. As is the case with many agribusiness sectors, consolidations and mergers have provided much fluidity to ownership structures. However, Seneca Foods is one of the major frozen vegetable (including sweet corn) processing companies, with ten facilities in Minnesota and Wisconsin.

Though most wait to harvest full grown sweet corn, a small market does exist for the fully edible unhusked baby corn.

Direct Marketing

Direct market opportunities vary by region and production capabilities. These are typically in-season, point-of-sale markets either at on-farm stands, farmers’ markets or direct delivery to retailers.

Sources

New: Enterprise Budget for Vegetables, Iowa State University Farm Food and Enterprise Development

National Agricultural Statistics Service (NASS), 2017
Global Agricultural Trade System, Foreign Ag Service, USDA.
Sweet Corn, 2007 Census of Agriculture, National Agricultural Statistics Service (NASS), USDA.
Sweet Corn for Processing, Vegetables and Melons Outlook, Economic Research Service (ERS), USDA, 2007.
U.S. Sweet Corn Statistics, ERS, USDA, 2010.
Vegetables, 2012 Summary, NASS, USDA. 2013.
Vegetables and Melons Outlook, ERS, USDA.
Vegetables and Melons Yearbook, ERS, USDA.

Revised February, 2019.

How Much Room Does Corn Need to Grow?

My husband decided to be more involved in the garden this year, beyond just the grunt work.
The idea was to work together and grow less variety of plants, but enough of each to last a year.
So at the planning stage he gave his opinion about growing one of our favorites, sweet corn.

“It takes up too much room,” he said, “grow something else and we’ll just buy corn from the farmer.”

Okay, sounds like a plan.

So he added the manure to the beds and I planted the seeds and seedlings. When all was finished there was one bed left.

This was an opportunity to plant something I have always wanted to, dry corn.
Corn meal, polenta, grits; things we never were able to make from homegrown before we will get a shot at this fall.

Yesterday we did pick up about 10 dozen sweet ears from our local corn farmer, and proceeded to remove the kernels and process it.
It took a few hours, and the conversation led to the question of how much room it would take to grow that amount of sweet corn ourselves.

So I took him into the garden and showed him the corn bed.
In a 4 ft by 10 ft bed, there are 14 rows of corn with 4 or 5 stalks in each row.

Not to mention the beans and squash growing below.

“Most sweet corn will produce 2 ears per stalk,” I told him, “this is all the room we would need.”

“Oh, I thought it took a lot more space. Next year we should grow our own corn.”

“Hmm…” I thought, “let’s see first how much better the polenta tastes.”

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How to Grow Corn

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May 19, 2016

The corn family

Sweet corn is the only grain that is eaten fresh as a vegetable. There are several types of corn.

Field corn is not eaten fresh. It is also referred to as dent corn because of the appearance of the dried kernels. Field corn is used as livestock or poultry feed or dried and ground into corn meal for people.

Indian corn or flint corn is often brightly colored and is starchy like field corn.

Popcorn is grown and dried to be eaten popped.

Sweet corn is the most popular corn used by many gardeners. Sweet corn is grown in most vegetable gardens and is eaten fresh. It is one of the most popular vegetables in the United States.

Corn needs a big garden

Since each plant produces only one or two ears, it would be necessary to plant at least 80 feet of row to produce enough sweet corn for a family of four. Corn is wind pollinated. It must be planted in blocks or squares of three or more rows. Do not plant in one or two rows because the ears will not be pollinated, meaning that there will be few kernels on each ear.

Corn is a warm weather crop

Sweet corn is a warm season crop that requires warm soils and full sun all day. For an early crop, although frost can injure seedlings, a small number of seeds can be planted early. You are gambling on the unpredictable weather. It’s risky, but it can give an earlier harvest.

Wait to plant most of the corn in late May to reduce the risk of frost damage.

Kinds of sweet corn

Sweet corn can be divided by colors, sweetness and time of the season it becomes ripe. Kernels of different varieties will be yellow, white or a yellow and white mixture often called bi-color. In regards to sweetness, there is standard, sugar-enhanced and the sweetest which are called super sweet. The sugar-enhanced and super sweets often do not germinate well in cool soil. Corn is also divided into early, mid-season and late varieties.

When planting, follow the directions on the back of the seed package or plant seeds 1.5 to two inches deep, five to six inches apart in rows that are two to three feet apart. Thin plants to 10 to 12 inches apart.

Many people find that the super sweet corn varieties do not germinate well. If seeds do not germinate, plant when the soil is warm to the touch and space the seeds closer than recommended.

Succession planting

To lengthen harvest, plant early, mid-season and late varieties all at the same time. Make successive plantings of mid-season and or late varieties until late June. Wait until each planting is about two inches high before planting more.

Keys to success

  • Plant four, short rows rather than long, single or double rows.
  • Plant mostly mid- and late season varieties for the best quality.

The basics

Corn will grow most soils if it is well-drained. Corn grows best in loam soils. For good germination of seeds, the soil needs to be 60°F or above.

Corn is a heavy feeder, especially of nitrogen (fertilizer). Follow your soil test recommendations or use two pounds of 5-20-20 fertilizer per 100 square feet of soil. When the plants are knee high or at the beginning of July, apply a high nitrogen fertilizer (4 lbs of 21-0-0 or 2 lbs of 46-0-0) per 100 square feet along the sides of the rows.

Keep corn free of weeds and grasses. Cultivate with a hoe, but be careful not to injure shallow roots. A mulch of straw or similar material can be used to control weeds and hold in moisture. Do not remove suckers (side shoots), as this may reduce yields.

Corn needs lots of water, especially from the time the tassels (silky, hair-like material growing out of the top of the ear of corn) appear until harvest. An inch of water per week, either from rain or the hose will ensure proper moisture. More water may be required on sandy soil.

Harvest sweet corn after the silks on the ear turn brown and are dry. Corn kernels should be round and filled out. Kernels that are square may be past their prime and the sugars converted to starch. Husks should appear fresh and not dried out.

Storage

The quality of sweet corn decreases very rapidly after picking. The sugars convert to starch and the unique flavor is lost. Use immediately or store for a short time in the refrigerator. Fresh sweet corn can be frozen or canned, if done correctly.

Problems

To help prevent seeds from rotting in cold soil early in the spring, it is possible to use seeds treated with a fungicide. Those that are treated will be colored, like a brilliant pink. The package will also have that information on it.

Cover the seeds well with soil to deter birds or animals from eating the seeds. If loss of seeds to birds or animals is a continuing problem in a small garden, use a narrow strip of hardware screening or chicken wire over the row until the corn plants just begin to emerge. Eaves troughs covers work well for this, too. Be sure to remove screening before the corn plants sprout and are damaged.

Insects or animals may be troublesome, especially corn earworms and raccoons. Contact your local Extension office for information on how to manage these pests.

Originally developed by Lee Taylor and adapted by Gretchen Voyle. Revised by Hannah Stevens.

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Related Topic Areas

Vegetable Gardening, Gardening in Michigan

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Saving Seeds from Sweet Corn

Growing Corn for Seed

Zea mays is a wind-pollinated annual crop that is widely adapted and successfully grown in most parts of the world. Cultivating corn plants is the same whether saving seeds or producing a grain crop because the mature seeds are the part of the plant typically harvested. The ears of sweet corn, which are harvested and eaten while the kernels are still immature, need to remain on the plants past market maturity until they reach botanical maturity for seed saving, but in all other ways sweet corn is cultivated in the same manner for seed as for eating.

Corn germinates and grows best when the soil temperature has reached at least 50°F (10°C); sweet corn generally germinates better at a slightly warmer soil temperature. Plants are spaced 6 to 12 inches (15 to 30 cm) apart with 24 to 36 inches (61 to 91 cm) between rows, the same as when grown for eating. It is better to plant corn in blocks at least six rows wide than in one long row to help ensure better pollination and good seed set.

Flowering, Pollination, and Seed Set

Corn is a monoecious species, producing male and female flowers on the same plant. The tassel that appears at the top of the main stalk is the male inflorescence. The anthers on the tassels dehisce and shed their pollen over several days. The shoot, the part of the plant that will develop into an ear of corn—is the female inflorescence. Corn silks, which are typically cleaned off of the ears of sweet corn during husking, are the stigmas, each silk attaches to a single ovary that will develop into a kernel if successfully fertilized. Corn kernels are actually single-seeded, indehiscent fruits, which are most often referred to as seeds.

Corn is an outcrossing, wind-pollinated species. During flowering, the silks protrude from the husks are fertilized by pollen grains disseminated on wind currents. On any one plant, it is possible that male flowers will shed their pollen before the female flowers have emerged from their husks. Because wind is a haphazard carrier, pollination is most successful when many plants are grown together.

Flowering in corn is determined by a combi­nation of decreasing day length and accumulated warm temperatures. When growing corn to seed maturity, it is important to know whether there will be a sufficient number of warm days to both induce flowering and allow enough time for the seeds to mature.

Variety Maintenance

Because corn is wind-pollinated, varieties should be separated by a minimum of 800 feet to half a mile (244 to 805 m). Corn pollen is heavy and generally does not travel as far as that of other wind-pollinated crops. However, in areas where large amounts of corn are produced, or when genetic preservation is a gardener’s goal, an isolation distance of 1 to 2 miles (1.6 to 3.2 km) between varieties is recommended. If isolation by distance is not feasible, which is often the case with corn because of its pollination method and its popularity as a garden and agricultural crop, hand-pollination is the most practical method for seed savers who wish to save true-to-type seeds.

Due to corn’s propensity to suffer from inbreeding depression, a population size of 50 to 120 plants is recom­mended for seed saving. While a population of just 10 plants or fewer could produce viable seeds, it is always best to save seeds from more plants, especially if seeds will be shared with others. A population of 200 plants or more is recommended if long-term preservation or stew­ardship of a rare variety is the gardener’s goal.

When roguing or selecting corn, seed savers should consider traits such as tassel color, plant size, ear shape, kernel arrangement, kernel color, kernel endosperm type, and cob color.

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In most crops, visible signs of outcrossing do not become apparent until the next generation of plants is grown, but this is not always so with corn. While fruit traits are always maternally derived, the transparent pericarp (fruit wall) of some corn kernels allows a gardener to see the endosperm of the seed. The endosperm is a prod­uct of fertilization, and endosperm qualities are distinct to each type of corn; thus an individual kernel can show evidence of outcrossing both in its color and in its shape.

Seed Maturity and Harvest

As corn matures, the kernel endosperm will slowly turn from liquid to solid, forming a distinct milk line that progresses to the base of each kernel. A change in husk color, from green to yellow to brown, is an outward sign of seed matu­rity. If weather conditions permit, ears should be left to dry in the field. When mature, ears can be handpicked.

To protect the kernels, corn is typically harvested with the husks still attached. Once the ears are brought in from the field, they can be hung in mesh bags or set out on screens to con­tinue drying; removing the husks can facilitate drying. Corn seeds should be dried until they are hard to the touch and easy to shell off the cob.

Cleaning and Storage

Individual kernels can be shelled by hand, with a hand corn sheller, or with a mechanical sheller. If using a sheller, seed savers must take care to avoid damaging the kernels, especially if saving a sweet corn variety, as sweet corn seeds are espe­cially fragile. Seeds savers often shell sweet corn by hand to prevent damage to the seeds. The large, heavy seeds separate easily from the chaff through screening and winnowing.

When stored under cool, dry conditions, sweet corn seeds can be expected to remain viable for two to three years. The expected lon­gevity for field corn seeds is at least five years.

Zea mays

FAMILY: Poaceae

LIFE CYCLE: Annual

SUGGESTED SPACING: Same as when grown as a grain crop or as sweet corn

OTHER REQUIREMENTS: None

FLOWER TYPE: Corn is monoecious (male and female flowers on the same plant) and self-compatible.

POLLINATION: Wind-pollinated

MATING SYSTEM: Cross-pollination, though corn can self-pollinate if wind moves pollen between male and female flowers on the same plant

ADDITIONAL CROSS-POLLINATION CONCERNS: None

FRUIT TYPE: Dry, indehiscent, single-seeded fruits (caryopses) are commonly referred to as grains. The fruit acts as a seed for propagation purposes.

SEED MATURITY: Seeds are mature when the husks are dry and the kernels are hard.

SCREEN SIZE: 10⁄64–26⁄64 inch (4–10.5 mm)

EXPECTED SEED LIFE: 2–3 years

ISOLATION DISTANCE: 800 feet–1⁄2 mile (244–805 m)

Population Size

For Viable Seeds: 10 plants

For Variety Maintenance: 50–120 plants

For Genetic Preservation: 200 plants

For more on seed saving, see our Seed Saving Guide.

Reprinted with permission from The Seed Garden, by Micaela Colley & Jared Zystro, edited by Lee Buttala & Shanyn Siegel and published by Seed Savers Exchange, 2015. Buy this book from our store: The Seed Garden.

When is best date for planting corn?

If you have a farm-level crop insurance product, as long as you plant corn after April 11 in Iowa, and soybeans after April 21, you still have the ability to claim replant coverage, if you have to replant.

That doesn’t mean you can’t plant corn before April 11 or soybeans before April 21. But if you do, you may lose your crop insurance coverage for a replant. Check your policy and talk to your crop insurance agent to make sure you understand the possible consequences before planting that early.

Should you plant corn early? What’s the biggest risk factor for corn planting? >>

Should you go ahead and plant corn early in cold soils?
Soil conditions can be the best-ever during the first week of April. But the question is, should you plant corn early when the soil is still cold? University of Illinois agronomist Emerson Nafziger says yes, but with a few cautions.

“We should not expect yields of corn planted in the first week of April to be higher than those of corn planted the third or fourth week of April,” he says. “We have had a few instances when corn planted in early April yielded less than corn planted later in April. This doesn’t happen often enough to rule out early planting, but it does mean the main reason to plant in early April is to get done by late April and avoid late-planting yield loss.”

For more corn news, corn crop scouting information and corn diseases to watch for, follow Tom Bechman’s column, Corn Illustrated Weekly, published every Tuesday.

Another caution is to plant early only when seedbed conditions stay favorable; if it rains or is still wet, growers should not try to get back in the fields too soon.

“It typically requires about 110 to 120 growing degree days for corn to emerge,” he says. “With highs in the mid-60s and lows in the 40s to low 50s, we accumulate less than 10 GDD per day, so it can easily take two to three weeks for the crop to emerge.”

Typically, this isn’t a problem. But it is a long time, and problems can develop to hinder emergence. Early-planted corn should be watched carefully, especially when GDD accumulations pick up and the crop approaches emergence.

Low soil temperatures aren’t the major risk factor for corn
Low soil temperatures are not the major risk factor that planted corn faces. Instead, heavy rainfall soon after planting, with seeds or seedlings dying from lack of oxygen, is the major cause of replanting. Chances of this happening are no higher for early than for later planting, he says.

Related: For Planting Corn, Soil Temperature Of 50 Degrees Is Magic Number

Planting into cooler soils may even improve chances for emergence following rainfall. Seeds are not triggered to germinate and emerge as rapidly in cool soils, so they often survive longer in cool, wet soils than in warm, wet soils. There is some risk of damage from frost after plants have emerged, but that’s fairly rare.

“While we hope we won’t need to replant, another advantage of very early planting is that if we do need to replant it, the replanting can be done early enough to avoid large penalties from late planting that you often incur when you have to replant corn,” adds Nafziger.

More: How deep should you plant corn?

This story originally appeared April 11, 2011.

Planting Sweet Corn in the Home Garden

Sweet corn, a warm season crop, is one of the most popular vegetables. An excellent summer treat, sweet corn may also be canned or frozen for year round use.

When purchasing sweet corn, home gardeners can select varieties that produce yellow, white, or bicolored ears. New novelty varieties produce multi-colored ( Indian Summer’) or reddish kernels ( Ruby Queen’). While there are numerous sweet corn varieties, there are three main types of sweet corn. Standard (su), sugar-enhanced (se), and shrunken-2 (sh2) types vary in sweetness, keeping quality after harvest, and cold soil vigor.

Standard sweet corn varieties have been grown for many years. These varieties possess the traditional sweet corn flavor and texture. (Sweet corn differs from field corn by a single gene called the sugary or su gene.) Unfortunately, the ears of standard sweet corn varieties retain their quality for only 1 or 2 days. Also, standard varieties don’t store well once harvested. Suggested standard sweet corn varieties for home gardens in Iowa include Seneca Horizon’ (yellow) and Silver Queen’ (white).

The sugar-enhanced varieties produce ears with sweet, tender kernels. The soft kernel pericarps make the corn tender and easy to chew. The harvest and storage periods of se types are slightly longer than the standard sweet corn varieties. They also have a higher sugar content. Suggested sugar-enhanced varieties for home gardens include Bodacious’ (yellow), Incredible’ (yellow), Legend’ (yellow), Precious Gem’ (bicolor), and Silver King’ (white).

The common name of the shrunken-2 varieties is derived from the shrunken or wrinkled appearance of the dried kernels. The sh2 varieties are also referred to as super sweets. Shrunken- 2 varieties possess the longest harvest and storage periods and have the highest sugar content. However, sh2 varieties do have some disadvantages. The seed coats on this type are fairly thick, giving the kernels a tougher or crunchy texture. Yields of super sweets are generally lower than standard sweet corn varieties. They are also slow to germinate and have reduced seedling vigor. Suggested sh2 varieties include Candy Store’ (bicolor), Challenger’ (yellow), Confection’ (bicolor), Honey N Pearl’ (bicolor), How Sweet It Is’ (white), Illini Gold’ (yellow), Northern Xtra Sweet’ (yellow), and Phenomenal’ (bicolor).

Sweet corn performs best in fertile, well-drained soils in full sun. Standard sweet corn varieties may be planted in late April in central Iowa. It’s generally recommended that se varieties be planted 1 week later than standard sweet corn varieties. The seeds of sh2 varieties germinate poorly when soil temperatures are below 65ÔF. As a result, shrunken-2 varieties should not be planted until mid-May in central Iowa. For a continuous supply of sweet corn, plant early, mid- season, and late varieties or plant every 2 or 3 weeks. The last practical date for planting early varieties is July 1.

Sow seed at a depth of 1 inch in heavy soils. In light sandy soils, the planting depth may be 2 inches. Space the seeds 8 to 12 inches apart in rows 2 1/2 to 3 feet apart. Sweet corn may also be planted in “hills.” Sow 4 to 5 seeds per hill with approximately 3 inches between seeds. Hills should be spaced 2 1/2 feet apart with 2 1/2 to 3 feet between rows.

Sweet corn is wind pollinated. To insure good pollination and ear development, plant several short rows or blocks rather than 1 or 2 long rows. Poor pollination results in poorly filled ears.

Since different types of corn can cross-pollinate and contaminate one another, they should be isolated from one another. All sweet corn types should be isolated from field corn, popcorn, and ornamental corn. Shrunken-2 varieties must also be isolated from sugar-enhanced and standard sweet corn varieties. Cross-pollination between the sh2 and se or su varieties will destroy the quality of both. It is not essential to isolate sugar-enhanced varieties from standard sweet corn.

Isolation can be achieved by planting the different types at least 250 feet from one another and by avoiding prevailing winds. Another method is to stagger planting dates or to select varieties that mature at different times. A minimum of 14 days should separate the tasseling time of the different types.

This article originally appeared in the April 20, 2001 issue, pp. 42-43.

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