Growing and Harvesting Sweet Corn

For consumers (and producers) there remains the delicious dilemma of whether to go with yellow sweet corn, a white variety like Silver Sweet or the best of both worlds with something like Butter and Sugar, which gives a mix of yellow and white kernels on the same ear. Harvesting Sweet Corn

Read about:  Greenhouse Crops for the Off-Season

Corn is America’s No. 1 crop (see sidebar). Focusing on sweet corn alone, between 2.2 and 2.9 billion pounds of sweet corn are produced annually in the United States. Sweet corn is a crop that lends itself well to small-scale and part-time farming operations. Initial investment is relatively low, and many field operations – such as land preparation, planting and harvesting – can be custom-hired. Equipment needs on a small-acreage farm are not great, and most equipment can be used for other purposes.

Over the past 10 years, national production has fluctuated around 260,000 acres. Nationally, the sweet corn crop is worth $750 million to $850 million per year. On the basis of value of production, the top five sweet corn states are Florida, California, Washington, New York and Georgia. Acreage in Pennsylvania has declined by about one-quarter during that time to around 16,000 acres annually.

Harvesting Sweet Corn

1. Where to grow

Sweet corn grows best on well-drained soils that have good water-holding characteristics.

If you grow sweet corn on sandy soil, irrigation is important for optimum pollination and kernel development. Soil pH should be between 5.8 and 6.6. When growing early sweet corn, it’s best to use soils that warm quickly and locations with a southern exposure to ensure early growth and harvest.

Corn, in general, is classified as sweet, pop, flour, silage or feed corn, depending on the type of carbohydrate stored in the ear. Sweet corn gets its name from special genes that prevent or retard normal conversion of sugar to starch during kernel development. In addition to the various sugar types, sweet corn cultivars differ in kernel color (yellow, white and bicolor) and maturation times – early (less than 70 days), midseason (70 to 84 days) and late (more than 84 days).

There are standard varieties, sugar-enhanced hybrids that give producers a three-day harvest period and demand soil temperatures about 10 degrees warmer than usual sweet corns, and the super-sweet, which is the trickiest of all to produce.

2. No-till planting

For mid- or late-season sweet corn production, no-till planting can be a benefit in relation to time, equipment and labor. Sweet corn can be planted with a no-till planter in a minimally prepared bed with only secondary tillage, such as an S-tine cultivator, or in a previously tilled field without any tillage treatment. This saves time and labor.

Because sweet corn seed germinates and develops when soil temperatures are at least 55 degrees Fahrenheit, early sweet corn production in no-till is difficult because of colder soil temperatures. However, by mid-June, soil temperatures in a no-till field are warm enough for rapid sweet corn seed germination and growth.

In addition, no-till reduces soil moisture loss early in the season so more water is available for corn growth later in the season. If you’re thinking about no-till sweet corn production, consider these factors to be successful: variety, planting date, soil fertility practices, insect pressure and control, planting equipment, cover crop type and stand, and weed species and population in the field.

3. Harvesting and storing

Harvesting can be done mechanically or by hand. New mechanical harvesters usually cost $25,000 to $30,000 and hand-harvesting costs about $150 per acre. Depending on your labor situation, it is usually not economical to purchase a mechanical harvester unless you have at least 10 acres of sweet corn.

Regardless of the harvesting method, check ears for worms, insects and bird damage to ensure you are marketing a high-quality product.

A number of sweet corn growers still harvest their crop by hand. Many, including the King family of Freedom Farms, Butler, Pennsylvania, and Gordon Bemis’ Hutchins Farm, Concord, Massachusetts, follow this practice because the final market for the corn is their own farm stand, according to Tim King and Bemis.

When harvested at optimum maturity, sweet corn 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 important for good quality and yield.

Immature ears have smaller diameters and the kernels are less developed, watery and less sweet.

Immediately after harvest, you should refrigerate and store sweet corn in plastic bags, preferably while still in the husk, to maintain quality. Sweet corn will retain fairly good ear quality for two to three days if stored at 90 percent humidity and 32 degrees Fahrenheit. If your refrigeration system is not keeping the corn cooled to the proper temperature, you will want to hire an HVAC expert to check your system. If you are using an evaporative cooler, you will want to make sure you hire a contractor that can diagnose and repair evaporative coolers

4. Corn conservation

Sweet corn not consumed or processed within a few hours after harvest should be precooled quickly 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, is conveyed through a shower of 31 degrees Fahrenheit to 34 degrees Fahrenheit 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 degrees Fahrenheit, 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 ensure that corn remains cold in transit.

Vacuum cooling can be more rapid, but if the ears are not kept wet, a 1 percent moisture loss for each 10-degree drop in corn temperature occurs. Following precooling, sweet corn should be refrigerated at 32 degrees Fahrenheit and marketed or processed as rapidly as possible.

It is important to harvest sweet corn at the proper stage of maturity. The critical time is the milk stage, a stage when the juice in the kernel appears milky when you puncture the kernel with your thumbnail. Sweet corn remains in the milk stage for a relatively short period, so check the ears frequently.

Corn that is too young will ooze a watery material, while ears that are too old will have a tough, doughy kernel. During the milk stage, the unhusked ear should feel firm, have full kernels at the tip of the ear, and have brown, dry silks. Generally, ears should be ready about three weeks from silking time.

When harvesting, break the shank (stem of the ear) close to the ear without breaking the main stock or tearing the shank from the stalk. Grasp the ear near the base and bend it down sharply, or bend it to one side with a rotary motion of the wrist.

At first it may be best to hold the shank with one hand and the ear with the other. After picking, use the sweet corn immediately for fresh eating, canning or freezing. At high temperatures, the sugar in sweet corn quickly converts to starch, giving it a bland taste. Although many new cultivars have extended storage quality, older cultivars will lose 50 percent of their flavor within 12 hours of picking if left unrefrigerated. If sweet corn must be stored before use, keep the temperature as close to 32 degrees Fahrenheit as possible.

According to Ted Maddox, a sweet corn farmer in Illinois, the crop is “high risk, labor intensive and a marketing nightmare.” And he’s still in the business. As anyone who has tasted really fresh sweet corn will say, the end result is worth it.

Read more: Choosing the Seed