Sweet Corn
Corn prefers well-drained soil with a pH of 5.5 to 7.0, but it will grow in all soil types and is moder-ately salt-tolerant. Magnesium deficiency may occur in sandy soils or at a low pH. If water is adequate, pale green leaves and shriveling of tip kernels as plants approach maturity often indicates N stress. This can be avoided by an N application at tasselling. The table below shows plant nutrient recommendations based on soil test results.
Planting
New seed should be used each year since seed quality (vigor) is reduced substantially within a year, especially in the supersweets. Sized, high vigor seeds result in more uniform maturity of the crop and better yields. Most corn seed is treated with a fungicide to help prevent losses from damping-off fungi. Shrunken-2 (sh2) seed may require special seed treatments because it is susceptible to a unique dieback syndrome that is not fully understood, predictable, or controllable. Typically, sweet corn populations are 18,000 to 22,000 plants per acre. Row spacings range from 30 to 42 inches, and in-row spacing from 6 to 12 inches. Planting depth should be 1.5 inches for all cultivars except supersweets, which are planted only 1-inch deep.
Sweet corn nutrient recommendations based on soil tests.
| Fertilizer timing | Nitrogen lbs/acre |
Soil phosphorus level-lbs/acre P2O5 | .. | .. | Soil potassium level-lbs/acre K2O | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | Med | High | V. high | Low | Med | High | V. high | ||||||
| Sweet corn for fresh market | |||||||||||||
| Total recommended | 125-150 | 160 | 120 | 80 | 40 | .. | .. | 160 | 120 | 80 | 40 | ||
| Broadcast three weeks before planting |
40-60 | 120 | 100 | 60 | 0 | .. | .. | 120 | 100 | 60 | 0 | ||
| Band-place with planter | 20 | 40 | 20 | 20 | 40 | .. | .. | 40 | 20 | 20 | 40 | ||
| Sidedress when corn is 12-18" tall | 50-75 | 0 | 0 | 0 | 0 | .. | .. | 0 | 0 | 0 | 0 | ||
| Sweet corn for processing | |||||||||||||
| Total recommended | 110-130 | 20 | 80 | 60 | 40 | .. | .. | 120 | 80 | 60 | 40 | ||
| Broadcast three weeks before planting |
40-60 | 80 | 60 | 40 | 0 | .. | .. | 80 | 60 | 40 | 0 | ||
| Band-place with planter | 20 | 40 | 20 | 20 | 40 | .. | .. | 40 | 20 | 20 | 40 | ||
| Sidedress 2 weeks after emergence | 30-50 | 0 | 0 | 0 | 0 | .. | .. | 0 | 0 | 0 | 0 | ||
Seedbed preparation and seed handling is critical for all types of sweet corn, but especially supersweets. Good soil to seed contact, uncrusted soil, and optimal soil moisture help seedlings emerge. Careful seed handling is also important because if the seed coat is cracked, solutes leak from the seed, attracting pathogenic fungi. Rapid uniform seed emergence also promotes uniform maturity.
Pollination
Unlike most vegetables, corn is wind pollinated and must be planted in blocks. Sweet corn of any type downwind from popcorn or field corn develops starchy kernels. Ears of supersweet sh2 corn pollinated by a normal (su) sweet corn cultivar or a cultivar with the se gene will develop hard, ugly, starchy dented kernels. To avoid this cross-pollination, different kernel types must be separated by at least 250 feet or planted at least 14 days apart.
Suckering
Removal of suckers is generally not beneficial and in some cases, yield is reduced by suckering. In a few cases, earliness is increased slightly and harvest labor reduced, but these benefits are unlikely to make up for the expense of suckering.