There are many ways to produce early sweet corn. Some growers cover their earliest corn planting with clear plastic or floating row covers. Most use early varieties that germinate well in cool soils and mature quickly for early marketing. At Cold Spring Brook Farm they use a combination of techniques to "push" sweet corn maturity and yields. Sweet corn is transplanted into raised-beds, covered with black plastic mulch, then covered with floating row covers and, when necessary, irrigated for frost protection. If you think that it is too expensive to include all these inputs for sweet corn, then you will probably be surprised to hear that they keep transplanting this way until mid-May, with mid-season and late-maturing varieties. No, they are not insane! Due to limited field space, they use this technique to produce high-quality/yield sweet corn for their retail market, while minimizing the land dedicated to this crop. These plastic-mulched plantings yield up to 300 bags (1,500 dozen) per acre, and at $3.60 to $5.40/dozen, may gross up to $8,100 at their retail stand!
To produce their transplants, they seed corn into deep-cell, 72-plug trays every 10 days, starting on April 1. The cells are filled 1/3 full with potting media, three seeds per cell are added, and the flats are then filled the rest of the way with media. The corn is transplanted 2 ½ to 4 weeks later into 6-inch-high, plastic-mulched beds, 5 feet on center. Plants are 6 to 10 inches tall when transplanted. Seedlings are spaced 18 inches apart within and between rows (2 rows per bed) with a water-wheel transplanter (like you might use for peppers or tomatoes). Be careful not to bury the top of the root plug and the corn growing point with soil when transplanting. In 2002, the first sowing included Seneca Arrowhead, Trinity and Temptation. Their second and third plantings included Temptation/Lancelot, and Harris Exp 1001/Lancelot/Jackpot, respectively. The first three plantings all take about 90 to 95 days from seeding in the greenhouse to harvest. May plantings with Mystique, Lancelot and Jackpot tend to mature in 75 to 80 days due to warmer conditions.
Farmers that attempt to transplant sweet corn, often end up with stunted plants with near-normal sized ears that develop just above ground level, which are tough to pick at harvest. Tom and Steve avoid stunted sweet corn plants at their farm by transplanting in a timely manner, so that seedling roots don't become overcrowded in the cells, and by encouraging steady plant growth with adequate water and nutrients. The black plastic and row covers also help provide warmer soil and air temperatures to help sustain plant growth.
These are high density plantings (35,000 plants/acre) on light sandy soils, so they tend to use a generous fertility program and plenty of water from transplanting through ear development. They start by broadcasting a 10-0-18 fertilizer blend, at 1,000 pounds per acre. Half of the nitrogen in their broadcast blend is formulated for slow-release. An additional 200 pounds of 26-0-26 is incorporated with the bed construction/mulching operation. In addition to warming the soil, the plastic mulch reduces evaporation, helping to maintain soil moisture for weeks to come. The transplants are watered in with a solution of 10-52-10 (3 lbs./150 gallons). After transplanting, the beds are covered with 36-foot-wide row covers (0.5 oz./m2) until the plants are knee high. As well as enhancing earliness, the row-covers protect their early plantings from frosts down to 28o F and overhead-irrigation is provided if temperatures dip even lower. The row covers and irrigation proved to be wise precautions in 2001 and 2002 when many farmers ended up replanting early blocks of sweet corn due to hard freezes. After removing the row cover, the beds are side-dressed with 100 pounds of urea, which is cultivated in alongside the plastic. Herbicides are not used in their mulched plantings. A fixed, overhead irrigation system is maintained in place through harvest to supplement natural rainfall. These intensive plantings are then protected from birds by rotating between scare-eye-balloons and amplified distress-calls as the corn nears maturity. European corn borer, fall armyworm and light to moderate earworm populations are controlled with microbial products (i.e. spinosad) to help preserve beneficials which may aid in pest control in their surrounding mixed vegetable plantings. When pheromone traps indicate high earworm populations (3-day schedules), they switch to Warrior to protect their corn.
Many growers wouldn't be willing to go to these lengths for early sweet corn or improved yields. Tom and Steve have found, that for their situation, intensive management practices pay off with plenty of early, high quality sweet corn for their customers, from the 4th of July through September.
Jude Boucher, Agricultural Educator, Commercial Vegetable Crops, UConn Cooperative Extension
Tom Nielson and Steve Bengtson, Owners/Managers, Cold Spring Brook Farm, Berlin, CT
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