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2022 Midwest Vegetable Guide

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Sweet Corn – Horticulture Midwest Veg Guide 2022 269 Sweet Corn – Horticulture Major update by Ben Phillips, Liz Maynard, Bill Tracy – Oct 2020 Reviewed by Liz Maynard – Aug 2021 Crop Description Sweet corn (Zea mays subsp. mays) originates from a wild relative in Central America. Sweet corn is usually described by color (yellow, bicolor, or white) and by the major gene names that make it sweet. Despite the many marketing terms and trademarked names, sweet corn can be categorized into five major types. The original sweet corn (called standard, sugary, or su) contains the su1 genetic variant that makes it sweet instead of starchy like field corn. Sugary sweet corn is grown today primarily for processing and specialized markets. A second type of sweet corn (called sugar-enhanced, sugary enhancer, EH, or se) contains the se1 genetic variant that increases sugar content and makes the kernels more tender. Heterozygous se corn has one copy of the se1 mutation and homozygous se corn has two copies of the se1 mutation, increasing its effect. Sugar-enhanced sweet corn is grown primarily for direct retail sales and local wholesale markets. A third type of sweet corn (called supersweet, ultrasweet, extra sweet, or shrunken-2) contains the sh2 genetic variation. This type typically has a higher sugar content than su corn, and the sugar content does not decline rapidly after picking, so it remains sweet for several days after harvest. Kernels typically are not as tender as se corn. Shrunken-2 (sh2) types are grown for retail sales, local fresh markets, and wholesale shipping markets. Many of the newest sweet corn varieties combine the sh2 (or similar genes) with se and/or su genetics. Sugar-enhanced sweet corn that also includes sh2 (or similar) genes is called synergistic, and may be abbreviated as sesh2, syn, or sy corn. Current synergistic varieties are typically very sweet and very tender. Shrunken-2 sweet corn varieties with genetics increasing tenderness and flavor are categorized as augmented or improved supersweet or sh2, sometimes abbreviated shA. These varieties are typically extremely sweet and tender. Many of these varieties have performed well in midwestern trials and receive top ratings for eating quality. The new types are often identified by trademarked brand names. Sweet corn varieties with resistance to certain insects, and/or glyphosate or glufosinate herbicides are also available. Planting and Spacing Common spacing is 30 to 40 inches apart between rows. Plant early varieties 8 to 10 inches apart in the row, late varieties 9 to 12 inches apart in the row. Seed 10 to 15 pounds per acre. Sweet corn flavor is affected by pollen source. Isolate all sweet corns from all other non-sweet corns, including dent (field), flint (Indian), flour, and popcorn by 250 feet or by a 14-day difference in tasseling dates. Likewise, supersweet (sh2) and augmented (shA) sweet corn varieties must be isolated from sugary (su), sugar-enhanced (se) and synergistic (syn) types. If not isolated, kernels of both varieties will be starchy instead of sweet. Refer to the table below for isolation requirements or check with your seed supplier. To maintain color purity, isolate white corn from yellow or bi-color corn. Pollen from yellow or bi-color corn will cause some yellow kernels in white varieties. Pollen from yellow corn will lead to extra yellow kernels in bi-color varieties. Pollen from white corn will not affect the color of yellow or bi-color varieties. Table of Sweet Corn Isolation Requirements Type Isolate from Sugary (su) sh2, shA Sugar-enhanced (se) sh2, shA Synergistic (se x sh2 = syn) sh2, shA Shrunken-2 (sh2) su, se, syn Augmented (su x sh2 = shA) su, se, syn Fertilizing pH: Maintain the soil pH between 6.0 and 6.5. Before planting, apply 40 to 60 pounds N per acre, 0 to 100 pounds P 2 O 5 per acre, and 0 to 150 pounds K 2 O per acre based on soil test results and recommendations from your state. For early plantings, apply a starter fertilizer at planting 2 inches below and 2 inches to the side of the seed, but do not exceed 80 to 100 pounds of N plus K 2 O per acre. On irrigated sandy soils reduce N to 10 to 20 pounds per acre and apply in a band of starter fertilizer. On sandy soils, broadcast 30 pounds or band 15 pounds of sulfur per acre. Sidedress with 30 to 60 pounds N per acre when plants are 5 to 10 inches tall. On irrigated sandy soils, apply two sidedressings of approximately 40 pounds N per acre each: one when 4 to 5 inches tall (4 th to 5 th leaf), and the other at 10 inches tall (10 th to 12 th leaf). Reduce the amount of fertilizer N applied by the value of N credits from green manures, legume crops grown in the previous year, compost and animal manures, and soils with more than 3 percent organic matter. The total amount of N

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