Supersweet and Augmented Supersweet Corn Variety Trial, 2014

University of Maine, Highmoor Farm, 2014
David Handley, Mark Hutton and Jim Dill, University of Maine Cooperative Extension

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Eighteen varieties of supersweet (sh₂) and augmented supersweet (sh₂+, etc.) sweet corn were grown in plots at Highmoor Farm, the Maine Agricultural Experiment Station in Monmouth, Maine during the 2014 growing season to evaluate their performance in stand, yield, and ear qualities. The seeds were planted by hand on June 9 and 10 with jab planters into plots 30 feet long and five rows wide, with 36 inches between rows. Each of the sixteen varieties was replicated in plots four times within the planting.  Fertilizer and pesticide applications followed regional recommendations.

Harvest began on August 29 with the earliest varieties and ended on September 12. Each plot was evaluated for stand, based on how many plants were established within 30 feet of row; plant height, ear height (distance off the ground), picking ease (rated on a scale of 1-3 with 3 being the best), tip cover (rated on a scale of 1-3 equaling approximately the number of inches of cover above the tip), ear length, and the number of rows of kernels per ear. Ear quality parameters were based on a sample of ten ears from each plot.

All of the varieties performed reasonably well in this trial (see table below). The soils were warm and dry at planting, so stand establishment was initially good.   However, rain after plant emergence reduced the growth rate in the more poorly drained areas of the field. XT2472 had the best stand, followed by XTH20173, Stellar, 7112R and Higlow 8902 MR. Primus, 7002R and XTH2673 had the poorest stands, but even these were acceptable, and the range may been effected by location in the field and drainage more than germination or seedling vigor.

XTH2472, XTH20173 and Stellar were the first varieties to mature, harvested on August 29, followed by XTH 2074 on September 2, and 7002R and Awesome XR harvested on September 3. XTH2673 was harvested on September 4, followed by Multiglow 7002R, 301 BC, and Primus on September 5. Allure and Essence were harvested on September 8, followed by 7112R on September 9, and 7602 and AP 358 on September 10. The last varieties to mature were Multisweet 2340, Mirai 315 and Higlow 8902 MR, harvested on September 12.

Yields were relatively uniform, and generally reflected plant stand. Most varieties averaged slightly less than one ear per plant. The highest yielding varieties included XTH2074, Higlow 8902 MR, XTH20173, Stellar, Awesome, Essence and Multisweet 2340. The lower yielding varieties included Primus, 7002R, XTH2673, and AP 358. None of the yield differences were statistically significant.

There were some significant differences among plant characteristics. Mirai 315 had the best ear height at 25 inches, making hand harvest easier, followed by Essence, Mutiglow 7220R, Stellar, 301 BC and Higlow 8902 MR. AP 358 had the lowest ear height at 13 inches, with XTH2673, Primus, XTH2074, 7602, and Multisweet 2340 also having relatively low ear height.

Multisweet 2340, Higlow 8902 HR, XTH20173 and Awesome XR were the easiest varieties to harvest on our scale of one to three. The most difficult ears to remove from the plants were Stellar, Primus, 7002R and Multiglow 7002R. The best husk tip cover over the ears was found on Awesome (3 inches), Primus, and Essence, followed by XTH2074, 7602 and 7112R. The poorest tip cover was found on Mirai 315 (1 inch), followed by XTH20173 and 7002R.

Ear size was good to very good this season, although there were some significant differences between varieties. Primus and Higlow 8902 HR had the largest ears; averaging 8.4 inches, Mirai 315, Allure, Essence and XTH2472 also had good ear size, averaging 8 inches or better. Awesome XR and XTH2074 produced the smallest ears in the trial, averaging just over seven inches. Other varieties averaged just below eight inches.

The highest row number of kernels on each ear was found on Multiglow, Allure, and 7602, followed closely by XTH20173, 7002R and Higlow 8902 MR. Higher row counts tend to give the ear a more refined look and better visual appearance. Stellar, XTH2074, Awesome XR, 301BC and Essence also had high row counts, followed by XTH2472, XTH2673, Primus, 7112R, AP 358, Multisweet 2340, and Mirai 315.

Highmoor Farm crew favorites for overall best growth habit and ear quality this year, listed in order of maturity (earliest to latest) were: Stellar, 7112R, and Higlow 8902 MR. Other varieties that performed very well include: XTH20173, Awesome XR, Multiglow 7002R, Allure, Essence, and Multisweet 2340. You can see photos of these below. We’ll be testing more varieties in 2015, and look forward to sharing our findings with you.

We would like to thank Patricia McManus, George Greene, Christina Howard and the Highmoor Farm summer student crew for substantial help with this project. We also greatly appreciate the support of the Maine Agricultural Center, the Maine Vegetable & Small Fruit Growers Association, the New England Vegetable & Berry Growers Association and the following seed companies: Harris Seeds, Seedway, Siegers, and Stokes Seeds.

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© 2015