Ohio State University Extension

Ohio State University Extension
Department of Horticulture and Crop Science
2021 Coffey Road, Columbus, Ohio 43210-1044


Growing Degree Days as a Method of Rating the Maturity of Corn Hybrids

AGF-101-90

Because of differences in the growing season for corn across Ohio, producers need a method of accurately rating the maturity of their crops to assure maximum yield and quality with low moisture at harvest. For this reason, many hybrid seed corn companies rate hybrid maturity on the basis of "Growing Degree Days" (GDD) or "Heat Units." Because a corn hybrid requires a specific number of GDD to reach maturity regardless of the number of days taken to accumulate them, this method is more accurate than the traditional "Days to Maturity" method and should be understood by anyone producing corn.

Though there are several ways of calculating GDD, the most used method is to subtract 50 degrees F from the mean daily temperature. The following adjustments are necessary: 1) temperatures below 50 degrees F are set at 50 degrees F, and 2) temperatures above 86 degrees F are set at 86 degrees F. This method of calculating GDD is often referred to as the (86,50) system. The Agricultural Weather Center of the National Weather Service reports GDD based on this system in the Ohio Weekly Crop and Weather Summary. Following is the formula used to calculate GGD along with some sample calculations.

Formula: GDD = (T High plus T Low) divided by 2, minus 50

Examples of GDD Calculations:

For High = 80 degrees F, Low = 60 degrees F:
GDD = 80 plus 60 divided by 2 minus 50 = 20;

For High = 60 degrees F, Low = 40 degrees F:
GDD = 60 plus 50(40) divided by 2 minus 50 = 5;

For High = 90 degrees F, Low = 70 degrees F:
GDD = 86(90) plus 70 divided by 2 minus 50 = 28

Growing Degree Days or heat units are calculated for each day starting the day after planting. The GDD accumulations for the growing season in Ohio range from less than 2500 GDD in northeastern counties to more than 3000 GDD along the Ohio River in southwestern Ohio. Growing Degree Day accumulations for specific locations in the state may be found in the following table.

The "length of growing season" of various hybrids is directly related to their GDD requirements - long-season hybrids requiring more GDD to reach maturity than shorter season ones. Since GDD accumulations per year increase as one moves southwestward across the state, the relative maturity lengths of adapted hybrids increase in the same direction (i.e., hybrids classed as long season in Wayne County will be a short or mid-season maturity in Clinton County). Mid-season hybrids require approximately 100 fewer GDD than full season hybrids to give a two-week spread in maturity between the long and mid-season selections.

Often GDD information on hybrids can be obtained from company information booklets and salesmen. In using company information, however, the buyer should be sure that company ratings are made using the (86,50) system, because this is the basis for published weather data. Most companies use the time from planting to maturity to rate hybrids. If the rating is from emergence to maturity, add 150 to get the GDD from planting.

Growing Degree Days (GDD) accumulated at various sites in Ohio from several dates in May through the 10% frost date in the Fall.

  GDD to 10 Pct. chance of frost from May
Station Name 1 8 15 22 29
Akron-Canton-AP 2324 2250 2176 2102 2028
Ashland 2650 2570 2489 2408 2327
Athens 2763 2663 2563 2463 2363
Barnesville 2391 2311 2231 2152 2072
Bellefontaine 2779 2691 2603 2514 2426
Bowling Green 2805 2718 2630 2542 2454
Bucyrus 2525 2444 2363 2282 2201
Cadiz 2820 2731 2642 2553 2464
Caldwell 2814 2718 2621 2524 2427
Cambridge 2676 2582 2488 2395 2301
Canfield 2277 2208 2138 2069 2000
Carpenter 2791 2691 2590 2489 2388
Celina 2782 2687 2592 2497 2401
Centerburg 2501 2416 2331 2246 2161
Chardon 2434 2366 2298 2230 2162
Charles Mill Dam 2245 2176 2106 2037 1968
Chillicothe 3158 3049 2940 2831 2722
Chilo 3099 2994 2890 2785 2681
Chippewa Lake 2389 2313 2237 2161 2085
Cincinnati-Abbe 3391 3283 3175 3067 2959
Circleville 3023 2917 2811 2704 2598
Columbus-OSU 2777 2683 2590 2496 2403
Coshocton 2787 2691 2596 2500 2404
Dayton 3237 3125 3014 2903 2792
Defiance 2570 2489 2408 2327 2246
Delaware 2726 2637 2547 2457 2367
Dennison 2491 2405 2319 2233 2147
Dorset 1977 1915 1852 1790 1728
Eaton 2769 2678 2588 2497 2407
Elyria 2682 2603 2524 2445 2368
Fernhank Dam 3324 3215 3107 2998 2889
Findlay 2598 2518 2437 2357 2276
Franklin 2896 2796 2696 2596 2496
Fredricktown 2372 2293 2213 2134 2054
Fremont 2828 2741 2655 2568 2481
Gallipolis 3160 3045 2931 2816 2701
Geneva 2525 2460 2395 2330 2265
Greenville 2707 2621 2535 2449 2365
Hamilton 3132 3024 2915 2807 2698
Hillsboro 2931 2835 2738 2642 2546
Hiram 2460 2409 2338 2267 2196
Hoytville 2623 2535 2447 2359 2272
Ironton 3359 3240 3121 3002 2884
Irwin 2574 2487 2400 2313 2226
Jackson 2739 2638 2536 2434 2332
Kenton 2604 2523 2443 2362 2281
Lancaster 2750 2654 2557 2461 2364
Lima 2706 2617 2529 2441 2353
London 2755 2665 2576 2487 2398
Marietta 2918 2818 2719 2619 2520
Marion 2721 2629 2538 2447 2356
Marysville 2630 2545 2460 2375 2291
McConnelsville 2898 2805 2712 2618 2525
Millersburg 2528 2444 2360 2276 2192
Millport 2182 2111 2041 1971 1901
Mineral Ridge 2513 2433 2354 2274 2194
Montpilier 2684 2580 2495 2411 2327
Napoleon 2692 2610 2528 2446 2365
NC-Substation 2510 2427 2344 2261 2179
Newark 2636 2545 2455 2365 2275
New Lexington 2595 2504 2412 2321 2229
Norwalk 2569 2490 2411 2332 2254
Oberlin 2618 2539 2459 2380 2301
Painesville 2642 2575 2509 2442 2376
Pandora 2518 2435 2351 2268 2185
Paulding 2651 2567 2484 2400 2317
Peebles 2898 2795 2691 2587 2483
Philo 2885 2784 2682 2581 2480
Plymouth 2569 2491 2412 2333 2254
Portsmouth 3476 3353 3231 3109 2987
Put-In-Bay 3087 3013 2939 2865 2791
Ravenna-Arsenal 2185 2112 2040 1967 1894
Sandusky 3030 2946 2863 2779 2696
S. Charleston 2617 2505 2394 2283 2172
Senecaville Dam 2497 2408 2319 2229 2140
Sidney 2653 2567 2481 2395 2308
Springfield 3103 3002 2900 2799 2697
Steubenville 2837 2747 2657 2567 2477
Tiffin 2762 2675 2587 2500 2412
Tom Jenkins Dam 2150 2072 1994 1916 1838
Upper Sandusky 2721 2632 2543 2453 2364
Urbana 2622 2535 2449 2362 2276
Van Wert 2778 2688 2598 2509 2419
Warren 2559 2479 2398 2318 2237
Washington CH 2909 2812 2716 2619 2523
Wauseon 2516 2439 2362 2285 2208
Waverly 2917 2811 2706 2600 2495
Wilmington 2958 2856 2754 2653 2551
Wooster 2350 2277 2205 2132 2059
Xenia 2893 2794 2695 2596 2496
Zanesville 2351 2266 2181 2096 2011
Source: Ohio Report 61:1 (3-4)

Prepared by:
Donald J. Eckert
Assoc. Professor, Agronomy Dept.

This publication was prepared and funded through a cooperative effort of the Ohio Department of Energy and Ohio State University Extension.


All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181



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