PUTNAM COUNTY — Rainfall this weekend helped some drought stressed corn fields. The U.S. Drought Monitor estimates 46 percent of Ohio was rated “moderate drought” in northern Ohio and 15 percent in “severe drought”. Two procedures to estimate corn grain yields prior to harvest are the YIELD COMPONENT METHOD and the EAR WEIGHT METHOD. Each method will produce yield estimates that are within 20 bu/ac of actual yield.

THE YIELD COMPONENT METHOD principle advantage is that it can be used at the milk stage of kernel development, currently similar to most Ohio corn fields. The yield component method uses a numerical constant sometimes referred to as a “fudgefactor” based on a predetermined average kernel weight. Since weight per kernel will vary depending on hybrid and environment, the yield component method should be used only to estimate relative grain yields, i.e. “ballpark” grain yields. When below normal rainfall occurs during grain fill (resulting in low kernel weights), the yield component method will OVERESTIMATE yields. In a year with good grain fill conditions (resulting in high kernel weights) the method will underestimate grain yields.

For the YIELD COMPONENT METHOD, Dr. Bob Nielsen at Purdue University suggests a “fudge factor” of 80 to 85 (85,000 kernels per 56 lb bushel) as a realistic value to use in the yield estimation equations. Dr. Emerson Nafziger at the University of Illinois says under current drought stress “…. If there’s a fair amount of green leaf area and kernels have already reached dough stage, using 90 [as the “fudge-factor “] might be reasonable. If green leaf area is mostly gone and kernels look like they may be starting to shrink a little, kernels may end up very light, and using 120 or even 140 [as the “fudge-factor”] might be more accurate”.

Calculate estimated grain yield as follows: 1) Count the number of harvestable ears in a length of row equivalent to 1/1000th acre or 17 ft. 5 in. for 30 inch rows. 2) On every fifth ear, count the number of kernel rows per ear and determine the average. 3) Count the number of kernels per row and determine the average. (Do not count kernels on either the butt or tip of the ear that are less than half the size of normal size kernels.) 4) Yield (bushels per acre) equals (ear #) x (avg. row #) x (avg. kernel #) divided by 90. 5) Repeat the procedure for at least four additional sites.

Example: You are evaluating a field with 30 inch rows. You counted 24 ears (per 17’ 5” row section). Every fifth ear resulted in an average row number of 16 and an average number of kernels per row of 30. The estimated yield for that site in the field would be (24 x 16 x 30) divided by 90, which equals 128 bu/acre.

THE EAR WEIGHT METHOD can only be used after the grain is physiologically mature (black layer), which occurs at about 3035 percent grain moisture. Sample several sites in the field and measure off a length of row equal to 1/1000th acre. Count the number of harvestable ears in the 1/1000th acre. Weigh every fifth ear and calculate the average ear weight (pounds) for the site. Hand shell the same ears, mix the grain well, and determine average percent grain moisture.

Calculate estimated grain yield as follows: A) Multiply ear number by average ear weight. B) Multiply average grain moisture by 1.411. C) Add 46.2 to the result from step B. D) Divide the result from step A by the result from step C. E) Multiply the result from step D by 1,000.

Example: You are evaluating a field with 30 inch rows. You counted 24 ears (per 17 ft. 5 in. section). Sampling every fifth ear resulted in an average ear weight of 1/2 pound. The average grain moisture was 30 percent. Estimated yield would be [(24 x 0.5) / ((1.411 x 30) + 46.2)] x 1,000, which equals 135 bu/acre.

Because it can be used at a relatively early stage of kernel development, the Yield Component Method may be of greater assistance to farmers trying to make a decision about whether to harvest their corn for grain or silage because there is greater benefit in harvesting fields with marginal corn grain yield potential for silage. From Dr. Peter Thomison OSU Corn Specialist, CORN Newsletter 2016-25.

Note: This is my last news article since I have taken a new job as NRCS Soil Health Specialist for Ohio and Southern Michigan, located in Findlay. Thanks for the opportunity to serve agriculture in Putnam County.