Pennsylvania Corn: Yield Estimation and Seasonal Assessment

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Here in central Pennsylvania the corn crop is looking very good, with excellent pollination and ear development. Overall, I think our corn crop is in good shape with 92% rated good to excellent in the latest USDA report. Maturity is lagging a bit due to late planting and cool temperature, so harvest will be delayed a bit in some areas.

Disease pressure is increasing but I am not hearing about too many serious reports of gray leaf spot and northern corn leaf blight. The cool temperature should reduce respiration and improve kernel size and grain yield.

There are several methods for assessing grain and silage yields pre-harvest but the one commonly used is the kernel count method. This consists of counting harvestable ears per acre using an ear count from a 1/1,000 acre section, and counting the kernel rows and kernels per row on each ear to estimate the number of kernels per ear.

Multiply the ears per acre by the kernels per ear and that will result in the number of kernels per acre. Divide that by 90,000 kernels per bushel for an estimate of bushels per acre. In some years with good grain fill and deep kernels, this factor can change to 75,000.

To convert these grain yields to silage, you can divide the grain yield estimate by a factor 6.5 to 7.5. This will give you an estimate of wet tons at 35% DM.

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This year we could see a few factors to consider in your yield estimates. Some fields could have exceptional grain size due to the cool, sunny conditions and lack of water stress during grain fill.

In some fields, I am getting reports of viable second ears. In other fields, there may be areas of the field with low yields due to water or slug damage. These low yielding areas are difficult to account for in many yield estimates. In these situations, it pays to err on the conservative side.

Pre-harvest yield estimates are valuable in marketing plans and harvesting decisions. They can also provide some preliminary feedback on variety or management impacts. Now is a good time to make some yield estimates to evaluate your corn crop and management decisions.

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