Immature and Variable Maturity Corn Silage for 2019

Kitty O’Neil, Ph.D, Field Crops & Soils Specialist and Team Leader – North Country Regional Ag Team, Cornell University Cooperative Extension

This has been a challenging year to grow corn in the North Country.  Extremely wet weather delayed or prevented field fitting and corn planting, and saturated soil conditions limited plant development in June and early July.  Despite this poor start, some corn fields look remarkably good, almost normal.  But most fields are weeks behind and may be sporting some version of the ‘rollercoaster’ look – with bare spots, replanted areas and plants of variable height and maturity.  Some fields, or parts of fields, will probably not reach full maturity while the best parts may.  Some corn plants will have normal ears; some plants may have unusually small ears or poor grain fill, or even no ears at all, at harvest time. Dr. Bill Cox at Cornell determined that corn requires 750 to 800 GDD_86/50 from silking, to reach 32% moisture, nearly harvesting stage.  This variable maturity will present some problems when chopping silage in a few weeks.  Dr. Larry Chase from Cornell University has outlined some key points to keep in mind during corn silage harvest in this sort of year.  He makes 4 main points.

Yield will be highly variable and difficult to estimate. Dr. Greg Roth at Penn State suggests that silage yield for corn without ears or with poorly pollinated ears may be 1 ton of wet silage yield (30% DM) per foot of plant height. An older study at Cornell by Dr. Bill Cox indicates that silage yields at the dough stage are 65 to 70% of yields at the milk line stage.  In the same study, yields at the silk stage were 40 to 45% of those obtained at the milk line stage.

Some growers like to estimate yield and quality of standing corn so that it may be sold for silage before harvest.  Estimating yield of highly variable fields is risky.  It’s possible to weigh DM from sampled row lengths and calculate yield of the whole field, but the number of samples required for an accurate estimate in these variable fields is prohibitively high.  Instead, as fields are chopped, silage wagons or trucks should be counted and a representative sample of them should be weighed to calculate a more accurate yield and price.

Harvest management requires some additional planning and checking.  When the most mature plants in a corn field are at the proper dry matter (DM) content for harvest (32-24% DM), the less mature plants will be much wetter (less than 30%).  For fields with variable maturity, wait until the average whole plant DM for the field is 32-34% DM.  Harvesting wetter forage will increase runoff losses from the silage and make it difficult to get a good fermentation.  If possible, store immature corn silage separately from proper maturity silage.

Check chopper settings and particle size of the material coming out of the chopper. If using the Penn State box, target 10-20% on the top screen and < 40% in the pan. This may require increasing length of cut.  Since ear and kernel development on under-developed corn is poor, kernel processing may not be needed.  Follow normal silage management practices of filling fast, packing and covering the top with plastic or with oxygen limiting barriers.  Immature corn silage is generally high in readily available carbohydrates to support good fermentation, however, it may be low in the natural bacterial population entering the silo on the corn plant. The addition of a lactic acid-based inoculant may be beneficial to stimulate fermentation in this case.  Lastly, give the silo 3-4 months of fermentation before feeding out.

Estimating value for corn silage when it is so variable – is tough.  The sale price of variable maturity or immature corn silage will depend on yield, dry matter content and nutrient composition. Dr. Bill Weiss at Ohio State indicates that immature corn silage is worth about 85% of the economic value of normal corn silage – if it is the same dry matter content.  Dr. Larry Chase provides examples of price calculations that consider the Ohio State conversion and variable DM content.

If the value of “normal’ corn silage = $70/ton (assuming 35% DM), then the value of immature corn silage = $70 * 0.85 = $59.50 (still assumes 35% DM). If the actual dry matter of the immature corn silage is only 27%, then the adjusted price = 27/35 *$59.50 = $45.90/ton.  To ballpark the value of the standing crop, use 70% of the adjusted price. This would be $41.65 for this example of immature corn silage at 27% DM standing in the field.

Penn State researchers have developed a more detailed spreadsheet for pricing standing corn for corn silage based on the value of grain corn.

When using any of these methods for valuing corn for corn silage in 2019, consider that estimating yield of the standing crop may be the most uncertain component in your calculations.  Therefore it may be best to count and weigh trucks or wagons rather than estimate yield.

Nutritional value of this immature and variable crop will present another challenge. In addition to variable moisture content, nutrient composition of the corn silage will also vary with maturity, so periodically collect samples of the chopped forage during harvest to provide information on the nutrient content of the silage for use in ration balancing.  Less mature corn is likely to be higher in crude protein, higher in fiber, higher in sugar and lower in starch than normal corn silage.  Because the fiber in immature corn is more digestible, the energy value of immature silage may be 85-95% of normal, despite the significantly lower starch content.  A wet chemistry analysis may be more accurate than NIR analysis since NIR calibrations for normal corn silage may not accurately predict immature silage composition.

Work with your nutritionist to determine the best use for your variable maturity or immature corn silage.  You may decide to feed immature corn silage only to specific groups of cows or young stock depending on its nutrient composition. Immature corn silage can have higher acetic acid content after fermentation which can decrease dry matter intake if not neutralized. The addition of sodium bicarbonate added to the ration at 0.75% of total ration dry matter may help.

Additional resources:

1. 1. Working with Immature Corn Silage. August 2013. L. E. Chase, Cornell University.  http://www.ccenny.com/wp-content/uploads/2013/02/Considerations-for-Working-with-Immature-Corn-Silage-2013.pdf.
   2. Pricing Standing Corn Spreadsheet. Beck et al.  Penn State Cooperative Extension.  http://www.ccenny.com/index.php/2013/08/22/pricing-standing-corn-for-silage-spreadsheet/

For more information about field crop and soil management, contact your local Cornell Cooperative Extension office or your CCE Regional Field Crops and Soils Specialists, Mike Hunter and Kitty O’Neil.