Making Corn Silage in Dry Conditions

Source: Bill Weiss, OSU

The primary goal of making corn silage is to preserve as many nutrients in the corn plant as possible, to produce a feed that is acceptable to cows, and to minimize any risks associated with feeding the silage.  The following are important considerations for making corn silage when growing conditions have been dry.

Chop at the correct dry matter concentration (Editor’s note: see accompanying article “Corn Silage Harvest Timing”). Drought-stressed corn plants are often much wetter than they appear, even if the lower plant leaves are brown and dried up.  Before starting chopping, sample some plants (cut at the same height as they will be with the harvester) and either analyze DM using a Koster tester or microwave or send to a commercial lab (turn-around time may be a few days if you send it to a lab).  If the plants are too wet, delay chopping until the desired plant DM is reached.  The plant may continue to accumulate DM (increase yield), and you will not suffer increased fermentation losses caused by ensiling corn that is too wet.

Use a proven inoculant.  When silage is worth upwards of $80/ton (35% DM) reducing shrink by 2 percentage units has a value of about $2/ton. Homolactic inoculants (these are the ‘standard silage inoculants’) produce lactic acid which reduces fermentation losses but sometimes can increase spoilage during feedout. The buchneri inoculants increase acetic acid which slightly increases fermentation losses but greatly reduce spoilage during feedout.  Severely drought-stressed corn can have a high concentration of sugars because the plant is not depositing starch into the kernels.  High sugar concentrations can increase spoilage at feed out because it is food source for yeasts and molds.  Use of a good (from a reputable company with research showing efficacy) buchneri inoculant may be especially cost-effective with drought-stressed corn.

Check for nitrates.  Drought-stressed corn plants can accumulate nitrates which are toxic (as in fatal) to ruminants.  Silage from drought-stressed fields should be tested before it is fed.  Ideally, corn plants should be sampled and assayed for nitrates prior to chopping (most labs offer very rapid turn-around times for a nitrate assay).  If values are high, raising the cutting height will reduce nitrate concentrations in the silage because the bottom of the stalk usually has the highest nitrate concentrations.  Because forage likely will be very limited this coming year, do not raise the cutting height unless necessary to reduce nitrate concentrations.  Nitrate concentrations are often reduced during silage fermentation so that high nitrates in fresh corn plants may end up as acceptable concentrations in the fermented corn silage.  Silage with more than 1.5% nitrate (0.35% nitrate-N) has a high risk of causing nitrate toxicity in cattle.  See the following University of Wisconsin-Extension fact sheet for more details on nitrate toxicity:

Chop at correct particle length.  Do not chop too finely so that the effective fiber concentration of corn silage is reduced.  If the corn plants have limited ear development, fine chopping is not needed for good starch digestibility.  Generally, a theoretical length of cut (TLC) of about ½ inch is acceptable (longer with kernel processing and BMR silage) but this varies greatly between choppers and crop moisture concentration.  If using a Penn State particle size sieve, aim for 5 to 10% on the top screen.

Use a kernel processor.  Kernel processed corn silage tends to pack more densely than unprocessed corn silage which may help increase aerobic stability.  Kernel processing will also increase starch digestibility by breaking the kernel.  Poor starch digestibility is a major problem with dry, mature corn silage.

Reduce Shrink. Fill quickly, pack adequately, cover, and seal the silo as soon as you are done filling.  Practicing good silage-making techniques can reduce shrink by more than 5 percentage units, which can be worth more than $4/ton of corn silage (35% DM).

More on Switching Corn Hybrid Maturities

Dr. Peter Thomison, OSU Extension

Corn GDD Tool to Identify “Safe” Hybrid Maturities for Late Planting.  Dr. Bob Nielsen at Purdue University has written an article describing a powerful decision aid, U2U Corn GDD Tool, which can be used to identify “safe” hybrid maturities for late planting. The GDD Tool is currently available for Ohio and it can estimate county-level GDD accumulations and corn development dates based on current and historical GDD data plus user-selected start dates, relative hybrid maturity ratings, GDDs to black layer, and freeze temperature threshold values. The article can be found here: ( ).

Silage Corn.  Although corn for silage responds to timely planting, it is more tolerant of late planting than is corn planted for grain. Silage growers can generally continue to plant adapted hybrid maturities for silage purposes until late June because silage harvest typically occurs several weeks before physiological maturity. Penn State University researchers have reported yields of more than 20 tons/acre with mid-June plantings in some years. Their studies indicate that corn silage can produce reasonable forage yields in many areas, even when planted in late June. Penn State University studies have shown that energy levels are reduced in later-planted silage, presumably because of lower starch levels due to reduced grain fill.

“Ultra-early” Hybrids.  Results of past OSU research indicate that some 100-104 day hybrids are available with yields comparable to hybrids of commonly grown maturities in early and late planting environments. The 100-104 day hybrids showed greater yield potential than the hybrids with maturity ratings less than 100 days (ultra-early hybrids). Grain moisture of the early 100-104 day hybrids were 3 to 5% lower than commonly grown maturities. At test sites with the highest level of stalk lodging, most of these early hybrids showed levels of stalk lodging comparable to those of the commonly grown hybrid maturities. However, our knowledge of early hybrid performance across Ohio production environments is limited. Some shorter season hybrids may not be suitable in terms of their stress tolerance and disease resistance.

Table 1 provides a comparison of grain moisture content at harvest in hybrids ranging from 102 to 113 days relative maturity (days relative maturity) planted in late April/ early May and in early/mid June (unpublished OSU research, 2009-2010).

Table 1.  Effects of planting delays and hybrid maturities on corn grain moisture at harvest. * number in parentheses indicates number of studies

Hybrid Maturity (days)
Location/Year Planting Date 102 104 111 113
—–% harvest moisture—-

S. Charleston 2009 (3)*


Late April/Early May 13.9 14.9 16.6 18.9
Early/Mid June 16.4 17.3 22.3 28.4

S. Charleston 2010 (3)


Late April/Early May 10.9 11.7 13.0 13.0
Early/Mid June 14.8 16.3 21.9 23.4

Hoytville 2010 (1)


Late April/Early May 15.7 15.2 22.1 23.0
Early/Mid June 23.1 24.5 28.8 30.0

Ensuring Quality Silage After Excessive Rains and Flooding

Source: Penn State University

Corn that will be harvested as silage, and was previously in standing water during the growing season can be of concern when it comes to forage quality and palatability. Bacterial contaminants and silt can lead to animal health and fermentation problems.

According to a Cornell University publication by Paul Cerosaletti and Dale Dewing, silt deposition on standing corn can result in greater risk for clostridial contamination, as the primary source of clostridium bacteria is found in soil. If silage does not undergo the desired lactate fermentation and undergoes clostridial fermentation, moisture levels can reach greater than 70%, the pH is typically greater than 5.0, and a rank odor can be detected. This type of fermentation also causes deadly botulism toxins. Soil-contaminated forage can also contain coliform and listeria bacteria.

Corn that has been flooded and has a large amount of silt deposition on the standing forage could be of less risk to animal health and improper fermentation if it dried down and is harvested for grain. If the silt is found only on the portion of the plant near the ground, consider raising the chopping height so soil particles are not integrated into the chopped forage.

A publication from Cornell University goes more in depth on what to look for with flood damaged corn and management factors to consider.