Check Moisture And Nitrates In Corn

Know your numbers for corn silage.

Published on: Aug 20, 2012

Earlier this month, University of Minnesota Extension specialist Dan Martens checked on chopped corn moisture in a couple drought-stressed corn fields on non-irrigated sand in the St. Cloud to Clearwater area.

He issued the following report:

The farmer chopped a couple hundred feet into the fields and took a five-gallon pail sample from that. Both fields were around 6 feet tall and had not made any corn yet, and probably wouldn't make much corn. One field looked quite brown from the road. The sample from this field was a mix of pale green and straw colored material, labeled "Brown". The second field had greened up some with recent rain and the sample was a fairly normal green color, labeled "Green."

Check Moisture And Nitrates In Corn
Check Moisture And Nitrates In Corn

The Brown sample tested around 75% moisture with the Koster tester; the Green sample tested about 80%. I took a sample to the feed testing lab in Sauk Rapids because I was curious about nutrient and nitrate content. The lab test showed 75.4% moisture on the Brown sample and 79.7% on the Green sample – basically around 75 and 80%. Based on the samples, both fields were too wet for putting in storage. General recommendations are 60-70% moisture for bags, 65-70% for bunkers and piles, 50-60% for oxygen limiting silos, and 60-65% for upright silos.

Another way to estimate moisture is by squeezing a sample of finely chopped material in your hand as tight as you can for about 90 seconds. If juice squeezes out between your fingers, it's probably 75 to 80%. That was true for the Green sample, and not quite true for the Brown sample. At 70 to 75% moisture, when you open your hand, the ball will hold its shape fairly well and your hand is moist. At 60-70%, when you open your hand the ball will expand slowly with little or no dampness on the hand. At less than 60%, the material will expand and fall and lose its shape.

When corn gets into a normal maturing and drying stage, with normal weather patterns, we'd expect to lose about 0.5% moisture per day. We can expect that to be different with a drought stressed crop with little or no corn in it.

The Brown sample tested at 2070 parts per million of nitrate nitrogen, and the Green sample at 518. The cost of this test was just $9 per sample. These fields had about 120 pounds of nitrogen applied in the spring through preplant, starter and sidedress applications.

Nutrients in these 2 chopped corn samples tested very much like a respectable grass hay silage: 11-12% protein, 27 to 42 ADF (Acid Detergent Fiber), 48-55% NDF (Neutral Detergent Fiber) and 65 to 69% TDN (Total Digestible Nutrients). Starch tested 4 to 6% compared to averaging about 32 to 36% in normal corn silage. University articles suggest that drought-stressed corn silage can have 80 to 100% of the feed value of normal corn silage. A lab feed test can be helpful in determining the value and in deciding how it might be used in rations.

For more information, do a website search for "Minnesota Extension Drought" or "Minnesota Extension Using Drought-Stressed Corn."