Nitrates in your forages – beware!

By Dr. Michelle Der Bedrosian
Most producers would probably say 2019 has been a stressful cropping season.  Many of our crops have experienced their own kinds of stress – and this could result in dangerous conditions as we harvest and put up forages.

In addition to drought, nitrates can develop in plants stressed during severe heat, hail, frost, cloudy weather or fertility imbalance.  Any sort of stress that contributes to stunted plant growth can result in nitrates.  That’s because the plant continues to take up nitrates from the soil even if it isn’t using the nitrates to make plant proteins.

Enterobacteria convert these nitrates into extremely poisonous silo gasses.  These gasses may smell like bleach or be odorless.  They may have an orange-brown color or be colorless.  Silo gas is dangerous regardless of its odor and color.

The good news is that a typical fermentation can destroy 30% to 50% of silo gasses.

Here are some tips to keep in mind as you harvest stressed corn:

1. Heavy nitrogen (N) fertilization can contribute to more nitrates in the plant and silo.
2. If you are green-chopping corn, we highly recommend hand-cutting and chopping about 10 to 15 plants from that field and send the sample to the lab to be tested for nitrates before feeding to cows.  (The sample should be dropped off directly or shipped on ice.)
3. If you see silo gas, stay away from it and notify all other members of your feed and farm team.  Keep kids and pets away from the area.
4. Never enter a silo or uncover a silo after less than three weeks of ensiling.
5. If you think your feeds may have high nitrate concentrations, after a minimum of three weeks of ensiling, send a sample to a lab for testing.

If you are in an area where crops have been stressed, particularly by drought:

• You are especially prone to silo gas formation.
• Don’t harvest drought-stressed crops for at least three days following a good, soaking rain.  Nitrates typically accumulate in the bottoms of drought-stressed plants.  When it rains, they travel up the plant.  They take some time to be turned into plant proteins, so chopping prior to three days could put a lot of nitrates into your silo.
• Raise the cutter bar for stressed crops since nitrates accumulate in the bottoms of plants.

Contact your Vita Plus consultant if you have any concerns.  We wish you a safe and productive harvest!

Click here for more information on silo gasses.

About the author:  Dr. Michelle Der Bedrosian is a Vita Plus forage products and dairy technical service specialist. Der Bedrosian earned her bachelor’s and master’s degrees in animal science at the University of Delaware. She continued there to earn her Ph.D. in animal and food science, specializing in forage research with Dr. Limin Kung. Her thesis research centered on the use of a protease to improve starch digestibility earlier in the ensiling process. A New Jersey native, Der Bedrosian gained much of her farm experience during her collegiate years, milking cows, working in a forage laboratory, and performing dairy research. Based in Madison, Wisconsin, Der Bedrosian’s responsibilities at Vita Plus include forage product research and development, dairy research, and dairy technical services.