Feed Nitrate Testing in Drought Years
Drought is an unwelcome but well-known phenomenon on the Great Plains and Canadian Prairies. Sparse and scattered rainfall and above-average temperatures can cause significant stress in small grains and other crops. The same conditions also wrack pastures, prompting livestock producers to think about alternative feed options. As producers consider what to do with drought-stressed crops, whether to harvest for grain or feed to livestock, an important part of that decision will be the nitrate concentration of the plant material for livestock feed.
When drought-stressed annual crops (e.g., wheat, barley, oat, corn) are grazed or cut for hay or silage, producers must exercise caution about livestock nitrate poisoning when feeding drought-stressed forages to livestock. Drought-stressed crops often accumulate nitrate because plant uptake of nitrate exceeds plant growth and nitrogen utilization. Nitrate is usually concentrated in lower plant parts (lower stem or stalk). When livestock ingest forages with a high nitrate concentration, nitrate poisoning can occur. This is especially concerning for ruminant livestock like cattle and sheep.
When collecting plant material for nitrate analysis, collect the plant parts that the livestock will eat. If plant material will be grazed, recall that lower plant parts contain higher nitrate concentrations; monitor grazing height closely. If plant material will be cut and baled, you should collect plant material above the cutter bar height. Alternatively, plant material can be sampled with a hay probe after being baled.
Instructions for collecting and submitting a feed nitrate test
- Collect the plant part that livestock will eat, which may be the whole aboveground plant. If grazing, be mindful of the grazing height; the plant nitrate concentration is usually greater near the base of the plant. If baling for hay or chopping for silage, cut at the intended cutter bar height.
- Chop plant material with sturdy garden shears into 1- to 2-inch pieces. Mix the chopped plant parts together and take one quart-sized subsample for analysis (about three or four good handfuls). Please do not submit whole corn stalks that have not been chopped and sized down.
- Place subsample in AGVISE Plant Sample Bag. Write “Feed Nitrate” as the crop choice and select “Nitrate-nitrogen” as the analysis option.
- If you are considering chopping corn for silage, also write “%Moisture” as an additional analysis because you will need to know if the moisture content is still adequate for silage fermentation. You may be surprised how much water will still be in drought-stressed corn stalks!
- Ship plant sample to AGVISE Laboratories as soon as possible. If you cannot ship the plant sample right away, store it in a refrigerator until you can ship it.
Photographic example of 1) cutting corn stalks at silage chopper height, 2) cutting the whole corn plants into 1- to 2-inch pieces and mixing well, and 3) placing one quart-sized subsample in AGVISE Plant Sample Bag.
It is wise to resample the baled hay or fermented silage before feeding to livestock. You need to know the nitrate concentration in the feed that is actually being fed to livestock, and you may need to blend it with other feed sources to dilute the nitrate concentration. For dry hay in bales, the nitrate concentration should not change in storage; use a hay probe to collect the best possible hay sample. For silage, the nitrate concentration may decrease 20 to 50% during the fermentation process, so a fresh sample is necessary before feeding.
AGVISE Laboratories offers next-day turnaround for feed nitrate analysis. Rapid turnaround on nitrate analysis is very important for producers debating to graze or cut and bale annual crops for livestock feed. AGVISE also provides livestock water analysis, which includes total dissolved solids, nitrate, and sulfate, to assess livestock drinking water quality. Water sources with high nitrate should also be considered in the total nitrate load for livestock rations.
Helpful resources on using drought-stressed crops for livestock feed
Nitrate Poisoning of Livestock, NDSU
Using Drought-stressed Corn as Forage, SDSU
Drought-related Issues in Forage, Silage, and Baleage, Univ. Missouri