With corn silage season coming up this is a good time to talk about nitrate poisoning. Typically associated with drought and rain after dry conditions, there are other factors to that can cause high nitrate in forage crops. High rates of N, low or high levels of molybdenum, low sulfur, and low boron, and events that upset normal plant growth like early frosts.
New pastures are known to be high in nitrate, especially the faster they grow, the more toxic they can become. Hybrid ryegrass is one of the most dangerous. If reseeding pastures this fall make sure to add edible clover which normally do not have high nitrate levels.
Nitrate poisoning has been on the rise in the past decade, this could be due to the reluctance of today's generation to lime pastures (molybdenum levels drop with acid soils), increase use of urea on pastures, and less sulfur naturally being applied due to clean air laws.
Nitrate Toxicity is aggravated by:
Excess N application in the autumn after a dry period of no growth
Rain and warmth after a no-grow period
Fast plant growth
Stressed plants, from drought, hot wind, frost, and hail
Fast eating by underfed, hungry animals
Low pasture molybdenum - below 0.5 ppm, 1.6 ppm is optimum
Molybdenum levels above 4 ppm, especially if pasture sulfur is low
Low sulfur levels, below 0.25 ppm
Low calcium and phosphorus levels
Nitrate is highest in the morning, when rotating cattle wait until mid afternoon
While environment can have an impact on nitrate levels, having the proper soil nutrients in the proper levels is great insurance from nitrate poisoning. As a bonus you'll enjoy better pasture performance, and high gains from your animals.
The Blogronomist is maintained by Craig Dick, head blogronomist and VP of Sales and Marketing. Here you will find a wide array of blog articles from Craig and expert guests on topics related to soil and crop health, farming, and so much more. If it’s not here, ask us!