The month of March for some of us still involves some cold and wet weather. Other areas with warmer trends may have better conditions with individuals beginning to think about fieldwork, planting and fertilization. While many of our cattle graze a good portion of the year on rangelands, many others are allowed to graze pastures in the spring/summer months and perhaps some crop residue/cover crops in the late summer and fall. These activities seem a ways out, but many operations will soon be applying fertilizers to pastures or in conjunction with planting crops. It is important to understand the soil nutrient needs of your land, particularly how much nitrogen is available and how much (if any) you may need to apply for the upcoming growing season.
Nitrogen is the most limiting nutrient for plant growth, so it is certainly a necessity for growing feed for our cattle. However, if there is too much nitrogen in the soil, (or under stressful growing conditions) some plants can uptake too much, which is then stored in the plant as nitrate (a nitrogen-oxygen molecule). If a plant has too many nitrates stored in it, this can then become toxic to many animals. Cattle are particularly susceptible to this since the rumen normally converts nitrates to nitrites and then to ammonia, which is then used by the microbiome. When in excess, these nitrites build to dangerous levels in the rumen and are absorbed into the bloodstream. The increase of nitrites in the bloodstream causes hemoglobin, an iron-rich protein in red blood cells which carries oxygen, to be changed into methemoglobin. This new form cannot bind to oxygen and carry it to the rest of the body which needs that oxygen to function and survive. Deprivation of oxygen in the body is eventually what harms cattle or unborn calves, and they ultimately suffocate if left untreated.
Some plants that tend to accumulate nitrates are oats, sorghum, corn, sunflowers and johnsongrass, among others. If you have any of these on your property or intend to plant them this year, it would be wise to test these for nitrate concentrations before feeding to livestock. Also, if any fertilizer is spilled on the ground, be sure to clean it up so cattle will not eat it, as this would certainly be a toxic level. If nitrate toxicity is suspected, call your veterinarian.
As you prepare to apply fertilizer to your fields in the next month or so, please work with your local agronomist, crop adviser or county extension agent to get a soil sample. Then based on those results, determine how much nitrogen is needed to be helpful to the plants but not excessive enough to cause toxicity concerns.
