We continue to have problems with high nitrate levels in forages this fall, especially in cereals such as wheat, rye, oats, barley, and triticale planted early for fall grazing following drought-damaged corn or sorghum, and in brassica crops such as canola, turnips, rape, kale, rutabagas, and tillage radishes. Since July 1, the K-State Soil Testing Laboratory has analyzed more than 1,200 forage samples from farmers and ranchers for nitrates. The following is a brief summary of what we have found in October:
Fall cereals, including wheat, rye, oats barley and triticale:
- 37 samples
- Mean nitrate level of 10,039 ppm
- Range of 130 to 38,990 ppm
- 17, or 46% of total, had levels greater than 6,000 ppm.
Brassicas for fall grazing, including turnips and radishes:
- 36 samples
- Mean nitrate level of 27,442 ppm
- Range of 16 to 81,279 ppm
- All but 4 samples had levels greater than 6,000 ppm.
- 19 samples
- Mean nitrate level of 7,037 ppm
- Range of 784-26,200 ppm
- 10, or 53% of total, had levels greater than 6,000 ppm
Corn stalks, baled or standing in the field:
- 100 samples
- Mean nitrate level of 3,922 ppm
- Range of 18 to 20,488 ppm
- 18, or 18% of total, had levels greater than 6,000 ppm
Grain sorghum stalks, baled or standing in the field:
- 78 samples
- Mean nitrate level of 1,791 ppm
- Range of 27 to 23,333 ppm
- Only 6 samples, or 8% of total, had levels greater than 6,000 ppm
Sudangrass, forage sorghum, cane, etc.:
- 115 samples
- Mean nitrate content of 3,503 ppm
- Range of 19 to 18,400 ppm nitrate
- 24 samples, or 21% of total, had levels greater than 6,000 ppm
Silage (corn and sorghum):
- Only 12 samples, but all were below 1,500 ppm
There are a couple of key take home messages from these samples. First, most of the forages we will likely be using for supplemental feed this winter have the potential to contain toxic levels of nitrates. Whether grazing corn or grain sorghum stalks, feeding baled stalks, or using late-summer or fall-planted forages such as wheat or other cereals, or brassicas such as turnips, radishes or canola, TEST IT FIRST.
The brassicas such and turnips and radishes are known accumulators of nitrate, and samples to date confirm that. Be especially careful when utilizing these materials for grazing. Nearly all the samples tested to date have extremely high levels of nitrate.
Volunteer corn is another problem. More than half the samples identified as volunteer corn had high nitrate levels. This is a special problem as the nitrate level will not go down as these plants die, and this material will be preferred grazing for many cows and calves compared to the stalks in the field from the full-season crops.
The good news from the sampling to date is a high percentage of the sorghum stalks have relatively low nitrate levels. Some are high, however, so testing individual fields will be important. If nitrate levels are acceptable, these acres could be available for grazing.
Also, about 75 percent of the sudan and forage sorghum forage samples tested by our lab have low nitrate levels. These are important supplemental forages for many Kansas cattlemen.
In summary, nitrate levels in many forages in Kansas are high this fall, and likely will stay that way until spring. This will require careful sampling of forage supplies to avoid nitrate poisoning of livestock this winter.