2005 Year in Review

From the Fields

Source: Jim Morrison, Extension Educator, Crop Systems, Rockford Extension Center, University of Illinois, 417 Ware Avenue, Suite 102, Rockford, IL 61107, Phone 815/397-7714, Fax 815/397-8620, email: morrison@uiuc.edu

Moisture-stressed corn that will be cut for silage may contain high levels of nitrate. Symptoms of nitrate poisoning (incoordination, difficult breathing, muscular weakness, coma, and even death) in livestock are related to the lack of oxygen in tissues.

It is important that producers review guidelines and know management strategies to minimize potential nitrate poisoning.

- Plants accumulate toxic levels of nitrate when soil nitrogen levels are high and available, but the plant is unable to utilize it (or convert it to plant protein). Corn with low grain yield potential or high percentage of barren ears often contains toxic levels of nitrate. Nitrate does not accumulate in the grain.

- In corn, highest levels of nitrate are found in the stalk (lower 12 to 18 inches of the stalk contain more nitrate) and lowest levels are in the ear. Nitrate levels are higher in the morning. Also, the nitrate level is elevated for a few days right after a rain as it causes the plant to take up soil nitrates very quickly. Allow about 5 days after a rain for the plant to convert nitrate to plant protein.

- A qualitative test using nitrate powder sprinkled onto the inside nodes of a split (from top to bottom) corn stalk can tell you if there are excess nitrates present. If nitrates are present, the powder will turn red. A laboratory analysis can indicate the specific level of nitrate present in a sample.

- A list of laboratories that test forages for nitrates is available at Extension offices. Try to obtain a representative forage sample and then send the fresh sample (one pint to one quart) in a sealed, airtight plastic bag. Ideally, it is best to take a sample directly to the laboratory; if this isn’t possible then freeze it and ship it frozen. Once the sample arrives at the laboratory, analysis should be completed in 2-3 days.

- Nitrate-nitrogen level (dry matter basis) of less than 1,000 parts per million is generally considered “safe” for livestock rations. Toxicity of nitrate varies among livestock of various ages, diets, and health status.

- Ensiling high nitrate forage and allowing the material to complete the normal fermentation process (requires at least 2 to 3 weeks) will reduce the nitrate level by one-third to one-half. Use the hand-squeeze test to determine if the plant contains too much moisture. If water drips from the squeezed sample, corn silage is too wet for ideal fermentation.

- For corn silage, be sure to wait until the corn plant dries to the correct moisture content for the storage method you use:
Bunker or bags = 30-35 percent dry matter
Conventional silo = 35-45 percent dry matter
Oxygen limiting silo = 45-55 percent dry matter

- In addition to corn, sudangrass, sorghum-sudangrass, pearl millet and certain weeds (including pigweed, smartweed, ragweed, lambsquarter, and nightshade) can accumulate toxic levels of nitrate.

- Baling does not reduce the nitrate level as compared to ensiling (see comment above regarding fermentation). If drought damaged crops (especially if nitrogen was applied) are baled or green-chopped, test the forage for nitrate levels.

Further information is available at your Extension office, including University of Illinois web sites on feeding drought stressed corn and nitrates in forages.

by  Editor, theCity1.com
August 25, 2005