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Wait Until Temps Drop to Apply Anhydrous AmmoniaOctober 5, 2006
Des Moines, Iowa - To decrease the risk of polluting groundwater and streams, prevent soil erosion and help save money on energy costs, conservationists are encouraging Iowa crop producers to wait until daily soil temperatures drop to below 50 degrees Fahrenheit and trending lower to apply anhydrous ammonia (NH3) this fall or, even better, wait until spring. Steve Brinkman, Nutrient Management Specialist with the USDA’s Natural Resources Conservation Service (NRCS) in Des Moines, says anhydrous ammonia applied in the fall tends to have a higher potential of leaching into streams than spring-applied NH3. “When soil temperatures are too warm, it increases the risk of nitrates polluting groundwater and streams,” he says. According to the Iowa State University Extension Service, applications of anhydrous ammonia should not start until mid-day soil temperatures, at a 4-inch depth, are below 50 degrees Fahrenheit and trending lower. Historically, soil temperatures at a 4-inch depth cool below 50 degrees in the northern third of the state during the first week of November. In central and southern Iowa, soil temperatures cool below 50 degrees during the second and third weeks of November, according to Iowa State University Extension. “Cooler soil temperatures slow biological activity,” says Brinkman, “allowing nitrogen to stay in the ammonium (NH4) form longer. Then it has a better chance of being retained in the soil.” Producers and fertilizer dealers are encouraged to visit the Nitrogen and Phosphorus Knowledge web page, http://extension.agron.iastate.edu/NPKnowledge/, to view daily average soil temperatures for every county in Iowa. Fall NH3 Can Increase Soil Erosion ISU Extension research indicates lower yields can result when anhydrous ammonia is applied in the fall versus spring, and crop residue cover can be reduced by the tillage action of NH3 application, increasing the risk of soil erosion. Fred Wilson of Clearfield, Iowa, has continuously no-tilled for more than 20 years. He quit applying fall anhydrous three years ago and went to a spring-only application. He applies only dry nitrogen now. “I don’t think I will ever go back to anhydrous,” he said. “I had more erosion from anhydrous a year ago than I’ve had in 20 years, so I just gave up. I switched to dry nitrogen. It costs a little more, but it’s worth it.” Energy Estimators To save energy and money, the NRCS recommends farmers use online energy estimators for tillage and nitrogen, at www.nrcs.usda.gov/technical/energy/index.html. The energy estimator for tillage estimates diesel fuel use and costs in the production of key crops. It compares potential energy savings between conventional tillage and alternative tillage systems. The energy estimator for nitrogen enables farmers to calculate the cost of nitrogen product use. It also evaluates options based on user input. According to the USDA, nitrogen fertilizer is one of the largest indirect uses of energy on an agricultural operation. Fertilizer accounts for 29 percent of agriculture’s energy use, according to USDA research data. Proper management of nitrogen fertilizer, including the use of organic sources of nitrogen such as animal manure and cover crops, can save producers energy and money. -30- Contacts: Steve Brinkman,
Nutrient Management Specialist, USDA-NRCS, 515-323-2243 |
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