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Nitrogen Applied

06.10.2008

Recent study results have shown have shown that using nitrogen fertilizer on off-season cover crops can not only increase the biomass of these crops, but can also have a beneficial effect on the nitrogen levels in the soil for the cash crop planted during the summer season. The results could significantly aid in preventing soil erosion in vulnerable agricultural regions.

Combating soil erosion is a primary concern for agricultural producers in the United States, and many have incorporated conservation tillage systems in their effort to maintain a profitable crop output.

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Cover crops are an important tool in this cycle, and while it is known that using nitrogen fertilizers can increase these crops biomass, the resulting levels of nitrogen for the following cash crops have been unknown.

Researchers found that areas that did have fertilizer applied to their cover crops had less biomass output for soil protection, while plots that did use fertilizer had greater biomass along with an increased amount of nitrogen available for the cash crop. Results from the study were published in the September-October 2008 issue of the Soil Science Society of America Journal.

“Use of high-residue cover crops is imperative to prevent soil erosion, to bank leftover nutrients during the winter for summer cash crops, and to improve soil quality,” said Mark Reiter, lead author of the study. “From this data we see that we can increase cover crop biomass by using nitrogen fertilizer and that the nitrogen will later be available to our cash crop. It is a win-win situation.”

The study was conducted by USDA-ARS scientists with the Conservation Systems Research Team in Auburn, AL and the J. Phil Campbell Senior Natural Resource Conservation Center in Watkinsville, GA, in cooperation with Auburn University. Scientists investigated the effects of using nitrogen fertilization on rye cover crops, as well as the subsequent fertilizer availability to cotton.

The focus of the study was on plots in the Tennessee Valley Region of northern Alabama, which is a highly productive region in the nation’s Cotton Belt. To study the effects of fertilizer, rye cover crops were varied in the amount of nitrogen used.

After the rye had dried up, cotton was planted in the same soils and fertilized with different amounts of nitrogen. Researchers collected the plant and soil samples and determined how much nitrogen had been integrated into the plant and soil systems. A nitrogen isotope was used to trace the nitrogen used in the fertilizer, as opposed to nitrogen that is native to those soils.

While the results of the study are positive to understanding conservation tillage, further research is still needed before establishing new fertility management guidelines in all crops using high-residue cereal cover crops. In applying this research, it is expected that soil quality, along with management of the nutrients in the soil, will improve the success of American agricultural producers.

The full article is available for no charge for 30 days following the date of this summary. View the abstract at http://soil.scijournals.org/cgi/content/abstract/72/5/1321.

Soil Science Society of America Journal, http://soil.scijournals.org, is a peer-reviewed international journal published six times a year by the Soil Science Society of America. Its contents focus on research relating to physics; chemistry; biology and biochemistry; fertility and plant nutrition; genesis, morphology, and classification; water management and conservation; forest, range, and wildland soils; nutrient management and soil and plant analysis; mineralogy; and wetland soils.

The Soil Science Society of America (SSSA) is a progressive, international scientific society that fosters the transfer of knowledge and practices to sustain global soils. Based in Madison, WI, and founded in 1936, SSSA is the professional home for 6,000+ members dedicated to advancing the field of soil science. It provides information about soils in relation to crop production, environmental quality, ecosystem sustainability, bioremediation, waste management, recycling, and wise land use.

SSSA supports its members by providing quality research-based publications, educational programs, certifications, and science policy initiatives via a Washington, DC, office. For more information, visit http://www.soils.org.

SSSA is the founding sponsor of an approximately 5,000-square foot exhibition, Dig It! The Secrets of Soil, which opened on July 19, 2008 at the Smithsonian's Natural History Museum in Washington, DC.