Two years of replicated field trials at the University of Wisconsin (UW) Hancock Research Station demonstrate that Nitamin^® Liquid fertilizer increases potato yield and quality compared to quick-release nitrogen (N) sources. Applying Nitamin to potatoes at emergence and tuberization increased marketable potato yield by 23-37% and decreased hollow heart by 5% compared to commercial fertilizer programs using ammonium sulfate at emergence and ammonium nitrate at tuberization.

In the studies, the areas treated with Nitamin had greater yield than the averages from the commercial fertilizer programs. The 2004 data shows that the Nitamin-treated potatoes had fewer culls and smaller percentage of hollow heart than potatoes that used the commercial nitrogen treatments. In 2005, higher total yields, greater than 2.5 tons per acre, were observed with the Nitamin treatment.

Nitamin is a slowly-available nitrogen source developed by scientists at Georgia-Pacific Corp. Nitamin Steady-Delivery® fertilizer releases nitrogen to plants over a 60-90 day period depending on soil type and temperature. In contrast, quick-release fertilizers such as ammonium nitrate are converted to useable N forms within the first few days or weeks after application leaving the nitrate fraction subject to leaching. Nitamin is composed of long- and short-chain urea polymers whose release and conversion to nitrate is dependent on microbial activity. Microbes become active at temperatures that are favorable for plant growth which helps to ensure that plants get N when they need it most.

Jim Wargo, Georgia-Pacific research agronomist, says, “Nitamin Liquid is an effective fertilizer for improving potato performance. It provides a continuous supply of nitrogen to the crop allowing for steady plant growth and higher marketable yields. Evening out the N supply can help reduce the amount of culls and physiological defects such as growth cracks and hollow heart caused by irregular plant growth from fluctuating N availability. Nitamin also minimizes nitrogen losses through leaching, which provides opportunities for growers to cut back on N rates and reduce the number of applications during the growing season.”

Study Results:

During the two-year study, Nitamin applied at 200 lb. N per acre resulted in 20 to 30 cwt/acre yield increase of U.S. #1A Grade potatoes compared to the commercial N program (see table for details).

In 2004, the Nitamin treatments tended to have fewer culls and a smaller percentage of hollow heart than commercial fertilizer treatments (1% vs. 6 %). The 50% Nitamin rate (100 lb. N/acre) produced lower yield compared to the 200 lb. N rate treatments, suggesting there was not enough nitrogen to meet crop demand.

Nitamin resulted in higher N uptake in 2004 and 2005 due to higher potato yield and comparable tuber-N concentration. Soil samples taken in early July 2004, when the crop biomass was small, showed delayed N release from Nitamin compared to ammonium-based fertilizers, which may have resulted in more efficient nitrogen use. In a separate study, a single application of Nitamin applied at emergence produced similar or slightly higher yields compared to split Nitamin applications at emergence and tuberization.

Experimental Details

Dr. Birl Lowery, professor of soil science, conducted Nitamin trials over two years (2004 and 2005) on Russet Burbank potatoes at the University of Wisconsin Hancock Research Stationin Hancock, Wisconsin. The soil was Plainfield loamy sand that, prior to the 2005 trial, measured 0.7% organic matter (OM), pH 6.7, and cation exchange capacity (CEC) 2.5. At such a low CEC level, the soil provides the plant little nutrition, a common concern for potato growers in the Central Sands area of Wisconsin.

Treatments for both years included a commercial fertilizer treatment of 200 lb. N/acre, which consisted of 66 lb. N/acre of ammonium sulfate at emergence and 134 lb. N/acre of ammonium nitrate at tuberization; and a Nitamin Liquid treatment of 200 lb. N/acre with 66 lb. N/acre at emergence and 134 lb. N/acre at tuberization.

In 2004, Nitamin Liquid was tested at a lower rate of 100 lb. N/acre with 33 lb. N/acre at emergence and 67 lb. N/acre at tuberization. The reduced rate was determined to be too low for commercial potato production and was therefore left out the following year.

In both years, a control treatment consisting of a starter fertilizer only was included. The starter fertilizer was applied at planting to all treatments using 550 lb. of 5-10-30/acre in 2004 and 500 lb. of 6-24-24/acre in 2005, both of which contained an insecticide to prevent potato beetle damage. The total N rates are approximately 230 lb. N/acre for the commercial fertilizer treatment and 130 and 230 lb. N/acre for the Nitamin Liquid treatment, including the starter fertilizer.

Photo 1. Nitamin^® plots from 2005 University of Wisconsin study one month prior to harvest. White tubes shown are suction lysimeters used to measure nitrates in soil water.

Photo 2. Nitamin^®treated Russet Burbank potato plots at the University of Wisconsin, 2005. Potato plants produced higher marketable yield when Nitamin liquid fertilizerreleases nitrogen to plants over a 60-90 day period depending on soil type and temperature.

Georgia-Pacific Resins, Inc. (GPRI) is a wholly owned subsidiary of Georgia-Pacific Corp., and is a market leader in chemical products for the paper, pulp and building products industries, as well as other industrial manufacturing processes. GPRI has been a major raw material supplier to leading fertilizer producers for over 20 years and has over 40 years of experience with urea-based polymer technology. GPRI operates 15 manufacturing facilities throughout the United States. The company also has plants in South Americaand a manufacturing presence in South Africa and China. The company's headquarters is located at 55 Park Place, 16th Floor, Atlanta, GA30303. For additional information, please visit the company’s web sites http://www.gp.com/chemical/ and http://www.nitamin.com/ or call the Nitamin hotline at 866-2nitamin.

# # #

* The University of Wisconsin does not endorse Georgia-Pacific, Nitamin, or the use of Nitamin.

Nitamin is a registered trademark and OPTIMAL NITROGEN DIET and STEADY-DELIVERY are trademarks of Georgia-Pacific Resins, Inc.

Media Contact:
Caryn King (404) 652-4247