Nitrogen Rate, Form and Timing Effects on Three Cultivars of Hard Red Spring Wheat

Nitrogen is the most common and widely used fertilizer nutrient (Stangel 1984). It is a constituent of both structural and non-structural components of the cell. Application of nitrogen (N) to wheat improves the yield and protein content of the grain (Lamb 1967). In 1980 sixty-one percent of the nitrogen (N) utilized on agricultural crops in the U.S. was applied to cereals (Martinez, Adolpho and R. B. Diamond 1984). In order to maintain a competitive edge in increasingly competitive international markets, it is critical that producers in the United States utilize productive, cost efficient and environmentally sound N management practices. Grain protein is an important quality characteristic of Hard Red Spring (HRS) wheat because it is related to nutritive value, milling properties and price received in the market. Periodically, the market price of HRS wheat has been discounted to producers of low protein (\u3c 14 %) wheat, while premiums have been paid for high protein (\u3e 14 %) wheat. Grain protein levels of wheat grown in South Dakota can vary substantially from year to year depending on cultivar, crop management practices and weather conditions. Foliar application of N during later stages 2 of growth has resulted in increased protein content in the grain (Lamb 1967). It may be possible to decrease the year to year variation of grain protein in HRS wheat by the application of foliar N and obtain wheat with consistently high protein content. Normally wheat takes N up in the form of nitrate. However yield improvements in wheat have occurred when a mixture of ammonium and nitrate is available to wheat plants grown in the greenhouse (Bock 1986, 1987). Leaching losses of N could result in lost profit for farmers and ground water contamination. For these reasons it is desirable [sic] to utilize ammoniacal forms of N. However under normal conditions ammoniacal-N is rapidly converted to nitrate-N in the soil. The use of nitrification inhibitors, which act to slow the conversion of ammonium to nitrate, could result in improved yields and reduced leaching in susceptible areas. There is a continued need to re-evaluate and improve N management practices. The experiment discussed in this paper, evaluated the effects of different N fertilizer treatments on three cultivars of HRS wheat. Nitrogen treatments included foliar N applications at different rates and times, as well as the use of both nitrate and ammonium-N fertilizer forms. The study has the following objectives: 1. To evaluate the effect of split N applications on yield and protein content of HRS wheat. 2. To determine if the use of nitrification inhibitors affect yield or protein content. 3. To determine if late N applications are economical. 4. To compare foliar applications of conventional 28% N solutions (UAN) to urea-N solutions (Nisol). 5. To evaluate the effect of N applications on cultivars with different yield and protein potentials