ISSUE 8 June 28, 2007
PROTEIN ENHANCEMENT OF WHEAT
Nitrogen losses through leaching and denitrification associated with the heavy rainfall this season have become significant in parts of the state. The most severely nitrogen-stressed wheat fields appear yellow and yields will obviously be negatively impacted. Other fields that have excellent yield potential may come up short on grain protein at harvest if nitrogen demand during grain filling exceeds the amount available from the soil. Given conditions to date, protein content may have substantial value at the elevator this year. Variety, environment, and management all play an important role in determining grain protein harvest. Varieties like Granite and Dapps consistently produce grain with relatively higher protein content, but even they may not meet the required protein content if conditions are unfavorable for protein accumulation (i.e. insufficient soil nitrogen for the amount of grain produced). On the other hand, varieties like Traverse, Bigg Redd and Trooper need relatively good N management to make 14% protein in most environments.
Though it may be too late to improve yield with a "rescue" application of nitrogen, as N applied after wheat starts jointing typically does not improve yield, it may be possible to improve protein content with additional N. This year, it appears that the protein premium for wheat will not be nearly as important as the possible dock for lower protein. As previously stated, some varieties naturally have higher protein, and may not need protein enhancement from late foliar N application.
Foliar N applications are more efficient than soil treatments. They are normally not recommended for yield enhancement because of their leaf-burn potential. However, protein enhancement requires less N to achieve a ½-1% increase compared to a large yield increase, and therefore the risk for burn is less.
The greatest and most consistent protein increase has been achieved in NDSU research through the application of 30 lb N/a (10 g/a of 28% liquid N fertilizer) mixed ½ and ½ with water, and applied immediately after flowering is complete. This application should be applied in the cool of the day to minimize burn. NDSU researchers are also exploring the use of a number of slow-release N products to determine if reduced rates of these relatively low burn-potential sources might be used also; however, research to date shows that similar rates of these products might also need to applied for full effectiveness.
The application should be made alone, without fungicide. Fungicides are seldom applied at this stage, and 28% at flowering will be harmful to pollination. Antigonism between higher rates of fertilizer and pesticides is common.
The increases in protein using 30 lb N/a as 28% have ranged from ½ to 1%, with ½% being more common. This application does not need rain to activate. My fertilizer industry reports indicate that 28% supplies are tight, and the prices are high, so it would be best to use protein enhancement only if an a good return on your investment is expected. Cost for 30 lb N/a as 28% is in the range of $16-$18/a plus application. Return on ½ % protein increase in 40 bu/a wheat would need to be around 60 cents/bu to make it worthwhile.
Dr. Dave Franzen
NDSU Extension Soil Specialist
Dr. Joel Ransom
NDSU Small Grain and Corn Agronomist