ISSUE 13 July 28, 2005
REALLY LATE SEASON N APPLICATIONS FOR WHEAT
NDSU has a fairly large database for the application of foliar N for protein enhancement at the kernel watery ripe stage of wheat as detailed in previous pest reports. Once the grain moves past that timing stage, the data become less abundant. We know that the chances of protein enhancement at the watery ripe stage are good. It is also logical to conclude that since leaf area decreases as the plants mature, especially with disease and natural senescence, foliar fertilization efficiency will decrease thereafter. With costs of 30 lb N from $15_20/acre applied and a possible Ĺ point protein increase, it doesnít take much lower efficiency to break-even in returns with the lower N uptake efficiency expected with plant age. Once the grain is in the dough stage, the grain is basically drying and uptake of nutrients is over.
On rare occasions, growers have applied liquid N to grain fields at the same time as a preharvest application of glyphosate herbicide in an attempt to enhance protein. The grain is approaching maturity at this time and glyphosate hastens crop drying. Any N applied at this time would not be expected to increase protein. In the event that liquid N contacts grain kernels within the head directly, the result would not be protein enhancement, however, it would give a false higher reading on the elevatorís protein sensor.
It is recommended that N applications do not take place during the preharvest interval. Either the application will be totally ineffective in enhancing protein and therefore be a waste of money, or it might result in an unethical non-protein increase reading at the point of sale. It is important for North Dakota and the region to keep its reputation as a source of high protein wheat, so practices that might result in false readings should not be conducted.
Dr. Dave Franzen
NDSU Extension Soil Specialist