Act Now! Do Not Delay Spring N Applications to Small Grains

Amy Shober, Extension Nutrient Management and Environmental Quality Specialist; ashober@udel.edu and Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu

We urge you to get out check your small grain fields now and make final spring N applications soon to maximize the potential of your small grain crop. Small grains are expected to be significantly ahead of last season, as we have already accumulated 958 growing degree days (GDD base 32ºF) since Jan 1 (through Mar 18) at Georgetown (compared with 644 GDD in 2019).

Feekes 5 (Zadoks 30) is the recommended stage for an application of N to small grains, as this is right before the period of maximum N uptake by the crop. The application at Feekes 5 will help with seed head formation. If nodes are observed above ground when scouting, the wheat has passed Feekes 5 and N applications should be made as soon as possible.

Typically, we would recommend that a Feekes 5/6 N application rate be based on a tissue test. However, since small grains must accumulate approximately 967 GDD from planting to get to jointing (Feekes 6/Zadoks 31), it seems safe to assume that some crops have already reached this stage. It takes approximately 1110 GDD for small grains to reach Feekes 7 (Zadoks 32) at which point crop response to N is minimal. As such, there may not be time to wait for results of a tissue test before applying N.

The University of Delaware recommends total N applications of 80-120 lbs/acre for wheat and 60-90 lbs/acre for barley. The higher end of the UD range is for sandy soils or fields receiving a single spring N application. If you do not have time to base your Feekes 5 application of N on a tissue test, then you should adjust the N rate by subtracting the rate of N applied during the previous fall to promote fall tillering or at green up in early spring to help with tillering.

If tissue testing is still timely, base your Feekes 5 application on the rates in Table 1, regardless of whether this is your first or second spring application to small grains. Avoid total N applications greater than 120 lb/ac for wheat and 100 lb/ac for barley, as excessive N can result in lodging and yield loss, as well as N leaching. Also, avoid making N applications once the small grain crop is at or past Feekes 7 (Zadoks 32).

Table 1. Nitrogen rate recommendations for single or split spring applications to small grains based on tissue N content. Based on research conducted by Virginia Tech scientists.