Predicting In-Season Nitrogen Requirements for Protein Content In Hard Red Spring Wheat.

A minimum grain protein content of 14% is required to meet the market requirements of hard red spring wheat (Triticum aestivum L.) and avoid discounts.  Previous studies have found that post-anthesis foliar applied nitrogen (N) applications can increase protein content by up to 1%. The current study was undertaken to determine if a simple diagnostic tool used prior to anthesis could reliably predict grain protein at harvest.  Such a diagnostic tool will aid in the decision whether supplemental foliar applied N immediately following anthesis is warranted.  Experiments were established at Crookston, MN, and Prosper, ND in 2011 and 2012 and consisted of a factorial combination on N rates (0, 68, 135, and 205 kg N ha^-1 applied at planting) and cultivars of hard red spring wheat (Faller, Glenn, Samson, and Vantage). Instruments used to estimate the N status of the spring wheat crop were the Greenseeker Model 505 handheld optical sensor, CCM-200 chlorophyll meter, and a leaf color chart. A leaf and stalk tissue test were also taken to estimate the N concentration in these plant parts. Measurements were collected at Zadoks’ growth stages (GS) 16 and 37. Initial results in 2011at Crookston suggested a positive correlation between grain protein content and Greenseeker readings taken at the GS 16 and 37. Leaf tissue and basal stalk N concentrations were also positively correlated with final grain protein, with the leaf tissue samples collected at GS 37 having the highest correlation with grain protein of all variables  (r =0.62). Results from 2012 will also be presented.