Managing Late‐Season Foliar Nitrogen Fertilization to Increase Grain Protein for Winter Wheat

Abstract

Late‐season applications of foliar N have the potential to increase protein content in hard red winter (HRW) wheat (Triticum aestivum L.), but the optimal N management strategy and economics of this decision have yet to be determined for the U.S. southern Great Plains. This study was conducted to determine the expected net return from HRW wheat managed for enhanced protein and marketed to receive a protein premium. Field experiments were conducted during the 2011 to 2013 harvest years at two Oklahoma locations to estimate the grain yield and protein content response of HRW wheat to N source (urea ammonium nitrate [UAN] or a low salt, controlled release [LSCR] specialty N), N timing (flag leaf or post‐flowering), and N rate (0, 7, 13, or 27 kg N ha−1). Late‐season N treatments significantly influenced protein, but did not significantly increase or decrease grain yield. However, the returns to protein management were US$10 to $194 ha−1 less than treatments that did not receive late‐season foliar N. Sensitivity analysis indicated that protein management could be profitable if wheat prices increase, but changes in N prices had only small impacts on net returns. Breakeven protein premiums ranged from $0.014 to $0.020 kg−1 suggesting the need to produce wheat with 12 to 13% protein content. Results from this study indicate that the ability to consistently achieve HRW wheat with this level of protein is limited. Therefore, to economically manage HRW wheat for protein content in the southern Great Plains will likely require within‐year/location‐specific N management.Core Ideas Late‐season foliar N applications may increase wheat grain protein percentage. Late‐season foliar N applications are costly. Southern Plains producers do not routinely receive a premium for high protein wheat. Additional returns were insufficient to offset the additional cost.

Influence of Droplet Size of Foliar‐Applied Nitrogen on Grain Protein Content of Hard Red Winter Wheat

“…There was no statistically significant improvement in grain yield with the addition of foliar N for any of the site-years (Tables 4-6). This was expected following similar work conducted by Dick et al (2016) and Woolfolk et al (2002), in which no increases in significant grain yield were observed with postanthesis foliar N applications. No consistent difference was observed in the effect of N rate on grain yield.…”

“…The ability to successfully increase GPC levels as a result of postanthesis foliar‐applied N has been reported in the literature (Woolfolk et al, 2002; Bly and Woodward, 2003; Dick et al, 2016). Using similar N rates to those used in this study, Woolfolk et al (2002) observed GPC (estimated from grain N data) could be increased on average by about 1.1% and as much as 2.1%.…”

Genotype‐specific nitrogen uptake dynamics and fertilizer management explain contrasting wheat protein concentration

“…This greater N requirement to maximize GPC as compared to grain yield is widely reported (Goos, Westfall, Ludwick, & Goris, 1982; Hawkesford, 2014; Kelley et al., 1995; Lollato et al., 2019a; Staggenborg et al., 2003; Woodward & Bly, 1998). However, increasing N rates to improve GPC might not be profitable unless price premiums are expected (Dick et al., 2016). Under these conditions, managing N timing arises as an opportunity to improve GPC at similar N rates.…”

Winter Wheat Response to Fertilizer Type and Timing in Western South Dakota

“…However, previous research has shown that late‐season N applications can result in higher protein content, which is supported by Treatment 7 of the current study. It is likely that this effect would be accentuated with the addition of N applications later in the season (Dick et al, 2016; Kratochvil et al, 2005; Woodard and Bly, 1998; Woolfolk et al, 2002). Moreover, where N supply is adequate early in the growing season, N applications at Feekes 6 or later are likely to have little effect on yield (Cassman et al, 1992; Woodard and Bly, 1998).…”

“…Applying the full rate of UAN mid‐row banded at planting was as economically effective in roughly half the cases, which makes this option a viable alternative, particularly where time constraints exist. Managing N for protein with applications later in the growing season remains physiologically feasible but economically questionable (Dick et al, 2016).…”