Plant Growth Regulator and Nitrogen Applications for Improving Wheat Production in Michigan

Abstract

Core Ideas Averaged across all plant growth regulator (PGR) application rates and timings, grain yields increased 5% across the four study years compared to no PGR application. Plant growth regulator applied at 12 oz/ac decreased lodging 67 to 83% compared to untreated plots in all three years that lodging occurred. Rates >12 oz/ac decreased plant height an additional 1.6 to 1.8 inches but offered no yield benefit. Despite a lack of consistent yield response, if a grower encounters a high‐yielding, intensively managed variety that is prone to lodging, then a PGR application might be a crop management tool to consider. To improve wheat (Triticum aestivum L.) production and harvestability in Michigan, growers are increasing nitrogen rates and utilizing plant growth regulators (PGR). The effects of PGR application rate and timing (Deckerville, MI, 2012–2013) and PGR application across N rates (Lansing, MI, 2014–2015) on wheat growth and grain yield were investigated. Plant growth regulator applications (12 oz/ac) significantly reduced mature plant height (2.0–4.2 inches) across all four site years. Application rates >12 oz/ac resulted in greater height reductions but offered no yield benefit. Plant lodging was significantly reduced (50–83%) following PGR application in all years except 2015, when no lodging occurred. Grain yield was significantly increased by 6.0 and 4.8 bu/ac in 2012 and 2014 following PGR application at 12 oz/ac. Timing of PGR application (Feekes 7 or 8) did not significantly affect grain yield in 2012 or 2013, but earlier applications increased grain yield. No interactions between N rate and PGR application were observed in 2014 or 2015. Results indicated that PGR application decreased the incidence of plant lodging in years where lodging occurred. Motives for utilizing a PGR in a wheat management regime may depend more on cultivar susceptibility to plant lodging and average plant height with less emphasis based solely on greater N application rates as the latter did not consistently result in taller plants.