Rice (Oryza sativa L.) is an important crop in the midsouthern United States. However, some high‐yielding cultivars are highly susceptible to lodging. The plant growth regulator, trinexapac‐ethyl (TE), has been shown to decrease lodging in upland cereal crops, but data are scarce that demonstrate rice response to TE. The objective of this study was to determine the effect of TE on rice plant height, lodging, and grain yield. Experiments were established at multiple locations during the 2012 and 2013 growing seasons in Mississippi. Trinexapac‐ethyl was applied to a lodging‐susceptible rice cultivar at 12, 24, and 48 g a.i. ha−1 at two timings: panicle differentiation (R1) and R1 + 14 d. Rice response to TE was determined for rice that received 100% of N applied at V3 and rice that received a two‐way split N strategy (75% N at V3 and 25% at R1). On both clay and silt‐loam soils all rates of TE reduced plant height and lodging compared to nontreated rice. The effect of TE on rice grain yield was variable. On silt‐loam soils 12 g a.i. ha−1 TE resulted in rice grain yield similar to nontreated rice when applied at R1, but decreased grain yield when applied to rice at R1+ 14 d. The 48 kg a.i. ha−1 rate decreased rice grain yield on both soil textures. The results of this study indicate that trinexapac‐ethyl may be a useful tool to manage lodging, but further research is needed refine TE use guidelines in rice. Trinexapac‐ethyl decreased rice plant height and lodging on both clay and silt loam soils. Trinexapac‐ethyl at 12 g a.i. ha−1 did not decrease grain yield when applied at panicle differentiation on silt loam soils. Grain yield response to trinexapac‐ethyl varied by soil texture and N management strategy.

core ideas• Split N application in rice limits lodging but also reduce grain yield.• High N rates and seeding rates increase lodging and harvest costs.• Appropriate early-season (prefl ood) N is necessary to maximize rice grain yield.

Laboratory experiments were conducted in 2010, 2011, and 2012 in Stoneville, MS, utilizing urea fertilizer to quantify the nitri cation potential of southern soils, and to evaluate a nitri cation inhibitor aimed to reduce nitri cation rates on clay soils. Field research was conducted from 2011 to 2013 evaluating the e ectiveness of dicyandiamide (DCD) and sulfur-polymer coated urea at reducing N loss compared to urea alone on clay soil. e number of days when half the total recovered inorganic N was in the NH 4 + -N form (half-life for ammonium) for each soil and stabilizer for the nitri cation potential and N stabilizer experiments was determined. Nitrogen was applied to the soil at 0.115 g kg -1 for both laboratory experiments while DCD was applied at three di erent rates for the N stabilizer experiment. ese studies con rmed that the Sharkey clay soil (very-ne, smectitic, thermic Chromic Epiaquerts) at Stoneville, MS, had signi cantly higher nitri cation potential compared to three other soil types studied and DCD increased half-life for ammonium by approximately threefold when compared to non-amended urea. Field experiment data indicated that increasing DCD rate to 17 kg ha -1 increased rice (Oryza sativa L.) grain yield response and resulted in yields comparable to the standard treatment, which was urea applied 1 day before ood establishment (dbf). e sulfur-polymer coated urea applied 12 dbf reduced nitri cation; however, it yielded less than the standard treatment. Products that limit nitri cation and subsequent denitri cation can optimize N e ciency, resulting in greater potential for increased yields and decreased production costs.