1. Effect of Nitrogen Sources, Rates, and Application Time on Spring Wheat Yield and Grain Protein Olga S. Walsh, Western Triangle Agricultural Research Center, Conrad, Montana JUSTIFICATION EVALUATED FACTORS Fertilizer Timing: Preplant vs Topdress Preplant  Supplies N to establish crop stand Better soil/weather conditions (Randall and Schmitt, 1998)  Risk of N loss (immobilization, volatilization) (Fowler and Brydon, 1989; Wuest and Cassman, 1992) Topdress  Supplies N at maximum plant uptake – higher NUE (Walsh et al., in press)  N fertilization after Feekes 5 – crop can catch up (Morris et. al., 2005)  Enables fertilization based on crop need/yield potential Fertilizer Sources: Granular vs Liquid Granular N (urea)  Up to 30% N loss as ammonia for broadcasted urea (Engel, personal communication)  Urea applied with the seed – seed damage, drying out of seed bed – affects germination Liquid N (urea ammonium nitrate = UAN)  Plants absorb water and nutrients through leaves (Wittwer and Teubner, 1959)  Efficiency of foliar fertilizers is higher (Mosali et al., 2006)  Crop injury/leaf burn (Wesley et al., 1998) MATERIALS AND METHODS  3 dryland experimental sites: Western Triangle Research Center, Conrad, MT, 2 on-farm studies (Jack Patton, Knees, Chouteau County, MT and Pat Wheeler, Valier, Pondera County, MT)  Choteau spring wheat variety  4 preplant N rates (0, 40, 80, and 120 lbs N ac)  3 topdress N rates (0, 40, and 80 lb N ac)  2 topdress N fertilizer sources (granual – urea, 46-0-0, and liquid – urea ammonium nitrate (UAN), 28-0-0)  2 topdress application times (before flowering and after flowering)  To determine the most efficient N fertilizer source, N rate, and N fertilizer application time combination for optimizing Montana spring wheat yield while maximizing grain protein OBJECTIVE AKNOWLEDGEMENTS: We are grateful to: Mr. Jack Patton and Mr. Pat Wheeler for support and cooperation, Mr. Clint Rouns and Mr. John Miller (WTARC, MSU), and Dan Picard (Pondera County Extension Agent, MSU), for their expertise and support We are grateful to Montana Fertilizer Advisory Committee for funding this project Dr. Olga S. Walsh, WTARC, MSU telephone: (406)278-7707 e-mail: olga.walsh@montana.edu web: http://ag.montana.edu/wtarc/  Nitrogen (N) - the most common nutrient limiting yield of spring wheat in Montana (Engel, 1993)  Spring wheat - key cereal crop grown in Montana  Wheat production represents ~ 25% of Montana’s agricultural revenue (stuffaboutstates.com, 2010)  Protein content - base for established market adjustments for spring wheat, with premiums paid for increase above the baseline levels DISCUSSION  Data from WTARC and Patton are evaluated for 2011  Spring wheat mean grain yield was higher at WTARC (1735 kg ha -1 ) compared to Patton (1544 kg ha -1 )  Yields ranged from 618 to 2047 kg ha -1 at WTARC and from 1262 to 2004 kg ha -1 at Patton  Greater response to fertilizer N observed at WTARC; unfertilized check yielded twice as high at Patton, compared to WTARC  Preplant N rate and topdress application time significantly effected yield at both sites (p<0.05)  At WTARC, fertilization before flowering resulted in greater mean spring wheat yield (1432 kg ha -1 ) compared to after flowering (1274 kg ha -1 )  Fertilizer N source had no significant effect on spring wheat yields CONTACT INFORMATION Figures 1a and 1b. Effect of fertilizer N rate, source and application time on spring wheat grain yield at WTARC (1a) and Patton (1b), 2011. bc cd e a cd a cd Figure 1a b ab ab ab b ab a ab ab b b Figure 1b RESULTS  Leaf burn apparent in spring wheat following application of UAN at 90 kg N ha -1 rate before flowering at WTARC  Spring wheat grain yields were not impacted by foliar UAN application before flowering at WTARC  Foliar application of UAN at 90 kg N ha -1 rate negatively impacted yields at Patton; plots topdressed at 45 kg N ha -1 rate yielded significantly higher, independent of application time.