1. Influence of Late-Season Foliar Nitrogen Applications on Grain Protein in Winter Wheat C.W. Woolfolk, W.R. Raun, G.V. Johnson E.G. Krenzer, and W.E. Thomason C.W. Woolfolk, W.R. Raun, G.V. Johnson E.G. Krenzer, and W.E. Thomason Oklahoma State University Department of Plant and Soil Sciences Oklahoma State University Department of Plant and Soil Sciences

2. IntroductionIntroduction Increasing grain protein in higher yielding wheat varieties while maintaining yields is often difficult Efficient utilization of nitrogen fertilizers is imperative for human nutrition (Smil 1997) Grain protein increases occur when foliar nitrogen is applied at anthesis and rapidly declines before or after that time (Finney et al., 1957) Gaseous nitrogen losses from wheat leaves occurs between anthesis and maturity (Harper et al., 1987) Maximum N accumulation generally occurs at flowering Increasing grain protein in higher yielding wheat varieties while maintaining yields is often difficult Efficient utilization of nitrogen fertilizers is imperative for human nutrition (Smil 1997) Grain protein increases occur when foliar nitrogen is applied at anthesis and rapidly declines before or after that time (Finney et al., 1957) Gaseous nitrogen losses from wheat leaves occurs between anthesis and maturity (Harper et al., 1987) Maximum N accumulation generally occurs at flowering

3. ObjectivesObjectives To determine the effects of late-season nitrogen applications at four rates and two N sources on:  grain yield  grain protein  straw yield  straw N To determine the effects of late-season nitrogen applications at four rates and two N sources on:  grain yield  grain protein  straw yield  straw N

4. Materials and Methods Application type  simulated aerial  175 ml mechanically pressurized spray bottles Nitrogen source  Urea Ammonium Nitrate: no dilution-28% N  Ammonium Sulfate: 700g in 1,000ml H 2 0-11%N Wheat (Triticum aestivum L.)  “Tonkawa” hard red winter Cropping system  conventional tillage Application type  simulated aerial  175 ml mechanically pressurized spray bottles Nitrogen source  Urea Ammonium Nitrate: no dilution-28% N  Ammonium Sulfate: 700g in 1,000ml H 2 0-11%N Wheat (Triticum aestivum L.)  “Tonkawa” hard red winter Cropping system  conventional tillage

5. Materials and Methods Experimental sites: Efaw, OK and Perkins,OK Experimental design: RCBD, 4 replications  Plot size: 7.43 m 2 N Source and rate:  UAN: 0, 11, 22, 33, 44 kg N ha -1  AS: 22 kg N ha -1 Timing of application:  Pre-flowering:Feekes 10.5  Post-flowering:Feekes 10.5.4 Experimental sites: Efaw, OK and Perkins,OK Experimental design: RCBD, 4 replications  Plot size: 7.43 m 2 N Source and rate:  UAN: 0, 11, 22, 33, 44 kg N ha -1  AS: 22 kg N ha -1 Timing of application:  Pre-flowering:Feekes 10.5  Post-flowering:Feekes 10.5.4

6. Feekes growth stages in cereal grains Large, 1954 Feekes growth stages in cereal grains Large, 1954 10.5 Pre Pre10.5.4 Post Post

7. Materials and Methods Treatment structure employed at both sites for both years

8. Grain yield, kg ha -1 Protein, % N rate, kg ha -1 Efaw 1998 SED=220 SED=0.22

9. Grain yield, kg ha -1 Protein, % Perkins 1998 SED=0.53 SED=302 N rate, kg ha -1

10. Grain yield, kg ha -1 Protein, % N rate, kg ha -1 Efaw 1999 SED=213 SED=0.52

11. Grain yield, kg ha -1 Protein, % N rate, kg ha -1 Perkins 1999 SED=380 SED=0.92

12. Significant increases due to foliar applied N Grain yield  1 out of 4: UAN-linear (post-flowering, Efaw 1999) UAN-quadratic (pre-flowering, Efaw 1999) Straw yield  1 out of 4: UAN-quadratic (pre-flowering, Efaw 1998) Straw N  2 out of 4: UAN-linear (post-flowering, Perkins 1998) UAN-linear (pre-flowering, Perkins 1999) Significant increases due to foliar applied N Grain yield  1 out of 4: UAN-linear (post-flowering, Efaw 1999) UAN-quadratic (pre-flowering, Efaw 1999) Straw yield  1 out of 4: UAN-quadratic (pre-flowering, Efaw 1998) Straw N  2 out of 4: UAN-linear (post-flowering, Perkins 1998) UAN-linear (pre-flowering, Perkins 1999) ResultsResults

13. Significant increases due to foliar applied N Grain protein  1 out of 4: AS (pre and post-flowering, Perkins 1998)  3 out of 4: UAN-linear (pre-flowering; 33 kg ha -1 )  4 out of 4: UAN-linear (post-flowering; 33 kg ha -1 ) Significant increases due to foliar applied N Grain protein  1 out of 4: AS (pre and post-flowering, Perkins 1998)  3 out of 4: UAN-linear (pre-flowering; 33 kg ha -1 )  4 out of 4: UAN-linear (post-flowering; 33 kg ha -1 ) ResultsResults

14. Increased grain protein was observed at 33 kg N ha -1 in three out of four experiments when N was applied pre- flowering (2.05%) Increased grain protein was observed at 33 kg N ha -1 in all experiments when N was applied post-flowering (1.57%) In general, grain yield, straw yield, and straw N were not affected by foliar N applications Foliar N applications prior to or immediately following flowering may significantly enhance protein contents Increased grain protein was observed at 33 kg N ha -1 in three out of four experiments when N was applied pre- flowering (2.05%) Increased grain protein was observed at 33 kg N ha -1 in all experiments when N was applied post-flowering (1.57%) In general, grain yield, straw yield, and straw N were not affected by foliar N applications Foliar N applications prior to or immediately following flowering may significantly enhance protein contents Conclusion s

15. UAN@28% N: $0.48/kg N x 33 kg N/ha (Post) = $16/ha Aerial application: = $ 9/ha Total application cost = $25/ha 12% protein: $106.50/ton x 2.688 tons/ha (Avg) = $286/ha 14% protein: $124.90/ton x 2.688 tons/ha (Avg) = $336/ha Difference = $50/ha $25/ha profit UAN@28% N: $0.48/kg N x 33 kg N/ha (Post) = $16/ha Aerial application: = $ 9/ha Total application cost = $25/ha 12% protein: $106.50/ton x 2.688 tons/ha (Avg) = $286/ha 14% protein: $124.90/ton x 2.688 tons/ha (Avg) = $336/ha Difference = $50/ha $25/ha profit Applied Calculation

16. Future Research  More in-depth focus on post-flowering applications  Alternative methods for increasing yield while increasing protein-(KH 2 PO 4 ) applied to delay senescence  Focus on products which decrease N losses and can be applied simultaneously with foliar N applications  More in-depth focus on post-flowering applications  Alternative methods for increasing yield while increasing protein-(KH 2 PO 4 ) applied to delay senescence  Focus on products which decrease N losses and can be applied simultaneously with foliar N applications