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Slide1: 

Current KSU N recommendations for corn & wheat John Schmidt Alan Schlegel Kansas State University

Slide2: 

Based on historical recommendations / concepts Modified to include soil N “mineralization potential” “Loosely” updated with more recent field research results Emphasis on Extension education tool Development of current N recommendations

Slide3: 

N rec = (Yield Goal x 1.6) – (SOM x 20) – Profile N – Manure N – Irr. Water N + Previous crop adj. Yield goal, bu acre-1 Soil organic matter, % Profile soil N test, lb acre-1, 0-2 ft, (0.3 x sampling depth, inches x NO3-N, ppm) Manure N applied, lb acre-1 Irrigation water N applied, lb acre-1 Previous crop adjustment, lb acre-1 Corn N recommendation

Slide4: 

Corn N recommendation, STN = 30 lb N acre-1 Soil OM, % N rec = (Yield Goal x 1.6) – (SOM x 20) – Profile N – Manure N – Irr. Water N + Previous crop adj.

Slide5: 

source: Alan Schlegel Corn yield response, Tribune, KS (92-00) P2O5, lb acre-1

Slide6: 

Corn yield response, Topeka, KS (97-01) P2O5, K2O, lb acre-1 source: Larry Maddux

Slide7: 

Corn yield response, Scandia, KS (01, Ridge-till) P2O5, K2O, S lb acre-1 source: Barney Gordon

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N rec = (Yield Goal x 2.4) – (SOM x 10) – Profile N – Manure N + Previous crop adj. + Tillage adj. + Grazing adj. Yield goal, bu acre-1 Soil organic matter, % Profile soil N test, lb acre-1, 0-2 ft, (0.3 x sampling depth, inches x NO3-N, ppm) Manure N applied, lb acre-1 Previous crop adjustment, lb acre-1 Tillage adjustment, 20 lb acre-1 for no-till Grazing adjustment, 40 lb acre-1 per 100 lb beef weight gain Wheat N recommendation

Slide9: 

Wheat N recommendation, STN = 30 lb N acre-1 Soil OM, % N rec = (Yield Goal x 2.4) – (SOM x 10) – Profile N – Manure N + Previous crop adj. + Tillage adj. + Grazing adj.

Slide10: 

source: Dave Whitney Wheat yield response, Manhattan, KS (98-00)

Slide11: 

source: Mark Claassen Wheat yield response, Hesston, KS (99, 01)

Slide12: 

source: Bill Heer Wheat yield response, Hutchinson, KS (96-01)

Slide13: 

source: Ray Lamond Wheat yield response, central KS (98-00), 11 site-years

Slide14: 

source: Alan Schlegel Wheat yield response, Tribune, KS (94-97), 13 site-years

Slide15: 

source: Alan Schlegel Optimal N for wheat, Tribune, KS (94-97), 13 site-years

Slide16: 

Sometimes it’s ok Is an average N recommendation adequate?