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

Development of current N recommendations 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 This needs to be modified to be more brief.

Corn N recommendation 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 This needs to be modified to be more brief.

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.

Corn yield response, Tribune, KS (92-00) KSU’s rec, 218 lb acre-1 P2O5, lb acre-1 source: Alan Schlegel

Corn yield response, Topeka, KS (97-01) KSU’s rec, 226 lb acre-1 P2O5, K2O, lb acre-1 source: Larry Maddux

Corn yield response, Scandia, KS (01, Ridge-till) KSU’s rec, 314 lb acre-1 P2O5, K2O, S lb acre-1 source: Barney Gordon

Wheat N recommendation (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 This needs to be modified to be more brief.

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.

Wheat yield response, Manhattan, KS (98-00) KSU’s rec, 82 and 88 lb acre-1 source: Dave Whitney

Wheat yield response, Hesston, KS (99, 01) KSU’s rec, 144 lb acre-1 source: Mark Claassen

Wheat yield response, Hutchinson, KS (96-01) KSU’s rec, 124 and 108 lb acre-1 source: Bill Heer

Wheat yield response, central KS (98-00), 11 site-years KSU’s rec, 136 lb acre-1 source: Ray Lamond

Wheat yield response, Tribune, KS (94-97), 13 site-years Inject Broadcast NO3-N, 55 lb acre-1 NO3-N, 21 lb acre-1 source: Alan Schlegel

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

Is an average N recommendation adequate? Sometimes it’s ok This needs to be modified to be more brief.