Question

Explain in as much detail as possible how you would make a N rate and source recommendation for a grower in eastern Washington wheat that is based on a soil test (20 lb N/A) and a yield goal (98 bu/A). Hint: refer to WSU wheat nutrient management guide by Rich Koenig.

Answer 1

Given:

Yield goal = 98 bu/A; Soil N = 20 lb N/A

Solution:

N supply needed = yield goal * bushel yield

Where bushel yield is 2.7± 0.2 lb N/bu² for soft white winter and club and 3.0± 0.2 lb N/bu² for hard red and hard white winter.

Recommended N = N supply needed - Soil N

i) For soft white winter and club:

N supply needed = 98 * (2.7± 0.2) = 264.6± 19.6

N supply needed = 264.6 ± 19.6 lb N/A

Recommended N = 264.6 ± 19.6 - 20 = 244.6± 19.6

  Recommended N = 244.6 ± 19.6 lb N/A

ii) For hard red and hard white winter:

N supply needed = 98 * (3.0± 0.2) = 294± 19.6

  N supply needed = 294± 19.6 lb N/A

  Recommended N = 294 ± 19.6 - 20 = 274

Recommended N = 274 ± 19.6 lb N/A