1. Conventional N Management for Oklahoma
G. V. Johnson and W. R. Raun
Dept. Plant & Soil Sciences
Oklahoma State University
Stillwater, OK

2. Fertilizer-N = Yield Goal-N Requirement - “Available” Soil-N.
Assumptions:
13 % crude protein in harvested crop.
Fertilizer-N and soil test-N are 70% efficient.

3. Identify “Available” Soil Test Nitrate-N
Yield goal-based N-requirement
- Soil test NO3-N_(surface and sub)__
Fertilizer N requirement
< 20% of wheat fields are regularly soil tested, few include subsoil

4. Fertilization N rate based on yield goal without benefit of soil test.
Most yield goals are overly optimistic.
Most N is applied preplant as for wheat.
Most fields are topdressed using
Strong trend for replacing with and

5. Conventional Strategy is Easy and Profitable.
Crop N requirement = 2 lb N/bu yield
Average profit from N = $36/acre/yr