Use of Soil Moisture Data to Refine GreenSeeker Sensor Based N Recommendations in Winter Wheat.

The Sensor Based Nitrogen Rate Calculator enables producers to estimate yield potential and obtain N fertilization rates based on GreenSeeker sensor measurements and the response index, number of days where GDD (growing degree days)>0, agronomic maximum yield, expected grain price, and fertilizer price. Soil moisture levels can vary significantly both site to site and year to year. Furthermore, soil moisture is known to significantly affect both yield potential and fertilizer use efficiency. The objectives of this trial are: to determine the effect of mid-season soil profile moisture on prediction of yield potential in winter wheat and corn using comprehensive Mesonet weather data, and to establish the functional relationship for adjusting fertilizer N recommendations based on profile moisture and to refine the on-line Sensor Based Nitrogen Rate Calculator. The current Sensor Based Nitrogen Rate Calculator does not take in account profile soil moisture at the time of sensing. Limited soil profile moisture leads to overestimation of yield potential and, low fertilizer use efficiency. At-sensing knowledge of the amount of water present in the soil profile will help to more accurately predict yield potential. This will in turn reduce the risk of applying N when it is not required, and to identify years when sufficient moisture is present in the soil profile to produce near maximum yields where more N is needed.