3.2.2. N Fertilizer Rates

The landscape, soil, and weather variables related with N rates in the estimated logit model were silt soil texture (Pr ≤ 0.01), loam soil texture (Pr ≤ 0.01), elevation (Pr ≤ 0.01), water-holding capacity (Pr ≤ 0.01), soil erosion index (Pr ≤ 0.01), and VRN 2 treatment dummy variable (Pr ≤ 0.01) (Table 5). Evaluating the percentage changes in the log odds probabilities of landscape, soil, and weather attributes indicated that silt- or loam-textured soils or soils at higher elevations are negatively associated with the probability that FP generates lower N rates than VRN (Table 6). Greater water-holding capacity, more erodible soils, or VRN 2 were positively associated with the probability that FP generates lower N rates than VRT.

The fertilizer N rate odds ratio for silt indicated that FP N rates were 0.0212 (*e*<sup>−</sup>3.8551) times as likely to be lower than VRT N rates. There was a 9.79 percent change in the log odds that the FP N rates were lower than VRN N rates. Fields with silt textures with the mean soil conditions would likely benefit from VRN in terms of N cost savings and environmental benefits due to significant chances of VRN generating lower N rates than the FP. Evaluating the odds ratio at the loam soil texture indicated that the FP N rates were 0.0243 (*e*<sup>−</sup>3.7156) times as likely to be lower than the VRT N rates. The percentage change in the log odds of FP N rates being lower than VRN N rates was 9.76 percent. Under these conditions, there was a relatively large chance that the VRN practice would be applied less N than the FP technology. A field with these conditions may benefit from VRN use for environmental benefits.
