3.2.3. N Efficiency

Soil, landscape, and weather variables related with N efficiency were sand soil texture (Pr ≤ 0.10), clay soil texture (Pr ≤ 0.01), loam soil texture (Pr ≤ 0.05), soil depth (Pr ≤ 0.05), soil erosion index (Pr ≤ 0.05), and growing degree days (Pr ≤ 0.01) (Table 5). The percentage changes in the log odd probabilities of landscape, soil, and weather attributes in relation to NEFF indicated that finer soil textures or warmer temperatures were positively associated with the probability of a lower VRN N efficiency compared to FP (Table 6). Deeper soils or soil with coarser textures were negatively related to the probability of lower N efficiency of VRN compared to FP.

Fertilizer N efficiency on the clay soil texture indicated that VRN N efficiency was 63.2 (*e*4.1468) times as likely to be lower than FP. There was a 622% change in the log odds of VRN N efficiency, lower than FP. Using VRN on clay fields, these may be inefficient in terms of N use relative to the FP. At the loam soil texture, the odds ratio indicated that VRN N efficiency was 0.3737 (*e*<sup>−</sup>0.9842) times as likely to be lower than FP. Evaluating the odds ratio for the loam soil texture, there was a 6.26 percent change in the log odds of lower VRN N efficiency compared to the FP on loamy textured fields with these conditions. This finding indicates that there is a significant chance of obtaining higher N efficiency using VRN on loam soil textures.
