3.1.2. N Fertilizer Rates

Many field soil, landscape, and weather characteristics were significantly related with N rate differences between VRN-generated N rates and the FP (Table 4). Fertilizer N rate differences were negatively associated with sand (the intercept term, Pr ≤ 0.01), silt (Pr ≤ 0.01), or loam (Pr ≤ 0.01) soil textures but positively related with clay (Pr ≤ 0.01) when VRN was compared to FP. Finer-textured soils required more fertilizer N applied due to the higher yield potential while coarser soils needed less applied N. Soils with greater water-holding capacity (Pr ≤ 0.01), larger soil erosion indexes (Pr ≤ 0.01), and higher GDD (Pr ≤ 0.01) were positive in relation to VRN N rates. All else equal, more N was applied using VRN compared to FP on fields with a greater water-holding capacity, more erodible soils, or warmer temperatures. Soils with deeper profiles (Pr ≤ 0.05) had a negative association to VRN N rate compared to FP. The estimated dummy variable for VRN 2 showed significantly higher N rates, indicating that OS plus yield monitor information calculated higher mean fertilizer N rates than the FP. However, the higher fertilizer N rates generated with the additional information embodied in the N managemen<sup>t</sup> regime were not associated with higher lint yields (Table 4) and, therefore, limit the profit

potential of VRN 2. In addition, the higher cost of information utilizing more expensive map-based information with VRN 2 also impedes its profit potential [28].
