1. USDA‐ARS, Dep. of Agronomy, Univ. of NebraskaLincolnNE68583‐0915
2. Central Platte Natural Resource DistrictGrand IslandNE68803
3. USDA‐ARS, Dep. of Agricultural Engineering, Univ. of MissouriColumbiaMO65211
4. Dep. of AgronomyUniv. of NebraskaLincoln68583‐0915