1. An Environmental Assessment of Sensor-Based Variable-Rate N Management in Corn Darrin Roberts Dr. Newell R. Kitchen, Advisor Thesis Committee Members: Newell Kitchen, Peter Scharf, Ken Sudduth

2. Research Objectives (I)Evaluate the relationship between EONR and active-light reflectance sensor readings (II)Evaluate the relationship between environmental measurements and EONR

3. EONR Reflectance by Sensors Environmental Measurements 3 Steps to Accomplish Objectives

4. 3 Environmental Measurements (2004-2005 cropping seasons) 1.Yield Efficiency: (Y i - Y check plot )/N i 2.N fertilizer recovery efficiency (NFRE): [(NR i – NR check plot )/N i ] * 100 3.Post-harvest soil sampling: Inorganic N levels were determined to a depth of 120cm

5. Within-field EONR variability for 2004 fields

6. EONR related to Vis/NIR ratios for 2004 fields

7. EONR = -794 + 2632.7087(index) + 1.3174(index)(EC) - 1798.747(index 2 ) R 2 = 0.47 EONR related to Vis/NIR and soil EC for 2004 fields

8. Yield efficiency related to EONR for 2004 fields

9. NFRE related to EONR for 2004 fields

10. Profile inorganic N related to EONR for 2004 fields

11. Research Conclusions  EONR was highly variable within and between corn fields  EONR was greatly affected by yearly climate conditions  Because sensor indices, in conjunction with soil EC, were able to separate low and high EONR values, further research might involve sensors in the development of N management zones within fields  Active-light reflectance sensors show promise to achieve EONR, increase Yield Efficiency and NFRE, and reduce N loss off fields

12. Thank you