1. DEPARTMENT OF ENVIRONMENTAL SCIENCE & TECHNOLOGY Laboratory for Agriculture and Environmental Studies Sensor Based Variable Rate N Management in Mid-Atlantic Cropping Systems Joshua M. McGrath, UMD Wade Thomason, VT Steve Phillips, IPNI

2. How Did I Get Here? Tom Sims, UD Chad Penn Josh McGrath

3. The Math

4. Background on the Mid-Atlantic

5. Nitrogen Management Basics (since early 1990s in MD) Corn: Apply N based on realistic yield goal –1 lb N/bu expected yield Split-apply N fertilizer on corn –apply 30 – 40 lbs/A at planting –remaining N as sidedress When utilizing manure or following leguminous cover crops use the Pre-Sidedress Nitrate Test Wheat: Apply a total 70 – 120 lbs of N 20 – 40 lbs at planting Split top-dress 80 – 100 –Green-up –Feekes 5 - 6

6. What makes us special? >90% side-dress N in Corn on Delmarva Yields vary widely 120 – 220 bu/ac >90% no-till corn 50 – 60% irrigated on the lower shore In Maryland farmers cannot exceed University recommendations

7. VIRGINIA APPROACH l Generated calibration models for wheat and corn grown in the Mid-Atlantic l Developed N fertilization algorithms for both crops l Validated these rate equations for performance

8. VIRGINIA APPROACH l Generated calibration models for wheat and corn grown in the Mid-Atlantic Predicted Yield Index Yield, Mg ha - 1 0 1 2 3 4 5 6 7 00.0010.0020.0030.0040.0050.0060.007

9. VIRGINIA APPROACH l Generated calibration models for wheat and corn grown in the Mid-Atlantic YPI

10. Wheat N Rate Algorithm

11. VIRGINIA APPROACH - Wheat

12. VIRGINIA APPROACH - Corn

13. What’s Needed Reference Strips –Difference between: High N reference (best possible with more than adequate N) Low N reference (0 N applied) And Area currently in sensor’s view.

14. In-season N management 1 st topdress based on estimated tiller # 2 nd topdress based on Tissue N concentration 30 to 40 lb N/ac preplant

15. Zadoks stage, in parenthesis In-season N timing Days From Planting 1 st topdress based on estimated tiller # 2 nd topdress based on NDVI and DFP

16. Validation in VA, MD, DE ~60 sites across Virginia since 2000 12 sites in DE and MD (2008, 2009) Irrigated and non- irrigated Conventional and no till Various rotations, hybrids, varieties, and soil types Wide range of pre-plant, starter, and in-season N rates (including VR) Collected spectral measurements and an assortment of plant physical and chemical characteristics at various growth stages Determine grain yield

17. Validation in VA, MD, and DE RCBD; 3-8 reps Plot size: 60 by 250 to 500 ft In-season N: –4-5 Fixed Rates –1 Standard Rate –1 Variable Rate Spra Coupe 220 w/ 60 ft boom and GreenSeeker RT200 Raven 440 flow rate controller

18. Recommended vs. Applied Rates 55% are within 2 gallons of prescribed rate 88% within 5 gallons

19. Wheat: Applied N GreenSeeker vs. Tissue 0 10 20 30 40 50 60 70 80 90 100 STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS STD GS 12345678910111213141516AVG N rate, kg ha -1

20. Average Wheat Performance Farmer Practice GS 0 10 20 30 40 50 60 70 80 90 100 Grain Yield, bu/ac GS 30 N Rate Applied, lb/ac NS 7% less N with GS

21. Corn Algorithm Performance 0 20 40 60 80 100 120 1234567891011 N Rate, lb/ac STD GS

22. 0 20 40 60 80 100 120 140 160 STD GS Average Corn Performance Grain Yield, bu/ac Sidedress N, lb/ac NS 21 % (21 lb/ac) less N with GS

23. Limitations and Challenges Corn: V-7 versus V-4 Wheat: Herbicide in second spring top-dress? Check strips How to tell if the system was “right” – Skepticism When parameters are entered the application graph often needs tweaking by faking parameters

24. Honest Answers Don’t Always Work!

25. Can’t just plug and chug (spray) Farmer would apply 46 gal/acre N_pre = 0 This has been corrected in the software

26. Part of the Adaptive Management Toolbox Systems approach –Manage soil N Focused on in-season N management –PSNT –Active Crop sensors –LCM End of season assessment –CSNT –Yield monitoring

27. The Future in the Mid-Atlantic The Chesapeake Bay and cost of fertilizer have us poised for rapid adoption –A few major farmers and ag service companies –Environmental Groups Likely to be covered through various cost share mechanisms soon Need to continue to refine algorithm to address –Accuracy of input values –Expand side-dress window –Straightforward user interface

28. Thanks to our partners

29. Questions? Joshua M. McGrath (301) 405-1351 mcgrathj@umd.edu Lab for Ag and Environmental Studies