Long-Term Field Research for Developing Nitrogen BMP’s

1. Long-Term Field Research for Developing Nitrogen BMP’s Gyles Randall Univ. of Minnesota Southern Research and Outreach Center grandall@umn.edu http://sroc.coafes.umn.edu/

3. Factors relating to BMP’s for N • Cropping systems • N rate applied • Time of application • Nitrification inhibitors • N source • Tillage • Cover crops

4. CROPPING SYSTEMS

5. Effect of CROPPING SYSTEM on drainage volume, NO3-N concentration, and N loss in subsurface tile drainage during a 4-yr period (1990-93) in MN.

6. Nitrate losses in tile drainage water from soil mineralization. Established grass Dry years

7. CONCLUSION • Cropping system has greater effect on hydrology and nitrate losses than any other management factor! “Preventive Management”

8. RATE OF APPLICATION

9. Continuous Corn, 2001–03 Olmsted Co.

10. Effect of N rate for corn after soybean on NO3-N concentrations in tile drainage water in 2001.

11. Effect of N rate on yield of corn after soybean, net return to fertilizer N, and nitrate-N concentration in tile drainage at Waseca (2000–2003).

12. Effect of N rate applied for corn in 2003 on nitrate-N concentration and loss in tile drainage during May–September 2004 from soybeans at Waseca.

13. Conclusion • Corn yields were increased 5% and nitrate losses in drainage were reduced by 27% when reducing the N application rate from 160 lb/A applied in the fall to the recommended 120-lb rate applied in the spring. • Reducing the N rate from 120 lb/A to 80 lb/A reduced yield by 17% and nitrate loss by 13%. • Forty-six percent of the nitrate lost in tile drainage from a corn-soybean rotation was lost in the year soybeans were grown.

14. TIME OF N APPLICATION

15. Effect of time of N application and N-Serve on corn yields after soybean from 1987–2001 at Waseca.

16. Nitrate-N concentration in tile drainage from a corn-soybean rotation as influenced by time of N application and N-Serve at Waseca.

17. 1999 tile water NO3-N loading at Waseca vs. NO3-N concentrations in the Le Sueur River 2.3 miles from Mankato.

18. Conclusion • Compared to late fall N application without N-Serve over the 15-year period: • Corn yields were increased 9 and 12 bu/A/yr (6 and 8%) by either fall N+N-Serve or spring preplant N, respectively. • Nitrate losses were decreased 14 and 15% by either fall N+N-Serve or spring preplant N, respectively.

19. Region Specific BMPs for N

20. Proposed BMP’s for South-Central MN • Recommended • Spring preplant or split applications of ammonia, urea, or UAN are highly recommended. • Incorporate broadcast urea or preplant UAN within three days. • Apply sidedress application before corn is 12” high. • Inject or incorporate sidedress applications of urea or UAN to a minimum depth of 4 inches.

21. Proposed BMP’s for South-Central MN cont. • Recommended, but with greater risk • Fall application of AA + N-Serve after soil temperature at 6-inch depth is below 50° F. • Side dressing all N before corn is 12 inches high. • Not recommended • Fall application of urea, UAN, or anhydrous ammonia without N-Serve

22. THANKS Gyles Randall grandall@umn.edu Southern Research and Outreach Center grandall@umn.edu http://sroc.coafes.umn.edu/