LongTerm Field Research for Developing Nitrogen BMPs

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Long-Term Field Research for Developing Nitrogen
BMPs

• Gyles Randall
• Univ. of Minnesota
• Southern Research and Outreach Center
• grandall_at_umn.edu
• http//sroc.coafes.umn.edu/

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Factors relating to BMPs for N

• Cropping systems
• N rate applied
• Time of application
• Nitrification inhibitors
• N source
• Tillage
• Cover crops

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CROPPING SYSTEMS
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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.
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Nitrate losses in tile drainage water from soil
mineralization.
Established grass
Dry years
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CONCLUSION

• Cropping system has greater effect on hydrology
  and nitrate losses than any other management
  factor!
• Preventive Management

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RATE OF APPLICATION
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Continuous Corn, 200103 Olmsted Co.
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Effect of N rate for corn after soybean on NO3-N
concentrations in tile drainage water in 2001.
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Effect of N rate on yield of corn after soybean,
net return to fertilizer N, and nitrate-N
concentration in tile drainage at Waseca
(20002003).
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Effect of N rate applied for corn in 2003 on
nitrate-N concentration and loss in tile drainage
during MaySeptember 2004 from soybeans at Waseca.
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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.

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TIME OF N APPLICATION
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Effect of time of N application and N-Serve on
corn yields after soybean from 19872001 at
Waseca.
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Nitrate-N concentration in tile drainage from a
corn-soybean rotation as influenced by time of N
application and N-Serve at Waseca.
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1999 tile water NO3-N loading at Waseca vs. NO3-N
concentrations in the Le Sueur River 2.3 miles
from Mankato.
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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 NN-Serve or spring
  preplant N, respectively.
• Nitrate losses were decreased 14 and 15 by
  either fall NN-Serve or spring preplant N,
  respectively.

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Region Specific BMPs for N
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Proposed BMPs 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.

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Proposed BMPs 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

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THANKS

• Gyles Randall
• grandall_at_umn.edu
• Southern Research and Outreach Center
• grandall_at_umn.edu
• http//sroc.coafes.umn.edu/