long-term field research for developing nitrogen bmp’s gyles randall univ. of minnesota southern...
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Long-Term Field Research for Developing Nitrogen BMP’s
Gyles Randall
Univ. of Minnesota
Southern Research and Outreach [email protected]
http://sroc.coafes.umn.edu/
Factors relating to BMP’s for N
• Cropping systems
• N rate applied
• Time of application
• Nitrification inhibitors
• N source
• Tillage
• Cover crops
CROPPING SYSTEMS
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.
Cropping Total Nitrate-N
System discharge Conc. Loss
Inches ppm lb/A
Cont. Corn 30.4 28 194
Corn – Soybean 35.5 23 182
Soybean – C 35.4 22 180
Alfalfa 16.4 1.6 6
CRP 25.2 0.7 4
Nitrate losses in tile drainage water from soil mineralization.
87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04
Year
0
10
20
30
40
50
60
F-W
Nitr
ate
-N C
on
c. (
pp
m)
Dry years
Est
ablis
hed
gras
s
CONCLUSION
• Cropping system has greater effect on hydrology and nitrate losses than any other management factor!
“Preventive Management”
RATE OF APPLICATION
Continuous Corn, 2001–03 Olmsted Co.
Effect of N rate for corn after soybean on NO3-N concentrations in tile drainage water in 2001.
Date
10
15
20
25
30
35
40
Nitr
ate
Co
nc
(mg
/L)
80 lb N/A 120 160
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).
N Treatment 4-Yr Yield Net 4-Yr FWTime Rate N-Serve Avg. Return NO3-N conc.
lb /A bu/A $/A/Yr mg/L
--- 0 --- 111 --- ---
Fall 80 Yes 144 30 12
“ 120 “ 166 70 13
“ 160 “ 172 78 18
Spr. 120 No 180 105 14
Effect of N rate applied for corn in 2003 on nitrate-N concentration and loss in tile
drainage during May–September 2004 from soybeans at Waseca.
N FW Nitrate-N Nitrate-NRate. Concentration LossLb/A mg/L Lb/A
80 9 36120 12 52160 20 81
Conclusion• Corn yields were increased 5% and nitrate
losses in drainage were reduced by 27% when reducing the N application rate from 160 lb/A applied in the fall to the recommended 120-lb rate applied in the spring.
• Reducing the N rate from 120 lb/A to 80 lb/A reduced yield by 17% and nitrate loss by 13%.
• Forty-six percent of the nitrate lost in tile drainage from a corn-soybean rotation was lost in the year soybeans were grown.
TIME OF N APPLICATION
Effect of time of N application and N-Serve on corn yields after soybean from 1987–2001 at Waseca.
Time of N Application
Parameter Fall Fall+N-Serve Spring
15-Yr Avg. Yield (bu/A) 144 153 156
15-Yr Avg. Economic return over fall N ($/A/yr) *
--- $9.30 $18.80
7-Yr Avg. Yield (bu/A) ** 131 146 158
7-Yr Avg. Economic return over fall N ($/A/yr) *
--- $22.50 $51.00
* Corn = $2.00/bu; N = $0.25/lb N
** Seven years when statistically significant differences occurred.
Nitrate-N concentration in tile drainage from a corn-soybean rotation as influenced by time of
N application and N-Serve at Waseca.
N Treatment
Time of application N-Serve Nitrate-N Conc.*
-- mg/L --
Fall No 14.1
Fall Yes 12.2
Spring No 12.0
* 10-cycle (1990-2000) rotation average.
1999 tile water NO3-N loading at Waseca vs. NO3-N concentrations in the Le Sueur River 2.3
miles from Mankato.
7.4
16.615.7
12.0
10.8
16.2
15.2
12.7
15.6
14.1
11.9 11.6
Sampling Date
0
10
20
30
40
50
60
Nitr
ate
-N L
oss
(lb
/A)
6.0
8.0
10.0
12.0
14.0
16.0
18.0
Nitr
ate
-N (
ppm
)
Fall AAPP AALe Sueur River
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.
Region Specific BMPs for N
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.
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
