Strategies for Reducing Nitrate Leaching from Irrigated Potato

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Strategies for Reducing Nitrate Leaching from Irrigated Potato
Strategies for Reducing Nitrate
Leaching from Irrigated Potato
Production
Carl Rosen
Department of Soil, Water, & Climate
University of Minnesota
Minnesota Ground Water Association Conference
U of M, St. Paul
November 9, 2010
Topics
„
Potato production in Minnesota
„
Specific potato production factors
contributing to nitrate leaching
„
Best management practices identified that
reduce nitrate leaching
„
Challenges involved - Case study in Perham,
MN
„
General conclusions and long-term solutions
Background
„
Irrigated
g
potato production in
Minnesota
‰
‰
~50,000 acres mostly on loamy
sand soils with low organic
matter
70% for processing
„
„
‰
30% fresh market
„
„
„
‰
‰
Russet Burbank
450 – 600 cwt/A
Early harvest reds
Some russets/whites
300 – 500 cwt/A
$100 million in ra
raw prod
product
ct
value
Irrigation is essential for
optimizing yield and quality
Background
„
Potatoes have a relatively shallow root
system – most roots in the top 12”
„
Sensitive to N and water stress
‰
„
Rainfall averages about 12” during the
growing season
‰
‰
„
Rates of 160 to 300 lb N/A applied
Rainfall after an irrigation is a problem
Water holding capacity ~ 1” in the top ft
All these factors contribute to a high
potential for nitrate leaching
Nitrate Concerns - Statewide Results
1993 2005
1993-2005
% of wells testing > 10 ppm
Nitrate Testing Clinic Program
(Over 50,000 observations – Data courtesy
of Minnesota Department of Agriculture)
„
10 to 20 % of the wells
tested in the potato
growing regions were
above 10 ppm NO3-N
„
Many individuals and
municipalities have had
to take
k action
i to
remediate the problem
BMPs to Address Nitrate Concerns
„
Response to Groundwater
Protection Act – 1989
‰
‰
N fertilizer management plan
Central tool is adoption of
BMPs
„
„
„
„
‰
Voluntary
Vol
ntar
Research-based
Focus is on N fertilizers
Manure management also
considered
Published in 2008 for potato
http://www.extension.umn.edu/distribution/cropsystems/DC8559.pdf
Specific N BMPs for Potatoes
„
Select a realistic N rate
‰
‰
‰
‰
‰
„
Variety
Harvest date (based on market)
Yield goal
P i
Previous
crop/manure
/
Irrigation water nitrate-N
Time N application to meet N demands of
the crop
‰
Split applications of soluble N
„
‰
No preplant N and limit the amount of N in the starter
Consider use of controlled release N sources
Potato Growth Characteristics
„
Five general growth stages
„
Each with a different nutrient
requirement
„
Length of each stage depends
on variety/climate
i t / li t
Growth Stage
g I
„
Sprout
p
development
p
„
Seed is the primary source of
nutrients
„
Occurs within 30 days of planting
„
Water and nutrient demand is low
Growth Stage
g II
„
Vegetative growth
„
30-55 days after planting
„
Relative water and nutrient
demand is low to moderate
Growth Stage
g III
„
Tuber initiation and set
„
Tuber formation is sensitive to
nutrient supply at this stage
„
50 to 70 days after planting
„
Vegetative growth increases
rapidly
„
Water and nutrient demand is
moderate to high
Growth Stage
g IV
„
Tuber bulking
„
Vegetative growth slows down
„
60 to 90 days after planting - early
„
70 to 110 days after planting – late
„
Water and nutrient demand is
moderate to high
Growth Stage
g V
„
T b maturation
Tuber
t ti
„
Vines begin to die
„
Transport of nutrients to tubers
„
Water and nutrient demand is low
Potato Seasonal N Accumulation &
Dail Acc
Daily
Accumulation
m lation Rate
Sprout
Veg
NA
Accumulation
l ti
Rate
Russet Burbank – Becker, Minnesota
T.I.
Bulking
Maturation
Suggested Nitrogen Timing
Timing of Application
% of Total Nitrogen to Apply___ ___ _
Early Maturing Variety Late Maturing Variety
Preplant/planting
10-40%
10
40%
10-20%
10
20%
Emergence
40-60%
20-40%
Final hilling (or tuber
initiation)
0-40%
30-60%
0
0-40%
Post-hilling
Total N applied to potatoes typically ranges from 160 to 250 lb N/A
Diagnostic Tools to Help Determine
In season N Applications
In-season
„
Petiole nitrate analysis
‰
‰
‰
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In-season soil nitrate testing
‰
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4th-5
5th leaf from growing point
Works well with indeterminate varieties and
when bulking conditions are optimum
Apply N when petiole nitrate-N is at or below
the optimum range
Sample to 1 ft in hill
Interpretations not well calibrated
Wide fluctuations due to rainfall
Chlorophyll meter & other
reflectance techniques
‰
Area of active research
Nitrate-N Con
ncn. (%
%)
Interpretation of Petiole Nitrate-N Concentrations
Through the Growing Season (d
(d.w.
w basis)
3.0
2.5
Excess
20
2.0
1.5
Optimum
10
1.0
Deficient
0.5
00
0.0
30
50
70
90
Days
y after Emergence
g
110
The Nitrogen Cycle
X
X
Enhanced Efficiencyy N Sources
ƒ Controlled release nitrogen
‰
Ph i l or chemical
Physical
h i lb
barrier
i tto slow
l
d
down solubility
l bilit
„
ƒ
‰
Sulfur coating around prill
Polymer coating around fertilizer prill (usually urea)
Example: ESN (manufactured by Agrium, Inc.)
„
„
„
„
“Environmentally Smart Nitrogen”
Only economically viable slow release currently available for potato
Coated urea - mode of action - lowers solubility
Release rate depends on soil moisture and temperature
Polymer Coated Technology
Agrium U.S. Inc., 2005
Release rate depends on: coating thickness, temperature, and moisture
N Release from ESN
- “Mesh Bag” Method -
Visual assessment of ESN
granules through the
growing
i season
% Total N U
Uptake or Grow
wth
Nitrogen Uptake and Growth
100
80
Vine
Tuber
T t lN
Total
60
40
20
0
0
20
40
60
80
100
120
140
Days After Planting
Vine kill
8-10” depth
2 3” d
2-3”
depth
th
Comments on Polymer-coated Urea
„
When used properly leaching is lower during the
growing season
„
Susceptible to damage during handling and
application
„
False
F
l sense off security
it – too
t high
hi h rate
t will
ill result
lt iin
leaching
‰
„
Growers tend to apply soluble N later in the season
when ESN is used
M
More
research
h on coating
ti ttechnology
h l
iis warranted
t d
Other Recommended Practices
Sound irrigation management
‰
‰
„
“Checkbook” method
W t monitoring
Water
it i devices
d i
Use of cover crops
‰
‰
Especially
E
i ll after
ft early
l h
harvestt
potatoes
Not effective for long season
potatoes
Grade A
A Yield, cwt//A
„
700
600
500
400
Russet Burbank
Alturas
300
200
0
100
200
Nitrogen Rate, lb N/A
„
Use of N efficient varieties/crops
‰
„
Active area of research
Amendments to increase soil
water
t holding
h ldi capacity
it
300
Case Studyy in Perham, Minnesota
„
High density of center
pivots with potato in the
rotation
„
One pivot near the
center of town
‰
‰
Giloman site
Believed to contribute to
elevated nitrate in
drinking water
In cooperation with MDA
The Giloman Site…
• Suction lysimeters installed
to a 4 ft depth
• The approximate area
where the lysimeters are
located
>24
>24”
deep
Field Surface
Reducing Nitrate Leaching is a Challenge!!
Giloman
120
Nitrate-Nitrogen (ppm
m)
100
Nitrogen Suction Lysimeter Data near Perham - 4ft Depth 250 lb N/A
250 lb N/A
Umatilla Potato 2008
(ESN) + fertigation N
Burbank
Potato
2000
80
170 lb N/A
60
40
20
Soybeans
2001
Alturas
Potato
2002
Alfalfa 2007
('06 winter kill)
Alfalfa
2003
Alfalfa
2006
Alfalfa
2004
Alfalfa
2005
0
Data – Courtesy of the Minnesota Department of Agriculture
120 lb N/A
Edible
Beans
2009
Overall Conclusions
„
„
Growing potatoes on irrigated sandy soils in
Minnesota is a leaky system
BMPs can help in reducing nitrate losses,
losses but
in many years leaching will still occur
‰
„
Integrated approach is needed
Long
g term solution
‰
‰
Grow N efficient varieties with lower N rates
Avoid growing potatoes in areas were there are
sensitive aquifers