Strategies for Reducing Nitrate Leaching from Irrigated Potato

Transcription

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

In-season soil nitrate testing

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
Controlled release nitrogen

Ph i l or chemical
Physical
h i lb
barrier
i tto slow
l
d
down solubility
l bilit

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