Strategies for Reducing Nitrate Leaching from Irrigated Potato ProductionProduction

Carl RosenDepartment of Soil, Water, & ClimateUniversity of Minnesota

Minnesota Ground Water Association ConferenceU of M, St. Paul

November 9, 2010

TopicsPotato 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 potato production in Background gMinnesota

~50,000 acres mostly on loamy sand soils with low organicsand soils with low organic matter70% for processing

Russet BurbankRusset Burbank450 – 600 cwt/A

30% fresh marketEarly harvest redsEarly harvest redsSome russets/whites300 – 500 cwt/A

$100 million in ra prod ct$100 million in raw product valueIrrigation is essential for optimizing yield and quality

BackgroundPotatoes have a relatively shallow root system – most roots in the top 12”

Sensitive to N and water stressRates of 160 to 300 lb N/A appliedRates of 160 to 300 lb N/A applied

Rainfall averages about 12” during the growing seasongrowing season

Rainfall after an irrigation is a problemWater holding capacity ~ 1” in the top ft

All these factors contribute to a high potential for nitrate leaching

Nitrate Concerns - Statewide Results1993 20051993-2005

10 to 20 % of the wells% of wells testing > 10 ppm 10 to 20 % of the wells tested in the potato growing regions were above 10 ppm NO3-N

Many individuals and municipalities have had

k ito take action to remediate the problem

Nitrate Testing Clinic Program(Over 50,000 observations – Data courtesy of Minnesota Department of Agriculture)

BMPs to Address Nitrate Concerns

Response to GroundwaterResponse to Groundwater Protection Act – 1989

N fertilizer management planCentral tool is adoption of BMPs

Vol ntarVoluntaryResearch-basedFocus is on N fertilizersManure management also considered

Published in 2008 for potatoPublished in 2008 for potato

http://www.extension.umn.edu/distribution/cropsystems/DC8559.pdf

Specific N BMPs for PotatoesSelect a realistic N rate

VarietyVarietyHarvest date (based on market)Yield goalP i /Previous crop/manureIrrigation water nitrate-N

Time N application to meet N demands of the crop

Split applications of soluble NSplit 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 stagesFive general growth stages

Each with a different nutrientEach with a different nutrient requirement

Length of each stage depends i t / li ton variety/climate

Growth Stage Ig

Sprout developmentp p

Seed is the primary source ofSeed is the primary source of nutrients

Occurs within 30 days of planting

Water and nutrient demand is low

Growth Stage IIgVegetative growth

30-55 days after planting

Relative water and nutrient demand is low to moderate

Growth Stage IIIgTuber initiation and set

Tuber formation is sensitive to nutrient supply at this stage

50 to 70 days after planting

Vegetative growth increasesVegetative growth increases rapidly

Water and nutrient demand isWater and nutrient demand is moderate to high

Growth Stage IVgTuber 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 highmoderate to high

Growth Stage Vg

T b t tiTuber maturation

Vines begin to die

Transport of nutrients to tubers

Water and nutrient demand is low

Potato Seasonal N Accumulation & Dail Acc m lation RateDaily Accumulation Rate

Sprout Veg T.I. Bulking Maturation

N A l tiN Accumulation Rate

Russet Burbank – Becker, Minnesota

Suggested Nitrogen Timing

Timing of Application% of Total Nitrogen to Apply___ ___ _

Early Maturing Variety Late Maturing VarietyTiming of Application Early Maturing Variety Late Maturing Variety

Preplant/planting 10-40% 10-20%Preplant/planting 10 40% 10 20%

Emergence 40-60% 20-40%

Final hilling (or tuber initiation)

0-40% 30-60%

Post-hilling 0 0-40%

Total N applied to potatoes typically ranges from 160 to 250 lb N/A

Diagnostic Tools to Help Determine In season N ApplicationsIn-season N ApplicationsPetiole nitrate analysis

4th-5th leaf from growing point4 5 leaf from growing pointWorks well with indeterminate varieties and when bulking conditions are optimumApply N when petiole nitrate-N is at or below the optimum rangethe optimum range

In-season soil nitrate testingSample to 1 ft in hillInterpretations not well calibratedWide fluctuations due to rainfall

Chlorophyll meter & other reflectance techniques

Area of active research

Interpretation of Petiole Nitrate-N Concentrations Through the Growing Season (d w basis)Through the Growing Season (d.w. basis)

%)

2 02.53.0

ncn.

(%

Excess

1 01.52.0

N C

on

Optimum

0 00.51.0

itrat

e- Deficient

0.030 50 70 90 110

N

Days after Emergencey g

The Nitrogen Cycle

X

X

Enhanced Efficiency N Sources yControlled release nitrogen

Ph i l h i l b i t l d l bilitPhysical or chemical barrier to slow down solubilitySulfur coating around prillPolymer coating around fertilizer prill (usually urea)

Example: ESN (manufactured by Agrium, Inc.)“Environmentally Smart Nitrogen”Only economically viable slow release currently available for potatoOnly economically viable slow release currently available for potatoCoated urea - mode of action - lowers solubilityRelease rate depends on soil moisture and temperature

Polymer Coated TechnologyPolymer 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 ESNgranules through the

igrowing season

Nitrogen Uptake and Growth

100wth

40

60

80

100

Upt

ake

or G

row

VineTuberT t l N

0

20

40

0 20 40 60 80 100 120 140

% T

otal

N U Total N

0 20 40 60 80 100 120 140

Days After Planting

Vine kill

8-10” depth

2 3” d th2-3” depth

Comments on Polymer-coated UreaWhen used properly leaching is lower during the growing seasongrowing season

Susceptible to damage during handling and application

F l f it t hi h t ill lt iFalse sense of security – too high rate will result in leaching

Growers tend to apply soluble N later in the seasonGrowers tend to apply soluble N later in the season when ESN is used

M h ti t h l i t dMore research on coating technology is warranted

Other Recommended PracticesSound irrigation management

“Checkbook” methodW t it i d i

700

/AWater monitoring devices

Use of cover cropsE i ll ft l h t

400

500

600

A Yield, cwt/

Especially after early harvest potatoesNot effective for long season potatoes

200

300

0 100 200 300

Grade

 A

Russet BurbankAlturas

potatoes

Use of N efficient varieties/cropsActive area of research

0 100 200 300

Nitrogen Rate, lb N/A

Active area of research

Amendments to increase soil t h ldi itwater holding capacity

Case Study in Perham, Minnesotay

High density of center pivots with potato in the rotation

One pivot near the center of town

Giloman siteBelieved to contribute to elevated nitrate in drinking water

In cooperation with MDA

The Giloman Site…

Field Surface>24”

• Suction lysimeters installed to a 4 ft depth >24

deepto a 4 ft depth

• The approximate area where the lysimeters are located

Reducing Nitrate Leaching is a Challenge!!

Giloman

100

120

m)

Nitrogen Suction Lysimeter Data near Perham - 4ft Depth

BurbankPotato2000

Umatilla Potato 2008 (ESN) + fertigation N

250 lb N/A250 lb N/A

120 lb N/A

60

80

Nitr

ogen

(ppm

Soybeans 2001

AlturasPotato 2002 Alfalfa

Alfalfa 2007('06 winter kill)

Edible Beans2009170 lb N/A

0

20

40

Nitr

ate- 2001 2002 Alfalfa

2003

Alfalfa 2004 Alfalfa

2005

Alfalfa 2006

0

Data – Courtesy of the Minnesota Department of Agriculture

Overall ConclusionsGrowing potatoes on irrigated sandy soils in Minnesota is a leaky systemMinnesota is a leaky system

BMPs can help in reducing nitrate losses butBMPs can help in reducing nitrate losses, but in many years leaching will still occur

Integrated approach is neededIntegrated approach is needed

Long term solution gGrow N efficient varieties with lower N ratesAvoid growing potatoes in areas were there are sensitive aquiferssensitive aquifers