Organic Potato ProductionAmber Moore, Ph.D.Extension Soils SpecialistUniversity of IdahoTwin Falls, Idaho

Similar to conventional in many ways

• Organic potato needs the same nutrients as a conventional potato

• Physiologically the same

Where they differ

• Management• Organic growers have:– More advanced planning– More pest pressure– Lower yield and quality• Conventional, 450 – 550 cwt/acre (22 – 28 ton/acre)• Organic, 300 – 350 cwt/acre (15 – 18 ton/acre)

What we will discuss today…

• Introduction to organic production• Potato Variety selection• Adapting fertilizer recommendations for

organic production• Organic fertilizer sources• Cover Crops

Organic Acronyms• N.O.P. – U.S. National Organic Program– Regularly allows or prohibits materials and practices as certified

organic• OMRI – Organic Materials Review Institute– National List of Allowed and Prohibited Substances

• WSDA (Washington State Dept. of Ag.)– Also distribute a list of allowed and prohibited substances,

followed by Idaho– Often more restrictive than OMRI’s list

• ACA – Accredited Certifying Agent– ISDA in Idaho (Idaho State Department of Agriculture)

N.O.P. Definition for Organic

• An ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity.

• Minimal off-farm inputs• Management practices that restore, maintain

and enhance ecological harmony

“Organic”

• Chemicals containing carbon are also called “organic”– Based on this definition, urea fertilizer and most

pesticides are “organic”– Different from USDA certified organic

• Are all certified organic practices chemically organic?– No– Manures, composts are chemically organic– Mineral compounds are not

Why grow Organic?

• Because you believe in the organic philosophy– Small-scale growers– Trend toward more sustainable practices

• Because you want to make a higher profit from your potato fields– Large-scale growers– Trend toward less sustainable

Week of February 26, 2014Organic Potato $ Value,

~2.3 times greater than conventional

http://www.rodaleinstitute.org/Organic-Price-Report

Challenges for organic potato growers

• Lowered yields– 250 cwt. (organic) vs. 400 cwt. (conventional)

• Effective Nitrogen sources• Weed control• Finding buyers/market demand

Transitioning from conventional to organic

• Three years of following organic regulations before a field is certified organic

• Most common method, alfalfa hay for 3-year period, then into more profitable and intensive row/grain crops for next 3 years or so

• Fertility issues seem to be more severe for newly transitioned field– Less organic matter?– Less microbial diversity?– Nutrients building up from manure/compost/cover crop

applications?

VARIETY SELECTION

Advice on variety selection

• Resistant to local diseases and disorders– Example – Late Blight issues, consider Defender

• Maturity– Short-season varieties tend to require less N– Exception, Alturas (late-season but requires less N)

• Early and vigorous plant emergence, help with weed competition

• Insect resistance

Seven potato varieties grown on a certified organic field at the UI Kimberly Research Station in Kimberly, Idaho in 2009 and 2010.

Potato Variety Market Type Total Yield (cwt/acre), two

year average

Total Yield (ton/acre), two

year average

Alturas Process 260 13.0

Defender Process/Fresh 262 13.1

Russet Burbank Process/Fresh 350 17.5

Yukon Gold Process/Fresh 237 11.8

Yukon Gem Process/Fresh 335 16.8

Dark Red Norland Fresh 240 12.0

Russet Norkotah Fresh 194 9.7

Presented at Idaho Potato Conference. 2011. Olsen and Moore.

Potato Variety Defoliation rating (1=healthy, 9=defoliated)

Defender 2.2Yukon Gem 3.2Alturas 4.2Russet Burbank 2.2Yukon Gold 3.4Dark Red Norland 5.2Russet Norkotah 2.8

Defoliation by Colorado Potato Beetle on July 8, 2009. Kimberly, Idaho.

Presented at Idaho Potato Conference. 2010. Wenninger.

Adapting fertilizer recommendations for organic production

Petiole Nitrates

• UI recommends over 15,000 ppm petiole nitrates during tuber bulking

• Based on potatoes receiving N fertilizers• We see good tuber yields but low petiole nitrates – On fields receiving manure/compost applications, – On fields following alfalfa

• Don’t recommend that organic growers rely on petiole nitrate values– Still useful for showing changes N status in the plant

over the growing season

0

5,000

10,000

15,000

20,000

25,000

30,000Pe

tiole

NItr

ate-

N (p

pm)

UI Target Petiole NGrower Petiole N

Soil N – 12.0 ppmPreplant N – 119Inseason N – 119

0

5,000

10,000

15,000

20,000

25,000

30,000Pe

tiole

NItr

ate-

N (p

pm)

UI Target Petiole NGrower Petiole N

Soil N – 12.0 ppmPreplant N – 119Inseason N – 119

Yield achieved – 634 cwt/acreYield goal – 550 cwt/acrePrevious crop – Alfalfa

Organic nutrient sources

Organic nutrient sources

• Animal manures and composts• Mineral fertilizers• Mustard/canola/soybean meals• “Specialty” fertilizers

Organic composted animal manure

Composted plant and animal materials produced though a process that:(i) Established an initial C:N ratio of between 25:1 and 40:1;

and(ii) Maintained a temperature of between 131 °F and 170 °F

for 3 days using an in-vessel or static aerated pile system; or

(iii) Maintained a temperature of between 131 °F and 170 °F for 15 days using a windrow composting system, during which period, the materials must be turned a minimum of five times.

Composted Animal Manure

BenefitsCertified organic compost can be applied to crops any

timeRich in P, K, S, and micronutrientsEven field application (relatively)

DrawbacksP accumulation in soilsPoor source of N for newly transitioned organic fields○ Stable organic N compounds need several years to mineralize

into plant available forms

Raw Animal ManureRaw animal manure must be composted unless

it is:(ii) Incorporated into the soil not less than 120 days

prior to the harvest of a product whose edible portion has direct contact with the soil surface or soil particles; or

(iii) Incorporated into the soil not less than 90 days prior to the harvest of a product whose edible portion does not have direct contact with the soil surface or soil particles;

Raw Animal Manure

BenefitsMore N than composted manureRich in P, K, S, and micronutrients

DrawbacksP accumulation in soilsCan not be used for short season potato varietiesRaw manure not considered as an organic

practice in some overseas markets

Mineral fertilizers

• Sodium nitrate—use is restricted to no more than 20% of the crop's total nitrogen requirement.– Good for getting over the

nitrogen deficit hump– Sodium toxicity and

accumulation– Not considered organic by some

overseas markets

Russet Burbank yields in 2009 and 2010. Potatoes grown on an organic production field in Kimberly, Idaho. Chilean nitrate applied in-season at 48 lb N/acre. Dairy

compost applied at 10 ton compost/acre in the fall of 2008 and 2009.

Control

Chilean

nitrate

added

050

100150200250300350

2009

Tube

r Yie

ld (t

on/a

cre)

Control

Chilean

nitrate

added

050

100150200250300350

2010

Russet Burbank yields in 2009 and 2010. Potatoes grown on an organic production field in Kimberly, Idaho. Chilean nitrate applied in-season at 48 lb N/acre. Dairy

compost applied at 10 ton compost/acre in the fall of 2008 and 2009.

Control

Chilean

nitrate

added

050

100150200250300350

2009

Tube

r Yie

ld (t

on/a

cre)

Control

Chilean

nitrate

added

050

100150200250300350

2010

10 ton dairy compost

10 ton dairy compost

Other mineral fertilizers

• Rock Phosphate– Do not dissolve well on alkaline soils

• Elemental Sulfur• Gypsum (Calcium sulfate)• Potassium Chloride (KCl)• Sulfates• Carbonates• Confirm that fertilizer is organic

Oilseed meals

• Mustard, canola, soybean meals

• Rich in nitrogen – (4 – 7 % N)

• Up to 60 % of N is plant available in first growing season

• Expensive, competition with animal feed markets

Russet Burbank yields in 2009 and 2010. Potatoes grown on an organic production field in Kimberly, Idaho. Dairy compost

applied at 10 ton compost/acre in the fall of 2008 and 2009.

0 1.1 1.6 20

50100150200250300350400

2009

Distillers Grains (ton/acre)

Tube

r Yie

ld (c

wt/

acre

)

0.0 1.1 1.6 2.00

50100150200250300350400

2010

Distillers Grains (ton/acre)

10 ton dairy compost

10 ton dairy compost

Specialty Fertilizers

BenefitsSome have very high N (3% or greater)

DrawbacksCan be cost prohibitiveCan be ineffective, especially if low N

COVER CROPS AND CROP ROTATIONS

Legume rotations

Alfalfa, clover, winter peas Nitrogen fixing rhizobia in root nodules

Convert nitrogen gas to ammonium compounds that can be used by the plant

Alfalfa combined with soil N155 and 240 lb N/acre (Westerman and Crothers,

1993)Most organic potato growers in Southern Idaho

include 3-5 years of alfalfa in their rotation

Pink coloring in dissected legume root nodules indicates an active population N-fixing rhizobia bacterium. Photo taken of hairy vetch root nodules in Aberdeen, Idaho.

Winter Wheat(spring harvested in Aberdeen)

Hairy Vetch(spring harvested in Aberdeen)

Austrian Winter Pea(spring harvested in Aberdeen)

Daikon Radish(fall harvested in Aberdeen)

Austrian Pea and Winter Wheat Shoshone

http://www.extension.uidaho.edu/nutrient/CC_Calculator/Cover%20Crop%20Calculator%207/Cover%20Crop%20Calculator%207.htm

Photo courtesy of Nick Andrews, and Dan Sullivan, Oregon State University.

Equations and calibration data supporting the University of Idaho Cover Crop Calculator, which estimates plant available nitrogen (PAN) in the soil over a growing season for spring-tilled green manure crops or crop residues on irrigated cropland in

Southern Idaho.

Pest Control

• Well-spaced rotations– Optimum – 7 years between potato rotations– Minimum – 4 years between potato rotations

• Include biofumigant crop in the rotation• Avoid nutrient deficiencies• Field Isolation

Weed control

• Intensive tillage and cultivation– Alternatives to improve tillage• Roller/crimper• Rotate with no-till/strip-till crops

• Hand weeding• Timing and crop rotations• Prepare for weed pressure in late season

July 20th, 2010

August 23rd

September 8th, 2010

Insect control

• Colorado Potato Beetle– Spinosad – Most effective control method• Timing is critical

– Pyrethrum– Neem

July 7th, 2010(edges that did not receive applications of spinosad)

July 8th, 2010

Bottom Line

• Variety selection can help to avoid anticipated issues with organic production– Pest pressure– Low nitrogen fertility

• Petiole nitrates may not be an optimal tool for organic growers

Bottom Line

• Nitrogen, difficult to get enough for good potato yields– Annual fall applications of compost, build of slow

release N– Apply higher N fertilizers during transition and

when N is low (above 4% N)• Keep up with organic regulations– Confirm that nutrient sources and practices are

organic

Bottom Line

• Include legumes in rotation– Free nitrogen!

• Consider cultivation for early weed control

Amber D. Moore, Ph.D.

University of IdahoTwin Falls Research & Extension Center315 Falls Ave., Evergreen Bldg.PO Box 1827Twin Falls, Idaho 83303-1827 Phone: 208 736-3629Email: amberm@uidaho.eduWebsite: www.extension.uidaho.edu/nutrient