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, 2014
Organic 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.
Defoliation by Colorado Potato Beetle on July 8, 2009. Kimberly,
Idaho.
Potato Variety
Defoliation rating
(1=healthy, 9=defoliated)
Defender
Yukon Gem
Alturas
Russet Burbank
Yukon Gold
Dark Red Norland
2.2
3.2
4.2
2.2
3.4
5.2
Russet Norkotah
2.8
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
30,000
UI Target Petiole N
Grower Petiole N
Petiole NItrate-N (ppm)
25,000
20,000
15,000
10,000
5,000
0
Soil N – 12.0 ppm
Preplant N – 119
Inseason N – 119
30,000
UI Target Petiole N
Grower Petiole N
Petiole NItrate-N (ppm)
25,000
20,000
15,000
10,000
5,000
0
Soil N – 12.0 ppm
Preplant N – 119
Inseason N – 119
Yield achieved – 634 cwt/acre
Yield goal – 550 cwt/acre
Previous 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
 Benefits
 Certified organic compost can be applied to crops any
time
 Rich in P, K, S, and micronutrients
 Even field application (relatively)
 Drawbacks
 P accumulation in soils
 Poor source of N for newly transitioned organic fields
○ Stable organic N compounds need several years to mineralize
into plant available forms
Raw Animal Manure
Raw 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
Benefits
 More N than composted manure
 Rich in P, K, S, and micronutrients
Drawbacks
 P accumulation in soils
 Can not be used for short season potato varieties
 Raw 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.
Tuber Yield (ton/acre)
2009
2010
350
350
300
300
250
250
200
200
150
150
100
100
50
50
0
0
Control
Chilean
nitrate
added
Control
Chilean
nitrate
added
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.
Tuber Yield (ton/acre)
2009
2010
350
350
300
300
250
250
200
200
150
150
100
100
50
50
0
0
Control
10 ton
dairy compost
Control
Chilean
nitrate
added
10 ton
dairy compost
Chilean
nitrate
added
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.
Tuber Yield (cwt/acre)
2009
2010
400
400
350
350
300
300
250
250
200
200
150
150
100
100
50
50
0
0
0
1.1
1.6
2
Distillers Grains (ton/acre)
10 ton
dairy compost
10 ton
dairy compost
0.0
1.1
1.6
2.0
Distillers Grains (ton/acre)
Specialty Fertilizers
Benefits
 Some have very high N (3% or greater)
Drawbacks
 Can be cost prohibitive
 Can 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 N
 155 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%2
0Calculator%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 Idaho
Twin Falls Research & Extension Center
315 Falls Ave., Evergreen Bldg.
PO Box 1827
Twin Falls, Idaho 83303-1827
Phone: 208 736-3629
Email: amberm@uidaho.edu
Website: www.extension.uidaho.edu/nutrient