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

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 Potato VarietyMarket TypeTotal Yield (cwt/acre), two year average Total Yield (ton/acre), two year average AlturasProcess DefenderProcess/Fresh Russet BurbankProcess/Fresh Yukon GoldProcess/Fresh Yukon GemProcess/Fresh Dark Red NorlandFresh Russet NorkotahFresh Presented at Idaho Potato Conference Olsen and Moore.

Potato Variety Defoliation rating (1=healthy, 9=defoliated) Defender2.2 Yukon Gem3.2 Alturas4.2 Russet Burbank2.2 Yukon Gold3.4 Dark Red Norland5.2 Russet Norkotah2.8 Defoliation by Colorado Potato Beetle on July 8, Kimberly, Idaho. Presented at Idaho Potato Conference 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

Soil N – 12.0 ppm Preplant N – 119 Inseason N – 119

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

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 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.

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 Potatoes grown on an organic production field in Kimberly, Idaho. Dairy compost applied at 10 ton compost/acre in the fall of 2008 and ton dairy compost 10 ton dairy compost

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

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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 20 th, 2010

August 23rd

September 8 th, 2010

Insect control Colorado Potato Beetle – Spinosad – Most effective control method Timing is critical – Pyrethrum – Neem

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

July 8 th, 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 Phone: Website: