CSS 322, Principles of Potato Production

A. Mosley, I. Vales, J. McMorran, S. Yilma

CS 421; 737-5835; alvin.r.mosley@oregonstate.edu

MWF 9:00 - 9:50 in CS 122; T 12-12:50 in CS 150

Discussion Topics By Class Session

  1. Introductory remarks; description of the potato – botany & taxonomy
  2. Botany, taxonomy continued; crop origin and history
  3. History; importance; Oregon, U.S., international production; propagation
  4. “Seed” production; certification; Limited-Generation scheme; breeding and
    varieties
  5. Varieties, continued – fresh, chipping, frozen processing, specialty; roles of starch, sugar in processing
  6. Field preparation; tillage, fertilization, herbicides, systemic insecticides, etc
  7. Preparing seed, planting, concurrent operations – herbicides, insecticides for
    wireworms, etc.
  8. Planting to emergence; emergence to “layby”
  9. Layby to vine kill; harvest
  10. Storage -- ventilation, recirculation, temperature, humidity, other.
  11. Fertilization and irrigation, in-depth
  12. Irrigation, continued; pest management – diseases, insects, weeds
  13. Laboratory and greenhouse tour; tissue culture, winter growouts; eye-indexing,
    etc. S. Yilma and J. McMorran
  14. Final exam, CS 122. See practice exams at the bottom of this document

 

1. Organizational

-Introductions -- students, instructors, guests

--Purpose

Much of the informattion covered in this class can be found on websites at http://oregonstate.edu/potatoes (The Potato Information Exchange, or PIE) and http://cropandsoil.oregonstate.edu/classes/CSS322/Cppina.htm -- Commercial Potato Production in North America published by the Potato Association of America, PAA). Rough class notes are located at http://oregonstate.edu/potatoes/CSS322WebNotes.html.

Three practice exams are included at the end of these notes. Please observe that exams typically involve an essay based on 10 questions selected from a dozen or so. If you answer more than 10, your 10 best responses will be used to calculate your class rank and grade.

CSS 322 Timeline -- MWF, 9 – 9:50 in CS 122 and T, 12-12:50 in CS 150

 

2. Botany, Taxonomy, Origin

-The White or “Irish” potato is typically thought of as Solanum tuberosum L.

Solanum tuberosum is a  tuber-bearing tetraploid species belonging to the Solanaceae (nightshade) family. The cultivated potato has 4 sets of chromosomes; however, there are approximately 150 species of "potatoes" or solanums which are tuber-bearing tetraploids, triploids, diploids, etc.

 

--The center of origin for potatoes is thought to be in the Andes of Peru, Chile, Boliva, Ecuador, etc. but species occur over a broad geographical area including even portions of the southwestern U.S.; wild species are mostly short-day plants for

flowering and tuberizing (many wild species originating near the Equator will not tuberize in Oregon).

 

--Most species are found in S. American highlands, above several thousand feet; some grow at 15,000 +

--Many scientists contend that potatoes originated in Mexico and moved southward while others assume the opposite.

--At least two potato species are native to the S.W. U.S. -- Solanum jamesii (U.S.

only) and Solanum fendleri (U.S., Mexico, Columbia – suggesting 

intercontinental movement?)

--Germplasm banks collect, study, preserve and distribute wild species from multiple locations. The U.S. potato germplasm bank is located at Sturgeon Bay, Wisconsin (http://www.ars-grin.gov/ars/MidWest/NR6/index.html#AU). Other collections are maintained at the International Potato Center in Lima, Peru, the Vavilov Institute in Russia and at various German, Dutch and Polish sites (See http://www.cgn.wageningen-ur.nl/pgr/collections/crops/potato/genbanks.htm for further details and a large listing).

 

--Close relatives of potato include tomato, tobacco, petunia, pepper, eggplant, jimson weed (loco weed), deadly nightshade (Belladonna).

 

--Many Solanum species contain poisonous alkaloids (potato = solanine, chaconine; tomato – tomatine; tobacco = nicotine (a good greenhouse insecticide); belladonna = atropine. Atropine is used to inhibit the actions of acetylcholine -- prevents actions of smooth muscles, used to dilate eyes, etc. Alkaloids are produced in the roots and typically translocated throughout the plant.

 

--Most Solanums are graft compatible; examples--tomato scion on potato rootstock = "pomato"; tobacco on tomato or potato rootstocks will be nicotine-free because alkaloids are produced in roots; without tobacco roots, no nicotine in tops. Similarly, hop plants grafted onto marijuana (hemp) rootstocks will contain various attractive foliar alkaloids and can be smoked (not recommended!).

 

Pomatoes, anyone?? Or nicotine-free tobacco?

 

--The potato is an annual dicot (two seed leaves as opposed to grasses, etc.) when grown from botanical seeds, but is treated as a perennial because of commercial regrowth/propagation from tubers; the tuber is not only the chief means for potato propagation, but also the primary storage organ and major human food source.

 

 

 

 

--The potato tuber is a modified stem:

  1. about 70-75% water, 25-30% dry matter; 
  2. contains high levels of starch (20% more or less);
  3. contains some sugars (<3%?);
  4. 5-8% protein on a dry wt basis;
  5. potato protein is almost perfect—complete set of amino acids, etc;
  6. good source of some vitamins & minerals; 
  7. only about 90 calories/average tuber when baked or boiled.

 

--Potato vs. wheat protein:

The potato is a good source of protein; for example, in Oregon

potato – (5% protein x 20% d.m. x 21 tons/acre = 400 lbs./acre of protein

(complete, equivalent to egg)

wheat (10% protein x 63 bu/acre x 60 lbs = 373 lbs/acre of protein (some amino

acids limiting)

-- Potato Nutritional Value

Note: A diet of milk and potatoes is relatively complete but might get boring. Michigan State University studies demonstrated that graduate students can survive indefinitely on a diet of potatoes and beer(?).

Apparently an Adult Irishman of the mid 1800’s ate up to 14 lbs/day. The potato tuber is a fairly good source of potassium and Vit. C and was sometimes used to prevent  scurvy by old-time sailors.

3.History

See Also http://collections.ic.gc.ca/Potato/histtimeline/index.asp

 

--Cultivated in Andes for 13,000 years!?

 

--Native peoples (Incas, etc.) freeze-dried potatoes at least 3-5,000 years ago by  freezing, thawing and squeezing juices out; product was called Chuno, with accent over the n.

 

--1500’s to Mediterranean Europe by conquistadores?

 

--1600’s Europe proper

 

--1600 – 1800, development of varieties in British Isles—Ireland

 

--1845 Irish Famine, 2 million dead or emigrated to N. America; typical adult Irish male ate 12-14 lbs/day; no other food sources because grains, other commodities were used to pay rent to English landlords; late blight appeared and was uncontrollable, killed vines, rotted tubers in field and storage; fungus confused with “bad air”, divine curses -- see:

 

 

 

 

--1700-1800’s, white fleshed varieties in North America

 

--1900’s, Pacific Rim and India

4.Importance

 

--4th leading world crop after wheat, rice, corn; fastest growing of top 4.

 

--greatest production of protein/food per acre of all major crops

 

--potato is most important in north temperate regions despite short-day origins

primarily in N. temperate zone, but also in Australia, New Zealand, S. America

Leading Potato Producers, Millions of Metric Tons

 
1996
2002
U.S.
18
21
Russia
36
32
China
35
65
Poland
33.6
15.4
Ukraine
21
16.1
India
15.5
24

 

Total U.S. Potato Exports, 2001
 
!,000 Lbs., Product Weight
$1,000
Fresh
693,195
122,297
Frozen Fries
1,051,670
342,007
Other Frozen
49,937
22153
Chips
163,835
165,945
Flakes & Granules
64,895
32,082
Dried
6,543
3,147
Other
58,458
35,686
Total
2,088,533
723,316

 

2002 U.S. Production – 3.15 $billion, farm gate; about 5.5 $billion in finished (processed) form

 

Farm Gate$ , 2002–

Idaho,720 $million; Washington, 514;California, 307, Wisconsin, 221; Oregon, 134

Oregon processed potato value = $300 - $350 million

Oregon potato personnel payroll = ~ $60 million, more than all other agronomic crops combined

Approximate Oregon acres – Columbia Basin, 26,000; Klamath, 12,000; Malheur, 10,000, Central Oregon, 3000; Willamette Valley, 1200; notheastern Oregon, 600 seed

 

Oregon crops, 2001: Farm gate, $millions – All hay, 333; all grass seed, 324; potatoes, 132; all wheat, 106; onions, 74; pears, 63 

finished/processed – potatoes = $300 million.

5.Propagation (for commercial production)

--Potatoes are cloned commercially

 

--Implications of cloning:

1.cloning assures genetic purity, uniformity of product (fries, chips, etc.) except for rare mutations

2.cloning increases disease spread, especially viruses (Y, X, A, M, PLRV, etc.), bacteria, fungi; examples, Bacterial Ring Rot, Late Blight

3.cloning favors high yields relative to true potato seeds  

--Seed Potato Production -- potato seed tuber production is highly technical with many built in procedural and quality assurance standards. At this time virtually all North American seed potatoes are derived from meristems (located in the heart of buds) via test tubes and greenhouses.

An excised meristem is typically 0.2 - 0.5 mm in diameter, or approximately half the diameter of a narrow pencil lead. The meristem is the meristematic center of a bud; meristematic cells divide to give rise to all other tissues. Meristems have no vascular system (several intermediate cells between vascular tisse and meristematic cells), so are less prone to viral, fungal and bacterial infection via the vascular system. All buds (apical, lateral, sprout) have meristems and can be used for seed increase purposes.

Meristems are placed on a nutrient-rich agar in test tubes and grown into plantlets.

Plantlets such as the one on the right above can be multiplied by 4 or 5x monthly as needed by dividing stems into "nodal cuttings" which are then rooted in either other test tubes or greenhouse potting medium depending on program needs. Nodes denote the locations of leaf/bud junctions on plant stems; they are frequently slightly swollen compared to the rest of the stem. Disease-free, certified Pre-nuclear minitubers are produced from rooted "nodal" cuttings in greenhouses. Cuttings without nodes obviously will not produce plants.

Because seed potatoes rapidly pick up viruses and other diseases in the field, all seed-producing states have adopted "limited-generation" seed production/certification schemes. Note that generations typically drop one number per year. However, disease levels above certification tolerances can cause seed lots to drop by several generations in a single season. Certification tolerances for potato seed diseases are typically very low (see http://www.oscs.orst.edu/potato/index.shtml). Note that the generational flow is always downward; that is, a specific generation of seed can only be produced from an earlier, more disease-free generation.

Typical Limited-Generation Seed Production Scheme

Class of Seed Planted
Class Produced
Prenuclear (Lab & Greenhouse)
Nuclear
Nuclear
G1 (Generation 1)
G1
G2
G2
G3
G3
G4
G4
G5

Some guiding principles for producing healthy seed potatoes: 

Problems—certification programs vary from state to state in standards/tolerances, quality of personnel, terminology, and reputation.

Certification Methods:

 

Certification inspectors typically inspect potato fields at least twice during the growing season. The first inspection tends to concentrate on viruses, off-types, blackleg (bacterial infection) and other diseases which show symptoms early. The second inspection covers the preceding as well as Bacterial Ring Rot, Late Blight and other late-occurring problems. Because of its devastating effects, there is an absolute zero tolerance for BRR in all certification programs. The zero tolerance is also in effect for other problems such as certain nematodes, tuber moth and powdery scab.

Certification inspectors typically inspect fields from one corner diagonally across the rows because some problems (BRR, for example) may be expressed row by row. The inspector assumes that he is viewing a certain number of plants in each row. By counting the number of problem plants and rows, he/she can fairly accurately estimate the number of problem plants. If the percentages exceed certification tolerances, the field is rejected.

Because field inspection is by necessity a visual process, some plants may be questionable and call for laboratory verification by ELISA, Latex Agglutination, Electron Microscopy or other methods. Most Limited-Generation schemes require laboratory testing for PVX through the first one or two field generations.

The second field inspection typically occurs well before plants have died. Therefore, the potential for undetected late-season infection is high. For this reason virtually all certification programs require some form of winter grow-out testing. For winter tests, a percentage of the tubers (usually 400 or so in Oregon) for each seed lot are planted and the resultant plants are visually examined for disease symptoms and herbicide injury. As in field inspections, questionable plants and all plants of varieties which do not express PVY symptoms are lab tested.

Because of all these constraints, seed potato production is a “white knuckle ride” and growers never know whether their crop will be certified until late in the winter in most instances.

Breeding and eye-indexing:

Because breeding clones (selections) must be kept healthy for further increase and testing, breeders go to extraordinary means to prevent disease buildup. These means include electron microscopy and a number of sophisticated serological tests including Enzyme-Linked Immunosorbent Antibody, Latex Agglutination and numerous others. 

One traditional tool used by all breeders, and perhaps the most effective, is “eye-indexing”.Eye indexing typically begins with single- or five-hill selections and continues throughout the remaining 10 or 12 years leading to release. Eye indexing involves removing an eye from a tuber using a melon scoop, numbering the eye and the mother tuber identically, and then planting the eye to produce a plant for symptom evaluation. Grow-out plants are evaluated for viruses and other problems when 8-12 inches tall. Those with obvious problems are noted and the corresponding tubers are discarded. Only tubers of healthy appearing plants are kept for replanting and increase. Eye-indexing is an essential component of most breeding programs because of the large numbers of progeny involved and severe virus pressure.

 

For more information on seed production, see http://cropandsoil.oregonstate.edu/fpsp/index.html; http://www.oscs.orst.edu/potato/index.shtml; and http://oregonstate.edu/potatoes/potliv.html#Seed

 

6. Variety Selection  

 

 

 

(see http://oregonstate.edu/potatoes/variety.htm for additional information and images of varieties)

 

Potato breeding typically proceeds as follows: Male x female crosses ® berries & seeds ® seedling transplants ® plants (clones) in pots ® tubers ® single-hill field trials (2% saved) ® 5 hill trials (5% saved), etc. ®etc. for 12 more years until the clone is named and released. These fairly typical steps are illustrated in the Oregon flowchart below.

 

Transferring pollen from one plant to another produces seeds (TPS) which can be grown into plants producing tubers.

Tubers can be propagated ad infinitum by division into seedpieces.

 

 

Considerations for selecting varieties

Many varieties and types are available to commercial potato growers; potato tubers come in many color combinations! Varietal selection at the commercial level is ultimately determined by the profit motive. Commercial growers will only use varieties they expect to be marketable and profitable. Home gardeners have more leeway.

 

The following are important varietal selection criteria if profits are to be maximized:

 

1.Intended use – frozen processing, chips, starch, fresh market (table) use, roadside marketing, etc.;

2.Color, shape, season of maturity, storage dormancy, yield, grade-out;

3.Resistance to diseases, pests and disorders; and 

4.Adaptability to local growing conditions

5.Express symptoms when pathogens are present

 

 

Common processing varieties include: 

Specific gravity is an indicator of potato density, dry matter and starch content. Starch content strongly affects potato usage as shown in the table below.

 Specific Gravity and Dry Matter Content Vs. Potato Usage*

Specific Gravity
% Starch
Texture
Common Usage
<1.060 (v. low)
<16.2
V. Soggy
Salads, pany fry, can, boil
1.060-1.069 (low)
16.8-18.1
Soggy
Pan fry, salads, boil, can
1.070-1.079 (medium)
18.2-20.2
Waxy
Boil, chips, fries, may slough when boiled
1.080-1.089 (high)
20.3-22.3
Mealy, dry
Bake, chips, fries, some varieties slough when boiled
>1.089 (v. high)
>22.3
Very mealy, dry
Bake, fries, chips; tendency to produce brittle chips and slough when boiled

*starch accounts for 60-80% of potato total dry matter.

Starch, why is it important to processors of fries, chips, flakes and granules?

1.Higher starch means less water in tuber tissues;

2.Water is displaced by fat/oil during frying, so high water/low starch potatoes soak up more oil;

3.Oily fries, chips are soggy and unappetizing and often dark in color;

4.Oil is expensive;

5. High starch favors high product yield; for example, 

20% dry matter potatoes (high starch) will theoretically produce more pounds of chips/ton of raw product than 15% (low) starch potatoes while also requiring less oil.

Specific gravity, as shown in the table above, is a direct indicator of dry matter content of potatoes and, indirectly, starch content. The relationships are not exact and can be influenced by a number of factors including water and tuber temperatures, wetness of the tubers, etc. The specific gravity of pure water is 1.000, so potatoes are heavier than water and will sink unless the water is amended with starch, sugar or other materials to increase the specific gravity of the solution. Specific gravities are often determined by weighing a sample of potatoes in water and then in air, according to the following formula:

 

Specific Gravity = weight in air/weight in air-weight in water

A potato hydrometer produced by gluing a long, sealed, indexed tube to a float from which a basket is hung is also used for determining specific gravity. The hydrometer requires that an exact weight of potatoes be placed in the basket so that specific gravity can be read directly from the index markings on the tube. The weight in air/weight in water method is typically preferred.

Sugar, why is it important to processors?

 

1.High reducing (6-carbon or hexose) sugars cause dark-colored fried products, especially chips and French fries. Reducing sugars reduce copper in some obscure chemical reaction.In potato, reducing sugars are predominantly the 6-carbon sugars glucose and fructose, which result from the breakdown of starch from tuber reserves or the breakdown of sucrose transported from the plant leaves to the tubers. Sugars, the plant’s energy currency, are stored in tubers as starch. Starch is basically a long-chain polymer of sugar molecules. The relationship between photosynthesis and tuber carbohydrate can be crudely described as follows:

·Photosynthesis > glucose/fructose in leaves > sucrose in phloem transport system > glucose/fructose at action site(s) for respiration and/or storage as starch (a long, endless polymer of sugars) in tubers; starch is therefore a reserve energy currency.

 

Principle: for processing, we want high starch and low sugars almost always.

 

 

Fresh market varieties accent appearance, but yield, storage life and resistances are also important. Taste has been largely ignored in most U.S. potato breeding programs but is slowly resuming its former importance. Most fresh market varieties are relatively low in starch and high in sugar compared to processing varieties. They are, therefore, typically moist-fleshed and fine-textured.

 

Fresh market varieties can be any of many shapes and colors

1.Round reds (red skin, white flesh) – Norland, Pontiac, Redsen, Winema, Mazama, Modoc, Bison, Viking, Red LaSoda

2.Long russets – Russet Norkotah, Century Russet, Klamath Russet, Russet Burbank, Russet Legend; Gem Russet,Klamath Russet

3.Round whites – Superior, Katahdin, Kennebec, Sebago

4.Specialty/gourmet types—red skin/yellow flesh (Desiree); purple skin, flesh (All-blue); yellow flesh (Yukon Gold, Bintje); fingerlings (LaRatte, Yellow Banana, Yellow Finn, Peanut) and so on. See http://oregonstate.edu/potatoes/variety.htm#OtherVarieties for additional listings, descriptions and pictures.

 

 

7. Planting Site Selection and Soil Preparation

·Soil type – As with most crops, potatoes appreciate a well-drained, coarse-textured soil--but in a very big way! A loose, well-drained loamy or sandy soil:

1.Favors a long season (early planting/late harvest);

2.Is more workable and resists crusting from rain or irrigation;

3.Maximizes yield and quality (yield is somewhat proportional to the length of the growing season; for example yields in the short-season Willamette Valley and Central Oregon average about 20 tons/acre while the Hermiston area produces 25-30;

4.Improves aeration which reduces seed piece and tuber decay; and

Note: Erwinia softrot bacteria prefer anaerobic (oxygen-free) conditions associated with wet, crusted or poorly drained soils; under wet conditions, bacteria easily move in free water and invade the tuber via wounds (from fungi such late blight or Fusarium sp., pinkroot,insects, etc.) and lenticels (substomatal cavities) in tuber skins. Once inside the tuber, bacteria multiply rapidly and decay seedpieces and/or tubers. Free moisture and bacteria are a lethal combination for potatoes either in the field or in storage.

A lenticel is a substomatal cavity (remember, the tuber is a modified herbaceous stem). Stomates are ruptured as the tuber skin expands during growth so that guard cells, etc., are displaced and only the cavity truly remains. Lenticels become whitish and very prominent in the presence of excess moisture. Enlarged, infected lenticels are a good indicator of wet conditions.

 

5.Reduces tuber malformations caused by mechanical resistance to expansion. Rocks can be especially deforming.

6.Improves fertilizer and water use efficiency

·Soil Preparation:

1.Potatoes do not require a fine seedbed as with grains and most seeded crops, so don’t overdo it! In fact, potatoes suffer from excess preplant tillage because of potential soil crusting and associated anaerobic (low oxygen) conditions which favor seed piece decay and stand loss.

2.Never irrigate prior to emergence unless a drought situation exists! If the soil is excessively dry, irrigate well ahead of time and plant when the soil is still moist but not wet.

Example: in 1998, the OSU Seed Certification crew over-watered the greenhouse between eye-index plantings and emergence and successfully destroyed (rotted) 90% of the eye index seed pieces! In contrast, under normal preemergence irrigation in 1999, more than 90% of the plants survived.

 

What is eye-indexing? Remember the explanation from earlier?

 

8. Preparing Seed 

North American producers mostly plant seedpieces cut from large, whole tubers.

 

 

Seed tubers should always be warm (>50F) and dry when cut. Warm tubers, especially those whose "eyes" are just beginning to “peep” (that is, with buds or eyes just beginning to enlarge), are physiologically active and begin to heal and emerge rapidly after planting.

Seed pieces should ideally be cut, treated with a suitable fungicide and planted immediately after under good field conditions. Good field conditions imply warm (>45F) and moist but not wet soils. If seed can not be planted immediately because of scheduling or weather complications, special storage precautions (55-60F, high humidity, good ventilation, shallow piles) should be taken to prevent overheating and disease spread and promote rapid healing.

·Cutting causes problems!. Most U.S. seed tubers are large and require cutting; however, some growers, especially in the midwest where seed piece decay is a severe problem, prefer small whole seed tubers called single drops. Because the tubers are not cut, single-drop seed is highly resistant to decay. Most of Europe and the rest of the world use whole seed.

Cutting is a very effective way to spread most potato diseases including some viruses and most bacteria and fungi. Therefore, strict sanitation should be observed at all times, but especially between seed lots. If the seed lot has an obvious disease problem, discarding the seed is a legitimate option. Local potato extension people or other experts should be consulted if serious disease levels are suspected.

Cutters and handling equipment should be thoroughly cleaned and sanitized between lots to prevent spreading diseases from one seed lot to another. For example, if a seed lot has Bacterial Ring Rot, a highly infectious disease, it is vital that the source of the BRR be tied to a specific lot/grower. Seed growers almost invariably pay for ring rot problems provided the commercial grower can provide proof of guilt. If BRR, or other serious seed quality problems are suspected, look for an independent third party inspection and unbiased “expert” witnesses for corroboration. Florida studies from a few years ago demonstrated that a 1% BRR seed infection could result in 100% infection of cut seedpiecs due to contamination and spread throught the cutting equipment.

A seed cutter’s checklist:

1. Warm seed to 50F+ for a few days before cutting to prevent tissue tearing, wake the seed up physiologically, and get it ready for rapid healing and early emergence. Sprouts should just be “peeping” when seed is cut.

2.Seed is mechanically cut at the rate of 1 to several tons/hour/cutter.

3.Keep cutter blades sharp and clean; a sharp blade does less tissue damage.

4.Keep a close eye on the seed being cut—diseases, varietal type, mechanical condition, excess debris, freezing or heat injury, etc.

 

5. Keep a record of planting sequences and where seed lots are located in fields for insurance, legal purposes.

 

6. Always sanitize between lots to prevent disease spread between lots.

·Seed Treatment: Apply fungicides to cut seed pieces immediately after cutting while surfaces are still moist enough for powder to adhere; fungicides are also sometimes applied as liquids either as a spray or dip. Liquids may cause bacterial problems in some situations because of the water involved, but typically not if the seed is handled properly.

Common seed piece fungicides include – Captan, Dithane, Manzate, Maxim, Tops; most are applied as a dust at the rate of 0.5 – 1.0 lbs/100 lbs. of cut seed and can be very beneficial, especially under less than perfect planting/pre-emergent field conditions. Labels for these and other agrichemicals can be found at http://www.greenbook.net or http://www.cdms.net. Other materials such as straight Douglas Fir Bark or talc are sometimes used with success. Douglas Fir bark may act as a simple drying agent to prevent anaerobism and movement of bacteria, but it is thought to have fungicidal properties as well?

·Precutting???

In general growers prefer to cut, treat and plant if conditions are good (moist but not wet soil > 45F). Some growers pre cut seed up to a month early, but Pre- cutting is dangerous because of possible decay.

 

9.Planting

 

 

·How do we plant? Potatoes are planted mechanically at 2-4 mph and from 2 to 6 rows at a time. Fertilizer and other materials such as systemic insecticides are often applied simultaneously depending on local conditions and customs.

·When do we plant? February through July depending on location, expected harvest date and weather. The vast majority of Oregon’s potatoes are planted in April and early May.

·Seed piece spacing — seed pieces are typically planted 9-12 inches apart in 34-inch rows. This rate requires about a ton of 1.5-2oz. seed pieces/acre at a cost approaching $200/acre for seed alone.

·Seedpiece depth — 2 – 6 inches depending on soil type and growing conditions; lighter soils typically benefit from deeper planting, and vice versa.

A number of accessory operations are often performed before or during planting. Application of fumigants, wireworm remedies, herbicides, systemic insecticides and fertilizer may be tied in with planting depending on grower preference and local conditions.

All planting is mechanical; up to 6 rows at a time, more commonly 2 or 4. A few mph. Various types of planters--cup or pick types. Seed, fertilizer are handled in bulk by various loaders, etc. Tractor driver and usually one or two on planter, but passengers becoming less common.

Planting methods vary widely depending on local customs and cultural requirements. Large potato fields are planted by machines moving at 2-5 mph and covering up to 6 rows at a time. The addition of various nutrients and pesticides at planting is optional in most cases and might depend on the ability of the planter to hold enough seed and other materials to go across a half-mile circle and back without running empty.

Systemic insecticides Temik, Thimet, Di-syston, Admire) sometimes applied in  furrow at planting. Systemic =  in this instance, absorbed by the roots and transported "systemically" to all parts of the plants both above- and below-ground.

 

in short season areas:

1.systemic insecticides (Temik, Thimet, Furadan, Admire, Di-Syston – see http://www.greenbook.net or http://www.cdms.net for labels and use directions) are often banded at planting, if at all. Pre-harvest restrictions preclude Temik from most short-season areas.

2.Not so in longer-season production regions -- materials can be side-dressed at final hilling to prolong seasonal activity..

Many pesticides and some fertilizer can be applied before, during, or after planting  herbicides, nematicides, soil insecticides, systemic insecticides such as  thimet, temik, Di-syston. A fair percentage of potato fields are fumigated ahead of  planting or the fall before.

In short season areas, usually apply half of the fertilizer (up to about 500lbs/acre of  15-15-15, broadcast and incorporated, for example) before planting and half at  planting (500 lbs/acre 15-15-15 banded beside and below seedpieces). Fertilizers, especially N, are applied throughout the season, often through the irrigation system, in long-season areas.

10. Planting to Emergence (3-4 weeks)

This can be either a relatively busy or lazy period depending on the situation. In some  areas, most of the fertilizer has already been applied along with herbicides, and systemic insecticides. In contrast, some growers in long-season areas may choose, or be forced to, apply much of their fertilizer, herbicides, and systemic insecticides post plant or even  post emergence depending on the length of season and local traditions; later application  of these materials will obviously extend their useful life longer into the growing season. 

Pre-emergence herbicides such as metribuzin (sencor, lexone) are often applied at  delayed preemergence when just a few of the plants are breaking through the soil surface but before weeks exceed about an inch in height. 

Drag-off, or the practice of removing planter ridges to hasten emergence, is not practiced much anymore in the west but may be common in some areas with wet, heavy soils  prone to slow emergence and seed piece decay.

With furrow irrigation—furrows are often fully prepared by removing soil from  between the rows and gradually adding it to the rows to build hills well ahead of  emergence. In such situations, the crop may be considered “laid by” at this stage since  tractor work virtually ceases except for agrochemical sprays in some situations. Furrow  irrigation frequently begins shortly after emergence, or even before in extremely dry  situations. 

 

11. Emergence to layby (final tractor work, 3-4 weeks)

 

Cropping activities typically get back into high gear at this stage. Irrigation commences along with foliar insect and disease control. The crop is typically cultivated and ridged once or twice to build adequate hills over the potato rows. Hilling reduces greening and aids harvest. It also protects the plants and tubers from excess stress since the roots, stolons and tubers are buried deep in relatively cool, moist soil. Careful hilling reduces tuber ivasion by the potato tuber worm.

Pest and disease control continue as needed. Fungicide sprays may be applied in late blight-prone areas. Systemic insecticides ((Thimet, Furadan, Temik, Di-Syston) are applied during cultivation and hilling in long season situations as are herbicides suc as Dual, Prowl, Sencor and Eptam depending on the variety in question.

Fertilization continues in long season areas such as the Columbia Basin and the Treasure Valley of Oregon/Idaho. Much of the seasonal nitrogen is applied through the irrigation system (Nitrogation) based on petiole anaylsis and soil tests.

Fertilization:

Fertilizer should never touch seedpieces because of salt injury (dehydration) and  sprout death. Never band fertilizer on, or directly above seedpieces. Always to the  side and below. Seasonal broadcast and nitrogation are not concentrated enough to  cause dehydration.

In short-season areas, half of the fertilizer complement can be broadcast and  incorporated before planting and the rest banded beside and below(2” x 2”) the seed  pieces at planting.

In long-season areas, only a small percentage of the fertilizer is applied at planting.  The bulk of the P and K can be applied before, some P in bands at planting would  help. Nitrogen, especially, is applied through irrigation systems during the season in  the Co. Basin, for example. Applications based on petiole analyses and/or soil  analysis

 

Optimum fertility rates are influenced by:

  • The preceding crop
  • The crop planted
  • Residual nutrient levels
  • Soil type, organic matter, pH
  • Expected lengh of cropping season
  • Irrigation/rainfall patterns

 

--How does a farmer decide how much of what nutrients to apply at planting?

1. Field history

2. Past experience

3. Soil test

-- How does he monitor/manage fertility during the season?

1. Soil test

2. Petiole tests, esp. for nitrogen applications

3. Crop appearance

4. Precipitation?

Fertilizer applications should always be based on soil and/or petiole analysis.

Question: what is petiole analysis and how does it apply here? Basically, petiole analysis allows the farmer to know exactly howm juch nitrogen his crop tissues contain at any given time. By comparing his levels with sufficiency ranges as illustrate above, he can manage nitrogen applications very precisely, and to a lesser extent phosphorus and other materials, especially nutrients which are highly soluble. The combination of petiole analysis and in-season soil analysis provide growers a very precise picture of not only current tissue levels but expected changes based on soil availability. Such data allows for so-called “spoonfeeding” in long-season areas. Spoonfeeding is typically not as highly recommended for short-season areas. Soluble fertilizer elements are typically applied throughout the cropping season in the Columbia Basin but typically only in the planting season or shortly after in the Klamath Basin. Terms such as “fertigation” and “nitrogation” are often used to denote fertilizer applications through irrigation sprinklers. Center pivots provide very handy vehicles for “chemigation” as well as fertigation.


 

Typical fertilizer rates for Oregon, lbs/acre

Location
N
P2O5
K2O
S B
W. Valley
80-200
140
200
40 1?
C. Basin
200-400
150
200
25 1
C. Or./K. Falls
60-270
175
225
65 1
Tres. Valley
120-220
140
200
25 1

Question: why only 60 lbs of N. in some areas of the Klamath Basin? Organic soils typically release high amounts of N during the growing season due to the breakdown of organic matter.

Irrigation x nitrogen leaching---nitrogen is extremely soluble. Heavy rainfall or excess irrigation can leach most of the nitrogen below the rooting zone and into ground water. Parts of the Columbia Basin and Treasure Valley have been declared groundwater control areas because of nitrogen and pesticides in ground water. It is vital, therefore, that irrigation be precisely scheduled to prevent excessive water movement below the 18-inch potato rooting zone. As described earlier, many methods and consulting companies are available to help growers refine irrigation to a precise science.

12. Lay-by to Vine kill (6-10 weeks)

Field

Continue most activities which began during the Emergence – Layby phase; continue weed, pest, insect, and disease control and irrigation and fertilization as needed.

Irrigation:

Additional information on irrigation scheduling, etc, is available at http://oregonstate.edu/potatoes/potlii.html#IrrigationandFertilization

Western potato growers are facing rapidly escalating costs for water and the power to pump it. Likewise, the price of nitrogen and other nutrient elements is increasing. Because of these trends, irrigation scheduling to maximize water-use efficiency and minimize leaching of nutrient elements, especially nitrogen, is becoming ever more imprtant. It is quite possible that government agencies will eventually demand strict accounting for every gallon of water used. It behooves growers to thoroughly understand principles governing efficient irrigation.

Potato irrigation typically commences shortly after emergence in the PNW and is continued as needed until shortly before harvest. Potatoes are relatively shallow-rooted with some 90% of the root mass in the top foot and most of the rest in the 12-18-inch depth. Regardless of the potato production area, good yields and quality require that available soil moisture remain above about 65%. While lower soil moisture levels may not adversely affect overall yield, quality (and marketable yield) can be drastically reduced due to tuber malformations and internal problems such as hollow-heart, stem-end sugar development and so forth.

 

Seasonal Crop Water Usage -- varies considerably depending on:

1. variety

2. length of growing season

3. local weather/climate -- a full-season Columbia Basin crop may fequire 30 inches compared to 20 for K. Falls.

Daily Crop Water Usage -- depends on:

1. crop growth stage (see water use curve below)

2. variety

3. climate/weather -- note that soil type does not affect crop water requirements, but it can affect irrigation methods

Decisions about irrigation typically come down to:
  • when to irrigate
  • how much water per irrigation
  • how fast should the water be applied (in/hour or equivalent)
  • how often should the field be irrigated

These decisions are based not only on weather and plant factors such as variety and crop growth stage but also on certain properties of the soil. Soil texture and other properties do not not measurably impact total seasonal crop water requirement but significantly impact irrigation methods in terms of how fast, how much and how frequently fields must be irrigated and how much water can be applied at one time.

Important soil properties:

  • Field capacity -- the amount of water a soil can hold against gravity after the soil has drained but before evaporation has occurred. Field capacity is, of course, a function/indicator of the soil's water-holding capacity.
  • Permanent wilting point -- the soil moisture level at which the plant will not recover from wilting even at night.
  • Crop available moisture -- the amount of water (in/ft) available to the crop between field capacity and the permanent wilting point
    • available soil moisture should always be held above 65% in the top 18 inches of soil for potatoes

    •  

  • Soil water-holding capacity -- amount of water the soil will hold, expressed as inches/foot or equivalent. Ranges from 0.75in/ft for some Columbia Basin sands to 4.5 in/ft for some easter Oregon silt loams. Compared to sands, heavier soils have greater water-holding capacity but a much lower infiltration rate. Some sands in the Columbia Basin may hold less than 1 in/ft of available water. If, as noted above, available soil moisture must be held above 65% for potatoes, and since most of the potato roots are in the top foot, the field must be irrigated after only about 0.4 inch of water has been evapotranspired (evapotranspiration = crop water lost from fields by a combination of evaporation and plant transpiration). As shown by the crop water use curve below, this may call for daily irrigation under severe weather conditions. In contrast to Columbia Basin sands, some silt loams and clays may hold more than 4 inches/foot of available water. Such fields would clearly require irrigation much less frequently since more could be applied per irrigation. Willamette Valley silt loams may require irrigation only twice, or even once/week even in midsummer.
  • Infiltration rate/soil permeability -- rate at which the soil will accept water without serious runoff. Infiltration rate strongly affects the rate (in/hour) at which water can be applied. Application rates exceeding the soil's infiltration rate can lead to serious runoff and erosion. Infiltration rate is largely determined by soil texture. Infiltration rate is difficult to measure in the field but can be estimated in a laboratory by observing water movement through a column of soil. Infiltration rates vary widely. For example, a loam with good structure may absorb 0.5 in/hour while some sands may absorb up to 15 inches/hour. Infiltration rate obviously plays a major role in determining the rate at which irrigation water can be applied to a soil. It also may determine the method of irrigation used. Furrow irrigation, for example, is not well suited to soils with high infiltration rates because lengh of run is very much restricted. Likewise, a center-pivot system may not be suitable for soils with low infiltration rates since the outer ends of the pivots must apply water at extremely high rates.

 

 

Based on the preceding water use curve for the Columbia Basin, and assuming a sandy soil with less than 1.0 in/foot of available water, a potato crop can lose only about 0.4 in. before irrigation is needed. So, in the Columbia Basin in midseason, some center pivots must run continually to supply enough water, and sometimes even that is not enough. On silt loams (high available soil moisture) in the W. Valley (about 0.3 in/day maximum water use) growers can lose well over an inch before irrigation may be necessary.

 

 

Application Methods -- water may be applied in any of several ways including:

• flood irrigation

• furrow irrigation

• impact – sprinklers (solid-set, big guns, lateral move, center-pivot)

• drip

Solid set (sprinklers) is mandatory for dependable frost protection through irrigation. For frost protection, water is applied before the temperature falls below 32F and continuously until all ice melts the following morning. In some situations, solid-set frost protection can protect tubers down as cold as 23F (foliage typically freezes at about 28F). One potato grower in Midland, Oregon (Klamath Basin) recently irrigated 19 nights in July to precent freeze out. Needless to say, crop yield and quality did not fare well, but much of the crop was saved. Solid set sprinklers, like all other sprinkler systems, can deliver fertilizers and various other agrochemicals quite effectively.

Center-pivot is the sprinkler system of choice in the Columbia Basin and other areas requiring frequent irrigation, having light-textured soils and mostly free of growing season frosts. The center pivot is especially well adapted to soils with high infiltration rates because of extremely high water delivery rates at the ends of the pivot arms. The center pivot provides a convenient vehicle for delivering fertilzers and all manner of agrochemicals as frequently as every 18 hours in a pinch. A progressive farmer, without additional labor, can irrigate dozens of pivots via a computer without leaving his/her office (not recommended!).

Drip irrigation is currently not widely used in Oregon because of expense and aggravation; however, it may increase in popularity as the availability of water and energy to pump it decline.

Scheduling Irrigation

Growers use a number of tricks to schedule irrigation, ranging from shoveling to nuclear radiation. Precision can be greatly improved through use of various online resources listed at http://oregonstate.edu/potatoes/potlii.html#IrrigationandFertilization, http://oregonstate.edu/potatoes/irrigation.htm and elsewhere. The US Department of the Interior Agrimet Stations (http://www.usbr.gov/pn/agrimet/index.html) list various types of useful information (crop water use, etc.) by location for Oregon and other states plus a handy synopsis of irrigation scheduling methods (http://www.usbr.gov/pn/agrimet/irrigation.html). See also http://waterquality.montana.edu/docs/irrigation/introagrimet.shtml, http://wwwagcomm.ads.orst.edu/agcomwebfile/edmat/pnw288.pdf and http://www.cropinfo.net/irrigschedule.htm.

• Checkbook (evapotranspiration) –this method is widely used in the Columbia Basin and depends on the extrapolation of open pan evaporation readings to evapotranspiration (evaporation plus transpiration through the crop canopy, or or total crop water use) values. Crop water loss is basically equivalent to evapotranspiration which, in turn, is often a predetermined percentage of pan evaporation corrected for time of year and plant growth stage. Water use depends on time of year (canopy size & vigor), weather (wind, humidity, temperature), variety, other.

Pan evaporation, or checkbook irrigation scheduling, calls for periodic irrigation to replace water which has been lost as indiciated by evaporation.

Pan evaporation and crop water loss readings are frequently provided by consultants who also recommend irrigation regimes which account for crop species, soil type, stage of growth, time of year and so on. A great deal of precision can be achieved using this approach but occasional measurements of actual soil moisture are required for insurance.

• Soil Water Content --Evapotranspiration provides a good, but indirect, method for estimating crop water use and remaining soil moisture. Soil moisture can also be estimated directly by use of the:

o Feel method – stickiness, ribboning, shovel feel & color; demands experience

o gravimetric – A soil sample is collected, weighed, oven dried to virtually zero moisture content and then reweighed. Soil moisture content can be calculated based on the before and after weights.

o Neutron probe – neutrons are emitted and counted to determine the amount of reflection which is related to soil moisture. Probe readings are made in access tubes ranging as much as 3 feet or more into the soil profile.

• Soil water potential -- Is measured as tension (pressure or vacuum) or electrical conductivity.
o tensiometers (actual soil suction on a water column, etc., is measured directly as pressure/vacuum.
o gypsum blocks (electrical conductivity)
o Granular matrix sensors (electrical conductivity)

 

Pest Management

Insect Control

 

Insect and disease control begin even before planting and continue throughout the rest of the season. As noted, systemic soil-applied insecticides applied before, during and after planting will control most insects for a major portion of the season. However, some foliar sprays begin during this phase and increase throughout the remainder of the growing season. Additional information on insects and their control including color images can be found at http://oregonstate.edu/potatoes/pestmana.htm and http://oregonstate.edu/Dept/IPPC

Potato insects can be roughly divided three major groups:

Insects which chew foliage – Colorado Potato Beetle, Cutworms, Armyworms, Alfalfa Looper, grasshoppers, Blister Beetles, Fleabeetles, Cucumber Beetles and Slugs

Sucking Insects -- stylet feeders (aphids), raspers (leafhoppers), spider mites, lygus bugs, thrips

Note: if we had more resistance to net necrosis from PLRV, we wouldn't have to spray nearly so much for aphids; some insecticides such
as sevin and some pyrethroids when used alone can build up aphid populations to damaging levels because they kill predators which tend to help keep aphid populations under control.

Insects which chew tubers – Wireworms, Fleabeetle Larvae, Tubermoth, White Grubs,Symphylans, and Slugs. Most insects in this group are controlled by soil-applied insecticides with the exception of Tuber Fleabeetle larvae which must be controlled at the adult phase to prevent egg deposition at the base of the plants.

Control Measures:

Foliar insects -- are controlled primarily chemically using a combination of systemic (early to mid-season) and foliar (late) insecticides— systemics such as aldicarb, thimet, di-syston, furadan, admire and foliars such as Monitor, guthion, sevin, pyrethroids.

Insects which feed on tubers – A combination of chemical and crop rotation helps to control soilborne insects. A sod/grass pasture, for example, can lead to tremendous wireworm infestations.

Late season control of foliar insects is typically achieved by foliar sprays of materials such as Monitor, Guthion, Sevin, various pyrethroids, etc.

-- One note of caution, the use of materials such as Sevin which kill predators but do not harm prey species can cause prey species such as aphids to explode far beyond levels which would be present had the crop not been sprayed at all.

Russet Burbank and certain other potato varieties are highly susceptible to net necrosis caused by the Potato Leafroll Virus which is vectored by the Green Peach Aphid. Therefore, extraordinarily strict aphid control is required for such varieties.The presence of viruses in seed potatoes also call for heightened aphid control. Aphids typically do not damage potato plants excessively except in that they vector viruses.

Weed Management

Herbicides are typically applied before, during or shortly after planting. Some may be applied later in the season depending on need.
Roundup, metribuzin (sencor, lexone), dual, prowl, treflan, roundup
Seehttp://oregonstate.edu/potatoes/pestmana.htm#Weeds and http://pnwpest.org/pnw/weeds for additional weed management recommendations

Disease Management

 

See http://oregonstate.edu/potatoes/pestmana.htm for additional descriptions, organisms, cultural and chemical control recommendations). Disease 
Control is best achieved by the combination of good seed, intelligent cultural management, the use of resistant varieties, and agrochemical sprays. 

 

Fungi

Soilborne fungi—Several notable fungal diseases are primarily soilborne but can be spread by infected seed potatoes and moving soil and plant debris from field to field by dirty equipment.

Verticillium wilt causes a condition called “early dying” due to blockage of the vascular system which weakens the plant and eventually causes death. It is controlled by combatting the symptoms by maintaining low plant stress through cereful use of irrigation and fertilier.

Long rotations with non-susceptible crops such as corn and cereals really help.

Fumigation works well but is extremely expensive (~$300/acre?) and only temporary

Rhizoctonia and common scab are strictly cosmetic concerns. Both cause surfacelesions on tubers. Rhizoctonia lesions occur as small dark patches that won’t was off; scab lesions appear much as the name implies. The use of healthy seed, crop rotation, proper soil moisture and some agrochemicals seem to help reduce problems with these two diseases. Growers often attempt to maintain a relatively low (6.0, etc.) pH to control scab.

Pink rot (Phytopthora erythroseptica) typically occurs as a result of prolonged wet soils during the latter part of the season. Pink rot can lead to bacterial soft rots and the combination of those two can lead to devastating losses in storage. 

Fusarium sp. can lead to a number of diseases including Fusarium wilt, fusarium seed piece and tuber decay, etc.

Foliar fungi --A number of well-known diseases fall into this category.

Late blight (Phytopthora infestans) is perhaps the world’s most important potato disease because it not only attacks plant foliage but also attacks tubers in the field as spores drop from the foliage and travel through soil cracks and pores in irrigation and rainwater to attack tubers. Earlytuberinfections are difficult to detect and tubers may be stored with devastating results unless the grower takes special precautions. Late blight tuber decay is almost invariably followed by soft rot bacteria which can rapidly reduce tubers and an entire storage to mush. Late blight survives primarily on living plant debris, so volunteer plants, cull piles and infected seed are major sources. Infection is greatly favored by cool, wet weather. Control is usually achieved by spraying fungicides (Mancozeb, Bravo, Coppers, Duter, Polyram, Super Tin,etc.) both before and during infection. Prevention is much more effective than curing with regard to late blight. In situations with bad weather and heavy blight pressure, crop loss can be very difficult to prevent. Growers must sometimes salvage a crop and market it immediately without attempting to store. Severe late blight and long-term storaage are mutually exclusive.

Early blight (Alternaria solani) is primarily a “weak plant” foliar disease which attacks late in the season. Early blight can destroy enough foliage to reduce yields, but not often. It can attack tubers but symptoms are usually mild, rare and relatively minor compared to late blight. Early blight is controlled by most fungicides listed for late blight. Maintaining a healthy crop through careful fertilization and irrigation can also reduce problems with early blight. 

White mold or Sclerotinia (Sclerotium rolfsii).

Bacteria

Bacterial Ring Rot is 100% seedborneand does not survive for long in the absence of living potato tissue. It enters the plant through wounds, etc., and travels through the vascular system which becomes infected and filled with a white ooze or cheesy exudates. BRR symptoms are confined to the vascular ring in tubers early but soon moves throughout the tuber to cause total decay. This disease is so infectious that all seed certifying agencies insist on an absolute zero tolerance. In the past, fields with BRR were banned from seed production for up to 5 years and entire farms may be banned from seed sales for a period. Seed growers with a reputation for having BRR seldom survive for long.Because it is seedborne, the best control is to purchase non-infected seed and to observe good sanitation during cutting to avoid spreading the disease to non-infected seed lots.

Bacterial Soft Rots (Erwinia sp.) – Bacterial soft rots cause various forms of tuber, plant and seed piece decay, especially under anaerobic conditions which favor he bacterial but seriously constrain plant respiration, etc. Bacterial soft rot is typically a secondary invader following harvest injury, seed cutting, frost or other mechanical injury or fungal diseases such as pink rot, late blight, and sclerotinia. Cold, wet conditions often favor a disease called “black leg” caused by Erwinia atroseptica. As the name implies, plant stems or “legs” turn black and necrotic just above and below the soil line causing plant death and loss of stand. At one time blackleg was thought to be 100% seedborne but pathologists have since discovered that the causal bacteria are universal, occurring in well water, ocean water, snows at the top of Pikes Peak, and so on.

Control Measures

Because we have no true bacteriacides, bacteria are best controlled through prevention of wet anaerobic soils, careful handling of potatoes before storage, careful seed selection and handling (sanitary cutting, liberal use of seed piece fungicides), and the prevention of diseases which allow bacteria to invade. Also, avoid soil crusting, prolonged saturation.

Viruses see http://oregonstate.edu/potatoes/pestmana.htm for additional information including images, descriptions and recommended control measures. Potatoes are susceptible to a number of viruses including several Mosaic viruses (Potato Virus Y, PVX, PVS, PVM, PVA, etc.), Potato Leafroll Virus (PLRV) Potato Spindleltuber Viroid and several lesser viruses. Viruses are best controlled through the use of healthy seed and control of aphid vectors. No commercial "viricides" are available, at least none which kill viruses but spare the plants.

PLRV, unlike most potato viruses is spread systemically by the Greenpeach Aphid. That is, after the aphid feeds on an infected plant, the virus is multiplied in the aphid’s body and then spread each time the aphid feeds on a new plant throughout the aphid’s life. Some gpa overwinter with the virus still intact. Therefore, great efforts are taken to separate seed potato fields from peach trees and their relativies.

Mosaic viruses, with the exception of PVX which is mechanically spread, are vectored by aphids but not in a systemic matter. That is, the virus is borne on the aphid and can only be spread to the next one or two plants the aphid feeds on.

PVX is spread mechanically by equipment, clothing, cutting machines and so forth. Since it is “sap-transmitted”, it is also probably spread by chewing insects to some extent.

Check Disease Pyramid --------------- Pathogen, host, environment = disease

 

Sprout control – Sprout control measures can be taken either in the field with the use of Maleic Hydrazide or in the storage using CIPC, or Chloroipc. Both materials stop cell division and must be used carefully for that reason. 

MH-30 MH-30 (sprout inhibitor)—is applied to healthy plants, when the smallest tuber to be saved is no bigger than golf ball. Maleic hydrazide moves systemically from the leaves throughout the plant to the tubers where it effectively stops cell division but not cell enlargement. If the full complement of cells is not present, tuber size and yield can be much reduced. The potato tuber has most ifs cell well before it reaches golfball size and tuber growth after that stage is largely a matter of cell expansion. MH-30 must be applied to healthy, growing plants at least 2-3 weeks before vine kill to allow sufficient time for translocation and activation.

 

Vine kill—Potato vines are killed to “mature” the tubers and aid harvest by reducing overall mass. Tubers will not thicken or “mature” skins until they stop growing; otherwise, the tuber skins would stretch causing a problem referred to as “growth cracks”. Further, tuber growth will not cease until the vines are dead. For that reason, timely vine kill with 'contact' herbicides is an important component of most commercial potato operations. Systemic chemicals such as Roundup would obviously kill the tubers as well as the plants. Vine killers must not translocate from the vines to the tubers.

Vines are typically killed 2-3 weeks before harvest to allow sufficient time for the vines to die and the tubers to mature. Common herbicides used for potato vine desiccation include Diquat, Des-I-Cate, Sulfuric acid).  Some early fresh market and direct to processor spuds are dug green; that is, vines are still attached until they are removed in the harvest operation.

13.Harvest

 

Harvest dates – Oregon potatoes are harvested from July 1 through the end of November. Early-harvested potatoes are typically harvested green for the early tablestock market or for out-of-field processing. Stored potatoes are typically harvested in September and October but sometimes extending into October because of weather problems. The danger of freezing injury can be severe even in late November in some eastern Oregon producing areas.

Potatoes for storage should be harvested warm (>45F) but not hot (<65F) and moist (available soil water >60%) but not wet or muddy. Temperatures below 45F can lead to excessive mechanical damage during harvest including cuts and also shatter bruise. Tubers warmer than 65F can be very difficult to cool in storage because of the mass of the potato pile. It is often difficult to cool most Oregon potato storages faster than 0.5 degrees F/day. 

Harvest is virtually 100% mechanical. A potato “combine” typically digs 2-6 rows at once at a speed of 1-1.5 mph. The potatoes are moved over a series of chains which tend to eliminate all soil and vines. Sorters on the combine remove decaying potatoes and other debris and the clean potatoes are then dumped via a boom into a truck moving along beside the harvester. It is vital that drops be minimized so that tubers are not injured. All drops should be well padded insofar as possible and minimized in every instance. Needless to say, it is important that only healthy potatoes go into storage and that all mud, rocks, decayed potatoes, debris and other material be left in the field.Potatoes should be moved straight from the field to the storage to prevent overheating or freezing. If the crop is diseased or has other problems, potatoes are sometimes graded into storage to help reduce problems later.

14. Storage

Typical bulk storage pile -- may range from 10 - 20 feet deep

For additional info on potato storage, see http://oregonstate.edu/potatoes/storproc.htm and http://oregonstate.edu/potatoes/potliv.html#Storage

Purpose:

The objective of potato storage is to maintain tuber quality, not necessarily improve it:

  • conserve moisture in tubers by maintaining high humidity (crop can lose up to 9% through dehydration!)
  • prevent excessive decay by judicious air movement, humidification, temperature control
  • retard sprouting (low temperature plus CIPC?)
  • prevent greening (exclude light)
  • maintain acceptable carbohydrate (sugar vs. starch) balance through temp control
  • optimize respiration

Respiration

C6H12O6 + O2--------> CO2 + H2O + Energy (heat)

Sugar -----> carbon dioxide + water + energy (heat

Respiration is temperature-dependent; doubles for each 10F increase in temperature. It is lowest at about 36-38F, which means the tuber is using minimal carbohydrate reserves and decay is retarded; however, this temperature is too low for good processing quality because sugars build up (see temperature recommendations below). Storage operations must provide oxygen and remove respiratory products (heat, carbon dioxide and water)

Photosynthesis

CO2 + H2O + Energy (Light) ----chlorophyll ---> sugar + water + oxygen

Facilities/fixtures:

  • well-insulated building (to prevent condensation and "rain") with an intact, internal vapor barrier to protect insulation (explain)
  • humidifiers
  • aeration tools -- fans, louvers, duct systems, automatic controls (thermostats, proportioning dampers, humidistats)
  • few on-farm storages are refrigerated; they rely on judicious movement of air either through "ventilation" (exchanged of air between the storage and outside) or "recirculation" (movement of air strictly within the storage)

Question: how could a farmer lower storage temperature to 45F for processing potatoes when the average day-time temperature might be 50F or above? (Ventilate only at night or when temperatures are favorable)

Methods:

Storage objectivies are accomplished through, darkness, humidification and judicious movement of air. Air is generally moved upward through the pile of potatoes which may be 12-22 feet deep via a series of plenums and lateral ducts spaced about 8 feet apart.. Air is moved at 0.5-1.0 cfm (cubic feet per minute) per cwt, or 10-20 cfm/ton. Air movement may be constant at times, but is usually intermittent with fans running about half the time after the first month or so of storage.

Storage Duration:

Up to 10 or 11 months but usually less than 6

A typical storage sequence:

  1. storage is cleaned, made ready, all controls functioning before the first load of spuds
  2. during the first 10 days, temperature is held at 55-60F and high humidity, and lots of air movement to promote healing (or suberization) which will retard decay later in the storage.
  3. after suberization period, temperature is lowered by half a degree per day to the final storage temperature.
  4. CIPC may be fogged into storage for sprout control after wounds have healed but before sprouts begin to develop.
  5. final storage temp depends on use:
    seed---------36-38F
    tablestock---38-42
    froz. proc.--42-45
    chips--------45-50

Low temperatures -------> High reducing sugars

Low sugars <---------- High temperatures

High sugars ----------------> dark-colored fried products (not desirable)

 

If disease or excess moisture is present on tubers, high humidity is very dangerous. Dry diseased or wet potatoes by rapid movement of fairly dry air. Also, must prevent free water on potatoes from condensing on storage walls, ceilings, warm air on cold potatoes (water condenses on tuber skins like dew on a glass of cold water). Watch ventilation/recirculation air temperatures!

Practice Exams

Practice Exam No. 1

This is a "closed book" exam.Please respond to any 10 of the following Questions.The instructor is fond of concise but thorough answers.Good luck.

1. For what reasons do we grow potatoes from seed pieces in the United States and not from true botanical seeds?

2.Why do potato varieties used for processing (chips or fries) have high starch and low reducing sugar concentrations?What is the relationship between tuber specific gravity and starch content?Why do tubers float/not float on water?

3.Assume you have two fields of different soil types.Both will be planted to potatoes.Field no. 1 has a silt loam soil while field no. 2 is coarse sand.How would irrigation regimes for the two fields differ?Which would require the most water during the season?How would total application rates per irrigation event differ?How would irrigation frequencies differ between the two fields?

4.What is a potato tuber?List the major anatomical features, internal (compositional) components.

5.Describe typical storage regimes for chipping and seed potatoes (temperature, humidity, etc).How do they differ and why?

6.Why and how do we kill vines?Why is Diquat recommended for vine killing while Roundup is not?

7.What are the major products of tuber respiration and how are they controlled in storage?

8.What do we mean by "systemic" as opposed to topical pesticides?What advantages would a systemic fungicide offer for late blight control in rainfed production areas?

9.Are green potatoes poisonous?

10.Explain why potato yields are higher in the Columbia Basin than in Central Oregon?

11.What is the relationship between the green peach aphid and potato leafroll virus (PLRV).Why are seed potatoes not grown in the Willamette Valley?

12.Define the potato taxonomically.What genus?Species?List some important cultivated relatives.

Practice Exam No. 2

Please respond to the following questions.The instructor is impressed by concise, but thorough answers.Good luck.

1. .Define the terms: (1) "crop available water", (2) "infiltration rate" and (3) "soil water-holding capacity".

2.How do items 2 and 3 in question no. 1 affect: (1) the rate at which water can be applied (inches/hour, etc.), (2) the total amount of water which can be applied in a single irrigation and (3) irrigation frequency (i.e., irrigations/month, etc.).

3.Why is the potato tuber considered to be an underground "stem"?

4.Wy do growers store seed potatoes at approximately 36-38F and chipping potatoes at 50F?

5.Show the respiratory equation and describe how farmers control the process and its products in potato storages.

6.How do tuber carbohydrate fractions (starch and sugar) affect potato chip quality?

7.Assume you are planning to grow potatoes in a new field in the Willamette Valley.How would you determine fertilizer rates?Would a similar potato field in the Columbia Basin require more or less fertilizer during the season?Why?

8.Potato Leafroll Virus (PLRV) seriously reduces yield and quality in some varieties.How is the disease controlled?

9.What is the scientific name of the cultivated potato?What are some closely related crops?Why are wild, uncultivated potato species important to us?

10.Why must potato storages be well insulated?

Optional (maybe some extra credit if needed/warranted; total score cannot exceed 100)

11.What type of disease (name, type of organism--bacterium, virus, etc.) caused the "Irish Famine" of the mid-1840's?How is it controlled today? In Oregon, why is the disease more prevalent in the Willamette Valley than in eastern Oregon?In what geographical region did it probably originate?

Practice Exam No. 3

Please respond to the following questions.The instructor is impressed by concise, but thorough answers.Good luck.

1.Define the terms: (1) "crop available water", (2) "infiltration rate" and (3) "soil water-holding capacity".

2.How do items 2 and 3 in question no. 1 affect: (1) the rate at which water can be applied (inches/hour, etc.), (2) the total amount of water which can be applied in a single irrigation and (3) irrigation frequency (i.e., irrigations/month, etc.).

3.Why is the potato tuber considered to be an underground "stem"?

4.Wy do growers store seed potatoes at approximately 36-38F and chipping potatoes at 50F?

5.Show the respiratory equation and describe how farmers control the process and its products in potato storages.

6.How do tuber carbohydrate fractions (starch and sugar) affect potato chip quality?

7.Assume you are planning to grow potatoes in a new field in the Willamette Valley.How would you determine fertilizer rates?Would a similar potato field in the Columbia Basin require more or less fertilizer during the season?Why?

8.Potato Leafroll Virus (PLRV) seriously reduces yield and quality in some varieties.How is the disease controlled?

9.What is the scientific name of the cultivated potato?What are some closely related crops?Why are wild, uncultivated potato species important to us?

10.Why must potato storages be well insulated?

Optional (maybe some extra credit if needed/warranted; total score cannot exceed 100)

11.What type of disease (name, type of organism--bacterium, virus, etc.) caused the "Irish Famine" of the mid-1840's?How is it controlled today?In Oregon, why is the disease more prevalent in the Willamette Valley than in eastern Oregon?In what geographical region did it probably originate?