Organic potatoes Cultivating quality - step by step - The ...
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TECHNICAL GUIDE
Organic potatoes
Cultivating quality – step by step
Potatoes are very suitable for direct preparation to plant protection, nutri-
marketing due to their popularity ent and water supply to harvest and
and versatility. But good yields are storage.
needed for commercial production to This guide provides a good basis for
cover the high costs of cultivation and achieving high-quality products. Com-
mechanisation. The very high quality mercial potato farms complement their
requirements at every stage of market- knowledge with the help of experts
ing require the highest care from seed and further literature.
2017
This publication results from the Organic Knowledge Network Arable project
funded by the Horizon 2020 programme of the European Union. net
arable
Quality at every stage Crop practices during the course of the year
The quality of potato
tubers can be significantly
influenced before, dur-
ing and after cultivation.
Measures that have a
significant effect on the
final product quality are
Planting Emergence Foliation/ Main stem Crop F
marked in this manual Stem formation elongation covering
with the sign above.
Potato cyst nematode
Basic fertilising
(e.g. manure in autumn) Order boxes
Ploughing
Cover early potatoes
Harrowing Irrigation of early potatoes
for frost protection
Presprouting Planting
Irrigation
Organic/mineral fertilisers
Organic manure
Leaf blight
Nutrient supply
Harrowing
General crop maintenance
Field visit and assessm
Plant protection
Rotary hoe
Harvest
Ridge-shaping board
Biodynamic measures
Apply horn silica
Choice of production
First / Second early potatoes Processing potatoes
Only in places with suitable climatic conditions Depending on use, there are special requirements
on quickly warming soil where planting is pos- (variety, size, shape, starch content, test baking, etc.).
sible from end of February / beginning of March Only cultivate in agreement with a buyer (cultiva-
onwards. tion and supply contracts).
Requires equipment for chitting. Increasingly important.
Cultivation under fleece can speed up develop-
ment (see page 10). Peeled potatoes
If a pipe irrigation system is available, it can be Direct marketing of peeled potatoes to industrial
used to prevent frost. kitchens.
Careful harvesting is required. Marketing to peeling companies via contracted
Good for farms that can attain high prices for early cultivation.
produce. Direct marketing requires specialist knowledge of
peeling processes.
Maincrop potatoes
Suitable for wholesale and direct marketers. Baby potatoes
Fairly stable prices. Very small potatoes that have set skins.
Sufficient distance between fields with early and Lower yields and higher prices than ware potatoes.
maincrop potatoes to prevent transmission of Ideal for light and sandy soils without stones.
blight. Machinery needs to be adjusted (very close plant
spacing, fine sieve belt, boxes with small gaps).
Varieties with a high number of tubers per plant
should be used.
2 Organic potatoes 2017 FiBL & ORC
Site requirements Soil
Sandy, quick-drying
•• Light to medium soils that warm up easily, are soils lead to rougher
not too stony, and are deep with even water skins and russeting
supply and a pH of 5.5 to 7. as well as raised scab
•• Avoid compaction and poorly drained soils. infection.
•• During flowering and formation of tubers, pota- Moist soil conditions
toes are sensitive to long wet or dry periods. during formation of
Flowering Senescence Haulm Ripening
destruction of tubers Cultivation on plots with irrigation systems is tubers lead to netted
beneficial in dry periods. scab.
Acidic soils, soils heavy
in clay or contamina
ted with spores can
Sample dig
and tasting lead to powdery scab.
Haulm destruction Note:
In areas of high rainfall,
Harvest ploughing and manure
application in Autumn
would be inadvisable
due to the risks of leach-
ing and erosion.
Soil type affects the shape, colour and overall appeal
of the tubers. On lighter soils, most tubers develop a
Variety selection
ment in seed potatoes nicer shape and colour as well as flatter eyes. On heavy
soils that are slow to warm up, the tubers turn out more The risk of scab, hollow
smooth-skinned and occurrence of scab is lower. hearts, dry core, late
blight, silver scurf, black-
leg etc. is reduced by
selecting the appropriate
Variety selection variety. However, there is
a compound no variety immune to all
these conditions. Hence,
In organic farming, mainly varieties that are in mar-
the growing conditions in
ket demand and accepted by retailers are cultivat-
the region and on single
Seed potatoes ed. Direct sellers have a bit more freedom in terms
fields must be considered
Only possible in contract with seed producing of variety.
when making the selec-
organisations; requires specialist knowledge. Varieties that develop quickly at a young stage
tion. Regional recommen
Cultivate with sufficient distance from other and form tubers early (so that a good yield has
dations for varieties may
potato plots to avoid viral infection and blight. already been reached when blight starts to appear)
Production at higher altitudes results in more be helpful in organic
should be chosen. They should also have low sus-
slow-sprouting planting material. potato cultivation.
ceptibility to diseases, low nitrogen requirements
and quickly develop a canopy to suppress weeds.
Heritage varieties Notes:
However, the intended use and the wishes of cus-
Speciality: only cultivate them in agreement with The planting material
tomers or buyers play the biggest role in selection.
buyer or sell directly. must be derived from
Choosing a new variety should be discussed with
Conserving varieties: Organisations such as Skea
the buyer beforehand: before new varieties are cul- organic propagation
Organics in the UK may be able to help with
tivated, a market should be ensured. In direct mar- (see ‘Planting material’
sourcing Heritage varieties, but demand is mainly
keting, customers should be gradually introduced on page 5 and ‘Further
from domestic gardeners.
to the new variety. reading’ on page 28).
Often lower yields than modern varieties, higher
wholesale prices. In the UK, the AHDB Potato Variety Database
Planting material considerably more expensive provides independent data on GB-certified potato The Louis Bolk Institute
than for modern varieties. varieties that have undergone independent resis in the Netherlands has
Some are rather susceptible to late blight as well tance testing for key pests, diseases and patho- done a lot of work on
as viral diseases (provide regular change of seed breeding and marketing
gens. Testing is undertaken through the AHDB
planting material, increase distance from other blight resistant varieties
Potatoes-funded Independent Variety Trials (IVT)
potato fields, choose separate fields). (see pages 11–12 for
programme.
more information on
blight resistance).
Organic potatoes 2017 FiBL & ORC 3
Crop rotation Position within the crop rotation
Perennial grass/clover
as a preceding crop
may promote infesta- General rules:
tion with wireworms, •• Keep a rotation break of at least 4 years the winter months; however, tillage in spring is
scab, dry core and (includes early potatoes). often necessary due to frost on soils that con-
slugs. •• Avoid soil compaction when harvesting pre tain more clay. In the case of an early tillage,
Intensive tillage in the ceding and catch crops. cover crops that are killed by frost in winter
crop rotation reduces •• Potatoes have relatively high nutritional re should be cultivated.
the risk of wireworms. quirements; moreover, the nutrients should •• Potatoes leave a lot of soluble nitrogen in the
Large amounts of be available shortly after emergence. Hence, soil, with the potential risk of leaching. For this
organic matter with a potatoes develop especially well after preced- reason, the succeeding crop to be cultivated
high carbon-to-nitro- ing crops that support the looseness and should be one that utilises the nitrogen in
gen ratio as a preced- structure of the soil and leave a high amount autumn, such as winter cereals / brassicas or
ing crop can lead to of easily degradable organic material. Suita- green manure with late nitrogen absorption
locked-up nitrogen and ble preceding crops include a one-year grass/ (e. g. rye).
Rhizoctonia. clover ley, one-year fodder and grain legumes •• Potatoes generally leave a clean seed bed for
(especially field beans and grain peas with the succeeding crop. Ploughless tillage pre-
a cover crop, field vegetables and other root serves the soil structure and facilitates frosting
Grains CC/ Potato
Grains CC/
GM Potato crops, grains with legume cover crop). of remaining tubers to avoid volunteers.
GM •• Tillage in spring before potato cultivation
reduces the risk of nutrient leaching during
Grains CC/ Potato
GM
CC/
Vegetables crops
Preceding Suitability Notes
Vegetables CC/
GM
GM
Pure stands of legumes such as vetches, or a brassica such as fodder radish (may
Grains CC/ Potato help suppress PCN) are ideal as catch crops and green manure after grains.
GM
Vegetables CC/
GM
Grain CC/ Fodder radish and, on locations that do not tend to develop iron spots, also mustard
Grain
legumes CC/
GM are ideal as catch crops and green manure after grain legumes.
legumes GM
Pure grass or grains as catch crops should be avoided. The high carbon-to-nitrogen
Vegetables CC/ ratio in spring leads to a slow conversion of organic matter.
Grain GM
CC/
Grains CC/
legumes GM Potato
GM Grass /clover before potatoes should be for one year only. Longer-term grass/clover
Grass/clover increases risk of infestation with wireworms and the rate of turnover is slower than
Grass/clover with one-year grass /clover.
Grain CC/
legumes GM Potatoes are a good component of a vegetable rotation.
Grass/clover
Vegetables CC/ There is an increased risk of slug infestation.
GM
Maize GM After late harvested vegetable varieties, sowing green manures is more difficult.
Maize GM
Undersown crop On vegetable farms, vegetables often serve as follow-on crops to early potatoes.
Undersown crop
Grass/clover Since both maize and potatoes have a strong demand for nutrients, this combina-
Maize GM tion is only recommended for farms with a high nutrient base.
CC/
Grain crop
Undersown
legumes GM Soil compaction during maize harvesting can affect the soil structure.
Remaining stubble can increase the risk of Rhizoctonia in potatoes; hence, the stub-
ble should be shredded as small as possible.
Maize GM
Succeeding crops
Undersown crop
Grass/clover Winter cereal On lighter soils, barley, triticale and rye are more suitable than winter wheat or spelt
Winter cereal due to the early sowing date and tillering in the year of sowing.
On heavy soils, winter wheat is more suitable (there is, however, a risk of nitrate
loss).
Maize GM Spring Spring cropping is only recommended after a catch crop. Forage rye or grass are good
Undersown crop CC Spring catch crops. Mustard also tends to develop fast and captures nitrogen. Only choose
CC crop
crop cruciferous plants if there are no other brassica plants within the crop rotation.
Possible succeeding crops are summer cereals (e. g. oat), maize or vegetables.
CC = catch crop; GM = green manure
Winter cereal
Winter cereal
4 Organic potatoes 2017 FiBL & ORC
Planting material Planting material
Certified planting
In principle, the planting material must originate Preparation of planting material, chitting material reduces the
from organic propagation. Current availability of •• If possible, planting material should be chitted, risk of infection with
organic seed and planting material can be checked or at least vernalised. tuber diseases.
on the organic seed database www.organicxseeds. •• Chitted plants emerge faster and are better Watch out for a low
co.uk. The range of varieties from organic prop- weed suppressors. Moreover, chitting leads to infection of Rhizoctonia.
agation as well as the description of the varieties fewer sprouts and thus to fewer stems per unit Dressing of planting
and the ordering addresses can be requested from area of foliage. This, in turn, reduces the number material with antago-
organic advisory services or directly from seed asso- of tubers, but increases their size. nists (e. g Bacillus sub-
ciations. If there is no organic seed material availa- •• Disadvantages include: investment costs, addi- tilis and Pseudomonas
ble for certain varieties, a special derogation from tional workload and the risk of too long sprouts. sp.) may reduce infec
the inspection body is required before purchase. •• The costs of £ 500 to £ 600 (or 500 to 600 ¤) tion with Rhizoctonia
Sources of seed can be found on organicXseeds. per ha are reclaimed through higher yields and and dry core, but pota-
In general, only healthy and certified planting yield security. to seed dressing is not
material (seed) should be used. After receiving •• The age of the planting material, the vernalisa- common practice in
the planting material, one should empty the bags tion, the variety, the maturity group and the utili- the UK.
and bulk packs and wash a sample of the seeds. sation all influence the chitting procedure.
Quality defects (e. g. black scurf (Rhizoctonia) •• Temperature has the largest influence on the
marks, wet rot) should be reported to the supplier number of later sprouts.
immediately (keep the labels). •• New potatoes should have fewer sprouts in
The same quality criteria apply when using order to reach the required size quickly. Seed
saved, non-certified planting material. It is strong- potatoes should have more sprouts.
ly recommended to check it for viruses and other •• Chitted tubers should be planted only with the Chitting
defects like Rhizoctonia, leaf blight, bacterial wilt, appropriate technology (rolling-floor planter, belt Chitting is one of the
etc. Calibrating planting material facilitates cultiva- planters) to prevent breaking off sprouts. most important meas-
tion and improves the overall health of the crop. •• Empty chitting boxes and bags carefully, to pre- ures for yield security:
vent sprouts from breaking. it shortens the time
Amount of planting material needed to harvest by 10 to 14
•• Seed rate and plant density can be estimated Work steps for chitting days, reducing the risk
from target yield and optimum seed size, as 1. Start chitting 4–6 weeks before the desired of late blight infection.
well as seed age (time from emergence of planting date (new potatoes up to 10 weeks). Chitting accelerates
seed crop to planting of current crop). 2. Thermal treatment: 18–20 °C over 2–3 days. emergence and thus
•• Seed rate calculations are variety specific. For 3. Lower temperature to 10–12 °C (new pota- reduces the likelihood
guides see on the AHDB website. Where specific toes: 15 °C, seed potatoes: 8–10 °C). of the sensitive sprouts
varieties are unavailable interpolation is required. 4. As soon as the sprouts start to show, being infected with
•• Standard (emerged 1 June): Count 50 kg sam- expose the potatoes to daylight or artificial Rhizoctonia (Black
ple to determine tuber seed count. Determine light (lamps with warm tones, >100 W per scurf) or Erwinia
target yield (experience and field history) and t of planting material). 8–10 hours per day. (Blackleg).
optimum tuber size. This information will give Maintain a humidity of 70–80 %.
you the seed rate. Multiplying this by the area 5. At the end of the chitting period, lower the
to be planted gives you the total seed required. temperature to 5–6 °C for hardening off.
Within-row spacing (cm) can be calculated 6. Before planting, raise the temp. to 10–15 °C.
using plant density and row width (see page
9) according to the following formula: 100,000/
Chitting containers Notes
(plant density (000/ha) x row width (cm)) e. g.
with a row spacing of 75 cm and planting space Chitting boxes: •• Fill-in 2, max. 3 layers; about 10 kg per box.
of 33 cm within the rows, about 40,000 tubers white plastic trays, •• At planting, take tubers directly from the crates.
per ha are needed. With a grading between 35 60 × 40 × 18 cm, •• Sort out sick tubers during the transfer.
and 55 mm, this will result in about 2,500 kg of 4 piles on a Euro-pallet •• Large workload for transfer, stacking, transport.
planting material, depending on the variety. Chitting bags: hanging •• Hardly any manual work when using a fully
•• Plant populations below 26,000 plants/ha are mesh bags on metal automated machine.
not generally recommended. Planting at wide frames, 125 kg capacity, •• Low space requirement outside chitting period.
spacings can result in gappy crops particularly 5 tubers are juxtaposed •• Clumping of tubers in case of delayed planting.
where planting is irregular or emergence poor.
Large boxes: flat (wire) •• Low workload.
Total yield may be reduced as a result so plant-
crates with a second •• Unequal formation of sprouts, therefore limited
ing at higher densities should be considered,
'cage' holding the inside suitability.
although increasing plant density can be expect-
up to a coat of 30 cm
ed to reduce the average tuber size.
Organic potatoes 2017 FiBL & ORC 5
Nutrient supply Nutrient supply
In order to prevent
Rhizoctonia, use only Potassium •• A good nitrogen supply results in stronger leaf
processed, well-rotted •• Potatoes are among the most potassium-hun- growth. This leads to earlier crop covering and
manure and apply it in gry plants in agricultural production. Potassium better weed suppression.
autumn on the preced- is the mineral with the highest concentrations in •• The more nitrogen is stored in the leaves, the
ing or catch crop. the potato plants and tubers. more tubers develop daily and the longer yield
For fertilising in spring, •• Potassium is important for the development of production lasts (unless leaf blight occurs).
use aerated slurry or starch. Moreover, it improves the shelf life and While during the formation of the tubers, the
nitrogen rich manure. reduces the number of damaged tubers. How- plant continues to extract nitrogen from the soil,
A good supply of potas- ever, too high a supply of potassium can have the majority of the necessary nitrogen is trans-
sium and magnesium a negative impact on dry matter and starch con- ferred from the leaves. When the nitrogen sup-
increases the quality, tent. ply in the leaves is exhausted, the tubers mature.
prevents damage and •• A sufficient supply of potassium increases the •• In healthy crops, a good N supply leads to an
internal bruises and amount of organic acids and the vitamin C increase in large tubers and to a higher indivi
improves shelf life. content in the tubers. This, in turn, leads to a dual weight of the tubers. However, it can also
Liming before or dur- decrease of discolouration in the raw state and lead to an increase in hollow hearts, secondary
ing the cultivation of after cooking, as well as a reduction in bruising. growth, and growth tears.
potatoes increases the •• Potassium from farm fertiliser (manure, slurry, •• If the N supply is too high, the constant devel-
risk of scab infection. etc.) can be fully taken into account. If neces- opment of new leaves and stems can create a
A high nitrogen sup- sary, organically approved potassium fertilisers large, dense foliage. This can result in delayed
ply in late summer (potassium sulphate) are available with prior formation of tubers and a decrease in growth
can have a negative approval. rate. Early infestation of leaf blight could in this
effect on dry matter case lead to losses of revenue.
and nitrogen content, Nitrogen •• An N supply that is too high, or rather too late,
and hence on the •• From planting to emergence, the potato lives off has a negative impact on dry matter and starch
flavour. Furthermore, it the mother tuber’s reserves. content, as well as processing properties and
increases susceptibility •• The potato crop needs the majority of the nitro- flavour.
to damage, and to dis- gen during the short period between emergence •• A too high release of N in late summer with a
colouration in the raw and tuber development. An optimal nitrog en low K supply at the same time impairs matu-
state and after cooking, supply within the first 35 to 50 days after emer- ration due to re-sprouting. This, in turn, compli-
as well as reducing gence contributes to a good tuber growth and is cates haulm destruction.
storability. the most important requirement for good yields.
•• The nitrogen demand of potatoes depends on Release of nitrogen from the soil
the variety, local conditions and yield expecta- •• Biologically active soils deliver about 20 kg
tion. It varies between 80 and 140 kg available of N per ha (the higher the fertilisation or the
N per hectare. amount of pre-crop residues, the higher is the
N-mineralisation) under favourable mineralisa-
tion conditions during the vegetation period.
Important to know
•• With the first two field operations (ridging/hoe-
•• Organic farming uses organically bound
ing), approximately 10–20 kg N per ha are addi-
nutrients as fertilisers. Organic farmers ‘feed’
tionally mineralised.
the microorganisms in the soil, which make
the nutrients available for the plants.
Nitrogen from the preceding crop
•• The release of nitrogen from fertilisers
•• One-year fodder and grain legumes are among
depends on the amount of fertiliser, or rath-
the most favourable preceding crops.
er the nitrogen content, the type of fertiliser
•• Ploughed grass/clover provides 80–140 kg avail-
and the conditions for mineralisation in the
able N per hectare, if the conditions for mineral-
soil. The more active the soil is, the higher
isation and timing are good. Ploughing of grass/
the soil organic matter content is, and the
clover should be avoided in the autumn to limit
better the aeration and weather conditions
the risk of leaching.
(soil moisture) are, the higher nitrogen
•• Grain legumes leave, depending on the varie-
mineralisation is.
ty, between 50 and 100 kg of available N per
•• The P and K content of soil can be low after
hectare to the succeeding crop (grain peas:
years of organic farming. That is why the P,
50–80 kg, field beans: up to 100 kg). After
K and Ca content should be checked every
grain peas, a catch crop should be cultivated to
5 to 10 years by means of a soil analysis.
organically bind nitrogen during the winter and
Manure and slurry are great suppliers of
protect it from leaching.
potassium.
6 Organic potatoes 2017 FiBL & ORC
Fertiliser
Manure
•• Cattle manure is very rich in K; pig manure con-
tains less K but higher amounts of P.
•• A dose of manure can be recommended as
basic fertilising. If there is danger of Rhizoctonia
infestation, the manure should be applied to
the preceding crop in autumn and not directly
to the potatoes. A reduced effect of the fertiliser
and the risk of nitrogen leaching should be kept
in mind!
•• It is recommended to use at most 25–30
tonnes of manure per hectare. Too large a dose
leads to a prolonged nitrogen supply, which
impedes the maturation of the crop. In the case
The nitrogen supply has a
of dryness or heavy soils, only the succeeding significant impact on outer
crop might benefit from the nutrients. The regu- •• Slurry should be applied ideally during the and inner quality features
lations limit nitrogen use to 170 kg per hectare. preceding crop or before planting. It should be of the potato as well as
worked into the soil immediately after applica- on yield.
Slurry tion.
•• Cattle slurry has relatively high K and N contents; •• 15–30 m3 of cattle slurry per hectare is recom- Note:
on the other hand, pig slurry has higher N and mended if applied in spring and immediately In the UK The Fertiliser
P contents. The nutrient contents of anaerobic worked in. Manual (RB209) can be
digestate depend heavily on the fermented sub- •• As doses increase (up to 150 kg N or 45 m3 used as a reference for
strates but are generally high in available N; they of slurry per hectare), yields decrease. These nutrient recommenda-
can be used effectively in potato farming. amounts should be applied to the preceding tions and nutrient con-
catch crop to avoid loss of quality and flavour. tent of organic manures.
Analytical methods for assessment of the Compost
N supply •• Like manure, composted manure and other
Nmin-analysis: composts provide a good supply of potassium
•• Nmin-levels in the soil at the beginning of the and magnesium. Composted manure has a
vegetation period have only a small signifi significantly lower effect on N supply than fresh
cance with regard to the estimation of the manure, or rather stacked manure.
expected tuber yields. •• Composts from plant material can also be used.
•• The N min-levels at the time of the emer- They deliver both macro- and micronutrients to
gence of the potato plants are more suitable the soil.
for the estimation of the tuber yields (ideal •• Compost may also offer additional benefits
values: 110–140 kg Nmin per ha). by suppressing phytopathogens in the soil to
Fertilising
reduce crop disease.
A balanced dose of
Leaf and stem juice analysis: manure can have a
kg per ha
•• Measurements in the growing plants can be positive effect on the
used to derive future, site-specific cultivation K content of the tubers,
recommendations. whereas excessive
•• For leaf analysis the total nitrogen content fertilising with manure
and, if necessary, further nutrients are deter- leads to a decrease of
mined in the uppermost, fully developed starch and dry matter
potato leaves. The analysis must be carried content in the tubers.
out in a laboratory. The total N content in the Doses of slurry and
dry mass of the leaves at flowering of the N that are too high
potatoes should be between 4 % and 6 %. can increase nitrate
•• The stem juice analysis can be carried out rel- content and decrease
atively simply and cost-effectively directly in dry matter and starch
Nutrient requirements
the field, by the farmer or the consultant. The Nutrient supply with manure
contents in the tubers.
stem juice is pressed out from the lower sec- Nutrient supply with slurry
Compost from plant
tions of the main stems and the nitrate con- Nutrient requirements for a yield of 25 tonnes per hec- material that is applied
tent is analysed with the Nitracheck reflec- tare and supply by typical farm fertilisers (15 t of manure in the planting furrows
tometer. At flowering, the nitrate content and 20 m3 of slurry per ha). Soil and pre-crop also can reduce Rhizoctonia
should be between 3500 and 4000 ppm. supply nitrogen.
infestation.
Organic potatoes 2017 FiBL & ORC 7
Purchased fertiliser sory services if a specific mineral deficiency is
•• Organic commercial N fertiliser enables fertilis- identified. Magnesium is particularly important
ing in spring with a low risk of Rhizoctonia infes- (particularly on lighter soils that may not supply
tation. enough), as are boron and manganese for yield
•• For potato farming, fertilisers that mineralise and quality.
quickly should be used. They should be applied
at time of planting, or at the latest when hoeing Plant and soil additives
for the first time. In order to increase the plants’ resilience and
•• When using ground legumes, field beans (fine- soil fertility, plant strengtheners and tonics can be
ly ground) are preferable to peas. used on organic farms. Examples are whey, stone
•• Due to the high costs, the use of organic N fer- meal, compounds with microorganisms, herb al
tiliser is only recommended if not enough farm extracts, compost teas or herbal teas. In many
manure is available and the soil is not suffi- cases, the effect and mode of action have not yet
ciently supplied with nitrogen. been studied or clarified, and the resulting yield
•• Phosphorus needs are normally met by manure increases have not been scientifically proven.
or compost. If additional phosphorus is needed,
rock phosphates or organic chicken manure can
Cost calculation (example) for applying
be used as supplements.
55 kg N per hectare of a purchased ferti
•• The use of mineral K fertiliser is only allowed if
liser containing N:
the deficiency is proven (soil analysis). In case
Fertiliser (11 % N): £ 65 (¤ 65) per 100 kg
of need consult your certification body. Potas-
Application: £ 30 (¤ 30) per hectare
sium is best applied as sulphate of potash (as
Total: £ 355 (¤ 355) per hectare
potatoes are susceptible to chloride toxicity).
At a selling price of £ 60 per 100 kg and an
•• Lime should not be applied to potatoes or the
80 % share of expenses, these costs are com-
preceding crops.
pensated if there is additional yield of 700 kg
•• The need to use leaf and trace element fertil-
per hectare. An additional yield can be achieved
isers must be documented clearly by the farm-
without problems despite a low N supply if the
er, e. g. by performing soil or leaf analyses. It is
supply can be improved by N fertilisers.
advisable to consult the Control Body or advi-
Tillage Soil and seedbed preparation
Tillage or planting
during wet soil con- Soil preparation •• Primary soil tillage should only be performed if
ditions leads to clods, •• During soil preparation, harvest ridges should the soil has dried sufficiently. The ideal time for
deformed tubers and be free of stones and clods because they inhib- primary soil tillage depends on the soil conditions
damage during harvest. it growth, deform the tubers and damage them and the location.
Cold, wet soils promo during harvest. If the amount of clods in the ridge •• In heavy soils, the primary soil tillage should be
te Rhizoctonia infection is 5–10 %, the proportion of tubers and clods done in late autumn, so that the soil dries faster
as early as during within the crop is the same. in spring.
sprouting. To improve •• When grass/clover is tilled or soils are heavy, the •• Lighter soils (sand, clayey sand or sandy clay) can
warming of soils, shal- use of a plough is appropriate. Using a chisel be tilled in spring (after catch crop cultivation),
low ridges should be plough is recommended on medium-heavy soils possibly with reconsolidation.
built from the start. and in dry areas (to conserve water).
Seedbed preparation
•• The less the soil is compacted before planting,
the better.
•• On light soils, prepare the seedbed with a spring
tine cultivator including a cage roller / packer. On
heavier soils, use a rotary harrow (watch out for
soil moisture within the tilled area, otherwise soil
smearing might occur!).
•• If possible, only one operation should be per-
formed in spring: e.g. with a front-mounted rota-
ry harrow (possibly with shaping board) and a
rear-mounted potato planter.
For soft, gentle planting, the seedbed should have settled,
have fine crumbly soil, be free of clods and be dry.
8 Organic potatoes 2017 FiBL & ORC
Planting Planting
Quick emergence in
Planting date warm soil, shallow
Ridge spacing
•• The ideal planting date varies widely, depending earthing-up during
•• If all row crops on the farm (potatoes, maize,
on region and altitude. The most important factor planting and blind
sugar beets and vegetables) have the same
to determine the planting date is soil temperature. harrowing reduce the
track width, the time-consuming rearrangement
It should be around 8 °C, or 6 °C for pre-sprouted risk of infection with
of the machinery can be avoided.
diseases during emer-
potatoes. The soil should be sufficiently dry. Spacing 75 cm
gence (Rhizoctonia and
•• Standard, since most machinery is designed for
Planting depth Erwinia).
a track width of 1.5 m.
To prevent sprouts
•• The tops of seed potatoes should be level with Spacing 90 cm
the original soil surface. •• Potatoes can also be planted with a spacing of from breaking off chit-
•• New potatoes should be earthed up less than 90 cm. In that case, the tubers should be plant- ted tubers, the potato
ware potatoes to achieve quick emergence. ed at a spacing of about 25 cm within the row, planter should be used
to achieve a favourable plant density. This spa with a horizontal belt
Spacing within the rows cing is an alternative for industrial potatoes, for for distribution.
•• Basic rule: Less spacing between the plants which large tubers are desired.
leads to smaller tubers than more spacing. •• Advantages: larger ridges, fewer green tubers,
Standard: 30–35 cm better water storage in the ridge, better aeration
Seed potatoes: 22–26 cm of the plants, better nutrient supply, and wider
Baby potatoes: 13–20 cm tyres are possible. It may also help reduce the
•• Varieties that tend to form large tubers, or devel- risk of late blight spread.
op growth tears or hollow hearts (e. g. Agria), •• Disadvantages: more complicated road trans
should be planted more closely. portation of machinery (track width 1.8 m),
•• Early potatoes should be planted further apart crop covering will occur later or not at all; thus,
in order to achieve the necessary size faster. there is a higher risk of late weed infestation.
Tramlines for timely plant protection
Tramlines are not very common in organic potato farming, ting planting rows is partly compensated by additional yields
but they do offer an advantage: it is possible to drive on the in remaining rows. Tramlines are, however, only profitable
fields shortly after precipitation with wide or twin tyres with- when using larger spray booms. Repeated driving on tram-
out damaging the tubers or ridges. The yield loss from omit- lines is usually enough to suppress weeds in vacant rows.
Standard: Intact
Intact
Intact planting
no planting
row rowrow
planting
tramlines Tramline with two middle rows Tramline with one middle row
Driving
RowRow through
withRow
withwithis pressure
only
pressure
pressure possible with
damage
damage
damage Possible to drive on wide or twin Same advantages as tramline with
single tyres. Hence,
Omitted
Omitted
Omitted rowsrows rowslong waiting tyres. two middle rows, but without the
times after precipitation on heavy Compaction on the inner rows. compacted planting rows.
soils. Otherwise, it can result in Loss of yield due to empty rows. Recommended version when using
compaction of neighbouring planting Additional yield in remaining rows. tramlines.
rows, which can deform the tubers
and impede their growth.
Damaging the plants along the tram- Intact planting row
lines increases susceptibility to leaf Row with pressure damage
diseases.
Omitted rows
Organic potatoes 2017 FiBL & ORC 9Covering early potatoes
Covering early potatoes with a fleece, accel- As soon as the tubers reach the size of
erates development. cherries or the temperature beneath the
Covering requires work hours and material fleece / foil reaches more than 30 °C, the
costs; moreover, it increases the risk of leaf cover must be removed (choose a cloudy
blight and weed infestation. Covering is day or evening).
therefore only profitable for early planted After removing the cover, check the crop for
potatoes and high value crops. leaf blight infection.
The cover must be removed temporarily for
weed control.
Crop maintenance and weed control
The goal of measures for crop maintenance is to •• The ideal time for weed control is before the
Weed control create a large, stable, centrally positioned ridge, to weeds become visible (in the white-thread
Hoeing damages the open up surface crusts for better aeration and to stage /pre-emergence); at the latest when the
delicate root hairs at control weed growth until crop covering. weeds reach the two-leaf stage.
the side of the ridge, •• Going through the rows with a harrow before
and can also lead to General guidelines: emergence (blind harrowing) promotes fast
damage on the leaves. (See also maintenance plan on pages 2 and 3) emergence.
Roots and leaves can •• For driving though the crop, only light tractors •• The newly emerged plant is sensitive and
thus become ways for with narrow tyres should be used. should not be harrowed. As soon as the leaves
diseases to enter the •• After planting, the ridges should be harrowed turn green, only harrow gently up to a crop
plant. and earthed up, alternately. The harrow gets rid height of 10 cm. Plants of more than the size of
Potatoes that experien of the weeds on the ridges, while the hoeing a fist should not be covered anymore.
ce damage on their device reaches the weeds between the ridges. •• In order to establish well-covering ridges, apply a
root hairs respond with If both techniques are combined, the number ridge-shaping device during the last tilling round.
growth disturbance of passes through the field is reduced. Ideal •• Preferably, hoeing should be carried out in the
and lower yields. speed: 5.5–7.0 km/h. evening, when the leaves are upright (less
chance of covering them with earth).
Possible devices to control weeds
Multi-purpose device: harrowing, earthing
up and possibly hoeing in one go.
Rotary hoe: makes well-covered ridges; has a
tricky setting; not applicable on very stony soils;
less suitable for ridging at the end of the rows.
Ridge-shaping board: recommended for the
The rotary hoe is well suited
last tilling round.
for earthing up the ridges
Rotary hiller: makes well-covering ridges;
on heavy soils.
greater soil disturbance; risk of capping; only
recommended for difficult, cohesive soils.
Possible approach on different soils Ordinary harrow: versatile and quickly
Light soils Heavy soils employable; affects only the ridge crest (excep-
1st ridge formation Rotary hiller tion: Treffler harrow).
Harrow (for a quick emergence) Harrow Ridge harrow: only in combination with hoe;
1st harrowing
good adjustment to the ridge shape.
2 ridge formation (Harrow +) ridger /rotary hoe
nd Disc ridger or
ridge-shaping board Harrow groom: compared to the tined weed-
er, better effect in the entire row, very effective
3rd ridge formation Ridge harrow + ridger /rotary hoe Often unnecessary
or ridge-shaping board at pre-emergence stage, greater crop damage
at post-emergence stage.
A strict adherence to this programme of equipment use is not a good idea.
Hoeing equipment with rigidly mounted
The equipment used and number of processes should take account of the
weather, the development stage of the crop and weeds, and the sensitivity of duckfoot-blades: employ only when no risk
the varieties. of damaging roots.
10 Organic potatoes 2017 FiBL & ORCOther diseases
Protection of the leaves from diseases and pests and pests
Besides Leaf and tuber
Phytophthora infestans blight, the Potato
Leaf and tuber blight cyst nematode, and
the Colorado beetle
(outside the UK) other
diseases and pests
can attack the potato
plants. However, they
are often of minor
importance and there
are no specific control
methods in organic
farming.
The publications
Infection on the leaf surface Infection on the underside of the leaf Stem infection listed on page 28
offer detailed infor
mation on preventative
measures.
How to recognise •• Containment is most likely to be possible in
•• Leaf surface: brown spots, partly looking oily, the early stages. Hence, close monitoring of
blurred transition to healthy tissue. the crop is important! Integrated systems
•• Underside of the leaf: grey / black spots, •• The initial infection of the leaves can be approach
and white fungal growth during wet weather brought on by (latently) infected planting As for pest and disease
(especially on the edge); the fungal growth material, volunteer potatoes or tubers on com- management in organ-
can be cultured by keeping the leaf in a wet post heaps, or it can be brought in by wind ic farming in general,
bag overnight to facilitate identification. from a greater distance. Tubers are infected an integrated systems
•• Stems: symptoms similar to the leaf surface through seepage of spores from infected approach should be taken
•• Not to be confused with frost damage, ‘sun leaves, or smear infection during harvest. for leaf and tuber blight,
burn’ or grey mould (grey fungal growth on too. It should integrate
the surface /underside). How to prevent the use of (i) resistant
•• Select varieties that are as resistant as possible varieties, (ii) available
Important to know and grow tubers early (in the UK, see AHDB agronomic control stra
•• Optimal transmission (airborne spores) occurs National Potato Variety Database). In the long tegies, (iii) alternative
when the relative humidity is over 90 % and run, there is a risk of breaking the resistance of treatments (e. g. organi
the temperature around 18 °C. If the infec- individual varieties. In order to spread the risk, cally-based fungicides,
tion is very likely, the fungus can infect an several varieties should be cultivated. plant ‘strengtheners’ and
entire crop within a few days. Depending •• The Sarvari Research Trust (SRT) breeds new bio-control agents which
on the weather conditions, it takes between disease resistant varieties of potato traded can replace synthetic and
2–3 weeks and 2 months for the plants to die by Sarpo Potatoes Ltd. Several have excellent copper-based fungicides)
off after initial infection. In dry weather, the foliar blight resistance, including Sarpo Mira, and (iv) optimisation of
infection stops spreading; in wet weather, the and Sarpo Axona. Others have highly resistant blight control treatments
infection increases. tubers such as Blue Danube. utilising existing blight
•• In the UK, the information and alert service •• A successful breeding programme in the forecasting systems with
BlightWatch, supplied by the Met Office and Netherlands (Agrico Research BV) has also the aim of maximising
supported by AHDB Potatoes, informs farmers produced a wide range of blight resistant synergistic interactions
on the current risk of occurrences of blight dur- varieties for organic production in the UK. Two between (i), (ii), (iii) and
ing the growing period. Alerts are generated of the highly blight resistant organic varieties (iv).
and sent to users based on the update to the on offer are Alouette and Carolus. The development of this
traditional Smith period, the more advanced •• Plant only healthy looking tubers. Discarded systems approach took
Hutton Criteria (Criteria met on 2 consecutive tubers should be composted at 60 °C. place in the EU project
days: Minimum air temperatures are at least •• Chit the tubers. Infected tubers start to rot dur- Blight-MOP. More recently
10 °C, and relative humidity is 90 % or above ing the chitting and can be removed. Plants Co-Free investigated the
for at least 6 hours) or when a confirmed out- develop earlier from chitted seed tubers and potential for innovative
break in your area occurs. Optimal control of often form tubers before initial infection. methods, tools and con-
leaf blight serves to protect plants and neigh- •• Plant late and early varieties in separate fields. cepts for the replacement
bouring crops that have not yet been infect- If such a spatial separation is not possible, the of copper in European
ed, with Blightwatch alerts providing an early more susceptible (early) variety should be cul- organic and low-input
warning to aid management decisions. tivated on the side of the field downwind of production systems.
Organic potatoes 2017 FiBL & ORC 11the prevailing weather conditions. Cultivation •• Large ridges without dry cracks decrease
in multiple rows and alternating between sus- seepage of spores into the ridge.
ceptible and less susceptible varieties (‘mixed
crop’) can delay the spread of the disease. How to control
•• Cultivate a strip of at least 12 m of a different •• The only copper-based product licensed for
species (e. g. wheat or grass/clover) perpen- use in the UK, Cuprokylt, was granted emer-
dicular to the prevailing conditions. gency usage for the 2017 season. Certification
•• Avoid overly strong development of leaves (by bodies in the UK were applying for another
adapting nitrogen fertilising) and heavy weed emergency extension for the 2018 season.
infestation. This means that the crops dry faster. The long term future of copper for use in
•• Avoid volunteer potatoes in the succeeding organics for blight control is uncertain so those
crops (risk of primary infection). Pigs can be growers still relying on it must think about
good at removing groundkeepers. adapting their practices.
•• Either remove potato plants from waste heaps, •• After infection, the fungus cannot be stopped
or flame them or cover them with earth. from spreading through the plant.
•• Regularly check the plants and rogue by remo •• The affected plants must be removed and the
ving the stems and foliage of plants within a protection of healthy crops must be increased.
3 m radius of an infection (flame or mow the •• In practice, plant strengtheners/tonics are
leaves to leave the tubers in the soil). often used, such as rock dust, horsetail tea,
•• In the case of a severe infection, chop the skimmed milk or whey and compost tea.
leaves off plants with tubers that are ready for •• According to practical experience, rock dust
harvest and before heavy rains. Put the leaves strengthens the resistance and supports the
at the bottom of the ridge. drying of the leaves. Scientific tests by FiBL
•• After the leaves have died off or have been could not prove a sufficient efficacy of these
removed, wait 2–3 weeks before harvesting. agents for control of foliar blight.
This allows the skin to set, reducing the risk of
infection from sporulating leaves during harvest.
Application strategy for copper sion support on assessing the risk to a pota-
to crop. The models use local weather data
from the Met Office to calculate the current
risk of infection for every crop allowing the
farmer to take the necessary precautions. If
the yield production has progressed rather
No infection Infection in neighbouring crops
Level of infection within the region Infection or within the crop, or the
far (assessed by taking a yield sample) at
(50 km radius) within the region Hutton Criteria has been met the time of initial infection (often after mid /
Risk of leaf blight Low Medium High
end of July), the risk to the tubers is very
Dose of copper None Low High low. If the crop and wider environment of
0.75 kg/ha 1 kg/ha the site are not yet infected, the likelihood
of infection may be very low, especially in
A maximum of 6 kg per ha of copper a year is permitted. Apply at 10 to 14 day intervals.
dry weather. In the case of wet weather and
infection in the surrounding region or within
The control strategy for late blight in organic farming was one’s own fields, the likelihood of infection is
based on the use of copper fungicides but at the time of rather high.
writing there are currently no copper products licensed
for use on crops in the UK following the rejection to
When to spray
relicense Cuprokylt (Certis). An application by AHDB
for authorisation for emergency use of Cuprokylt was
accepted in time for the 2017 season and was granted
for 120 days from 15th May 2017, before final prohibition
of copper based fungicides in organic potato production.
Blight management should be based on estimating
the current risk of infection in the crop. This depends on Weather
the infection in the region, the precipitation, the suscep-
Treatment
tibility of the variety and new growth. Sound knowledge
of the current situation in the region (alert systems) and The treatment should be carried out early
on one’s own farm (frequent field checks) is required enough before heavy precipitation to let it dry,
for optimal control. The Blight Watch system offers deci- in order to protect the crop.
12 Organic potatoes 2017 FiBL & ORCMeasures for improved application
Copper products only have a fungicidal effect upon ral rule of thumb: where the leaves are moved,
contact. An even wetting of the leaf surface and the agent is applied. An improved application can
underside in the entire crop is required to ensure be achieved through various means. They vary in
a good effect. To control the distribution of the effect and cost. Combining them is a possibility.
spraying mixture within the crop, there is a gene
Benefit: ++ Use enough water for spraying:
•• The amount of water should be chosen to properly wet the leaves; however,
Cost: +
the spray mixture should not drip off.
•• The amount of water should be adapted to the leaf mass: 400–600 l per
hectare is common. In lush crops, 600–1000 l per hectare may be needed.
•• Average driving speed of 4–5 km / h is favourable.
Benefit: + Improve the spraying angle:
•• Turn the spray pipe 40° to the front (not possible with all brands). This allows
Cost: +
droplets to enter the crop better.
Benefit: ++ Install double flat fan nozzles:
•• The slanted spraying angle allows droplets to enter the crop better.
Cost: ++
Benefit: ++ Use high pressure:
•• Choose pressure of 7–10 bar.
Cost: ++
•• To reduce spray drift, install rebound or injection nozzles that form larger drop-
lets than regular nozzles.
Benefit: +++ Use under-leaf spraying:
•• The spray elements specifically wet the underside of the leaves and the lower
Cost: +++
levels of the foliage (pressure: 4–5 bar).
•• Installation is not equally possible on every spraying machine because the
spraying elements and the tubes must not interfere with folding-in of the
machine.
•• The under-leaf spray elements of more recent models rarely become entan-
gled in the dense foliage.
•• More suitable with a row spacing of 90 cm (due to a later crop covering).
•• The distance between the elements must coincide with the spacing of the
rows in the crop. For use in other crops, the distance must be adjustable.
•• Due to strong resistance only a relatively small bar width is possible.
Benefit: ++ Spraying with compressed air:
•• The compressed air moves the leaves and transports the droplets far into the
Cost: +++
foliage.
•• Low drift.
•• Less water needed.
•• Larger investment and thus only useful for large-scale application.
•• Especially suitable in combination with tramlines.
Organic potatoes 2017 FiBL & ORC 13In UK: Globodera rostochiensis (yellow PCN) and Globodera pallida (white PCN)
Potato cyst nematode (PCN)
Nematode cysts on potato roots.
Important to know How to recognise
•• Nematodes damage the roots and affect yield even when no •• In the initial stages plants may appear stunted with wilting,
symptoms are evident in the haulm. with poor patches of growth. In more severe cases plants
•• The potato cyst nematode is the most important potato pest may start to show chlorosis.
in the UK, with the potential to cause major yield losses. •• If infected plants are lifted, the nematode cysts should be
•• The white PCN is the most common nematode due to its visible on the roots.
prolonged hatching period and the selection pressure from •• Nematodes have slender, transparent bodies, reaching
the cultivation of several varieties resistant to the yellow PCN. approximately 1 mm in length.
•• PCN damages the roots of potatoes, resulting in poor growth, •• As females mature, they swell, forming spherical cysts 1 mm
wilting during periods of water stress, early senescence and a in diameter, which are white / cream coloured. At this stage
reduction in tuber yield by as much as 80 %. they can be seen attached to the roots.
•• In the UK, AHDB Potatoes offers a web based calculator tool •• As females mature and die, the cysts develop a reddish-brown
that acts as a decision justifier, demonstrating the implica- hard skin. Mature cysts can be seen attached to roots but
tions of a grower's actions on the level of infestation by the usually drop off at harvest, remaining in the soil as a source of
white PCN and the effect on predicted yield. infection for future potato crops.
•• If the infestation is very low, the yield reduction can be so •• The infestation level of a soil can be determined by soil
low as to be unnoticeable when a crop is commercially har- extraction. This service is available from a number of accredi
vested. This can lead to a false impression that PCN can be ted laboratories.
ignored due to no visible drop in the expected yield. The
effect on the final population after harvest could become an How to prevent
issue for subsequent potato crops. •• Take marginal land out of production and avoid growing on
•• The nematode is mainly spread by the movement of cysts the worst affected land.
in the soil attached to potato tubers, farm machinery or foot- •• Soil sampling should be done regularly to identify and moni
wear. Cysts can also be spread by wind or floodwater. tor the threat.
•• Under EU Directive 2007/33/EC, seed potatoes or potatoes for •• Biofumigant crops such as mustard can be chopped and
export must only be planted on land that has been found to be incorporated into the soil to help kill PCN eggs.
free from PCN infestation following an official soil test, under- •• Clean machinery between fields
taken by a PHSI inspector. The growing of ware potatoes is per-
mitted subject to the implementation of a Control Programme.
Leptinotarsa decemlineata Important to know
Potato or Colorado beetle •• The Colorado potato beetle is a distinctive yellow beetle
with ten longitudinal stripes on the wing cases. Adults are
up to 11 mm in length.
•• This species is not established in the UK and is a notifiable
quarantine pest of potato (plus tomato and peppers), with
the potential to greatly reduce yields.
•• Colorado potato beetle has been eradicated in UK, but is
widespread in continental Europe. In GUK it is most com-
monly intercepted in spring or early summer from Europe
on plant produce (e. g. salad vegetables, potatoes, parsley).
•• Potato growers in the UK should remain vigilant and contact
the local Defra Plant Health and Seeds Inspector, if pres-
ence of the beetle is suspected in a crop or import con-
Eggs Larvae Adult potato beetles
signment.
14 Organic potatoes 2017 FiBL & ORCFred Bonestroo’s late blight limitation strategy
At the heart of my late blight limitation strategy is the selection
of resistant varieties. I grow 6 main varieties that all offer reliabil-
ity and security. The 4 most blight resistant varieties today are
Allouette, Cara, Carolus, and Toluca. I also grow Agria because of
its all-round use and great yield even though it’s not very blight
resistant but is manageable. I grew Rudolph for the first time
this year which looks to be a nice potato, but I will try something
different next year. Agrico run field days with trial plots of blight
resistant varieties that allow me to select what to grow. Each year
I try out new varieties and will give out free samples of these to
the box schemes to help introduce them to the consumer.
Measures combined for late blight control:
•• Number one is selecting resistant varieties, either from Biose-
Fred Bonestroo farms in the Cotswolds near Tetbury at Close Farm.
lect or from the Sarvari Trust.
•• I try to sow as early as possible as I can’t extend the growing
season at the other end due to the risk from blight. I do chit •• I don’t apply too much farmyard manure as there is usually
very early potatoes but as a small grower don’t have the time, enough fertility from the ley, but if I do use it, I make sure it’s
facilities or labour to chit the main crop. well composted. I don’t believe in pushing the crop too hard.
•• I use wider in the row spacing (approx. 41 cm) to decrease I’ve found that growth cracks and scab can occur when too
the competition between crop rows and also reduce the leaf much farmyard manure is added, and I prefer a slightly lower
wet period as I get more air circulating around the foliage. yield that stores well and tastes better.
•• I’ve stopped cropping the headlands as this is often com- •• Once the blight infection has come into the crop, I’ll burn off
pacted and the area where the crops struggle and are least the foliage of infected plants to prevent the disease spread-
healthy. ing to the other plants and to the tubers.
Irrigation Irrigation
Sufficient moisture
•• Dry soil during early development promotes a •• Drip irrigation is often most effective as it reduc- at the time of tuber
wide root system. es the humidity in the canopy (reducing the formation (initiation)
•• Early irrigation promotes the conversion of blight risk) and is more efficient in terms of prevents common scab
organic matter and, thus, the N supply. water application. infection (S. scabies).
•• After stem elongation has started, the soil Sufficient moisture dur-
should be kept moist, otherwise tuber forma- Irrigation for frost protection ing tuber development
tion might start too early and more than one •• Can prevent frost damage in short-term frost reduces secondary
generation of tubers might form. periods down to –6 °C. growth and growth
•• Dry periods during tuber formation lead to a •• Turn on irrigation shortly before the temperature tears, and leads to uni-
growth check, reduced tuber formation and thus falls below freezing point; in the case of cov- form cooking quality.
to yield and quality losses. ered potatoes, turn on when the fleece freezes Soil that is too wet at
•• From tuber formation to flowering, the water to the moist soil. Irrigation that is performed too tuber initiation can
content within the ridge should be kept to a late can lead to damage! promote powdery
minimum of 50 % of the field capacity. •• Amount: 3 mm per hour (4 mm nozzles). scab (S. subterranea)
•• Depending on the soil and the potatoes’ devel- infection through
opment stage, the irrigation rates are 20–35 mm lenticels and occasion-
per application, but the soil should not be filled ally through eyes or
up by the sprinkler application to more than wounds.
80–90 % of the usable field capacity.
•• During tuber growth, sufficient water content
is crucial for yield production, especially from
3 weeks after flowering until maturation.
•• In case of need, it makes sense to irrigate the
potatoes directly before harvesting to carry Irrigation contributes to
more soil onto the filter belt and thus reduce yield and quality security,
the risk of damage. especially on lighter soils.
Organic potatoes 2017 FiBL & ORC 15You can also read
