Principles of Potato Production

Varieties of potatoes

Potatoes are grown for 2 reasons: 1.Human consumption

2.Seed potatoesThere are 3 main types of potatoes

-First earlies-Second earlies-Maincrop

First EarliesHarvested immature for immediate sale

Generally sown in late January or early February(depending on the weather)

Harvested in May

Early harvesting may result in lower yield but the grower is compensated by the higher market value of the crop

First Earlies

The Home Guard is considered one of the most superior of the first earlies in terms of eating quality

Home Guard: oval in shapelight skinshallow eyescreamy white flesh

Second EarliesCan be harvested immature and sold

orMay be harvested at maturity and stored

If harvested immature: Sown in mid-February/early MarchHarvested in mid-June

Superior variety: British Queen: Oval in shape

Floury white flesh

Main CropSown in mid-March to late April

When soil conditions are suitable (7C)

Harvested in September/October

Because they are harvested at maturity the yield is higher

Main crop varieties: Roosters, Kerrs Pinks, Records and Golden Wonders

Main Crop Varieties

Records Golden Wonders Kerrs Pinks

Soil Suitability• Deep, well-drained, sandy loam soils

• pH 5-6

• Stone free

• Light, sandy soils (Brown earths or grey brown podzolics)

• South facing slopes for the first earlies

Climate• Must be sown when plants will not be killed by frost

• Only coastal areas are suitable for growing earlies (no risk of frost).

• Irelands Climate of mild showery weather is ideal for potato growth.

• Drought at tuber development reduces yield (irrigation could be used)

Rotation• If grown too often in the same filed potatoes may be

affected by potato cyst nematode (eelworm)

Eelworm: Soil borne nematodemicroscopicAffects root system

-Can be controlled by crop rotation-Nematicides can be sprayed onto crop-Some varieties are eelworm resistant-Seed potato is only accepted from fields that are

eelworm free

Eelworm

Eelworm Potato affected with eelworm

Rotation

• Potatoes should not be sown for more than one year in four in a field

• Potatoes grow well at any point in a rotation

• Farmyard manure (FYM) can increase organic matter levels in the soil, a benefit for all crops

Seedbed Preparation

• Autumn plough to a depth of 22cm

• A fine seedbed is required

• Ridges should be high and wide

Varieties• 40 – 50 varieties appear on the ‘National Catalogue of

Agriculture Plant Varieties’• Potato varieties do not change as quickly as cereal

varieties. Some common potato varieties:

Home Guard First EarlyBritish Queen Second EarlyKerr Pink’sRecords MaincropGolden Wonders

Cultivation

• Deep cultivation required• Should be autumn ploughed to a depth of

22cm at least• Cultivation in spring to give fine seed bed• Rotavator or power harrow are used to give a

deep non-compacted seed bed

Rotavator: used to break up the land in preparation for sowing for e.g. potatoes

Cultivation • Stones can also be removed. This prevents brusing /

contamination when harvesting• Machine deposits stones in a heap at the side of

machine. • Ridging is done so stones are in furrows between

two ridges.• Potatoes are grown on ridges. The ridging is either

the final cultivation operation or is done during sowing

Potato Cultivators

Grading of seed

• Seed potatoes are graded into 2 sizes35 – 45mm45 – 55mm

35 – 45mm seeds are spaced at 20 – 25cm apart giving about 60,000 seeds/ha

45 -55mm seeds are spaced at 30 – 35cm apart giving about 40,000 seeds/ha

before planting

Sowing the Seeds• Sown 10cm below the surface of the ridge• Ridges should be 76cm apart• Potatoes may be stored prior to planting

Sowing the Seed• As the size of the seed increases, the number

of ‘eyes’ increases.

• Each eye grows into an individual plant

• Potato seeds can be sprouted prior to planting by placing in shallow boxes and placing them in greenhouses or well lit sheds

Sowing the Seed

• This is important for earlies, as it speeds up growth, plant emergence and increases yield

• Commercially seeds are sown using an automatic or semi-automatic planter

• Planting by hand can be done in small areas

• Certified seeds are not used annually – too expensive

Sowing potatoes

Potato with ‘eyes’ Planting potatoes by hand

Producing home grown seed

• An isolated area is sown with certified seed• It is sprayed with pesticides to control aphids (e.g.

greenfly which spread disease)• The plants are killed off early to ensure maximum

number of potatoes in seed size range (35 – 55mm in diameter)

• Methods of killing off potato: Burn offHarvest Herbicide

Fertiliser RequirementsCarry out a soil test

Usual rates of 10-10 20 applied are:- Nitrogen: 125-150 kg/ha-Phosphorous: 125-150 kg/ha-Potassium: 250-300 kg/ha

Application is usually decided on after soil testsFertiliser is broadcast onto the soil before

planting

Fertilisers

• Too much nitrogen leads to high yields which have poor eating quality

• Higher water content leads to poorer quality

Fertilisers

Experiment to estimate eating quality of potato:• Cut potato into cubes• Find mass of potato cubes• Place in an oven at 100°• Find mass after heating for 30 mins• Repeat steps 3+4 until cubes have constant mass• Calculate the loss in mass of potato cubes

Fertilisers

50g 100200g 1 = 25%

Results:

Potato content (75%) Water content

Fertiliser

Low dry matter in potatoesToo much nitrogenNot enough potassiumLack of sunshine

Weed control

• Weeds are controlled indirectly by crop rotation and stubble cleaning

• Deep ploughing buries weeds• Weed need to be controlled until potato stalks

and leaves meet across drills• After this, the haulms meet and prevent

sunlight reaching the weeds (shading)

Weed Control• Crops should be sprayed when 15-20% of

potato plants are visible above soil• Spray should be a mixture of total herbicide

and residual herbicide of medium resistance.• The total herbicide kills the potato tips but

they recover and continue growing• In small areas hand weeding could be done• Earthing upResidual Herbicide: A herbicide placed on the target are that remains active in the soil for a period of time

Earthing up• Carried out when crop is 20 - 25cm highRidges become flattened out due to rainfall,

gravity etcPotatoes may not be covered with soilTherefore the earth is placed up around plantObjective: to protect the crop from light• Light exposure causes greening of tubers and

leads to alkaloids (poisonous) forming skins• It is illegal to sell greened tuber – so they must

be discarded

Harvesting

• Earlies are harvested from early June onwards• Early crops (new potatoes) have low yield but get high

price.• Maincrop are harvested in late September or October

at full maturity.• Haulms are killed off 3 weeks before harvesting. Use

contact herbicide.• In these 3 weeks skin on tuber hardens leads to less

bruising and scratching on harvesting

Harvesting• Most common potato digger –

elevator digger• Wide, flat share running

through ridge under the potatoes

• The soil and potatoes are moved onto the elevator where the soil drops through the bars and deposits the potatoes on top of the soil. These are then hand picked

Elevator Digger

Harvesting• Complete potato harvesters can also store the

potatoes in a bin or alternatively the potatoes may be transferred to a trailer with a side arm

Experiment to estimate the yield per hectare of a root crop

1. Name the crop being estimated2. Mark out an area of 1m2

3. Dig the crop out of the ground (remove crop) in the marked area.4. Remove tops off the crop if necessary e.g. sugar beet.5. Find the mass of the crop dug out6. Record the mass7. Repeat the process in a different part of the field8. Find the average mass per square metre9. Find the area of the field10. Calculate the yield per hectare11. Work out the total yield of the area to be harvested.1 hectare = 10,000 m2

1 tonne = 1000kg

Yields

• Maincrop (average) 30 -40 tonne /ha• First earlies, yield can be as low as 7 – 10

tonne / ha

Disease Control

BlacklegBacterial diseaseTreatment: Avoid badly drained fields and storing

wet tubers

Gangrene:Fungal diseaseTreatment: Spray the crop with systemic fungicide

StorageBuildings for storage should be:• Leak proof • Frost proof discourage rotting

• Well ventilated- Less risk of sprouting and rotting• Forced draught ventilation systems are needed where stacks

exceed 1.8m in height• Easy access for tractors and trailers• Strong, reinforced wallsPotatoes to be sold after February 1st should be treated with

sprout inhibitor or else refrigerated

Disease and Pest control• Most common potato disease – blightCaused by: fungus Phytophthora

infestansSymptoms: yellow (later black)

blotches to develop in the leavesPremature death Conditions: Warm, humid weatherWarnings are given by Met Eireann

Disease ControlCommon ScabOccurs if potatoes are sown in soils with high pHDo not apply lime to the potato crop or the

previous crop

Fungal diseaseSpray with systemic fungicide

Disease Control

BlacklegCaused by: bacteriumSymptoms:Blackening of lower parts of stem

Blackening of stored tuberControl: Use certified seeds

Avoid poorly drained fieldsAvoid putting wet tubers in stores

Blackleg in potatoes

Disease Control

GangreneCaused by: Soil borne fungusSymptoms: Dark coloured depressions on

stored tubersSecondary infection by bacteriaControl: Use certified seeds

Avoid damage by harvestAppply chemicals if necessary

Disease Control

Leaf rollViral diseaseSpread by aphidsTreatment: spray with insecticide

Leaf mosaicsViral diseaseSpread by aphidsTreatment: spray with insecticide

Pest Control

Wireworm: use poison baits

Slugs: use slug pellets

Aphids: use insecticides or ladybirds

Potato cyst nematode: Employ crop rotation

Potato cyst nematode

Yield

First Earlies: 7-10 tonnes/haMain crop: 30-40 tonnes/ha

Storage• Well-ventilated• Frost and leak proof• Easy access for tractors and trailers