Potatoes

It is believed that potatoes were first cultivated in Ireland around the 1600s. By the 1700s, they were part of the staple Irish diet, especially of the poor. This had devastating consequences when blight destroyed the potato crops between 1845 and 1852; this period of history is now remembered as the Great Famine. Despite this, the potato remains one of the most popular vegetables in Ireland, with 95% of households buying potatoes regularly. Approximately 9000 hectares of land is planted with potatoes each year.

Potatoes belong to the family Solanaceae. Other members of this family includes tomatoes and tobacco. A potato tuber is a modified stem used for food storage by the plant.

Year Area grown (000 ha) Yield (tonnes/ha)

2017 9.2 44.9

2016 9.0 38.9

2015 8.5 42.3

2014 9.5 40.5

Potatoes are a biennial plant. However, potatoes that are grown and harvested for human consumption are usually harvested 3-6 months after they were initially sown. The potato plant goes through five stages of growth prior to harvest.

1. Sprout Development: Sprouts develop from the eyes on the seed tubers and grow upwards, emerging from the soil. Roots begin to develop from the base of the emerging sprouts.

2. Vegetative growth: Leaves and stems develop from nodes on the emerged sprouts. Roots and stolons begin to develop from nodes below the ground. Once the leaves have emerged the plant begins to photosynthesize.

3. Tuber initiation: Tubers begin to form at the tips of the stolons but do not develop further at this stage. Flowers begin to emerge on the plant.

4.  Tuber bulking: Water, nutrients and carbohydrates begin to accumulate in the tubers. The tubers begin to grow. Most of the carbohydrates storage in the potato plant at this stage of development is in the tubers.

5. Maturation: The plant begins to turn yellow and lose its leaves. Photosynthesis decreases, and tuber growth also decreases. The dry matter (DM) content of the tubers reaches its optimum level and the potato skins begin to harden.

Potatoes are classified as:

• First earlies

• Second Earlies

• Main Crop

First and second earlies are planted as early as February. However, potatoes are not frost-resistant, and for this reason they are grown in coastal areas of counties Cork and Wexford. The soils in these regions are sandy soils and warm up early in spring. Earlies are harvested immaturely from May onwards. As a result, there is a lower yield, but they obtain  higher price. Home Guard and British Queen are the most popular early varieties grown in Ireland.

Maincrop potatoes are harvested fully mature in September and October and giver higher yields than early varieties. Maincrop potatoes are used to supply the consumer market until May of the following year.

Rooster, Kerr's Pink, Record and Golden Wonder are the most popular maincrop varieties in Ireland, since these varieties have high DM content and produce floury tubers. Over half of all land planted with potatoes in Ireland is planted with Roosters. In contrast, Cara, a variety that is popular on the Continent, has low DM content but is very high yielding. Production of maincrop potatoes is mainly confined to counties Meath, Dublin, Louth, Cork and Wexford

Potatoes are assessed under several characteristics. Growers may choose different characteristics based on their needs.

1. Disease resistance: The ability to resist certain diseases is important in potato production. Loss in yield can be minimized by choosing a variety that is resistant to certain diseases and being aware of the measures necessary to control other diseases.

2. Yield: Most potato growers are involved in maincrop production. The higher the yield the more profitable the crop will be. Some varieties are higher yielding than others.

3. Maturity: When a potato matures will determine when it can be harvested. As most potatoes are harvested as maincrop potatoes, growers want varieties that will be mature by October.

4. Keeping quality: maincrop potatoes supply the Irish market for most of the year. This means that they must be kept in storage for many months. Some varieties such as Roosters are better suited to prolonged storage.

5. Eating quality: Irish consumers prefer potatoes with a high DM content (floury potatoes). Red skinned varieties such as Rooster and Kerr's Pink are popular in Ireland.

6. Seed availability: While the Irish market is dominated by a few popular varieties, the availability of other variates can be determined by seed availability.  

Commercial potato production can be divided into two categories:

1. Certified seed potatoes

2. Ware production (potatoes for human consumption).

Seed potato production is centred in Donegal. The windy conditions keep the aphid population low and Donegal is isolated from other potato-growing counties, preventing the spread of diseases. Certified seed potatoes that are distributed to commercial ware growers are grown under strict regulations. Seed potatoes can be produced only from fields free from potato cyst nematode and they must be free from plant viruses, e.g. leaf mosaic virus, leaf roll and virus Y. Certified seed is also produced using micropropagation. Some growers reduce the cost of producing their ware potatoes by using their own potatoes for seed, which can produce a good yield. However, it is advisable to purchase certified seed every 3 years, since viruses can build up in a producer’s stock.

Potatoes are grown in a wide variety of soils. However, deep, well-drained loams and sandy loams are ideal. Potatoes prefer a pH of 5.5 to 6.0. If the pH of the soil is very alkaline (>7), it can cause scab on potatoes. For this reason, potatoes are not grown in

recently limed fields. If the soil pH is less than 5.5, the availability of trace elements is affected, and as a result crop growth is affected. When potatoes are grown in sandy or sandy loam soils, irrigation may be required if drought occurs in late summer. Drought affects tuber development and reduces crop yield. Adding manure to the soil helps it to retain more water, especially in sandy soils, and this helps prevent drought damage to the potato crop

Rotation is vital in the production of potatoes, since it prevents the build-up of potato cyst nematode and other soil- borne pests and diseases. Ware potatoes should not be grown in the same area for more than one year in four, and in seed production that is increased to one year in five.

Potatoes need deep and well-cultivated soil. Since potatoes are sown in spring, soil should be ploughed to a depth of 22 cm. It should be rotavated and beds should be formed at this time. Each seedbed contains two drills and is 172—182 cm wide. If potatoes are grown in a rotation after grass, grass should be burned off with glyphosate prior to cultivation.

Commercial growers also practise stone and clod removal. This prevents bruising and contamination of the potatoes at harvesting. The stones and large clods are removed, using a machine similar to a potato harvester, and are placed in a line at the side of the machine. The following year the land is ploughed at a right angle to

distribute the stones again. Clods in seedbeds can cause slow crop growth, irregular emergence and lower rates of stem emergence. To ensure a good yield of potatoes, rapid emergence and subsequent crop growth is necessary. Wet soils are also susceptible to compaction, which impacts on root development and yield of potatoes. Soils should be well drained to maximise crop production. Drill formation is the final stage of cultivation and is done either before sowing or when the potatoes are sown.