STRAWBERRY PRODUCTION

STRAWBERRY FARMING

The strawberry plant is a typical hardy, perennial, rosette plant in the family Rosaceae. The fruits are a high value crop in Kenya for both export and local market. The fruits that can be done in a small land parcel and this makes it suitable for production in the urban and peri-urban areas

Utilization

Strawberries are eaten whole, in fruit salads and can also be processed into preserves, flavoring in various products such as milk shake, yoghurt and juices, concentrates and extracts.

The plant leaves can be used for decorations as a component of bouquets due to their beautiful shape and sweet scent.

Varieties

The most popular strawberry varieties grown in Kenya are Chandler and Pajero.

Other suitable varieties in Kenya include: Sulphur, Tioga selva, Douglas, Tristar, Domanil, Rabunda and Tribute.

Chandler, Pajero and Sulphur fall are hybrid varieties grown for export.

Ecological Requirements

Altitude

Production takes place in tropical highlands above 1000m above sea level

Rainfall

Strawberry requires well distributed annual rainfall of about 1200mm. Where rainfall is less than this, an average of 300 -450 mm of irrigation water is required over the growing season. The plants are shallow rooted; hence permanent moisture is necessary to maximize production.

Temperature

Strawberry grows a wide range of temperatures ranging from mild to hot. The optimal temperature is 15- 25 ⁰ C; it does not tolerate freezing.

Soils

• Strawberry plants are shallow rooted and they can grow on a wide range of soils, however fertile, well-drained soils such as sandy loam soils are best for production. 
• Plants can also be grown on heavy clay soils provided drainage is improved by adding coarse sand or pumice. On poor sandy soils, add well-decomposed manure or compost.

·         The soils should be slightly acidic soils with a pH of between 5.5 and 6.5.

·         The plants are extremely sensitive to salinity, especially at the transplant stage.

·         Soil test is important to determine nutrient requirement

·         Poor drainage can cause "yellowing" in strawberries. This condition can significantly reduce yields. 

• Highly alkaline soils can cause yellowing or chlorosis of the plants, a condition that can lead to significant yield losses or complete plant die-back.

Site selection

• A favorable microclimate for strawberries is an area with full sun of at least six hours per day, uniform temperature, rainfall and good drainage and protected from wind.

·         In most cases strawberry production in Kenya is done in open field, however for high quality produce, protected environment such as greenhouses and hydroponics production system can also be used.

·         Level or slightly higher grounds are recommended

• Strawberries should not be planted in soils where strawberries, raspberries, potatoes, tomatoes, peppers, eggplants, beans, carrot or okra have been grown in any of the previous 4 years, unless the soil has been fumigated.

·         Soils previously planted with Solanaceous crops may contain Verticillium wilt, a persistent fungal organism in the soil.

Land preparation

• If planting in the open field, plough land to a medium tilth and remove all weeds. Make bed raised to 20cm with a width of 1metre by any convenient length and a path of 50cm.
• Incorporate well decomposed manure into the soil. 
• Strawberry stays in the field for 3 yrs hence there is need to prepare the land well and use high quality planting material.

Strawberries can also be grown in container or hanging baskets this prevents the build up of soil borne diseases; however pests may still be a challenge.

Planting material

Strawberries are planted as splits. Strawberries have runners grow away from the parent plant and attach to the ground forming roots. These can be split from the parent plant for use as seeds. Rooting media may be used to enhance strawberry plant establishment.

Spacing

Dig holes of approximately 7.5cm deep, 30-45 cm between rows and 30cm between plants giving a plant population of 75,000 plants per ha. Vigorous varieties are spaced at 90 x 30cm (55,000 plants/ha).

Planting

• Before planting apply the planting chemical e.g. Molcap, Nembidicene in the hole and mix with the soil.
• Strawberries roots should be spread out and ensure that the crown is above the soil level (do not cover the crown!)
• Plant the split firmly and level the ground. The roots should be covered but not too deep so as to avoid rotting of the stem.
• Irrigate immediately after planting.

Fertilizer application

• Avoid planting with fertilizers to prevent dehydration of the splits, since the plant goes into dormancy for 14 day. After 30 days apply CAN at the rate of 10g per hole in between the plants.
• In the second month, top dress the plants with a compound fertilizer such as NPK 17:17:17 at the rate of 10gms (1 tablespoon) per hole between the plants. Subsequent application is necessary every 3 months.
• Strawberry being a heavy feeder needs to be regularly boosted with foliar feeds. Calcium is required to firm the skin of the fruit and to decrease fruit deformities.
• High soil organic matter increases yields. Therefore manure should be applied during the land preparation.
• Do not over-fertilize the plants because this will cause excessive vegetative growth and reduce yields.

Irrigation

• Strawberries are sensitive to periods of severe drought; the plants should to be adequately watered at all times of the year as lack of water hinders fruiting.
• A minimum of 25 mm of water per week is required and up to 50 mm of water should be given weekly while the fruit is forming, from early bloom until the end of harvest.

·         Drip irrigation or low pressure hose pipe should be used to ensure adequate water to the plant; high pressure sprinkler cause flower abortion, fruit bruises and contributes to fungal diseases on the leaves.

·         Continuous optimal water status ensures continuous flowering and therefore high and quality fruits.

• Waterlogging should be avoided since it encourages development of soil-borne microbial and fungal diseases.

Mulching

To retain moisture in the soil, mulch the surface well using crop residue e.g. straw, hay, or black polythene after planting. The mulch suppresses weeds, conserves moisture and keeps the fruits clean. Keep the mulch slightly clear at the crown of the plant as covering the crown may lead to rot and loss of the plant.

Weeding

Weeding should be done frequently (once a week) for the first 6- 8 weeks. Cultivation kills the weeds and loosens soil for better runner penetration. If necessary, herbicides can be an effective tool in controlling weeds in strawberries.

Pollination

Pollination is very important to the fruits especially those grown in enclosed environment. This can be aided by use of pollinators such as bubble bees or artificially using a paint brush.

Wind protection

If the site lacks wind protection, shelterbelts should be planted to reduce wind velocity as this may cause drying of fruits and plants.

Field management

De-flowering

This is necessary to control premature cropping which is induced by short day conditions occurring in Kenya, which leads to stunting and poor development of the crop.

The plant starts flowering before it is established. Deflowering is recommended for the first 2 months until the crop establishes itself. After the 2 months, bud clusters should be left to develop and set fruit. These will reduce chances of early exhaustion of the plant.

Management of runners (Pruning or stripping)

• As strawberries grow they produce runners that spread out and root to produce additional plants. Runners and old leaves are removed.
• Cut off runners regularly except for those needed for planting. One or two runners from the runner types can be rooted for the next planting.
• Thinning to 2- 3 splits per crown should be done every 7 months to allow rejuvenation and increase strawberry yields.  

Pests

• Spider mites, Flower Thrips, Strawberry Bud Weevil or Strawberry Clipper, Meadow Spittlebug, Nematodes
• Slugs and snails destroy the ripe fruit as well as fruit-eating birds.

Control

• Adequate watering during dry period
• The slugs and snails can be collected by hand and destroyed
• Use netting that is supported about 1 metre above the plants to protect fruits from birds.
• Use recommended insecticide when necessary

Diseases

• Fungal diseases include:  Angular leaf spot, Botrytis fruit rot (Grey mould), Fusarium Wilt, powdery mildew and Anthracnose.
• Viral diseases e.g. Verticillium wilt

·         The planting material is strawberry very expensive especially for those starting production. A commercial farmer requires at least 1,000 splits.

Control

-Integrated disease management techniques are highly recommended in strawberry growing. Cultural practices include:

• Choice of sites with good drainage, disease free, with good air circulation and with no shading.
• Field sanitation -Remove diseased plants, old leaves, buds and flowers promptly.
• Reduce humidity by improving ventilation and do avoid overcrowd plants.
• Avoiding excessive use of nitrogen fertilizers as this may result in excessive vegetative growth making the plants more susceptible to diseases.

• Crop rotation with non susceptible crops. Avoid land where susceptible crops e.g. capsicums, okra, tomatoes, and eggplant/brinjals were planted
• Timely weeding

-Recommended fungicides may apply when necessary.

Note: Do not spray plants when in flower because pollinating insects may be harmed.

Harvesting

• Harvesting of strawberry fruits starts 75 - 90 days after planting depending on the variety. The fruits of strawberries should be harvested when the whole fruit is completely red, that is when they contain maximum sugar content, flavour and size.
• Fruits that are still white near the stalk are immature and should not be harvested
• Strawberry fruits should be picked in the early morning preferably as soon as they are dry. They should be carefully handled to avoid bruising which promotes disease infections and reduces marketability.
• Fruits for export should be harvested when they are 1/4 ripe to avoid over-ripening when they are on the market

Post harvest handling

Sorting should be done to remove damaged, deformed and dirty fruits. Remove all the fruits without a calyx.

Pre- cooling the berries and storing at temperatures below 40⁰ C minimizes deterioration of berries.

Yield

About 10 tons/acre of strawberries are expected in the first year, while 7.5tons and 5tons in the second and third year respectively. The economic lifespan of the crop is 3 years; hence the plants should be renewed by the end of the third year.

Management of plants after harvest

• After the final harvesting remove any unwanted runners

• Cut off the old foliage to about 10cm above the crown the crown and new leaves untouched. This allows sunlight into the centre of the plant, ensuring a better crop in the next season.

• Clearing away debris from around the plants.