Physiology, fruit initiation, environmental conditions and yield of strawberry.

It has been noted; the physiology of strawberry plant,the environmental conditions where strawberry is grown, how strawberry is established in the field, the use of plastic mulch on strawberry, thinning of strawberry runners determine the yield per acre of strawberry plants.

My focus is to give a brief explanation on how the aforesaid conditions interact to determine the yield of strawberry and the practices a farmer can follow to maximize the yields of strawberry plants.

Physiology of strawberry plant

Strawberry is a compressed woody herbaceous perennial plant that produces stolons from auxiliary buds on the second node.

This means that the plant can survive for more than one season and the plant is propagated vegetatively.

Branches may form at auxiliary buds; at times, the bud produces an inflorescence or remains dormant depending on environmental conditions.

It has been observed that the roots produced by the plant don’t go deep in the soil; 50-90% of them are found in the top 15 cm of the soil.

New roots grow above old roots, this makes it necessary to cover the plant roots with more soil after harvesting otherwise they will  dry and the consequence will be poor subsequent harvests.

The fruit  produced heart shaped and appears to be tri-lobbed symbolizing trinity. The shape of fruits varies; some are oblate or globular, but the common fruits are heart shaped.

conditions favoring FRUIT INITIATION OF STRAWBERRY

Short days and temperatures of 20-24⁰ C are some of the conditions that induce flower initiation.

If weather is warm throughout the year, blooming is continuous. Too cold or too hot temperatures inhibit flowering.

It has been discovered that growing conditions experienced by the plant during flower initiation and pollination determine the size and quality of the berries.

Any thinning or frost damage after flower initiation does not change ultimate size of berries. This is because the cells in the fruit have divided and their number fixed.

Fruit development starts when  fruit-lets develop on the surface of the receptacle after the terminal buds produce an inflorescence.

Achenes are present in the receptacle; their purpose is to produce auxins [a hormone]  responsible for fruit expansion; some auxins e.g. 2-4-D over-stimulate fruit expansion.

First flowers to be produced by the plant give larger fruits; such flowers are known as king flowers.

 

STRAWBERRY ESTABLISHMENT

Each plant produces 15 stolons that survive up to 3 weeks before they die. Stolon production is very important for crop multiplication.

Once the stolons are produced, they are cut off and used to produce new plants.

Spacing between plants and rows varies but one that is used is 60 cm between rows and 40 cm between plants.

The beds are raised above the ground to reduce the splashing of rain or irrigation water on the plants that encourages foliar diseases.

 

PLANTING of strawberries

The land should be prepared thoroughly to a fine tilth.

Mix compost or well decomposed farmyard manure with the top soil in the planting bed.

Mix 200 kg of Double Super Phosphate (DSP) fertilizer per hectare if the beds have the dimensions of 1 Meter by 40 Meters.

The beds should be raised so as to improve soil drainage and control root rot diseases.

Plants should be soaked in water for at least 10 minutes before planting and should be planted as soon as possible.

The roots should be spaced out so that they establish easily in the soil and ensure the soil is at the crown level to avoid rotting.

If you plant the crop shallowly; roots will be exposed and dry easily. The plants should be firmed well daily, until they are well established.

 

USING PLASTIC MULCH ON STRAWBERRY

Runners can also be planted through plastic mulch however, this increases production cost. Make holes on mulch and let the runners touch the mulch.

If watering is done under mulch, black mulch warms the soil resulting in early flowering and suppression of weeds.

Clear plastic mulch allows light to reach the beds, thus weeds continue growing but it has the advantage of preventing frost. If you are using plant covers, they should be removed when flowering starts.

Straw mulch protects the plants against cold injury. They should be placed on top of the plant late in the season as the plants go dormant. Straw mulch is removed early in the next growing season. Strawberry can be grown hydroponically.

 

THINNING OF RUNNERS IN STRAWBERRY

After planting, runners should be trimmed off so that they channel energy into vegetative growth first. The flowers should be removed for the first 4-6 months to allow adequate runners to develop first.

Once flowering starts, you need one to two rooted plants for the next planting.

Strawberries produce few runners so spacing is close. The beds should be replanted every 2-3 years using disease free runners. The lifespan of strawberries is 3 years.

Weeding should be done by cultivating shallowly in between the rows. Other types of mulch e.g. straw that will smoother the weeds, other alternatives are using of herbicides.

 

HARVESTING AND YIELDS

Harvesting is done regularly three to four weeks after flowering; start targeting green to light brown/red fruits. Handle the fruits carefully to avoid bruising them.

You can harvest 12-15 tones of strawberry per hectare if the crop is managed well. After harvesting, old leaves are cut off after duration of 3 months.

Cutting off old leaves helps in controlling diseases and results in new clean growth. Irrigate and apply a nitrogenous fertilizer at a rate of 200 kg of DSP after harvesting.