ABCs of growing watermelons

To yield five to six watermelons per plant, it is critical that pollination is successful. The farmer must also choose a variety that is resistant to wilt, for example, Charleston Gray and Sukari F1, writes Lominda Afedraru.

Growing watermelon has become a lucrative business in the country for farmers engaged in the same.
Development partners such as the Association of Volunteers in International Service (AVSI) have engaged the youth in Eastern Uganda in skilling them and encouraging them to grow the plant as a business initiative to improve their income. One such youth is Emmanuel Othieno from Tororo District who is engaged in growing the plant after acquiring skills in the general agronomy of growing water melon.
He gives excerpts of what he learnt from Agromax in Gayaza Wakiso about green house plant management and the agronomy for growing watermelon. Watermelon contains carbohydrates, calcium, phosphorous, ascorbic acid and vitamins.
It requires sun, water, bees, nutrients and a lot of space to grow. They thrive in sandy loam soil.
Give each plant at least five feet of space, as their vines spread rapidly.
Watermelon can be grown from seed or transplants from a nursery. Honeybees must pollinate the watermelon for fruit to be produced.
In Uganda, farmers grow it mainly in the districts of Luweero, Mpigi, Kayunga, Bugerere, Mayuge, Masaka, Mubende, Masindi and Bushenyi.

Land preparation and site selection
The following steps will guide you to cultivate a successful watermelon garden;

• Melons are vining crops that require a lot of space. For this reason they are not well suited to small gardens and should be grown only on a large land in both urban and rural areas.
• Secondly, the site for watermelon must have enough sunlight. Remove all shade plants; the soil must be fertile with good organic matter content. Melons grow best on a deep, well drained sandy loam soil.
• It grows and produces fruit during dry, sunny periods. Excessive rainfall and high humidity reduce productivity by affecting flowering and encouraging the development of leaf diseases.
• Clear the land of all vegetation covers and plant debris. Spray a systemic herbicide (Glyphosate) to control weeds such as spear grass.
• It is important for farmers to prune trees and remove shrubs that could impose shade.
• Conservation tillage is best for watermelon especially when the soil is of sandy loamy texture class.
• If organic matter or manure is added, it should be well composted. Apply manure or compost at 23kgs to 45kgs per 1,000 square feet, or about two to four tonnes per acre.
• Farmers should make sure the soil has ridges of four to eight inches high and 12 to 14 inches wide.

Seed preparation
The seed of watermelons is notoriously sensitive to very specific conditions during germination, as the tiny embryo is contained in a relatively large, hard seed coat.
Temperature and moisture control is crucial to success and too much moisture during germination can kill the seed.
It is important to process seed by nursery operators and farmers need 500 grammes for an acre
Seedlings must be transplanted and watered as soon as possible after they have been obtained from the nursery.
Planting trays should be kept cool and moist in the shade until used. When transplanting, roots should not be damaged by application of unnecessary pressure around the root module.

Planting
• Put enough manure in the soil before planting and plough to mix well with the soil.
• It is necessary to apply table spoon of Diammonium phosphate (DAP) in every hole and properly mixed with the soil to make sure that the fertiliser does not burn the seed. It helps in root development.
• Always fertilise the soils after every three to four weeks with Calcium ammonium nitrate which helps to fix nitrogen in the soil.
• Spacing the watermelon seed two metres between rows and one metre between the holes.
• Dig holes of 45cm wide, 45cm length and 30cm deep. Mix top soil with two spades full of manure and fill the hole leaving a space of 15cm. Sow two seeds per hole. It can be planted twice a year during rainy season.
• Watermelons are warm weather annual crops but they can be planted in both tropical and temperate regions. It is possible to grow watermelons in temperature around 50-950C and 10-350C. The optimum growing temperature is around 18-300C.
• The plant root system formation begins prior to emergence of cotyledons to the soil surface and reaches maximum extension by the time of flowering. Watermelon features a highly branching taproot extending up to one metre deep into the soil.
• Fruit shape and appearance are quite varied, ranging from round to cylindrical and a single colour to various striped patterns on the fruit surface.

Weeding
It is important to weed the land to remove weeds that compete for water and nutrients with the plant.
It can be done in the second or third week after germination.
Farmers can use hand hoe or selective herbicides.
Apply pre-emergence herbicide prior to or within 12 hours of planting.
Watermelon vines should be mulched to keep down the weeds and conserve moisture but the mulch should not be applied until the soil is thoroughly warm.
In the meantime, keep the area clean with shallow hoeing. Straw, hay or chopped leaves are the best mulching materials to use.

Seed varieties
and selection
Farmers are expected to select the best varieties which are high yielding and suited for the market. Farmers are advised not to use seed from previous plant.
The varieties include Sukari F1 with dark green and white strips which are early maturing taking 90 days and weighs about 10 kilogrammes. If well managed, it can yield up to 25 tonnes per acre.
Another is Zuri F1 which is also early maturing and it is dark green in colour containing small seeds. The yield rate is 25-30 tonnes per acre.
There is Galia F1 variety which is a popular green-fleshed hybrid.
It is resistant to powdery mildew.
The fruit is round with a small cavity and weighs about 1-1.2 kilogrammes. Another is Charleston Gray weighing approximately nine kilogrammes and matures between 85-110 days and is drought resistant. There is the Early Scarlet F1 variety which weighs about 12 kilogrammes and the yield rate is 60 tonnes per acre.