Watermelon Farming

Watermelon (Citrullus lanatus) is a warm season annual plant which produces large and juicy fruits that are mostly composed of water and are eaten raw. Watermelon farming requires minimal management processes and its market is readily available.

Watermelon (Citrullus lanatus) belongs to the Cucurbitaceae family and is a warm season annual plant which produces large and juicy fruits. Fruits are mostly composed of water and can be eaten raw or pickled and the rind is also edible when cooked.

Watermelon farming requires minimal management processes and its market is readily available. In Kenya, it is done mostly in hot regions like Makueni, Machakos, Kajiado and the coastal regions. Watermelon can also be grown in highland regions, although the quality of the fruits is inferior compared to those grown in hot regions.

Health benefits and nutritional value of watermelon

  • High in lycopene, a powerful antioxidant which is effective in preventing some forms of cancer and cardiovascular diseases.
  • High in Vitamin A, C and B6.
  • Rich in Potassium which is helps in controlling blood pressure and preventing strokes.
  • Rich in folate, amino acids, among other healthy components
  • Low in calories
  • Very nutritious

Ecological Requirements of watermelon

Soil – the crop does well in loamy, well drained soils, rich in nutrients and slightly acidic.  If grown in heavy soils, the crop grows slowly and fruit size are usually of low quality.

Temperature – warm temperatures of between 15-30 0C are fit for the growth and development of this crop.

Attitude – watermelons can do well at attitudes of up to 1500m above sea level. However, lowlands are best growing areas.

Rainfall – the crop flourishes in regions with an optimum rainfall of 600mm per cropping season. Irrigation is important in order to ensure consistent moisture availability.

Watermelon seed selection

In order to get excellent results, the choice of seeds is very important.  Some of the commonly used varieties include Sukari F1, Zuri F1, Kubwa F1, Sugar Baby, Crimson Sweet, and Sweet Rose F1. Hybrid seeds are preferred for production of quality fruits. These are available in agrovets/agro dealers’ shops.

Seed rate

Approximately 500 g of seeds is required for direct sowing in a one-acre piece of land.


The crop is spaced at 1.5metres between the rows and 1 meter from one crop to the other. The vines require enough space for their spreading.

Land preparation & Planting of watermelon

Land preparation should be done early to allow for weeds to dry and decompose before planting.

Seeds are usually planted directly in the field. However, it is also possible to first raise them in a seedbed and transplant into the main field although this can cause disturbances to their root systems.


  1. Spray weeds with CATAPULT® 480SL 200ml/20L.This kills both the broadleaf and grass weeds.
  2. Plough land and make it level with a fine tilth.
  • Mix soil with manure and DAP. For efficient and improved nutrient uptake as well as stabilizing soil pH, mix 1kg HUMIPOWER® with 50kg DAP and /or 1 ton of manure.
  1. Make holes at a spacing of 1.5m by 1m and place 2 seeds at a depth of about 2-4cm.
  2. Cover seeds with loose soil.


  • Use certified seeds.
  • Seeds soaked in OPTIMIZER® 20ml/1L overnight prior to planting germinate uniformly and faster.
  • The crop needs at least 6-8 hours of direct sunlight which is very essential for fruit development.
  • Germination occurs in 7 days.


Weeds can significantly lower the productivity potential of the crop as they compete with crop for nutrients, water and light and harbor diseases and pests, which lowers yields. Therefore, proper weed control is very important for good yield and it also makes harvesting easier. This can be done by shallow cultivation. Hand weeding is recommended when the crop has grown enough to cover the soil.


Excess fruits should be pruned in order to allow the right number of fruits to develop properly and obtain marketable quality. All of the unmarketable fruits i.e., the misshapen and blossom-end rot fruits are removed.


Watermelon requires relatively a lot of water, therefore, sufficient irrigation should be done in order to maintain moisture consistency. If this is not done, the fruits dry inside while too much watering makes the fruits to become tasteless and watery.

Irrigation can be done through furrow, overhead or drip irrigation.


  • Fruit splitting/cracking may occur as a result of excessive irrigation after the crop had been water stressed.
  • Irrigation should be reduced as the fruits reach harvesting stage. It should be stopped about two weeks prior to maturity.

Fertilizer Application on Watermelon

In order to achieve optimum yields, timely application of both basal and foliar fertilizers is highly recommended. Manure should be added especially for soils with little or no organic matter. Proper nutrition during the initial growth stages of crop helps boosting nutrients and make the fruits grow bigger.

During planting

Apply 50 kg of DAP in one acre before planting. Alternatively, place a teaspoonful of fertilizer into each planting hole, mix it thoroughly with the soil to make sure that the fertilizer doesn’t burn the seeds and then place the seeds.

DAP is preferred because it contains relatively higher levels of phosphorus which helps the crop with root development.  Other phosphatic fertilizers like TSP can be used.

Young watermelon plants should be sprayed with LAVENDER SUPER STARTER® 20ml/20L or GOLDCHANCE SUPER START® 50g/20L one week after germination, which promote early crop establishment among other benefits.

Top dressing

Use CAN 3 – 4 weeks after sowing. Apply 1 teaspoonful of the fertilizer at the base of each plant in a ring or along the rows, about 15 cm away from the plant at a rate of 50 – 100kg per acre.

CAN fixes nitrogen in the soil which increases the green color of the leaves, responsible to make food for the plant. Other nitrogenous fertilizers like urea can also be used.


During the flowering and fruiting growth phases, spray the crop with GOLDCHANCE SUPER FLOWERS & FRUITS® 50g/20L or DIMIPHITE® 20ml/20L or GOLDCHANCE MULTISUPER K® 50g/20L or LAVENDER SUPER FLOWERS & FRUITS® 20ml/20L.These are rich in nutrient elements which promote production of quality fruits.


  • Soil analysis is highly recommended in order to determine the soil fertility level.
  • All basal fertilizers should be mixed with HUMIPOWER® at a rate of 1kg of HUMIPOWER® into 50Kg of fertilizer.
  • OPTIMIZER® is an organic biostimulant which is essential for plant growth and stress management. It can be applied at all or any growth and development phase of the crop.


Watermelon yield varies according to the variety and general maintenance of the crop. However, an acre of land, in favorable ecological conditions and under good maintenance can produce 20 to 35 tones.

Crop rotation

Watermelon can be rotated with non – cucurbitaceae crops like cereals, legumes or brassicas. This helps in pest and disease management as it breaks their development cycles, among other benefits.

Major Watermelon Pests and Diseases


Cutworm – these are brown biting and chewing pests mostly found in the soil near the plant root zone which cut down young and tender stems. Heavy infestations cause significant crop loss.

Drench soil with PROFILE® 440EC 60 ml/20L or PENTAGON® 50EC 20 ml/20L

Melon fly – it attacks the young fruits altering their cell development and multiplication leading to production of deformed fruits as well as immature dropping of the infested fruits.

Spray KINGCODE ELITE® 50EC 10 ml/20L or PROFILE® 440EC 30 ml/20L or OCCASION STAR® 200SC 3 ml/20L

Red spider mites – these are a great problem in dry and hot conditions. They feed by piercing and sucking while damaging the crop. Attacked leaves have a stippled appearance which turn yellowish to whitish and dry up. Plants under water or drought stress are more likely to suffer serious damages by the pest. They form webs on the undersides of the leaves.

Spray ALONZE® 50EC 5 ml/20L or OCCASION STAR® 200SC 3 ml/20L

Whiteflies – these suck plant sap and excrete honeydew where molds grow, which affects plant growth and vigour. Affected plant loses its vitality due to sap sucking resulting yellowing, downward curling and finally drying of leaves. The tobacco whitefly is considered a major pest due to its ability to vector various virus diseases which cause considerable damage to watermelons.

Spray TAURUS® 500SP 10 g/20L or LEXUS® 247SC 8 ml/20L or KINGCODE ELITE® 50EC 10 ml/20L

Leaf miners– the larvae mine under the leaf surface, creating white mines which are irregular in shape and increase in width as the larvae mature.  This reduces photosynthetic area eventually leading to leaf wilting.

Spray ALONZE® 50EC 5 ml/20L or ESCORT® 19EC 10 ml/20L or LEXUS® 247SC 8 ml/20L or OCCASION STAR® 200SC 3 ml/20L

Epilachna beetles – adults and larvae feed on leaves leaving a fine net of veins and the damaged leaves shrivel and dry up. Young plants can be entirely destroyed while the older ones can tolerate considerable leaf damage. This beetle is a vector of squash mosaic virus.

Spray KINGCODE ELITE® 50EC 10 ml/20L or SINOPHATE® 750SP 20 g/20L or LEXUS® 247SC 8 ml/20L

Aphids– they feed by piercing and sucking the plant sap and reproduce very fast and thus, if not controlled, they cause significant damages. Infested leaves curl and crinkle. As they feed, they excrete honeydew which facilitates the development of sooty mold which reduces photosynthetic area. Stunted growth is noted.

Spray KINGCODE ELITE® 50EC 10 ml/20L or PENTAGON® 50EC 10 ml/20L or LEXUS® 247SC 8 ml/20L

Thrips– both the adult and nymph are destructive. They feed on the leaves and most preferably flowers by sucking the sap thus causing damages which may lead to flower damage/abortion.

Spray ALONZE® 50EC 5 ml/20L or OCCASION STAR® 200SC 3 ml/20L

Nematodes– these are microscopic parasites found in the soil. Infestation leads to wilting of plant, and when the infested plants are pulled from the soil, the roots are seen to be distorted, swollen and bearing knots/ galls which eventually rot causing an eventual death of the plant.

Drench the planting holes with ALONZE® 50EC 10ml/20L or mix basal fertilizer, 50kg with 2kg of ADVENTURE® 0.5GR.


Damping off– this is a soil borne disease. Diseased seeds do not germinate while seedlings rot and eventually die. White cottony growth is evident on the roots of the infected seedlings.

Drench the planting holes with PYRAMID® 700WP 100 g/20L

Powdery mildew – symptoms first develop as whitish talcum like powdery growth on upper leaf surface and as infection progresses, the stems also get infected. Severely infected parts turn yellowish and eventually wilt.

Spray RANSOM® 600WP 15 g/20L or DOMAIN® 250EC 10 ml/20L or ABSOLUTE® 375SC 10 ml/20L

Anthracnose – symptoms are mostly noticeable on fruits as circular black or brown sunken lesions. When wet the centres of the lesions become purplish coloured due to a mass of fungal spores. However, water soaked lesions are also seen on the leaves and stems. On the stem they can girdle the stem causing wilting of the vines.

Spray RANSOM® 600WP 15 g/20L or DUCASSE® 250EW 20 ml/20L or ABSOLUTE® 375SC 10 ml/20L or KATERINA® 720SC 40 ml/20L

Downy mildew – infection leads to formation of yellow patches on the underside of the leaf. These diseased leaves eventually turn brown and fall off. Infected plants get stunted and die while the produced fruits may not mature and therefore have a poor taste.

Spray GEARLOCK TURBO® 250WP 25g/20L or FORTRESS GOLD® 720WP 40g/20L or TOWER® 720WP 50g/20L or KATERINA® 720SC 40ml/20L

Watermelon Mosaic – this is a viral disease. The virus is mechanically transmitted and also spread by several species of aphids in non- persistent mode. Leaves show symptoms of reduced size, patches of dark-green tissue alternating with yellow-green. Generally, the plant becomes stunted and fruits develop water soaked lesions with central solid spots.

Control aphids by spraying KINGCODE ELITE® 50EC 10 ml/20L or PENTAGON® 50EC 10 ml/20L or LEXUS® 247SC 8 ml/20L

Leaf spots – infection causes development of spots on leaves which are angular in shape and variable in size due to the size of the leaf veins. Initially these spots are water soaked.

Spray RANSOM® 600WP 15 g/20L or CHARIOT® 500SC 20 ml/20L or ABSOLUTE® 375SC 10 ml/20L or MILESTONE® 250SC 10 ml/20L

Fusarium wilt initially, symptoms appear as chlorosis of the leaves and as infection continues, leaves begin wilting from bottom to top. The brown vascular discolouration inside infected stem or root leads to the death of plants.

Drench with GREENCOP® 500WP 100g/20L

Foliar spray PYRAMID® 700WP 50g/20L or ABSOLUTE® 375SC 10 ml/20L after every 2 weeks.


  • In all foliar sprays, mix the chemical with INTEGRA 3ml/20L, which is a sticker, spreader and penetrant which increases the efficacy of the product.
  • Use CADILAC® 800WP 50g/20L, which is a preventative fungicide against diseases including anthracnose, downy mildew and leaf spots.

Watermelon Harvesting

This starts about 3 to 4 months after planting depending on the variety and the ecological factors. Harvesting is best done early in the morning when field heat is low and the fruits are most turgid.

Maturity indicators

They include the following;

  • dull hollow sound when the watermelon fruit is tapped with the knuckles
  • cracking of the stem near the mature fruit
  • skin colour change from white to cream or pale yellow where the fruit has been resting on the soil
  • breakup of green bands at the blossom end of the fruit
  • death of the tendrils near the fruit as it reaches maturity
  • skin gets resistant to penetration by the thumbnail and is rough to the touch


  • Fruits should be cut off the vine using a sharp object like a knife rather than pulling, twisting or breaking off.
  • If the fruits are harvested while immature, the red color forms but the flesh does not develop the acceptable sweetness since sugar content does not increase after harvest.

Handling, Storage & Transportation

Minimum handling of the fruits should be ensured because they are quite fragile and prone to breakages and bruising.

In storage, temperature management is very crucial for optimum quality of the fruits. They are not adapted to long storage periods.

Fruits should not be tossed up onto the truck and they should be arranged properly to minimize any movement, which protects the fruits from interior bruising.

Watermelons should not be transported in closed trucks or stored with ethylene-producing produce like bananas as this causes them to break internally, the flesh becomes water-soaked and soft and losses its sweet flavour.

NB; Do not store harvested watermelons on the sun.

Physiological Disorders

These are conditions that are caused by non-pathogenic agents. They can result either due to one or a combination of nutritional, environmental or genetic factors. They include the following;

Blossom-End- Rot (BER)

This is deterioration of the blossom end of the fruit which starts with softening, slight shriveling, browning, blackening with increased shriveling, and sometimes secondary decay. It is caused by lack of calcium nutrition and moisture stress. Application of calcium-rich fertilizers like FERRARI GOLD and maintenance of moisture consistence are recommended.

Sunscald /sunburn

This occurs as a result of exposure to intense solar radiation which causes dehydration and overheating damage of the rind tissue.. Sunburns most occur in varieties that produce fruits with dark-green rinds. Covering the fruits with materials like straw or the crop vines can prevent this condition.


During a dry period the rind becomes fairly inelastic and when this is followed by irrigation or rainfall, large amounts of water are absorbed by the fruit, forcing the rind to burst at its weakest point. Proper nutrition and correct irrigation reduces the occurrence of this disorder.

Misshapen fruits (gourd or bottle-necked)

This is caused majorly due to moisture stress and is common in varieties which produce long fruits. Correct irrigation is recommended.

White heart

Usually white streaks or bands of unwanted flesh at the central part of the fruit forms which is caused by excessive moisture and excessive nitrogen during fruit maturation. Avoid excessive use of nitrogenous fertilizers especially during fruiting stage and ensure correct irrigation.

Misshapen (pear-shaped fruit)

This condition can be as a result of poor pollination which causes restricted growth at the stem end due to absence of developing seeds. It can also happen if temperatures are lower than expected. Increasing the number of bee hives around the farm and using environmentally friendly agrochemicals help in increasing the number of pollinators thereby promoting pollination.

Hollow heart

This disorder is indicated by cracks in the heart/central part of the fruit due to increased growth rate in response to ideal growth conditions facilitated by ample water and warm temperatures.

Rind necrosis

It is an internal disorder of the watermelon rind in which brown, corky, textured spots on the rind form, which may enlarge to form large bands of discoloration that rarely extended into the flesh. Bacterial infections and drought stress have been reported to cause this disorder.


  • Watermelons of any variety can be misshapen especially if they lie on uneven ground or get damaged while small in size.
  • OPTIMIZER® is an organic biostimulant which is essential for plant growth and stress management. It can be applied at all or any growth and development phase of the crop.

Last updated on Tuesday, March 14, 2023 at 6:28 pm

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