Watermelon Farming

Watermelon (Citrullus lanatus), a member of the Cucurbitaceae family, is an annual plant that thrives in warm seasons and produces large, juicy fruits. The fruits are primarily composed of water and can be consumed either raw or pickled, while the rind is also edible when cooked.

Watermelon cultivation requires minimal management processes, and there is a readily available market for its produce. In Kenya, it is predominantly grown in hot regions such as Makueni, Machakos, Kajiado, and the coastal regions. Although watermelon can also be cultivated in highland regions, the quality of the fruits tends to be inferior compared to those grown in hotter regions.

Health benefits and nutritional value of watermelon

  • It is rich in lycopene, a potent antioxidant known for its ability to help prevent certain types of cancer and cardiovascular diseases.
  • Watermelon is a good source of essential vitamins such as Vitamin A, C, and B6, which contribute to overall health and well-being.
  • It contains a significant amount of potassium, a mineral that aids in blood pressure control and helps prevent strokes.
  • Watermelon is also abundant in folate, amino acids, and various other beneficial components that contribute to its nutritional value.
  • Despite its nutritional richness, watermelon is low in calories, making it a healthy and guilt-free choice for those seeking a nutritious diet.
  • Overall, watermelon is highly nutritious and offers a range of health benefits.

Ecological Requirements of watermelon

Soil: Watermelon thrives in loamy, well-drained soils that are nutrient-rich and slightly acidic. When grown in heavy soils, the crop tends to have slow growth and produces fruits of lower quality.

Temperature: The optimal growth and development of watermelon occur in warm temperatures ranging between 15-30°C.

Altitude: While watermelons can tolerate altitudes of up to 1500m above sea level, lowland areas are considered the best growing regions for this crop.

Rainfall: Watermelons flourish in regions with an average rainfall of 600mm per cropping season. However, to ensure consistent moisture availability, irrigation is essential.

Watermelon seed selection

Achieving excellent results in watermelon cultivation requires careful selection of seeds. Several commonly used varieties have proven successful, including Sukari F1, Zuri F1, Kubwa F1, Sugar Baby, Crimson Sweet, and Sweet Rose F1. It is recommended to opt for hybrid seeds, as they have demonstrated the ability to produce high-quality fruits. These seeds can be readily obtained from agrovets or agricultural dealers’ shops.

Seed rate

For direct sowing on a one-acre piece of land, an approximate quantity of 500 g of seeds is required.

Spacing

When cultivating watermelon, it is important to provide adequate spacing for the crop. Typically, the recommended spacing is 1.5 meters between rows and 1 meter between individual plants. This allows sufficient room for the vines to spread and grow without obstruction.

Land preparation & Planting of watermelon

To ensure optimal conditions for watermelon cultivation, it is advisable to prepare the land well in advance. This early preparation allows for weeds to dry up and decompose before planting.

Traditionally, watermelon seeds are directly planted in the field. However, an alternative approach involves initially raising the seeds in a seedbed and later transplanting them to the main field. It is important to note that transplanting can disrupt the root systems of the seedlings, so careful handling is required.

Procedure

To effectively control weeds, it is recommended to spray them with CATAPULT® 480SL at a rate of 200ml/20L. This herbicide is effective against both broadleaf and grass weeds.

Prior to planting, the land should be ploughed and leveled to achieve a fine tilth.

For improved nutrient uptake and soil pH stabilization, it is advisable to mix the soil with manure and DAP (diammonium phosphate). To enhance efficiency, mix 1kg of HUMIPOWER® with 50kg of DAP and/or 1 ton of manure.

During planting, create holes at a spacing of 1.5m by 1m and place 2 seeds at a depth of approximately 2-4cm. Cover the seeds with loose soil.

Tips:

  • Always use certified seeds for reliable results.
  • Soaking the seeds in OPTIMIZER® at a rate of 20ml/1L overnight prior to planting promotes uniform and faster germination.
  • Watermelon crops require at least 6-8 hours of direct sunlight per day, as it is crucial for fruit development.
  • Germination typically occurs within 7 days.

Weeding

The presence of weeds can greatly reduce the productivity of the watermelon crop by competing with the plants for essential resources such as nutrients, water, and light. Weeds can also serve as hosts for diseases and pests, leading to further yield reduction. Therefore, effective weed control measures are crucial to ensure optimal yields and facilitate easier harvesting. One method for weed control is shallow cultivation, which helps to suppress weed growth. Additionally, as the watermelon crop grows and covers the soil, hand weeding is recommended to remove any remaining weeds.

Pruning

To ensure proper fruit development and achieve marketable quality, it is important to prune excess fruits. This involves removing any surplus fruits to allow the remaining ones to grow and develop optimally. It is essential to remove unmarketable fruits, including misshapen fruits and those affected by blossom-end rot, to maintain the desired quality standards.

Irrigation

Watermelon plants have a high water requirement, necessitating adequate irrigation to maintain consistent moisture levels. Failure to provide sufficient irrigation can lead to fruits drying up internally, while excessive watering can result in tasteless and overly watery fruits.

Irrigation can be accomplished through various methods such as furrow irrigation, overhead irrigation, or drip irrigation.

Tips:

  • Excessive irrigation following a period of water stress may cause fruit splitting or cracking.
  • As the fruits approach the harvesting stage, it is advisable to gradually reduce irrigation. About two weeks before maturity, irrigation should be completely stopped.

Fertilizer Application on Watermelon

To maximize yields, it is crucial to apply both basal and foliar fertilizers in a timely manner. For soils lacking organic matter, the addition of manure is particularly important. Providing proper nutrition during the initial growth stages of the crop is essential for enhancing nutrient uptake and promoting the development of larger fruits.

During planting

For pre-planting fertilization, it is recommended to apply 50 kg of DAP (diammonium phosphate) per acre. Alternatively, a teaspoonful of fertilizer can be placed into each planting hole, ensuring thorough mixing with the soil to prevent seed burn before placing the seeds.

DAP is preferred due to its relatively higher phosphorus content, which aids in root development. Other phosphatic fertilizers, such as TSP (triple superphosphate), can also be used.

To promote early crop establishment and provide additional benefits, young watermelon plants can be sprayed with either LAVENDER SUPER STARTER® at a rate of 20ml/20L or GOLDCHANCE SUPER START® at a rate of 50g/20L one week after germination. These products assist in establishing the crop during its early stages.

Top dressing

CAN fertilizer should be used approximately 3-4 weeks after sowing. Apply 1 teaspoonful of the fertilizer at the base of each plant, either in a ring formation or along the rows, maintaining a distance of about 15 cm from the plant. The recommended application rate is 50-100 kg per acre.

CAN fertilizer plays a role in fixing nitrogen in the soil, which contributes to the vibrant green color of the leaves and aids in the production of plant food. Alternatively, other nitrogenous fertilizers like urea can be used.

For enhanced growth and vegetative development, spray the crop with GOLDCHANCE SUPER GROWTH® at a rate of 50g/20L or LAVENDER SUPER GROWTH & VEGETATIVE® at a rate of 20ml/20L.

During the flowering and fruiting stages, spray the crop with GOLDCHANCE SUPER FLOWERS & FRUITS® at a rate of 50g/20L, DIMIPHITE® at a rate of 20ml/20L, GOLDCHANCE MULTISUPER K® at a rate of 50g/20L, or LAVENDER SUPER FLOWERS & FRUITS® at a rate of 20ml/20L. These fertilizers are rich in nutrient elements that promote the production of high-quality fruits.

Tips:

  • Conducting a soil analysis is highly recommended to determine the soil fertility level and guide fertilizer application.
  • Basal fertilizers should be mixed with HUMIPOWER® at a rate of 1kg of HUMIPOWER® per 50kg of fertilizer for improved effectiveness.
  • OPTIMIZER® is an organic biostimulant that is beneficial for plant growth and stress management. It can be applied at any stage of the crop’s growth and development.

Yield

The yield of watermelon can vary based on the variety of the crop and the overall management practices employed. However, under favorable ecological conditions and with proper maintenance, an acre of land has the potential to produce a yield ranging from 20 to 35 tonnes of watermelon.

Crop rotation

Watermelon can be incorporated into crop rotation systems, alternating with non-cucurbitaceae crops such as cereals, legumes, or brassicas. This practice offers several advantages, including effective pest and disease management by disrupting their development cycles. Additionally, crop rotation provides other benefits that contribute to overall soil health and productivity.

Major Watermelon Pests and Diseases

Pests

Cutworms are brown biting and chewing pests that commonly inhabit the soil near the plant’s root zone, causing damage by cutting down young and tender stems. Severe infestations can lead to significant crop loss.

To control cutworms, drench the soil with either PROFILE® 440EC at a rate of 60 ml/20L or PENTAGON® 50EC at a rate of 20 ml/20L.

Melon flies attack young fruits, disrupting their cell development and multiplication, resulting in deformed fruits and premature dropping of infested fruits.

To manage melon flies, spray the crop with KINGCODE ELITE® 50EC at a rate of 10 ml/20L, PROFILE® 440EC at a rate of 30 ml/20L, or OCCASION STAR® 200SC at a rate of 3 ml/20L.

Red spider mites pose a significant problem in dry and hot conditions. They feed on the plants by piercing and sucking, causing damage. Leaves attacked by red spider mites develop a stippled appearance, turning yellowish to whitish and eventually drying up. Plants under water or drought stress are more susceptible to serious damage from this pest. Red spider mites also create webs on the undersides of leaves.

To control red spider mites, spray the crop with ALONZE® 50EC at a rate of 5 ml/20L or OCCASION STAR® 200SC at a rate of 3 ml/20L.

Whiteflies suck plant sap and excrete honeydew, leading to the growth of molds that negatively affect plant growth and vigor. Affected plants lose their vitality due to sap-sucking, resulting in yellowing, downward curling, and eventual drying of leaves. The tobacco whitefly is particularly concerning as it can transmit various virus diseases that cause significant damage to watermelons.

To manage whiteflies, spray the crop with TAURUS® 500SP at a rate of 10 g/20L, LEXUS® 247SC at a rate of 8 ml/20L, or KINGCODE ELITE® 50EC at a rate of 10 ml/20L.

Leaf miners are larvae that create mines under the leaf surface, resulting in irregular-shaped white mines that increase in width as the larvae mature. This reduces the photosynthetic area and can lead to leaf wilting.

To control leaf miners, spray the crop with ALONZE® 50EC at a rate of 5 ml/20L, ESCORT® 19EC at a rate of 10 ml/20L, LEXUS® 247SC at a rate of 8 ml/20L, or OCCASION STAR® 200SC at a rate of 3 ml/20L.

Epilachna beetles, both in their adult and larval stages, feed on watermelon leaves, leaving a fine net of veins. The damaged leaves shrivel and dry up. Young plants can be completely destroyed, while older plants can tolerate a considerable amount of leaf damage. Epilachna beetles are also known vectors of the squash mosaic virus.

To manage Epilachna beetles, spray the crop with KINGCODE ELITE® 50EC at a rate of 10 ml/20L, SINOPHATE® 750SP at a rate of 20 g/20L, or LEXUS® 247SC at a rate of 8 ml/20L.

Aphids feed by piercing and sucking plant sap and reproduce rapidly, causing significant damage if left unchecked. Infested leaves curl and crinkle, and aphids excrete honeydew, facilitating the development of sooty mold that reduces the photosynthetic area. Stunted growth is also observed.

To control aphids, spray the crop with KINGCODE ELITE® 50EC at a rate of 10 ml/20L, PENTAGON® 50EC at a rate of 10 ml/20L, or LEXUS® 247SC at a rate of 8 ml/20L.

Thrips, both in their adult and nymph stages, can cause extensive damage. They feed on leaves and preferentially target flowers, sucking sap and causing damage that may lead to flower damage or abortion.

To manage thrips, spray the crop with ALONZE® 50EC at a rate of 5 ml/20L or OCCASION STAR® 200SC at a rate of 3 ml/20L.

Nematodes are microscopic parasites found in the soil that can cause wilting of plants. Infested plants exhibit distorted, swollen roots with knots or galls, which eventually rot and lead to the death of the plant.

To control nematodes, drench the planting holes with ALONZE® 50EC at a rate of 10 ml/20L or mix the basal fertilizer with 2kg of ADVENTURE® 0.5GR.

Tips:

  • Conducting a soil analysis is highly recommended to determine soil fertility levels.
  • To enhance the effectiveness of basal fertilizers, mix them with HUMIPOWER® at a rate of 1

Diseases

Damping off is a soil-borne disease that prevents the germination of diseased seeds and causes the rotting and eventual death of seedlings. Infected seedlings exhibit white cottony growth on their roots.

To manage damping off, drench the planting holes with PYRAMID® 700WP at a rate of 100 g/20L.

Powdery mildew initially appears as a talcum-like white powdery growth on the upper surface of leaves. As the infection progresses, the stems may also become infected. Severely affected parts turn yellow and eventually wilt.

To control powdery mildew, spray the crop with RANSOM® 600WP at a rate of 15 g/20L, DOMAIN® 250EC at a rate of 10 ml/20L, or ABSOLUTE® 375SC at a rate of 10 ml/20L.

Anthracnose is characterized by circular black or brown sunken lesions primarily observed on fruits. When wet, the center of the lesions becomes purplish due to the presence of fungal spores. Lesions can also be seen on leaves and stems, appearing as water-soaked areas. In severe cases, the lesions can girdle the stem, causing wilting of the vines.

To manage anthracnose, spray the crop with RANSOM® 600WP at a rate of 15 g/20L, DUCASSE® 250EW at a rate of 20 ml/20L, ABSOLUTE® 375SC at a rate of 10 ml/20L, or KATERINA® 720SC at a rate of 40 ml/20L.

Downy mildew infection leads to the formation of yellow patches on the underside of leaves, which eventually turn brown and fall off. Infected plants exhibit stunted growth and may die prematurely, while the resulting fruits may not mature properly and have an inferior taste.

To control downy mildew, spray the crop with GEARLOCK TURBO® 250WP at a rate of 25g/20L, FORTRESS GOLD® 720WP at a rate of 40g/20L, TOWER® 720WP at a rate of 50g/20L, or KATERINA® 720SC at a rate of 40 ml/20L.

Watermelon mosaic is a viral disease that can be mechanically transmitted and spread by several species of aphids in a non-persistent manner. Infected leaves show reduced size and patches of dark-green tissue alternating with yellow-green. The overall growth of the plant is stunted, and the fruits may develop water-soaked lesions with central solid spots.

To manage watermelon mosaic, control aphids by spraying the crop with KINGCODE ELITE® 50EC at a rate of 10 ml/20L, PENTAGON® 50EC at a rate of 10 ml/20L, or LEXUS® 247SC at a rate of 8 ml/20L.

Leaf spots result in the development of angular-shaped spots on the leaves, varying in size depending on the leaf veins. Initially, these spots appear water-soaked.

To control leaf spots, spray the crop with RANSOM® 600WP at a rate of 15 g/20L, CHARIOT® 500SC at a rate of 20 ml/20L, ABSOLUTE® 375SC at a rate of 10 ml/20L, or MILESTONE® 250SC at a rate of 10 ml/20L.

Fusarium wilt symptoms initially manifest as leaf chlorosis, progressing to wilting from the bottom to the top of the plant. Brown vascular discoloration inside infected stems or roots ultimately leads to plant death.

To manage fusarium wilt, drench the soil with GREENCOP® 500WP at a rate of 100g/20L. Additionally, foliar spray the crop with PYRAMID® 700WP at a rate of 50g/20L or ABSOLUTE® 375SC at a rate of 10 ml/20L every two weeks.

Tips:

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

Watermelon Harvesting

The watermelon harvest typically begins approximately 3 to 4 months after planting, although the exact timing can vary based on the specific variety and ecological conditions. For optimal results, it is recommended to conduct harvesting in the early morning when the field heat is low, and the fruits are at their most turgid state.

Maturity indicators

The indicators of watermelon fruit readiness for harvesting are as follows:

  • When tapped with the knuckles, a dull hollow sound is produced.
  • The stem near the mature fruit may show signs of cracking.
  • The skin color changes from white to cream or pale yellow in areas where the fruit has been resting on the soil.
  • Green bands at the blossom end of the fruit start to break up.
  • Tendrils near the fruit may die off as it reaches maturity.
  • The skin becomes resistant to penetration by the thumbnail and feels rough to the touch.

Tips:

  • It is recommended to cut off the fruits from the vine using a sharp object such as a knife rather than pulling, twisting, or breaking them off.
  • Harvesting immature fruits may result in the development of the red color, but the flesh will not attain the desired sweetness since sugar content does not increase after harvest.

Handling, Storage & Transportation

It is important to handle watermelon fruits with minimal contact to prevent breakages and bruising, as they are fragile in nature.

Proper temperature management is crucial during storage to maintain optimum fruit quality. Watermelons are not well-suited for extended storage periods.

During transportation, it is recommended to avoid tossing the fruits onto the truck and instead arrange them carefully to minimize any movement, thereby protecting them from interior bruising.

Watermelons should not be transported or stored in closed trucks, and it is advisable to keep them separate from ethylene-producing fruits like bananas. Exposure to ethylene can cause internal breakage, resulting in water-soaked and soft flesh, leading to a loss of the sweet flavor.

Important Note: Harvested watermelons should not be stored in direct sunlight.

In periods of drought, the watermelon rind tends to become less elastic. Subsequently, when irrigation or rainfall occurs, the fruit absorbs a significant amount of water, causing the rind to burst at its weakest point. This disorder can be minimized by ensuring proper nutrition and implementing appropriate irrigation practices. Adequate nutrition and precise irrigation management help reduce the occurrence of this issue.

Misshapen fruits (gourd or bottle-necked)

This condition primarily arises from moisture stress and is commonly observed in varieties that yield elongated fruits. Proper irrigation practices are recommended to mitigate this issue.

White heart

Typically, the occurrence of white streaks or bands of undesired flesh in the central part of the fruit is caused by excessive moisture and nitrogen levels during fruit maturation. To prevent this, it is important to avoid the excessive application of nitrogenous fertilizers, especially during the fruiting stage. Additionally, implementing proper irrigation practices is crucial in managing this condition effectively.

Misshapen (pear-shaped fruit)

This condition can occur when there is poor pollination, leading to restricted growth at the stem end due to the absence of developing seeds. It can also be influenced by lower-than-expected temperatures. To address this, increasing the number of beehives around the farm and using environmentally friendly agrochemicals can help enhance the population of pollinators, thereby promoting effective pollination.

Hollow heart

Rind necrosis

This is an internal disorder of the watermelon rind characterized by the formation of brown, corky, textured spots. These spots may enlarge, forming large bands of discoloration that rarely extend into the flesh. Bacterial infections and drought stress have been identified as potential causes of this disorder.

Tips:

  • Watermelons of any variety can become misshapen, particularly if they rest on uneven ground or sustain damage while still small in size.
  • OPTIMIZER® is an organic biostimulant that plays a vital role in plant growth and stress management. It can be applied during any growth and development phase of the crop.

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