How to cultivate watermelon sustainably

When short-term returns on investments constitute the driving factors, watermelon is among the crops to plant. The gestation period is between 75 and 90 days, depending on varieties. Watermelon is one of the highly cultivated and consumed crops believed to have originated almost 5,000 years ago from the Kalahari Desert of Africa. Cultivated all over tropical climate, it is produced in Nigeria at different specific periods for optimal bumper harvest.

Ecology and timing of planting
Watermelon does well in both forest and savanna ecologies. It is planted in the North and it equally does well in the South. Timing of planting, however, differs.

Dr Kayode Ajayi, a plant physiologist at the Horticultural Research Institute of Nigeria (NIHORT), Ibadan, told The Guardian that watermelon is best planted at the outset of rainfalls and towards the end of the raining season.

Farmers in the northern and north central parts of Nigeria, Dr Ajayi advised, could plant around mid May and late August for early and late production respectively, while farmers in the southern Nigeria could plant the fruit crop between mid March and April ending or early September. However, with functional irrigation in the north, watermelon could be planted round the year.

He explained that watermelon requires water in regulated quantity to perform optimally. This, he said, accounts for why it is often planted early and later parts of the rainfall periods.

To get maximum yields and high returns on watermelon investments, the following should be strictly adhered to.

Sourcing improved seeds
Improved seeds could be purchased from accredited seeds and agro-allied inputs suppliers around the country. Most standard watermelon seeds are usually packaged in tin and sealed containers, with certification and expiry dates, germination percentage and other details. Buying roadside seeds means planting second filial generation seeds of hybrids (seeds extracted from fresh watermelon you buy), which reduce harvest by over 50%.

Land preparation
Land preparation for watermelon starts with land clearing, plowing, and harrowing to break the soil for adequate oxygen. Seed beds or ridges are made for the crop to enhance soil to drain, especially in the forest ecologies. “Watermelon does not tolerate water logging and so, if planted on heavy soil, ridging will be helpful to improve drainage,” Ajayi suggested. “On loamy soil,” he added, “it is usually planted on the flat land after harrowing.”

Mechanical land preparation is faster, better and cheaper, but a manual land preparation is equally done if access to tractors, ridgers and harrowers is limited.

Planting, spacing, population and yield
After spraying the prepared land with vegetable-compatible pre-emergence herbicides and waiting for some days, the next step is planting. Planting could be done in phases to allow different batches of harvest if the farmland is large. However, it should be planted in a day on a small farmland.

One metre by one metre spacing is ideal, according to the NIHORT plant physiologist, but it could be reduced to one metre by 75 centimetres. With these spacing ranges, between 10,000 and 12,000 plants of the crop would be on one hectare of land.

Dr Ajayi said if 10,000 or 12,000 watermelon seeds are successfully grown, each could produce a minimum of one big watermelon. So, no fewer than 10,000 or 12,000 watermelons would be expected at harvest time.

Weed management
Weed infestation competes with and drains the plant of essential nutrients, thereby stunting growth and drastically reducing yield per hectare. A watermelon farmer in Ilorin, Kwara State, Kabir Lawal, said to control weed, he uses pre-emergence vegetable selective herbicides immediately after land preparation, about 10 days or more before planting watermelon seeds. This way, he added, manual weeding would be reduced to only one or two times before harvest.

On small farmland, some farmers control weed by covering the floor with nylons, but commercial application could be less cost effective, time wasting and unsustainable.

Watermelon. PHOTO:

Watermelon suppresses weeds if accurate planting spacing is followed, for the foliage and vines spread and form a canopy over the weeds, just like potatoes.

Crop protection
Watermelon needs maximum protection almost immediately after planting. Failure to protect the crop from insects and fungi is always very devastating, and can lead to total loss or significant reduction of yield.

Watermelon is usually sprayed with contact and systemic insecticides and fungicides starting from about 14 days after planting and subsequently, 14 days intervals. However, chemical applications should stop about 20 days before harvest.

It should be emphasised, the NIHORT plant physiologist said, that crop protection with agrochemicals is one of the success factors in watermelon production, closely followed by weed control.

Capital requirement
Planting one hectare (two and a half acres) of watermelon would require between N260,000 and N300,000. Breaking the cost down, a watermelon farmer/dealer in Oyo State, Mr Tajudeen Oyinlola, corroborated by Dr Ajayi at NIHORT, land clearing, plowing and harrowing one hectare mechanically would cost about N40,000; improved seeds, N25,000; planting and weeding labour would cost N70,000; fertiliser (four bags) and application labour, N40,000; insecticides and application labour, N40,000; sprayer, N15,000 and other expenses, N30,000.

Return on investment, marketing & sale
According to street value survey of watermelon, a mini truck containing 500 units of the product is sold for N50,000. Dividing 10,000 estimated harvest by 500 would make 20 mini trucks of watermelon. Multiplying this by N50,000 would mean N1 million. This was the minimum estimate, according to the NIHORT plant scientist. This price was confirmed by one Usman Mohammed, a watermelon seller in Ibadan, Oyo State.

Mohammed said: “I usually buy a mini truck of watermelon at the rate of N50,000 and I sell each of the 500 units between N200 and N500.”

Direct sale to supermarkets, homes, offices and selling at strategic places could fetch more money to ingenious farmers, especially those who have mini buses or pick-up vans for city display of the produce. In this instance, one watermelon would averagely fetch the farmer N250, multiplied by, say, 5,000 watermelons.

One way to determine when watermelon is ripe is to watch the tendril closest to the melon stem. A tendril is a modified stem in the shape of slender and spirally coil opposite the base of watermelon on the vine. Of all the indicators of ripeness, this is the most reliable. When it turns brown and dries up, the melon is ripe. The trouble with this method is that with some watermelon varieties, the tendril dries and drops off more than a week before the melon is fully ripe, and sampling would tell whether to start harvesting or not.

Another sign of ripeness in most watermelon varieties is the color of the bottom spot, where the melon sits on the ground. As the watermelon becomes ripe, the spot turns from almost white to a rich yellow. Also, all watermelons lose the powdery or slick appearance on the top and take on a dull look.

One good thing about watermelon is that a plot or two of land can be used to produce the crops about three to four times in a year with drip irrigation. Dry season planting of watermelon with a mini drip irrigation facility does better and attracts more income. It allows larger plant population on the plots because there is no weed competition with the crop. In this way, there is less infestation of pests and weeds. Two, the produce would be ready off season and hence, sells faster and with better prices.

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