What Fertilizer Is Best for Growing Watermelons? Key Points of Watermelon Fertilization Techniques

When it comes to watermelons, I think everyone is more than familiar with them. When the hot summer arrives, watermelon becomes everyone's favorite fruit. When we pass by the front of a fruit shop, the watermelons are piled up like a mountain. Buy one and put it in the fridge to chill, and eating cold watermelon feels even better!

What Fertilizer Is Best for Growing Watermelons

Farmer friends often ask: “If I want sweet watermelons, what fertilizer should I use?” Whether a watermelon is sweet or not depends first on the variety, then on sunlight and the temperature difference between day and night; fertilizer usually ranks after these factors. With the same variety, in adjacent fields, planted at the same time, whether the watermelon is sweet and whether the taste is good depends on the fertilizer. The fertilizer requirements of watermelon: for every 1000 kg of watermelons produced, 2.25 kg of nitrogen, 0.9 kg of phosphorus, and 3.38 kg of potassium are needed (this refers only to the mass of each element in the fertilizer applied, not 2.25 kg of nitrogen fertilizer, 0.9 kg of phosphate fertilizer, and so on; the same applies below), and it is relatively sensitive to trace elements such as boron, zinc, molybdenum, manganese, and cobalt, and also has certain requirements for calcium, magnesium, iron, and copper.

In soil of medium fertility, on the basis of applying sufficient rotted organic fertilizer, applying 11 kg of potassium per mu (equivalent to 22 kg of potassium sulfate), 11 kg of nitrogen (equivalent to 55 kg of ammonium sulfate or 24 kg of urea), and 5.7 kg of phosphorus (equivalent to 48 kg of superphosphate) gives watermelons good quality, high yield, and good returns. Or apply 40-60 kg of 45% Jiayou organic fertilizer and 70-80 kg of 45% potassium sulfate compound fertilizer per mu. Of the organic fertilizer and chemical fertilizer, 30-50% is used as base fertilizer and applied before land preparation. The rest is used as topdressing, applied in split doses. Only then will the watermelons produced be large and sweet. Jiayou organic fertilizer, after being tested in use for nearly two years, has shown remarkable results. Its nutrient content is high, it is well absorbed, it improves soil properties, and even increases the disease resistance of the plants and lowers the leaf disease rate. Most importantly, it improves watermelon quality: the fruit is smooth and glossy, large and sweet, with thin rind and sandy flesh. In choosing watermelon fertilizer, avoid chlorine-containing fertilizers, such as ammonium chloride, potassium chloride, chlorine-containing compound fertilizers, and so on, especially in greenhouse watermelon fields, use them with caution. Because these fertilizers make the melon taste bland and salty, and make fruit rot extremely easy. In short, to grow good watermelons, you must achieve a reasonable combined application of organic and inorganic fertilizers, and a reasonable ratio of nitrogen, phosphorus, and potassium as well as other elements. Applying only inorganic fertilizer will compact the soil and will also lower watermelon quality. Good watermelons need good fertilizer, and I hope the broad community of farmer friends can soon grow watermelons of superior quality and astonishing yield.

How to Fertilize When Planting Watermelons  

1. Seedling-promoting fertilizer. In northern regions, at the 4-5 true-leaf stage, apply 1.5-2.5 kg of urea per 667 sq m. In southern regions, before vine extension, water with diluted human manure 2 or 3 times, applying 20-30 kg of human manure each time per 667 sq m; combining with intertillage and loosening the soil gives better results.  

2. Vine-extension fertilizer. In northern regions, at the early stage of vine extension, apply 5-10 kg of urea and 3-5 kg of potassium sulfate per 667 sq m; in southern regions, after vine extension, apply 50-70 kg of cake fertilizer or 500-750 kg of rotted poultry manure per 667 sq m.  

3. Fruit-setting fertilizer. Apply when the young fruit is the size of an egg. In northern regions, apply 10-15 kg of urea and 5-6 kg of potassium sulfate per 667 sq m; in southern regions, mix 0.7-1 kg of urea or compound fertilizer per 667 sq m into human manure and apply it as a liquid.  

4. Fruit-swelling fertilizer. When the fruit is the size of a bowl, apply 7-10 kg of urea and 5-6 kg of potassium sulfate per 667 sq m. Stop topdressing 1 week before harvest. In the late fruiting stage, a mixed solution of 0.3%-0.4% potassium dihydrogen phosphate and 0.2%-0.3% urea can be used for foliar topdressing, generally sprayed once every 5-7 days, for 2 or 3 consecutive times.

When to Sow Watermelons  

For greenhouse watermelons, the planting time is March 10 to March 20; small-arch-tunnel watermelons are delayed by 10-15 days; solar greenhouse watermelons are appropriately 5-7 days earlier than greenhouse watermelons; early-spring protected cultivation watermelons are planted accordingly. Management should be strengthened, focusing on temperature, humidity, fertilizer and water, and flower and fruit retention, to promote the growth and development of the crop.  

For watermelon cultivation, land preparation and bed making: 15 days before watermelon planting, prepare the land and make beds in advance to build up soil moisture. For greenhouse watermelons, it is best to use high-ridge double-row cultivation, with large rows 90 cm apart and small rows 40 cm apart, making small raised banks, with ridge width 30 cm and ridge height 15 cm; after the bed surface is prepared, cover it with plastic film ready for planting. For greenhouse cultivation, the plastic greenhouse can be set up before land preparation, with an inner diameter width of not less than 6.5 m and a height of not less than 1.6 m; in the middle of the greenhouse, a small arch tunnel 2.2 m wide with an arch height of 0.7 m. The thickness of the straw matting is not less than 5 cm. For greenhouse cultivation, prepare the beds 6-7 days before planting and cover with plastic film ready for planting.

Precautions for Growing Watermelons  

1. Watermelon is a plant with relatively high fertilizer needs, but too much nitrogen fertilizer, plus abundant rainfall or irrigation, will cause thick vines. Thick vines do not set fruit easily and also affect watermelon yield. The way to prevent thick vines is not to apply too much nitrogen fertilizer, and to strengthen ventilation and light transmission. If thick vines appear before flowering, the vine tip can be removed to damage their growth vigor and inhibit their growth.  

2. Watermelon is a chlorine-sensitive crop; applying chlorine-containing fertilizer will affect melon quality.  

3. Do not apply concentrated fertilizer during drought. 

4. The fertilization site must not be too close to the roots. The fertilization site for watermelon is generally required to be about 10 cm from the main root; too close easily burns the roots.

We all know that watermelon is a very juicy fruit, and it tastes very sweet, and in summer watermelons are also very cheap. It can be said that watermelon is a good fruit with fine quality and low price, deeply loved by many people, but such good watermelons are all painstakingly grown by our melon farmers.