Fertilizing watermelon at each growth stage: choose the right fertilizer and determine the amount needed per mu
Watermelon, also known as cold melon, summer melon and so on, is a common fruit in summer in our country. Because its flesh is sweet and fragrant and it has the effects of cooling and relieving summer heat and promoting urination, it is deeply loved by people. Whether a watermelon is sweet or not depends not only on the variety, but also on factors such as fertilization and sunlight. So what fertilizer is good for fertilizing watermelon? How should it be fertilized at each growth stage? How much fertilizer is needed per mu?
I. Fertilizer requirements of watermelon:
For every 1000 kg of watermelon 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). 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.
II. What fertilizer is good to use?
On soil of medium fertility, on the basis of applying sufficient decomposed 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 watermelon good quality, high yield and good benefits. Alternatively, apply 40-60 kg of 45% Jiayou organic fertilizer and 70-80 kg of 45% potassium sulfate compound fertilizer per mu. 30-50% of the organic fertilizer and chemical fertilizer is used as base fertilizer and applied before land preparation. The rest is used as topdressing and applied in divided doses. Only in this way will the watermelons produced be large and sweet. Jiayou organic fertilizer has been tested in use for nearly two years and its effect is remarkable. Its nutrient content is high and it is well absorbed, improving soil properties and even increasing the disease resistance of the plants and reducing the rate of leaf disease. 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 and chlorine-containing compound fertilizers, especially in greenhouse watermelon fields. This is because these fertilizers make the melon taste bland and salty, and also make the fruit very prone to rot. In short, to grow good watermelons, it is necessary to apply organic fertilizer and inorganic fertilizer in a reasonable combination and to balance nitrogen, phosphorus and potassium as well as other elements. Applying only inorganic fertilizer will make the soil compact and will also reduce watermelon quality. Good watermelons need good fertilizer. It is hoped that the broad community of farmers can soon grow watermelons of superior quality and astonishing yield.
III. Fertilization techniques:
1. Base fertilizer for watermelon
Watermelon is not strict about soil requirements, but sandy loam is best, as it is beneficial to root development. Grafted watermelons with replaced roots have even more developed root systems. Before planting, the soil should be deeply plowed 40 cm to allow the root system to grow fully. Apply 4000-5000 kg of fully decomposed high-quality organic fertilizer, 15-20 kg of urea, 25-30 kg of superphosphate and 10-15 kg of potassium sulfate per mu, or 50-60 kg of watermelon special fertilizer, incorporated in combination with deep plowing and land preparation. Apply half during plowing and the other half when making ridges, and mix the chemical fertilizer and organic fertilizer evenly with the soil in the furrow.
The specific amount of fertilizer applied can be determined according to local soil fertility and yield level. Within a certain range, the amount of fertilizer applied increases as yield increases.
2. Topdressing for watermelon
(1) Watermelon fruit-swelling fertilizer: when normal young fruit grows to the size of an egg, the fruit begins to expand rapidly, and the plant's fertilizer requirement gradually reaches its peak for the whole growth period. At this time, heavy application of fruit-swelling fertilizer should be made to promote fruit expansion and prevent premature aging. Topdressing for watermelon should be mainly phosphorus and potassium fertilizer, with little or no nitrogen fertilizer, so as to avoid a decline in watermelon quality caused by excessive nitrogen fertilizer. Apply 15 kg of diammonium phosphate, 15 kg of potassium sulfate and 10 kg of urea per mu, or 20 kg of watermelon special fertilizer. Gengzhongbang Planting Network recommends hole application beside the ridge 30 cm from the melon roots, or application between two plants near the irrigation ditch. After fertilizing, promptly water well for fruit swelling to promote nutrient absorption and accelerate fruit expansion.
(2) Watermelon rejuvenation fertilizer: after the first crop of watermelons is harvested, immediately apply a quick-acting chemical fertilizer once as topdressing. Generally, apply 15-20 kg of urea, 15 kg of potassium sulfate and 10 kg of diammonium phosphate per mu, and in combination with topdressing, water heavily once to replenish nutrients and water in the soil, maintain relatively strong plant growth and prevent premature aging of vines and leaves.
(3) Foliar fertilizer application: foliar spraying is a necessary means to make up for insufficient root absorption and to supplement and balance nutrients for the plant. It has the characteristics of low practical cost, uniform application, quick fertilizer effect and high nutrient utilization rate. Generally, starting from the fruit-swelling stage of the first crop of watermelons, spray 0.3%-0.5% monopotassium phosphate or potassium treasure solution once every 7-10 days. This can enhance watermelon stress resistance, increase the fruit-setting rate and sugar content of the fruit, and has a fairly significant yield-increasing effect.
(4) Carbon dioxide gas fertilizer: supplementing carbon dioxide gas fertilizer during the watermelon fruiting period can increase the photosynthetic intensity of leaves and prevent premature aging of the plant. This is an important measure to increase sugar accumulation and raise yield in greenhouse watermelons. At present, the acid reaction fertilization method is mostly used in production. Place 1 plastic bucket every 50 cubic meters in the greenhouse, add 6 liters of clean water to each bucket, then slowly add 2 kg of industrial sulfuric acid and stir evenly with the water. At around 9 o'clock every day, wrap 250-400 g of ammonium bicarbonate fertilizer in a plastic bag, poke a few small holes, and put it into the bucket, allowing the ammonium bicarbonate to slowly release into the dilute acid solution and react to produce carbon dioxide gas, raising the carbon dioxide concentration in the greenhouse to about 1000 mg/kg. The ammonium sulfate solution produced by the reaction can be used as nitrogen fertilizer after being diluted 300 times and applied to the watermelon field with irrigation water.
3. Key points of fertilization techniques:
(1) Method of applying farmyard manure: when preparing land and applying fertilizer, apply more farmyard manure with complete ingredients, such as chicken manure and sheep manure. The watermelons grown this way are uniform in size, good in flavor and high in sweetness.
(2) Method of applying potassium bacteria: the “Manyuanchun” microbial inoculant containing potassium bacteria, biological organic fertilizer and black-plus-white biological fertilizer are compound high-tech microbial fertilizers. Applied in stages according to formula throughout the whole growth period of watermelon, they can make watermelon leaves dark green, fruit shape regular and sweetness increase by 1 to 1.5 degrees.
(3) Method of applying stevia: take 500 g of stevia and 10 g of soybeans, add 25 kg of water, soak until swollen and then boil until the water is gone. When watermelon flowers and sets fruit, apply in holes 13 cm away from the melon seedlings at a depth of about 13 cm. The melons grown this way are large and sweet.
(4) Method of spraying boron-calcium liquid: fully dissolve 150 g of sodium borate, 50 g of calcium chloride and 1000 g of sucrose in 100 kg of water, and spray on a sunny afternoon during the watermelon swelling period. This can increase sweetness by 20%.
(5) Method of spraying rare earth: at the 5-6 true leaf stage, initial flowering stage and swelling stage of watermelon, spray 75 to 100 kg of 0.03%, 0.06% and 0.08% rare earth nitrate solution on the leaves respectively in 3 applications. This can increase sweetness by 0.6 to 0.7 degrees.