Watermelon is one of the most popular fruits. In recent years, with the adjustment of the industrial structure in rural areas, the growing area of ​​watermelons has been expanding. Especially in the suburbs of some cities, the development of watermelon as an industry serving urban agriculture has become one of the major cash crops for farmers to increase their income. The planting area of ​​watermelon around Wuhan has now reached about 220,000 mu, and it has been expanding year by year. However, with regard to the current status of fertilization, the phenomenon of unbalanced fertilization with blindness, excess fertilization and insufficient fertilization remains serious. As a result, the output stagnated or even declined, and the quality of the watermelon declined. According to a three-year experimental study, during the early stage of watermelon growth, ie, the seedling stage and the extension stage where vegetative growth is dominant, the contents of nitrogen, phosphorus, and potassium all increase as the concentration of phosphorus increases. At this time, nitrogen, phosphorus, phosphorus, and potassium are expressed. Promote each other, and into the trophic growth and reproductive growth, and in the flowering, fruit-setting and maturing stages of reproductive growth, the change trends of nitrogen, phosphorus and potassium content in the leaves have changed: nitrogen content with phosphorus The increase of the concentration shows a downward trend, while the phosphorus and potassium have a tendency of increasing with the increase of the phosphorus concentration. This shows that the importance of nitrogen to the early stage of watermelon, the importance of phosphorus at the flowering stage, and the need for potassium at the later stage gradually increase. According to the characteristics of watermelon's demand for nutrients, combined with the experience of previous generations, the balanced fertilization measures for local watermelons are presented as follows:
First, soil testing
(1) Sample area of ​​sampling watermelon refers to vegetables, that is, take a mixed sample in the range of 50 mu (performed according to sampling specifications formulated by the Ministry of Agriculture). Sample depth 0 to 20 cm. Sampling must be mixed at multiple points, taking 15 to 20 samples per sample. S-shaped sampling is generally used to overcome the errors caused by farming and fertilization. In the case of small topographic changes, relatively uniform ground forces, and small sample cell area, plum-shaped spot sampling can also be used. Avoid special parts such as roadsides, ridges, ditches, and heaps. Sampling before watermelon planting in early spring. It is advisable to mix soil samples with 0.5-1 kg of earth.
(b) Analyze the basic items of pH, organic matter, alkali-hydrolyzing nitrogen, available phosphorus, available potassium, effective calcium, effective magnesium, available boron, effective zinc, and effective molybdenum.
Second, the type of fertilization
Watermelon is a chlorine bogey crop so it is not appropriate to use chlorine-containing fertilizers. For example, if potassium fertilizer is used, potassium sulfate or potassium dihydrogen phosphate should be used instead of potassium chloride; when selecting compound fertilizers, chlorine-based composite (mixed) fertilizers should be selected. Compound fertilizer.
Third, determine the amount of fertilizer
(I) Determination of nitrogen, phosphorus, and potassium Fertilizer amount Fertilizer consumption = target yield per unit of nutrient uptake (1 - contribution rate of soil nutrient) Fertilizer season utilization Fertilizer nutrient content
1 The target output is generally determined by the increase of 10% to 20% in the balance production of the local two years under normal climatic conditions.
2 Unit Yield The amount of nutrient absorption refers to the amount of nutrients needed to be absorbed per unit of economic output produced. (can be found from data)
3 Soil nutrient contribution rate refers to the percentage of nutrients absorbed by the fruit tree from the soil supply part.
Soil nutrient contribution rate = soil effective nutrient content (soil test value) critical concentration value;
When the soil organic matter is 1%, the critical concentration of nitrogen is taken as 120, the critical concentration of phosphorus is 30, and the critical concentration of potassium is 190.
(4) The utilization ratio of fertilizers varies according to different fertilization methods. Soil fertilization, base fertilizer plus top dressing, and fertilizer fertility distribution are all reasonable. The seasonal utilization rate of nitrogen fertilizer is 45%, the seasonal utilization rate of phosphate fertilizer is 30%, and potassium fertilizer is used. The utilization rate of the season is taken as 60%. When base fertilizer and drip irrigation are used to fertilize with water, the seasonal utilization rate of nitrogen fertilizer takes 70%, the utilization rate of phosphate fertilizer is 40% in the season, and the utilization rate of potash fertilizer is 80% in the current season.
(B) Organic fertilizer application amount of soil organic matter content
(C) Supplementation of trace elements in effective soil trace elements, effective zinc
Fourth, fertilization period
The whole life of watermelon is divided into five periods, ie, seedling stage, extension stage, flowering stage, fruit setting stage, and maturity stage. According to its nutritional characteristics, different growth stages have different requirements for NPK.
The use of nitrogen fertilizer can be divided into three periods: due to rich local organic matter (according to local organic matter content, the ratio of base fertilizer is adjusted, the content of organic matter is high, and the proportion of base fertilizer is reduced, but the proportion of base fertilizer is increased, otherwise the base fertilizer only accounts for 45% of the base fertilizer): Fertilizer accounts for 30%: Fruit fertilizer accounts for 25%. Phosphate fertilizer, base fertilizer accounted for 2/3, the first 1/3 of the fruit set;
Potash, base fertilizer accounted for 1/3, expansion of the guaranty period 2/3.
Fifth, fertilization method
1, base fertilizer in the transplanted 10 days before all the organic fertilizer, 45% of available nitrogen fertilizer, 60% of available phosphate fertilizer, 40% of the available potassium fertilizer mixture, plough cover.
(Note: Based on this principle and the calculation method of the amount of fertilizer, watermelon base fertilizer can be formulated: 18-13-14)
2, top dressing
(1) Extend vines to recover 30% of the total nitrogen fertilizer, using a distance of 15 cm from the plant, or 0.2% urea foliar spray.
(2) Fruit fertilizer: In the fruit-bearing period, the total nitrogen fertilizer of 25% and the total phosphorus fertilizer of 1/3 of the total amount of phosphate fertilizer and the potassium fertilizer of the total amount of potassium fertilizer 2/kg are uniformly mixed and applied into the hole using the above method. -20 cm.
3, leaf fertilizer
See seedling fertilization, if the seedling growth is weaker, in the seedling stage to add high nitrogen type foliar fertilizer, or 0.2% of urea spray once. Trace element boron and zinc fertilizer spray fertilization in the early blooming period.
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