What are the requirements of watermelon for environmental conditions?

The most suitable environmental conditions for watermelon growth are high temperature, large temperature difference between day and night, sufficient sunshine, dry air and good soil permeability.

1. temperature

Watermelon is a heat-resistant crop, and the whole growth and development process needs high temperature. The optimum temperature range is 10 ~ 40℃, and the optimum temperature is 25 7℃. High temperature resistance, when the temperature is 40℃, it can still maintain a certain assimilation efficiency; However, it is not resistant to low temperature. The growth was slow at 15℃, stopped at 10℃, and the aboveground parts suffered from cold damage at 5℃. Vegetative growth can adapt to low temperature, the optimum temperature at seedling stage is 22 ~ 25℃, and the highest temperature at fruiting stage is 30 ~ 35℃. The accumulated temperature from female flower opening to fruit ripening is 700 ~ 1000℃.

The lowest temperature for root growth is 8 ~ 10℃, the highest temperature is 38℃, the optimum temperature is 25 ~ 30℃, and the lowest temperature for root hair generation is 13 ~ 14℃. The lowest temperature of stem and leaf growth is 65438 00℃; The lowest temperature of fruit growth is 65438 05℃; The fruit formed at low temperature is oblate, deformed, thick and hollow, and its quality decreases.

Watermelon is most suitable for continental climate cultivation, with large temperature difference between day and night, which is beneficial to the healthy growth of stems and leaves and the accumulation of sugar in fruits.

lamplight

Watermelon is a light-loving crop, and it needs sufficient sunshine hours and intensity during its growth and development.

Watermelon generally needs 10 ~ 12 hours of sunshine every day; When the weather is clear and the sunshine is sufficient, the plants are characterized by vigorous growth, compact plant type, short internodes and petioles, stout stems and vines, large and thick leaves, dark green leaves, early flower bud differentiation and high fruit setting rate. However, under the conditions of continuous rain and insufficient light, the plants are slender, the internodes and petioles are long, the leaves are long and narrow, the leaves are thin and pale, the protective tissues are underdeveloped, and they are susceptible to diseases, flowers and fruits, and the fruit quality is poor.

Light intensity directly affects the yield and quality of watermelon. The light saturation point of watermelon seedling is 80,000 lx, and the fruiting period is 654.38+100,000 lx. The light compensation point of watermelon is 4000lx.

Short sunshine hours and weak light intensity not only affect the vegetative growth of watermelon, but also affect the ovary size and pollination and fertilization process, but the light conditions have little to do with the formation of the ratio of male to female flowers.

In addition, light quality has obvious influence on the growth of watermelon seedlings. Long-wave light of red and orange can accelerate the elongation of stems and vines and make internodes slender, while short-wave light of blue and purple can inhibit the elongation of internodes.

Step 3: Moisture

Watermelon is a crop that needs more water. Watermelon plants grow rapidly, the growth period is short, the leaves are luxuriant, the fruit is huge, the fruit contains a lot of water, and the yield is high, so it consumes a lot of water. In the whole growth process of a watermelon, the water consumption is generally as high as1000 kg; . If the water is insufficient, it will affect its vegetative growth and fruit expansion.

Watermelon is also a crop with strong drought tolerance, and its strong drought tolerance stems from its ecological characteristics of drought tolerance above ground and its strong absorption ability of roots and root hair cells. The physiological characteristics of watermelon in dryland are high water content in leaves, low concentration of cell sap, high protein solidification temperature, high chlorophyll content, low transpiration intensity and high xylem shunt intensity.

Different growth stages of watermelon require different soil water content. The suitable soil water content at seedling stage is 65% of the maximum field water capacity, 70% at vine extension stage and 75% at fruit expansion stage. Insufficient water will affect the yield. But the root system of watermelon is extremely intolerant to waterlogging. When Gua Tian suffers from waterlogging and the soil moisture is too high, it often leads to root rot or even suffocation and death of the whole plant due to lack of oxygen. Therefore, if you want to choose high-lying plots for planting, you must pay attention to field drainage in rainy areas and rainy seasons.

Watermelon requires air drying, and the suitable air relative humidity is 50% ~ 60%. Lower air humidity is beneficial to promote fruit ripening and increase fruit sugar content; When the air humidity is too high, the plants grow thin, the fruit setting rate is low, the quality is poor, and they are easy to get sick. When the air humidity is too low, it will affect the vegetative growth and pollen germination.

4. Soil and nutrition

The root system of watermelon is obviously aerobic, and the optimum oxygen pressure for its growth is 18%. Only in the soil with good physical structure can there be enough oxygen supply. Watermelon has wide adaptability to soil conditions, and can be cultivated in sandy soil, clay, acidic red-yellow soil, coastal saline-alkali land and newly reclaimed land, but it is most suitable for planting in sandy loam or sandy land with deep soil layer, good drainage and high fertility. This is because sandy soil has good ventilation and water permeability, high ground temperature and large temperature difference between day and night, which is beneficial to root growth, early maturity, sugar increase and quality improvement.

Watermelon is suitable for growth in neutral soil, with wide adaptability to soil pH, and can grow normally in the range of pH 5 ~ 7. But in strongly acidic soil, it is easy to wilt. Therefore, when planting watermelons in strongly acidic rice stubble fields in south China, more alkaline fertilizers such as lime and plant ash should be applied to neutralize the acidity and improve the soil. Watermelon growth is sensitive to salt, and it can grow normally only when the soil salt content is below 0.5%.

The growth and development of watermelon needs a lot of nitrogen, phosphorus and potassium, so the amount of fertilizer applied during its growth is generally large. Watermelon absorbs the most nitrogen, phosphorus and potassium, followed by nitrogen and phosphorus, with a ratio of 3.8: 1: 4.33. Applying more potassium fertilizer and phosphorus fertilizer, avoiding partial application of nitrogen fertilizer, is conducive to controlling plant growth and improving fruit quality. In addition, reasonable fertilization should be carried out according to different growth periods and different plant growth conditions; Organic farmyard manure and phosphate fertilizer are the main base fertilizers, and a small amount of nitrogen fertilizer can be lightly applied at seedling stage, and the amount of nitrogen fertilizer should be properly controlled at vine extension stage, and a large amount of available nitrogen and potassium fertilizer should be mainly applied after fruit setting.

5. Carbon dioxide

In order to maintain the high photosynthesis of watermelon plants, the concentration of carbon dioxide should be kept at 0.25 ~ 0.3 ml/L. Adding organic fertilizer and carbon fertilizer can increase the concentration of carbon dioxide in the air. Measures such as improving soil, timely drainage to prevent waterlogging and strengthening intertillage loosening are beneficial to the absorption and utilization of carbon dioxide by watermelon.

In winter, early spring and late autumn, when watermelon is cultivated in greenhouses and greenhouses, outdoor air is generally not suitable or can only be outdoors for a short time because of the large temperature difference between indoor and outdoor. Therefore, the greenhouse is closed for a long time, which leads to the concentration of carbon dioxide far below the normal level, so it is necessary to replenish carbon dioxide in time. At present, the common method is to use a carbon dioxide generator.