Detailed Explanation of the Key Technical Points for the "Three-Avoidance" Cultivation of Melons
Scientific fertilization. According to the fertilizer and water requirements during the melon's growth period, supply fertilizer and water in a balanced manner; do not irrigate or fertilize blindly. When fertilizing, not only should sufficient base fertilizer be applied to meet the needs of the melon's early growth, but also timely topdressing should be carried out in the later stage of melon growth to meet the fertilizer requirements of the melon's later growth. Reasonable irrigation...
1. Cultivation season and crop rotationIn recent years, the market period of thick-skinned melons has tended to advance year by year. Combined with the temperature and light conditions of solar greenhouses, most seedling sowing periods are around December 10, planting in mid-January, flowering around February 10-15, entering the initial harvest period in late March, harvesting the second crop of melons from late April to early May, and finishing vine removal in mid-May. When the second crop of melons has not yet been harvested, if the vines are robust and management is strengthened, a third crop of melons can be harvested, and the time for vine removal is correspondingly delayed by 1 month. In the past two years, the earliest sowing period has been advanced to around November 10, planting in mid-December, flowering on January 10-15, the initial harvest period of the first crop of melons in late February, and the harvest period of the second crop of melons in early April. In order to increase the early-stage yield, the planting period must have stable ground temperature, and sowing can be done in mid-to-late December. This crop of melons is relatively proactive in management, with sufficient light, especially during the seedling-stabilizing period after planting, when the seedlings are quite robust.
For thick-skinned melons in winter-warm solar greenhouses, regardless of appropriately early or late sowing, the latest vine removal period is May, that is, the crop should be cleared 1 month before sowing the next crop. The next crop that can be sown or raised as seedlings in advance and planted includes loofah, bitter melon, cucumber, yardlong bean, sweet (hot) pepper, eggplant, celery, fennel, coriander, cabbage, cauliflower, etc.
2. Variety selection
The main variety is the early-maturing Elizabeth, and in recent years varieties such as Taiyang, Fengtian, and Zhuangyuan have also been introduced, with Elizabeth as the main planted variety. From the perspective of market demand, Zhuangyuan may have good development prospects in the future. For those harvested in early to mid-March, if leaving a single melon, the single melon weight is between 350-600 grams, with 400-450 grams being the majority; if leaving two melons, the two fruits are uneven in size, with a single melon weight of 200-300 grams, mostly around 200 grams. Although the yield per plant of leaving a single melon and two melons is roughly the same, the price difference is relatively large, and large melons fetch a high price, so it is advisable to leave a single melon.
3. Key technical points for seedling raising
Thick-skinned melon seedling raising is mainly conventional seedling raising, and in recent years the area using electric heating hotbeds for seedling raising has increased year by year. As Fusarium wilt becomes increasingly serious, using New Tosa pumpkin as rootstock for grafted cultivation will become the main form of winter-warm greenhouse cultivation in the future. The key technical points of different seedling raising forms are described below:
(1) Conventional seedling raising
① Farmyard manure should be fully decomposed
The coarse fertilizer used for seedling raising must be fully decomposed and fermented. In terms of time, that decomposed in July-August is better. It should be repeatedly and evenly fermented, and avoid using semi-decomposed fertilizer for seedling raising. Pig manure is more suitable and safe as nutrient soil, with pig manure accounting for about 30%-40% of the total nutrient soil.
② Watering the seedbed
When using plastic pots or paper pots for seedling raising, the bottom water of the seedbed must be watered sufficiently. The seedbed should be watered once 3 days before placing the nutrient pots, and watered again after placing the nutrient pots, with the water amount preferably submerging the nutrient pots by 3-5 cm.
⑧ Increase ground temperature
The ground temperature of the seedbed should reach 16-18°C. This can ensure a full stand of seedlings at one time, and damping-off disease is not likely to occur after emergence.
④ Seedbed temperature control
Adopt the "three highs and three lows" method for seedling raising, that is, under the condition of sufficient bottom water, the bed temperature should be controlled as follows: first, high before emergence and low after emergence; second, high after the true leaves show their hearts and low after two leaves and one heart; third, high before seedling stabilization and low near planting. The first high is for uniform and complete seedlings, and the first low is to prevent rapid elongation of the hypocotyl and the formation of tall, weak seedlings; the second high is to accelerate the increase of leaf area and promote root growth, and the second low is to control excessive growth of seedlings; the third high is to promote root growth again under the condition of lower soil moisture in the later stage of seedling raising, and the third low is to enable the seedlings to adapt to the environmental conditions after planting.
The specific method of temperature control is: when the ground temperature is between 16-22°C, take the higher end rather than the lower end. The air temperature should be controlled within the range of 13-28°C. For example, for "one high and one low," raise it by 3°C on the basis of 13-28°C, forming 16-31°C; after emergence, lower it by 3°C from the 13-28°C base, that is, 10-25°C. This is "one high and one low." At other stages, increase or decrease by 2-5°C according to the temperature conditions required by the seedlings.
(2) Electric heating hotbed seedling raising
In addition to following the basic methods of conventional seedling raising, special attention should be paid to the following points:
① Power supply
The power of the electric heating hotbed is generally controlled at 80-100 watts per square meter according to the seedling raising season, light, and temperature conditions.
② Watering amount of the seedbed
The watering amount of the seedbed should be greater than the conventional water amount, and can be about 1 time higher than the conventional seedling raising water amount.
③ Suitable ground temperature
The ground temperature for electric heating hotbed seedling raising is preferably 20-24°C.
④ Combination of hotbed seedling raising and conventional seedling raising
Use electric heating for seedling raising during the early low-temperature period, and carry out conventional seedling raising in the later period or when the temperature is suitable. ⑤ The nutrient pots should be larger. The nutrient pots for electric heating hotbed seedling raising should be somewhat larger than conventional ones to meet the growth of roots and leaves.
(3) Grafted seedling raising
If grafting seedlings in the early winter season, temperature, light, humidity, etc., except during the grafting period, are basically managed according to electric heating hotbed seedling raising or conventional seedling raising methods. The key points of grafted seedling raising are as follows:
① Choose the sowing time well
Using New Tosa pumpkin as rootstock and thick-skinned melon as scion, sow melon first and pumpkin later. Due to the influence of climatic conditions, the pumpkin sowing period is generally 4-6 days later than that of melon, and the pumpkin sowing period should be accurately determined. That is, when the melon cotyledons are flattened, begin soaking pumpkin seeds; when the melon true leaves show their hearts to half-unfolded, sow the pumpkin. When the pumpkin cotyledons are flattened and the melon has one leaf and one heart, it is the suitable period for grafting. ② Sowing method
There are two sowing methods: one is to sow melon and pumpkin in separate beds, and after grafting, plant them in nutrient pots. The other is to sow the melon 1.5 cm beside the center point of the nutrient pot, and after the melon true leaves show their hearts, sow the pumpkin rootstock seeds in the center of the nutrient pot, and when the pumpkin cotyledons are flattened and the melon has one leaf and one heart, carry out approach grafting. This method is convenient to operate and has a high survival rate.
③ Grafting method
The local method used is the approach insertion grafting method. Cut obliquely upward at a 40° angle 1-2 cm below the cotyledons of the pumpkin seedling; for the melon, cut obliquely downward at a 35°-40° angle at a position 1.5-2 cm higher than the pumpkin cut. Make the cuts of the rootstock and scion closely connect. After a few days, the pumpkin grows rapidly, and the stem heights of the pumpkin and melon become consistent. Otherwise, because the pumpkin stem grows too fast, the pumpkin seedling bends at an angle and growth is hindered.
④ Control temperature, humidity, and light intensity
Strict moisture retention, temperature control, and shading are the keys to improving the survival rate of grafting. After grafting, water appropriately, cover with an arched film, seal tightly, and use reed blinds to create dappled shade, so that the relative humidity reaches above 95%. For the first 3 days, the temperature is 25-28°C during the day and 18-20°C at night. The survival rate and seedling quality are closely related to the nighttime temperature. From the fourth to the seventh day, gradually open both ends of the arched shed for ventilation, with the ventilation opening going from small to large; after 7 days, the arched film can be removed. From the third day, cover with shading reed blinds when light is strong, and remove them when light is weak. After 5 days, if the seedlings do not wilt, the reed blinds can be removed. After 4 days, the daytime temperature can be controlled at 25-28°C, nighttime at 18°C, and the ground temperature should always be maintained at 20-22°C.
⑤ Root cutting should be early rather than late
Generally, with the above management, the wound heals in 3 days, the vascular bundles connect in 7 days, and a small portion is selected for root cutting in 10 days. When light is strong, there may be slight wilting, and proper shading with straw mats can restore normal growth. After 10 days, all melon roots can be cut off, and the stubble should be small; after root cutting, the melon roots should be pulled out immediately.
4. Planting period and planting density
The planting period is preferably mid-to-late January, but from the perspective of market and economic benefits, it can be advanced to early December to early January. The key issue here is to keep the ground temperature not lower than 12°C, and the ground temperature during the flowering period should be above 18°C.
For winter-spring cultivation, too high a planting density will affect the ground's exposure to light and cause low ground temperature, but low planting density will also cause low yield and directly affect income. According to large-scale surveys, the more suitable planting density is about 2,200 plants per mu. Generally, a row spacing of about 60 cm and a plant spacing of about 50 cm are used. This is not only conducive to ventilation, light transmission, and increasing ground temperature, but also conducive to safe overwintering.
5. Regulation of temperature and light in the greenhouse
The regulation of temperature and light in the greenhouse should consider, on the one hand, the physiological needs of the melon plants at each stage, and on the other hand, the use of ecological methods to prevent the occurrence of diseases.
After planting, the light time should be extended as much as possible, the temperature in the greenhouse should be increased, and the ground temperature should be raised, creating favorable conditions for good seedling stabilization from planting to flowering. After melon seedlings are planted, it is precisely the low-temperature season, and heat preservation is more important than other management. During the seedling stabilization period, deep rooting and multiple rooting are the central goals of management. Under normal circumstances, uncovering the straw mats at 8:30 a.m. and covering them at 4 p.m., maintaining 17-15°C in the first half of the night and 14-12°C in the second half of the night in winter-warm greenhouses is feasible. When encountering 3-5 consecutive cloudy days and the minimum temperature briefly appears at 8-9°C, there is no obvious adverse effect on them. If there are consecutive cloudy days, measures such as wiping the greenhouse film, ventilating less or not at all, and appropriately covering the straw mats earlier for heat preservation can all ensure safe overwintering. According to a survey in Daxinge Township, in January-February 1994, when the outside temperature dropped to -16.3°C and a short-term low temperature of 4.3°C appeared in the greenhouse, the melon seedlings could also endure the low temperature. However, it has a certain impact on the early expansion and early ripening of melon fruits. After entering the fruit expansion period, with the extension of light time and the increase of light intensity, the temperature rises, and the focus of temperature and light regulation shifts to the ecological control of diseases.
6. Pruning and trellising methods
For winter-spring cultivation of melons in winter-warm solar greenhouses, under the density of 2,200 plants per mu, the single-vine pruning method is adopted. When the main vine grows 6-7 leaves, begin tying and hanging the vine, leaving no secondary vines at the base, and using secondary vines above the twelfth node of the main vine to bear melons. Due to short light time and low light intensity, generally 2 melons can be retained. With changes in market demand, in the past two years the method of retaining one melon has been adopted, which can significantly improve benefits. After fruit setting, leave 2-3 leaves before the melon, and top the main vine when it grows to 25-30 leaves. At present, melon trellises mostly use nylon rope hanging frames, which are characterized by saving labor and money and being conducive to light.
7. Fertilizer and water management
Apply sufficient base fertilizer before planting, with emphasis on applying sufficient coarse fertilizer. Generally, apply 10-12 cubic meters of decomposed chicken manure per mu, 50-60 kg of diammonium phosphate, and 20-30 kg of potassium sulfate. After the chemical fertilizer and coarse fertilizer are applied, deep plow 40 cm and harrow twice to mix the soil and fertilizer evenly, then water sufficiently for the bottom moisture and firm the soil.
Watering sufficiently at planting is an important measure in seedling-stage management. In the early stage after planting, the ground temperature is relatively high. If the planting water was not watered sufficiently, immediately replenish with seedling recovery water. After this water, the seedling stabilization period begins. If small amounts of water are often applied during the seedling stabilization period, it will seriously affect rooting and create obstacles for later fertilizer and water management. Because the base fertilizer is relatively sufficient and the seedling stage requires little fertilizer, generally there is no need to fertilize when watering at planting. After the melon sets fruit, combine with watering and apply 150 kg of cake fertilizer per mu, or apply 15-20 kg of urea per mu, and 10 kg each of diammonium phosphate and potassium sulfate. Watering should be appropriate to prevent flood irrigation. When some fruits grow until they turn white, water the third time. During this period, 0.1%-0.5% potassium dihydrogen phosphate can be sprayed on the leaves.
8. Pest and disease control
Locally, this crop of thick-skinned melons has fewer insect pests, and the common diseases are mainly Fusarium wilt, powdery mildew, and downy mildew.
Fusarium wilt mostly occurs on continuous cropping land. If the previous crop is cucumber for 3-5 consecutive years or melon continuous cropping for more than two years, Fusarium wilt occurs relatively seriously. Generally, the disease can cause about 30% dead vines. In severe plots, if consecutive cloudy then suddenly clear weather occurs during the fruit expansion period, the diseased plant rate can reach 50%-80%. Root irrigation with 50-100 times dilution of 50% carbendazim wettable powder can be used, with 2 kg of pesticide per mu, applied in 2-3 portions, and the control effect is relatively good. According to a survey in Jiabalizhuang Village, after irrigating the pesticide for control, irrigating the second time 5 days later, the death rate of diseased plants can drop to below 10%. For those not controlled in time, the death rate reaches above 40%. For downy mildew and powdery mildew, ecological control is the main method, supplemented by chemical control. These two diseases do not occur when the temperature is suitable but the humidity is not suitable, nor when the humidity is suitable but the temperature is not suitable. For example, for downy mildew, the most suitable temperature for onset is 18-24°C, and infection can be caused between 15-30°C. Measures can be taken such as covering the straw mats late, controlling the nighttime temperature below 15°C, and then not ventilating in the morning when below 30°C, and opening large ventilation openings when above 30°C to discharge more moisture and reduce relative humidity, reducing the relative humidity during the suitable temperature period to below 70% as much as possible, thereby effectively controlling the occurrence of the disease.