Key Points for Seedling-Stage Management in Muskmelon Cultivation

① Temperature management: Before the seedlings emerge, a relatively high temperature (25-30°C) is required. After 70%-80% of the seedlings have emerged, lower the temperature to 20-25°C during the day and 15°C at night, because from seedling emergence to the flattening of the cotyledons, the hypocotyl grows fastest during this period, and this is the stage when the seedlings are most prone to leggy growth, so special attention must be paid to temperature control to prevent the melon seedlings from becoming leggy; after the first true leaf unfolds, the seedlings are no longer prone to leggy growth, so the bed temperature should be raised again to around 30°C, with a nighttime minimum temperature of 15°C. After the seedlings have two true leaves, the bed temperature should be gradually lowered so that the temperature inside the bed gradually approaches the outside temperature, carrying out hardening before transplanting. In addition, using a large day-night temperature difference for seedling raising is an effective measure for cultivating strong seedlings. After the true leaves of the seedlings appear, keep the temperature inside the bed at around 30°C during the day, with the night temperature not lower than 15°C; this is beneficial to root growth and can also inhibit respiration and aboveground growth, which helps cultivate strong seedlings.

To meet the above temperature requirements when raising seedlings in severe cold seasons, attention should be paid to the following management: ensure that more sunlight enters the seedling bed to raise the bed temperature, such as promptly uncovering straw mats and other opaque coverings, and keeping the film on the seedling bed clean; cover the straw mats tightly at night to maintain bed temperature without ventilation; once the young sprouts begin to push through the soil, immediately remove the plastic film; ventilation and airing are the main measures for regulating the temperature and humidity inside the bed, and should be flexibly controlled according to melon seedling growth and weather conditions. When severe weather occurs, pay special attention to local weather forecasts, promptly carry out all cold-protection work, and take appropriate heating measures. When continuous low-temperature overcast and rainy (snowy) weather occurs for several days, pay special attention to uncovering and covering the straw mats to improve temperature and light conditions, and use a 0.1%-0.3% glucose solution to spray the leaves to supplement nutrition. During the day, as long as it is not raining or snowing, uncover the straw mats so that there is some scattered light inside the seedling bed; when the sun comes out between rain or snow, seize the opportunity to open small vents for ventilation and air exchange. On the first sunny day after continuous overcast days, seedling wilting or collapse is likely to occur; in response, immediately cover the straw mats for shading, or adopt the method of alternately covering and uncovering the straw mats, and remove all the straw mats after the melon seedlings return to normal.

Seedling bed temperature management in hot seasons: High summer temperatures make seedlings susceptible to viral diseases, so shading facilities must be provided on the seedling bed to lower the air temperature. Cover with shade netting during strong sunlight on sunny days, do not cover on cloudy days, in the morning, or in the evening; cover during the day and do not cover at night. Before and after transplanting, let the seedlings receive more direct light to prevent leggy growth.

② Water and fertilizer management: Muskmelon seedlings have very low water requirements during the seedling stage. After sufficient bottom water is applied before sowing, generally no further irrigation is needed. In addition, irrigation will cause the ground temperature to drop, leading to poor root development and slow seedling growth, and will also create a low-temperature, high-humidity microclimate that induces damping-off disease. When irrigation is truly necessary, choose a sunny morning and water lightly; do not irrigate heavily. Pay attention to reducing the air humidity in the seedling bed, especially during long periods of overcast and rainy weather, and also maintain ventilation; in summer seedling raising, water evaporates quickly, and the seedling bed should not be excessively dry either. When seedlings lack water, a small amount of spraying can be done. After the seedlings emerge, strictly control watering to control the seedlings with water and prevent leggy growth. Carry out water control treatment on the melon seedlings to appropriately inhibit growth, enhance the stress resistance of the seedlings, and help them adapt to the climatic conditions after transplanting.

Topdressing is generally not needed during the seedling stage, because from sowing and emergence until the two cotyledons unfold, the seedlings basically rely on nutrients stored in the cotyledons, and afterward the root system already has a relatively strong absorption capacity. Under normal circumstances, as long as the nutrient soil has a reasonable nutrient ratio, it is no problem to sustain the seedlings until they have 3-4 true leaves. If the melon seedlings become weak later and the leaves are pale, showing symptoms of fertilizer deficiency, use 0.2%-0.3% urea and monopotassium phosphate for foliar topdressing outside the roots.

③ Pest and disease control: The common disease during the seedling stage is damping-off, and the common pests are squash beetles and cutworms, among others. For their identification and control methods, refer to the pest and disease control section.

The seedlings cultivated are considered strong seedlings when they meet the following standards: among 3-4 true leaves at a seedling age of 30-35 days, large seedlings have a height of less than 10 cm, a thick and sturdy hypocotyl, the cotyledon node is best no more than 3 cm above the ground, the cotyledons are intact, the true leaves are thick and dark green, with no disease spots or pest damage, the nutrient soil block is intact, the root system is well developed, the main root and lateral roots are thick and sturdy, and both the aboveground and underground parts are undamaged.