When is the best time to transplant chili pepper seedlings, how to transplant them, and how long until they flower and bear fruit?

Chili pepper is a common Solanaceae plant in China, generally coming to market starting in April-May. Because of its high yield and ease of cultivation, it is widely grown. However, due to low transplant survival rates, if you want to grow chili peppers well, you need to master transplanting techniques. So when is the best time to transplant chili pepper seedlings? How to transplant them? How long until they flower and bear fruit?

I. Transplanting time:

When transplanting chili peppers, choose large, strong seedlings with a height of 15-20 cm, 6-10 leaves, already showing buds and flowers, a well-developed and intact root system, and carrying old seedbed soil. Seedlings with dark green leaves are normal. Around Guyu (Grain Rain), that is, from late April to early-mid May, when soil temperature stabilizes at 17°C-18°C, transplanting is more suitable. Transplanting too early makes seedlings prone to frost damage, they will not grow new roots, recovery is slow, and small old seedlings easily form; transplanting too late affects yield.

In short, transplanting chili peppers depends on the sky, the soil, and the seedlings. Looking at the sky means doing it in the evening of a sunny day or on a cloudy day, and rainy-day transplanting is most taboo. Looking at the soil means checking soil moisture, with black moisture (moist dark soil) being ideal for transplanting. Looking at the seedlings means selecting large, strong seedlings and transplanting seedlings with well-developed roots, which can increase the survival rate of transplanted seedlings.

II. Transplanting methods:

Generally, a continuous one-pass transplanting method is adopted: lifting seedlings (take more soil, harm roots less), transporting seedlings (prevent mechanical damage), digging holes (or trenching or flat planting), fertilizing (a handful of organic fertilizer per hole), planting seedlings (plant straight and press firm), watering (pour a bowl of life-saving water, the seedling-recovery water), scattering poisoned bait (per mu, dissolve 150 g of 90% crystalline trichlorfon in 1.5 kg of warm water, evenly spray onto 5 kg of roasted wheat bran, and let it sit for 4 hours), and earthing up (to prevent lodging and preserve moisture), all as continuous operations completed in one go. As long as every step in transplanting is tightly linked, full stands can be established in one planting.

III. Planting techniques after transplanting:

1. Reasonable close planting

Chili peppers have a compact plant shape, weak branching ability, are not prone to excessive vegetative growth, and are relatively shade-tolerant, so they are suitable for close planting. Reasonable close planting can fully use sunlight and soil fertility, allow individual plants and the population to develop in a coordinated way, bear more peppers, larger peppers, and more seeds, while also promoting early plant development and early fruiting, improving pepper quality. According to measurements, compared with sparse planting, reasonably close-planted chili peppers lower the temperature by 1°C-2°C in high-temperature months, can reduce air temperature by 2°C-5°C, and increase average [value] by 13%. It can reduce [value], thereby lowering the virus disease incidence rate by about 17%, with a disease index of 6.4. Therefore, density can change the microclimate and increase yield per plant, and is an important technical measure for achieving high yields. The transplanting density is 8,000-10,000 plants per mu, or two plants per hole with 4,000-5,000 holes per mu.

2. Do good shading to improve chili pepper quality

Practice has shown that chili peppers like semi-shaded [conditions]. Growing in a semi-shaded corn belt, their condition is even better than in open fields: lower leaf-drop rate, fewer diseases, higher fruiting rate, no speckled peppers, higher single-fruit weight, and per-plant yield about 20% higher than open-field plants, though fruit coloring and ripening are later. Therefore, the corn-chili pepper [intercropping] should be vigorously promoted, that is, for every 6 rows of chili peppers, 1 row of corn must be interplanted, with 2-3 corn plants per hole and a hole spacing of 50 cm. In this way, chili pepper yield is not reduced, and corn can still yield 250-300 kg per mu without problem.

IV. Management techniques after transplanting:

1. Temperature and light management

After chili peppers are planted, maintain a high-temperature, high-humidity environment to promote seedling recovery. If there is no ventilation during the day, cover the curtain appropriately earlier and raise the room temperature to 28-30°C to help store heat. However, the maximum temperature should not exceed 30°C. If it exceeds 30°C or seedlings wilt, add a flower curtain appropriately for shade. From transplanting through the entire fruit harvest period, the midday temperature generally should not exceed 30°C. Too high a temperature will adversely affect fruit set and fruit development in chili peppers, leading to reduced yield.

For nighttime temperature control, from after covering the curtain until 22:00, gradually lower it from 23-20°C to about 18°C according to specific conditions, to promote the transport of photosynthetic products. By the time the curtain is lifted the next day, the minimum temperature should be limited to 15°C; sometimes a brief low temperature of about 10°C may occur.

Before March, if light duration is short and heat accumulation is difficult, while large seedlings and large vines require high heat accumulation, you can use little or no ventilation, appropriately supplement carbon dioxide, accumulate soil temperature, and at the same time add reflective film to the back wall and add an extra layer of straw curtain on the front slope at night (during the coldest time). Reduce the occurrence rate of room temperatures below 13°C. If conditions permit, a biogas digester can be built inside the greenhouse, and in severe winter use biogas lamps to supplement light and raise temperature. This can, on one hand, prevent plants from being in a state of light starvation for a long time and affecting normal growth and development, and appropriately increase the temperature inside the greenhouse; on the other hand, it can increase the carbon dioxide concentration inside the greenhouse, avoiding poor ventilation and the impact on yield caused by excessively low carbon dioxide concentration.

As the weather warms, gradually increase ventilation. If top ventilation alone cannot solve the problem, then use bottom ventilation.

2. Topdressing

Chili peppers need little fertilizer at the seedling stage, mainly concentrated in the fruiting stage. During the entire fruiting period, absorbed nitrogen accounts for 57% of the total, while phosphorus and potassium account for 61% and 69% respectively. Before the first pepper (door pepper) is harvested, not only does the plant continue to grow, but the second and third layer fruits (paired peppers and four-door peppers) are also expanding and growing, while flowering and setting fruit successively above, which is the key period for topdressing. When the door pepper grows to about 3 cm, carry out the first topdressing together with watering.

Because chili peppers have a particular preference for nitrogen and potassium fertilizers, fertilizer management should focus mainly on nitrogen and potassium fertilizers. The per-mu topdressing rate is 10 kg urea each time, 10 kg biological potassium fertilizer (or 5 kg monopotassium phosphate, or 5-10 kg potassium sulfate), and about 2,000 kg fully decomposed organic fertilizer can also be applied with irrigation. After that, according to conditions, apply topdressing once every 2-3 waterings. Topdressing should be done frequently and in small amounts.

3. Watering

Before planting chili peppers, water the planting base water; when planting, water the seedling-recovery water. Afterwards, spraying on the leaf surface every day can speed up seedling recovery. When planting in early winter, if the base moisture is good, seedlings may not need watering after recovery and can directly undergo seedling hardening; if planted before spring, after seedling recovery, lightly water 1-2 times in shallow furrows under the film, then carry out seedling hardening, until after the door pepper expands and grows, combine with topdressing and choose a sunny day for the first formal watering. After that, according to growth and weather changes, use the method of frequent small waterings.

The irrigation water should be pre-warmed in advance so that the water temperature stays above 12°C. Chili peppers are not suitable for flood irrigation or uneven drought-and-flood conditions. Excessive drought followed by sudden watering can cause flower drop, fruit drop, and leaf drop. The soil should often be kept in an appropriately moist state, creating a soil environment that is neither short of water nor compacted and airless, which is suitable for the growth and development of chili peppers.

Using drip-infiltration irrigation equipment to supply water and fertilizer to chili peppers is best. After entering the initial harvest period, an average of 1 sq m of water per mu per day is enough, using the method of supplying water and fertilizer together. The fertilizer supply amount is converted according to the harvest amount and evenly added into the water through a fertilizer injector. If diseased plants with blight are found, drip irrigation can be used to apply pesticide locally in the root zone for control.

4. Application of photorespiration inhibition and hormone fruit preservation

Sodium bisulfite is a cheap indirect photorespiration inhibitor. After the door pepper sets fruit, begin using a 120-240 g/kg sodium bisulfite solution for field spraying, spraying once every 7-10 days, for a total of 4 sprays, with the concentration increasing from low to high. Generally, yield increases by about 20%.

In solar greenhouses, low temperatures in the early flowering stage of chili peppers easily cause flower drop and yield reduction, and bring trouble to later management. Therefore, during flowering, 25-30 g/kg Tomato Auxin should be used to dip flowers, preserving flowers and promoting fruit and growth.

V. Flowering and fruiting time:

Generally, about one month after small seedlings are planted, they flower and bear fruit, and the harvest period is 2-3 months.

Precautions:

The temperature requirements of chili peppers fall between those of yarrow and eggplant. The suitable temperature for seed germination is 23-30°C; below 15°C they cannot germinate. Chili pepper seedlings require relatively high temperatures; when the temperature is low, growth is slow. In the early flowering and fruiting stage, the suitable daytime temperature is 20-25°C and nighttime is 15-20°C. During the fruiting period, if soil temperature is too high, especially with strong light directly hitting the ground, it is unfavorable to root growth and easily causes viral disease and sunscald.