Detailed Explanation of Key Techniques for Greenhouse Cultivation of Figs

The fig (Ficus carica L.) is a deciduous small tree or shrub of the mulberry family, native to the southern Arabian Peninsula in the subtropical region. It was introduced to China via the Silk Road during the Tang Dynasty. Its fruit is also called the "sacred fruit," rich in nutrients with a unique taste and novel flavor. It can not only be eaten fresh or processed into dried fruit, preserved fruit and other processed products, but also has high medicinal value and broad development prospects. By using greenhouse cultivation, we avoided the adverse factor of low winter temperatures in Beijing, enabling figs to be cultivated in the Beijing area, with the fruit ripening period advanced by 1-2 months.

1 Overview of greenhouse cultivation

The trial site is located at the Zizhuang Demonstration Garden of the Quality Agricultural Product Development Service Center of the Ministry of Agriculture in Chaoyang District, Beijing. Beijing has an annual average temperature of 11.9°C, an average January temperature of -4.7°C, an extreme low temperature of -18°C, a frost-free period of 180-200 d, and precipitation of 600-700 mm. The experimental greenhouse is 75 m long, with a span of 7.5 m, a ridge height of 3.3 m, a rear wall height of 2 m, and a wall thickness of 0.6 m. It has a brick-concrete structure with steel bar arches, and a planting area of 442 sq m. The soil is light clay with deep soil layers, a pH value of 8.2, and an organic matter content of 2.2%.

The fig variety is Masui Dauphine, originally from California, USA. This variety has moderate tree vigor, soft branches, is easy to spread open, has a small canopy and many branches, and is parthenocarpic, so no pollinator trees need to be configured. The chilling requirement during dormancy is 80-200 h. It was planted on December 1, 2002, with a total of 82 plants planted and 78 surviving. In 2003, the yield was 156 kg (235.3 kg/666.7 sq m), achieving the cultivation goal of planting and fruiting in the same year. The fruit is obconical and relatively large, with a single fruit weight of 80-100 g and a maximum of 150 g. It is mainly autumn fruit, with a fruit development period of 70-90 d. Ripe fruit is purplish brown with pinkish-red flesh. The fruit has a sugar content of 11%-14%, relatively good quality, and sells for 15-20 yuan/kg.

2 Main techniques

2.1 Planting

In the greenhouse, planting is done in north-south rows, with a row spacing of 1.8 m, for a total of 41 rows; 2 plants per row, with a plant spacing of 3 m. Along the row direction, planting trenches 50 cm wide, 60 cm deep, and 5 m long were dug. For every 666.7 sq m, 4000 kg of decomposed organic fertilizer, 150 kg of superphosphate, and 10 kg of potassium sulfate were applied, mixed evenly with the soil, then backfilled to 4/5 of the trench depth, trampled firm, watered, and covered with a layer of topsoil.

Planting is done on sunny days. One-year-old seedlings are selected, dipped in rooting powder, and planted at the predetermined points. First cover with soil, then lift the seedlings so the root system spreads out, trample firm, then cover with soil again to close the opening, and make a channel for irrigation. Water again after an interval of 1 d. After the soil dries on the surface, loosen the soil, level it, and cover with plastic film.

After planting, timely trunk heading is carried out, with the heading height lower in the south and higher in the north: 10 cm for southern plants and 15 cm for northern plants. When heading the trunk, the cut should be flat, the cut sealed with paint, and then the trunk covered with a special fruit tree bag to prevent the sapling from drying out and dying.

Increase the survival rate

2.2 Temperature management

Fig seedlings planted in winter have already passed dormancy, so heating can be started directly. The daytime temperature is controlled at 20-25°C, and the nighttime temperature is not lower than 8°C. The relative air humidity is controlled at 80%-90%. When the temperature rises during the day, the humidity will relatively decrease, so artificial water spraying is needed. When the soil temperature at 15 cm below the surface is above 10°C, the fig root system begins to become active, and in early January (one month after planting), budding begins. Remove the special bags and water heavily once.

Within 50-70 d after budding, when the effective accumulated temperature of ≥10°C reaches 1400°C, fruiting begins. In order to lower the fruiting position and prevent excessive vegetative growth, the temperature should be relatively lower at this time: the daytime temperature is controlled at 25°C and the nighttime temperature at 13°C. In May, the straw mats can be removed. To prevent summer rainwater from affecting figs, the greenhouse film should be kept, and the top and front skirts opened for ventilation and temperature control. When summer is hotter, artificial water spraying is used to cool down.

2.3 Water and fertilizer management

The fig root system is relatively developed and has strong drought resistance. However, the leaves are relatively large and transpire a lot of water. If the water supply is insufficient, new shoot growth will be inhibited, affecting fruit yield and quality. Figs are generally watered heavily once after fertilizer application in autumn, watered lightly twice during the bud-breaking period, and from July to September during flower bud differentiation and fruit ripening, they need more water, so water once every 7-10 d. However, irrigation should not be excessive, with soaking through the root layer as the standard. After each watering, shallow plowing and soil loosening should be carried out. During the rainy season, water once, but not too much, otherwise it will not only reduce the sugar content but also cause fruit cracking.

Figs have luxuriant branches and leaves, a large growth volume, and bear many fruits, so they need a lot of nitrogen, phosphorus, potassium, calcium and other fertilizers. Fertilize according to Table 1 in mid-March during new shoot growth, in May during flower bud differentiation, and in mid-July during fruit ripening. In mid-November, dig trenches 50 cm deep and 30 cm wide, and apply 4000 kg of decomposed farmyard manure per 666.7 sq m, while adding 150 kg of superphosphate and 10 kg of potassium nitrate.