High Efficiency Cultivation Technology of Fruit Cucumber in Plant Factory

Hong WANG

Abstract Plant factory, as the most advanced stage of the controlled environment, has drawn extensive concern in the world. In order to study high-yield vegetable varieties suitable for plant factory cultivation, we used fruit cucumber as an experimental material to study their high-yield cultivation technique in plant factory, and to clarify their planting management, cultivation cycle, yield and annual output. In our experimental condition, the average yield of the cucumber was about 2 500 g and their annual total yield per square meter could reach to 70 kg.

Key words Cucumber; Plant factory; Yield; Cultivation techniques

Received: June 21, 2022  Accepted: August 22, 2022

Supported by Shanghai Agriculture Applied Technology Development Program, China (Grant No.20170201); Shanghai Academy of Agricultural Excellent Team (No.2022［022］).

Hong WANG (1979-), female, P. R. China, PhD, devoted to research about regulation of light environment in greenhouse.

*Corresponding author.

Cucumber (Cucumis sativus L.) is one of the most popular horticultural crops in the world. China has the largest cucumber planting area in the world. The total cucumber production area in China (2020) was about 1.28 million hm2, and the annual yield was about 72.8 million kilos［1］. Because of its rich in nutrients, such as mineral compounds, vitamin, phenolic and flavonoid, cucumber has widely concerned by the consumers［2-3］. However, cucumber is usually affected by combined stress of strong light and high temperature in greenhouse in summer, as a thermophilic vegetable. Therefore, temperatures above 35 ℃ can decrease the yield and the quality［4］, which affects the annual production of cucumber.

Plant factory is probably the most advanced stage of a controlled environment. It is the integration of many modern technologies, such as mechanical technology, engineering technology, electronic technology, computer management technology, modern information technology, biotechnology, AI and so on. With the optimal control of the environmental condition, plant factory is expected to obtain high yield, good quality, high efficiency and safe food. In such factories, crops can grow all through the year with shorter growth cycles. Therefore, in this paper, a small-sized experimental plant factory with artificial light source was used to study the high efficient cultivation technology of fruit cucumber.

Species Selection and Germination

Fruit cucumber seeds with good quality and strong disease resistance, such as "Deltastar RZ", "Chunqiu Wang" were used.

The seeds were sown on the rock wool pellets (Grodan, Netherlands) and then fixed in plug trays (77-cell, 42 cm×28 cm×5 cm). Rock wool has a negligible EC and little effect on substrate pH. It can increase substrate aeration and drainage while also increasing the water-holding capacity, so it can be used in hydroponic production. After sprouting, the nutrient solution (as shown in Table 1) was irrigated every second day, at pH 6.0 and electrical conductivity (EC) 800 μs/cm. White LEDs for plants cultivation were used as the artificial light source. The photosynthetic photo flux density (PPFD) was about 200 μmol/(m2·s), and the photo/dark period was 16/8 h. The temperature and relative humidity were maintained at 25 ℃/20 ℃ (day/night) and about 70%, respectively.

Transplanting

When the cucumber seedlings had grown to 4-leaf stages, the well-developed seedlings were collected and transplanted to Grodan blocks (10 cm×10 cm×6.5 cm) and then planted in cultivation units with artificial lighting source. The planting density was 10 plants/1.5 m2. The type of hydroponic system used in this experiment was aeroponic system. The planting system was controlled by the computer. The mother nutrient solutions (Table 2) used in aeroponic system were based on Hoaglands solution with little modifications, according to Ding et al.［1］. The electrical conductivity (EC) and pH were maintained at 2 000-3 000 μs/cm and pH 5.5-6.5, respectively. The growth conditions were maintained at: temperature 25 ℃/20 ℃ (day/night), relative humidity 70%±10%. The light intensity was set at 500 μmol/(m2·s) photosynthetic photon flux density (PPFD) with a 16 h photoperiod. The light spectral distribution of artificial light source was shown in Fig. 1.

Planting Management

① Hanging vine: When grown to 30 cm, the plants were fixed with the hanging ropes from the roots, in order to prevent the cucumbers from lodging after transplanting.

② Pruning: Pruning of maintenance was done by a single stem and removing leaves and branches that had grown before the third section. The branches were removed once every 2-3 d.

③ Falling vine: When the growing point was near to the LEDs, the vine should be declined as soon as possible to avoid leaf scorch.

④ Fruit thinning: A part of female flowers should be extirpated adequately, in order to increase the expansion of the young fruits. Normally, we maintained one flower for each node.

⑤ Removing leaf: Old and diseased leaves needed to be removed in time, which was convenient for ventilation and transmission. The cucumber fruit should be harvested in time and the leaves below them should be removed.

⑥ Tip cutting: When the number of panicles reached 20, the top of stem should be cut.

⑦ Nutrient solutions management: Normally, the seedlings before eight leaf stages used leaf nutrient solution shown in Table 2 (EC=1 500 μs/cm); and then, EC was kept at 2 000 μs/cm before harvesting. When harvest began, EC should be changed to 2 500 μs/cm.

Harvesting

Harvesting was carried out 20 d after transplanting. The harvesting period was about 40 d. The average yield of each plant was about 2 500 g with growth cycle of 60 d. The annual yield of fruit cucumber per square meter was calculated according to the ratio of planting area and aisle area to 2∶1. In this way, the annual total yield per square meter could reach to 70 kg.

References

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