Eggplant with the scientific name Solanum melongena

Eggplant (Scientific name: Solanum melongena)
Eggplant (Solanum melongena) is a herbaceous plant belonging to the Solanaceae (nightshade) family and is native to India (3). This plant has been known since ancient times in India, and its center of origin is considered to be the India–Burma region. Eggplant has many different types; excluding ornamental types, at least three eggplant varieties are widely cultivated in Iran (2,3), which can be distinguished based on the characteristics of their flowers and fruits (3). These three varieties include:
Common American eggplant: The plant height ranges from 60 to 120 cm. The fruit is thick, and its length is approximately twice its width.
Long (slender) eggplant: This variety has been cultivated in Iran for a long time. It produces long, narrow fruits, about 2.5 cm in diameter and 30 to 35 cm in length.
Large American (bell-type) eggplant: This is a short-statured type with a wide fruit, the width being about twice the length. The fruit color is usually purplish-red or purplish-black.
Climatic Requirements
From a botanical point of view, eggplant is a perennial plant in tropical and warm regions, but it is grown as an annual crop in temperate and cold regions because winter cold causes the plant to dry out (2). Therefore, eggplant is sensitive to cold and requires long days and a long growing season.
Eggplant requires warm conditions and full sunlight. It can tolerate some shade; however, during winter under low light conditions in greenhouses, fruits may become misshapen and flowers and buds may drop. The plant tolerates drought relatively well, but yield is reduced. Optimal growth occurs within a temperature range of 18 to 25°C. The optimal temperature range is presented in the table below.
Soil and Fertilization
The soil for eggplant cultivation should be fertile and not waterlogged. Sandy loam soils with good drainage, a pH of 5.5–6.5, and high organic matter content are suitable for eggplant growth. Regular supply of organic matter is very important. Depending on soil type and fertility, about 25 to 30 tons of well-rotted animal manure and approximately 75 kg nitrogen, 100 to 150 kg phosphorus, and potassium per hectare are recommended.
If animal manure is not available, leguminous crops can be grown as green manure in the year prior to planting to improve soil fertility. Green manure is used to protect the topsoil layers and to supply nutrients for microorganisms and plants, while compost application improves long-term soil fertility. When eggplant is well nourished, it produces more fruits over a longer period, especially when fertilization is applied during the flowering stage. Eggplant has a high requirement for phosphorus and boron, which can be supplied by adding phosphate rock to the compost used.
Planting
The cultivation method of eggplant is similar to that of tomato; however, unlike tomato seeds, eggplant seeds require a long dormancy period to germinate. In some cases, even after the dormancy period and sowing under favorable conditions, only a portion of the seeds germinate, and the growth of young seedlings is very slow (2,3).
Seedling Production Stages
Seeds should be sown in seedling trays or plug trays and placed in a suitable environment. Seed germination takes 10 to 25 days. Transplanting is carried out when seedlings reach about 15 cm in height or the 5–6 leaf stage. The period from sowing to transplanting into the main field varies from 6 to 12 weeks (2). Transplanting should be done after all risk of frost has passed (3).
Eggplant plants are slightly larger than tomato plants; therefore, planting distances are set wider. The distance between plants is considered to be 0.8 to 1 m, and the distance between rows is 1.2 to 1.5 m (3).
Post-Planting Care
Post-planting care includes irrigation, weed control, and soil crust breaking.
Irrigation:
Irrigation is very important at the time of transplanting because eggplant seedlings are highly sensitive to water stress. Shortly after transplanting, irrigation should be performed daily. Subsequently, depending on soil type and climatic conditions, irrigation should be carried out every 2 to 4 days. Soil type does not affect the total amount of water required but influences irrigation frequency; lighter soils require more frequent irrigation with smaller amounts of water per event. Under suitable conditions, reducing irrigation for several weeks after planting can improve root development. Regular moisture supply is essential for nutrient uptake, plant health, and fruit quality.
Irrigation can be performed using drip or flood irrigation methods. The advantages and disadvantages of different irrigation systems should be evaluated before organic eggplant cultivation. For example, flood irrigation may increase soil-borne diseases, while drip irrigation may increase salt concentration in the surface soil layer. Depending on mechanical and climatic conditions, the use of mulching can help conserve soil moisture (3).
Weed Management
Weed control is particularly important during the early growth stages. After that, the plant grows sufficiently tall and strong to compete with weeds.