Longan (Dimocarpus longan Lour.) is one of the members in Sapindaceae family that also includes litchi and rambutan under the genus Nephelium. It is originated in temperate area then adapted well in tropics. In Indonesia, longan is usually consumed fresh although the fruit can also be found as canned product and dried fruit. In Chinese, the fruit is known as “ong ya guo” or “long yan” which means dragon’s eye. There the fruits are used for health and beauty purpose. Longan fruits are claimed to improve vitality, insomnia, anxiety, loss of appetite, weak stomach, headache, diarrhea, cough and asthma, blurred vision and smoothing the skin. Apart from the fruit, the leaves also contain useful substance such as quercetin, which has antioxidant and antiviral activity and is also used to treat allergies, cancer, diabetes, and cardiovascular disease. Its seed powder contains saponin which is the basic ingredient of shampoo. In China dan Vietnam, longan fruit is used as antidote.
Initially, longan fruits were found in the mountain area in Central Java and East Java. Later, the fruits developed to lower altitude such as in Selarong Yogyakarta in which cv Selarong comes from, Singkawang and Pontianak in West Kalimantan, and also Demak and Semarang in Central Java in which Diamond River, Pingpong and Itoh were developed initially. These three varieties received more attention due to their good quality, namely early maturity, frequent fruit bearing, thick fruit flesh, sweet taste, and easy maintenance. These introduction longan varieties are adapted well in Indonesia despite their various origins; Pingpong and Diamond River introduced from Vietnam, Itoh from Malaysia, Bie Kiew, Ido, and Sichompu from Thailand. This indicated that longan has potential to be developed in low land in Indonesia. Apart from land suitability, the massive population of Indonesia is also a market opportunity that should be taken into consideration. Increase in population that accompanied by improvement in prosperity and nutrition awareness will lead to increase in demand for fruits.
As other perennial crops, longan development should be planning carefully since it takes large capital investment (vast field, seeds, tools and facilities, human resources, etc.) and the result will be obtained in a long term. One important factor that should be taken into consideration in planning is the location since optimal result will only be obtained on favorable field with suitable environmental characteristics. Based on the fact that natural growth and yield of longan are influenced by environmental factor and also considered that low land longan is a new thing in Indonesia and there is little information available; here in this article, some results from research on Low Land Longan Field Characterization which was done by ICSFRI will be presented concisely. It is expected that this article could serve as a reference for those who are interested in developing low land longan or would like to know more about longan.
Longan has apical flowering characteristic and shows biennial bearing. Naturally, flowering and fruit bearing are influenced by climate and soil. To decide the location for longan development, important climate elements such as temperature and rainfall need to be concerned. In addition, soil factor such as physical properties (depth, texture, drainage, and surface rocks) should be emphasized since this factor is difficult and expensive to improve compared to that of chemical properties. Thus, climate and soil physical properties are the main components used to assess land/location suitability for longan development.
Temperature and Rainfall.
Despite a temperate plant origin, longan could grow and flowering well in tropics as long as there is an explicit seasonal change. Most longan plants are found in the areas with average temperature 15 – 30oC. Fine growth and yield are observed in the areas with short cold season (temperature 15 – 22oC for 3 months), and long, warm, humid and wet (heavy rainfall) dry season. The ideal idle (rest) period that could stimulate flowering occurs after harvest season and plants pass through the period of leaf maximum growth; temperature goes down below 25oC with low water supply. To induce flowering, low temperature (< 22oC) for two months is required; if the temperature goes higher, flowering could fail. Based on field survey and collected data, Itoh, Ping Pong and Diamond River could grow well until 700 m above sea level (asl), and show optimum growth on altitude less than 500m asl. Higher altitude causes late flowering which then makes it longer to gain the investment back.
Longan could be developed in areas with rainfall 1.000 – 3.000 mm with 3-6 dry months (< 60 mm). One of them is Tumpang District, Malang, East Java. In ten years in a row, this area has in average annual rainfall about 2.250 mm with 5 dry months from July to October.
There are 5 phases of longan growth: harvest, leaf growth, idle (rest), flowering induction, and flowering. They are influenced by climate and local environment condition such as temperature, water and nutrients availability (Figure 2). The most water requirement is in the period of flowering induction to late of the leaf growth period. On the other hand, in the rest period, water and N supply should be reduced.
Longan plant could reach 10 m in height and 15 m in canopy width, has heavy branches and leaves. To avoid plant lodging, the plant requires good root system: deep taproot and wide lateral root. Therefore, old plants of longan usually found in the areas where the soil has quite effective soil depth. Shallow soil that usually has less than 30 cm effective soil depth may not hinder the initial plant growth, but in a long term this could affect the growth and yield.
Soil fertility in some longan production centers in Indonesia varies (Table 1) with various textures (except heavy clay and sandy soil). Heavy soil with high particle content has compact consistence and impeded to heavy impeded drainage that causes disruption in root system, hamper the root growth, or root disease. Sandy soil that has loose consistence and fast drainage could cause growth and flowering disorder due to low water availability and low chemical fertility. Longan development in such areas needs expensive input technology thus concluded not suitable.
|Symbol||Land Quality and Characteristic||Suitability Class|
|– Altitude (m asl.)||< 500||500 – 700||>700|
|– Rainfall||1.500 – 2.500||1.000 – 1.500||>3.000|
|2.500 – 3.000||<1.000|
|r||Condition of root media|
|– Effective depth (cm)||> 75||30 – 75||<30|
|– Soil texture||other||other||Heavy clay and sandy|
|– Soil consistence||friable||compact||Very compact, loose (sand)|
|– Soil drainage class||Well drained||Moderately well drained to somewhat poorly drained||Poorly to very poorly drained|
|– Slope (%)|
|– Relief (% flat)|
|– Surface rocks (%)||< 30||30 – 50||>50|
S : Suitable
CS : Conditionally Suitable
N : Not Suitable
Author : Sutopo
(translated by BDM)