Current practices and research in off-season longan production in Thailand

Longan is a major fruit crop in Thailand and is classified as one of 'The Production Champion' crops. Planting area in 2017 consisted of about 187,564 ha with total production of 1,027,493 metric t and average yield of 5.4 t ha^‑1. In general, the longan season in Thailand starts in June but reaches over supply production in July and August. Due to the suitable location and development of the technology, Thailand can produce longan all-year-round. Production outside June, July and August is classified as off-season longan. The ratio between in-season and off-season longan has dramatically increased in the past ten years. Recently, off-season longan in Thailand is about 50% of the total production. Chantaburi province is well-known for its off-season production where most growers produce longan only for 9 months out of June, July and August. The technology for off-season longan production in Thailand has been initiated from the research achievements in Maejo University led by Asst. Prof. Pawin Manochai in 1999 when the use of potassium chlorate (KClO₃) was discovered. In recent years, however, growers in Thailand had been using not only KClO₃ but also NaClO₃ to induce off-season longan. The application rate of KClO₃ to induce flowering depends on canopy size, season, method of application and the stage of leaf development as the most important factors. Beside these factors, suitable weather should also be considered. There are two major methods for KClO₃ application: soil drenching and foliar spraying. Leaves should be mature or at least fully expanded, for example more than four weeks old, before application. The greatest problem for the growers after KClO₃ application is leaf flushing instead of flowering due to high precipitation. To overcome this problem, growers are suggested to apply paclobutrazol before application of KClO₃. The key factors for off-season longan production in Thailand are technology, environment and farmer experience, which does not only include experience in cultural practice, but also in strategic planning for suitable time of the year to produce off-season longan.