G.J.H. Grubben
Timing of vegetable production in Indonesia is increasingly important for a regular supply to the city markets and the processing industry. Large seasonal fluctuations in production and prices occur. Prolonged rains cause crop damage, increase disease infestation and leaching, and also solar radiation may become limiting. A good farmer of shallots (Java 41,000 ha/year) in the lowlands can harvest over 10 t/ha in 70 days during the dry season but only 5 t/ha in 55 days during the rainy season. This variation may be overcome partially and yield levels may increase by improved varieties and cultural practices.

Higher altitudes result in decreasing temperatures, higher rainfall and lower solar radiation. Two main ecological zones can be distinguished: lowland (0–450 m) and highland (above 450 m). Mediumland 200–700 m is a transition zone. In August (dry season) the day/night temperature at sealevel is 31/22 degrC and at 1200 m 25/13. Commercial growing of most vegetables is usually restricted to one zone, i.e. chayote, carrot, cabbage, French beans, garlic, Japanese bunching onion and potato are typical highland types while yardlong bean, luffa, cucumber, amaranth, watermelon, eggplant and kangkung are mainly grown in the lowlands. Collection and interpretation of data is hampered by intercropping, a common practice in Java. Some vegetables (shallots, tomato) thrive better in the mediumland but are also important in the highland and lowland areas, with special cultivars in each ecological zone. Statistical data on areas and yield lead to the hypothesis that the temperature optimum for shallot cultivation is around 24 degrC, with a rather wide temperature range between 20 and 30 degrC.

Research data on growth, physiological development (flowering, fruitsetting, ripening, senescence) and on yields of crops at different elevations and in various seasons will be assembled in a growth model for a more accurate timing. Some preliminary results are presented in this paper.

Grubben, G.J.H. (1990). TIMING OF VEGETABLE PRODUCTION IN INDONESIA. Acta Hortic. 267, 261-270
DOI: 10.17660/ActaHortic.1990.267.33

Acta Horticulturae