Yonny Koesmaryono1), Suman Sangadji2), Taufan Hidayat1), Perdinan1), Irman1) and Hideki Sugimoto3)

1) Bogor Agricultural University, Bogor, Indonesia 2) Darussalam University, Ambon, Indonesia 3) Ehime University, Matsuyama, Japan

ABSTRACT

Buckwheat is grouped as a subtropical plant but can be grown well at upland plain in tropical region, which has cooler air temperature. This plant produces high carbohydrate and can be used as alternative and healthy food. An attempt has been done to study the response of buckwheat plant to tropical climate in West Java, Indonesia. The experiment was done in two years, in 2000, two sites have been chosen which are located at 1150 m and 500 m above sea level, respectively. A cultivar of kitawasesoba was grown at three population densities, viz 130, 160 and 200 plants m-2. Then, the experiment in 2001 has been planted two cultivars of kitawasesoba and hitachi-akisoba at two population densities, viz 100 and 150 plants m-2. The growth were observed weekly and yield were sampled at harvesting. Whilst, thermal unit were calculated through the growing season till harvest, the photosynthetic rate at stage of full canopy has been measured at the experiment in 2000. The experiment indicated that growth and yield of buckwheat plant were great influenced by climatic difference between two sites. The results revealed that the cooler the site was, the higher the growth, dry matter production and yield per unit land. The highest average yield per hectare was reached at upland plain, those were 2.849 - 5.320 ton ha-1 for kitawasesoba and 3.766 ton ha-1 for hitachi-akisoba. While at the lower place the average yield ranged from 1.466 ton ha-1 – 3.345 ton ha-1 for kitawasesoba and 3.260 ton ha-1 for hitachi-akisoba. Those values, however are higher than world average yield of buckwheat namely 0.898 ton ha-1. At the upland, the buckwheat plant matured at accumulated thermal unit level of 847 – 909 degree days for kitawasesoba and 901 degree days for hitachi-akisoba. While at the lowland, the plant matured at 849 – 914 degree days for kitawasesoba and 975 degree days for hitachi-akisoba. The harvest period at upland was took about 55 days, while that of lowland was only about 45 – 50 days. The photosynthetic rate has been measured at level of 20 µmol CO2 m-2 s-1 and 12 CO2 m-2 s-1 for exposed leaf to sunlight at 1150 m and 500 m above sea level, respectively.