Higher level of KCl application stimulated both leaf area index and leaf area duration in all cassava varieties, while the leaf and tuber number of the bitter varieties (high cyanide-level varieties) decreased in proportion to the level of KCl application. The root/shoot (R/S) ratio and harvest index (HI) were negatively related with the level of KCl application in all cassava varieties. The bitter varieties obtained the lowest R/S ratio at the level of 100 - 150 kg KCl ha-1 , while the sweet varieties (low cyanide-level varieties) acquired the highest values at the level of 50 - 150 kg KCl ha-1 . Also, the sweet varieties showed the lowest HI at the level of 250 kg KCl ha-1 , but the bitter varieties at the level of 150 kg KCl ha-1 . At 6 - 8 months after planting, the sweet varieties tended to obtain higher starch content of roots (tubers) at the level of 50 - 150 kg KCl ha-1 , while the bitter varieties at the level of 150 - 250 kg KCl ha-1 . Relatively lower level of 50 - 150 kg KCl ha-1 was more appropriate for decreasing hydrocyanic acid (HCN) content of roots (tubers) in the sweet varieties at the harvest time, and the level of 250 kg KCl ha-1 was adequate to decrease not only HCN content of leaves but also that of roots (tubers) in the bitter varieties during the growing period. To obtain higher yield and starch content of tubers, and lower HCN content of roots (tubers), it was recommended that the sweet varieties are applied with the level of 50 - 100 kg KCl ha-1 and the bitter varieties with the level of 150 - 200 kg KCl ha-1 , respectively, in Latosol soils of Bogor areas, West Java.

This study was carried out to investigate the effect of stem-cutting (SC) length and portion on the major agronomic characters related with dry matter production and accumulation, and to examine their relation­ships in cassava. When cassava was planted with longer SCs or with older portion SCs, major canopy or source characters like leaf number and leaf area index developed excessively, while tuber yields could be reduced due to the decrease of root/shoot ratio, relative growth rate, root dry weight, and harvest index, particularly in the bitter varieties (high cyanide-level varieties). It was considered that the sweet varieties (low cyanide-level varieties) be early­bulked with higher tuber yield when they are planted with the 25-30 cm long SCs or with the SCs from young type to semi-mature portions of mother stems, while the bitter varieties with the 15-20 cm long SCs or with the SCs from semi-mature to hardwood portions of mother stems, respectively. However, a significant interaction between length and portion of SC was not observed in all agronomic characters.

This study was carried out to investigate the patterns of dry matter (DM) production and accumulation, and to screen the relationships between related major growth characters and DM accumulation in four cassava varieties in Bogor (6~circ19, West Java, Indonesia. Gading and Adiral developed an enough source and canopy in short at the early growth phase and then translocated assimilates to storage roots with a higher partitioning rate, even these varieties were considered as early-bulking varieties, which have superior source and sink potentials in increasing yield and DM of tubers. The root/shoot ratio (R/SR), total dry weight (TDW), leaf area duration, leaf area index (LAI), and number of tubers showed higher positive correlations with the dry weight of roots (DWR), and the direct effects of TDW, R/SR, and LAI on the DWR were higher. These characters were considered to be useful target characters to screen cassava varieties with high yield potential and high DM in aspect of tuber production.