INDONESIAN JOURNAL OF AGRICULTURAL SCIENCE

54-67

Authors: Markus Anda, Anny Mulyani, and Suparto

Problems of soil limiting factors affecting crop growth were not fully understood owing to little attention has been given to soil mineralogy and its association to soil chemical properties. The objective of the study was to assess soil mineralogical and chemical properties of seven soils derived from different parent materials as an integrated strategic consideration to establish soil management. Field study was carried out in 2009. Soils were sampled from each horizon of profiles. Results showed that primary and secondary minerals had a strong effect on soil chemical properties. The sand fraction of soils derived from basalt, gabbro, mica schist and serpentinite was dominated by resistant minerals (quartz or opaques), leading to very limited, if any, nutrients released from parent materials. The clay fraction was dominated by kaolinite for soils derived from basalt, mica schist and gabbaro, and by amorphous materials for the soil derived from serpentinite resulting in low soil cation exchange capacity (CEC). For other three soils derived from volcanic tuff, volcanic basaltic andesite and volcanic ash, the easily weatherable minerals (feldspar and ferromagnesian) were dominant, suggesting the high reserved nutrients. The presence of halloysite and smectite minerals in the soil derived from volcanic tuff resulted in high soil CEC, while the dominance of amorphous materials in soils derived from volcanic basaltic andesite and volcanic ash was responsible for the low CEC. For soils derived from basalt, serpentinite, mica schist and gabbro, therefore, the strategic management should be directed to restore soil CEC, pH, exchangeable cations and P content. For soils derived from volcanic tuff, volcanic basaltic andesite and volcanic ash, the presence of easily weatherable minerals indicated many reserved nutrients; hence the soil management is directed for replenishment of nutrients removed by crops.

80-85

Authors: Aidi-Daslin, Sekar Woelan, and Syarifah Aini Pasaribu

Rubber clones of Indonesian Rubber Research (IRR) 200 series have been produced from intensive breeding program started in 1985. Some clones showed superior characteristics such as high latex yielding, vigorous, and disease resistant. This study aimed to test their performances in a field trial conducted since 1999 at Sungei Putih Experimental Garden, North Sumatra. The experiment was designed in a randomized block, using twelve IRR clones as treatment and PB 260 clone as control, three replications. Planting distance was 5 m x 4 m and plot size was 10 rows x 50 trees. Observations were made on girth size of the 2, 3 and 4 year-old trees, dry rubber yield following the 1/2S d/2 and 1/2S d/3.ET2.5% tapping systems, bark thickness, rings number and diameter of latex vessels, as well as leaf fall diseases intensities of 3-5 year-old trees. The results showed four IRR 200 clones, i.e. IRR 207, IRR 208, IRR 211 and IRR 220 produced high latex. Using the 1/2S d/2 tapping system, three clones with highest dry rubber yield were obtained, namely IRR 208 (49.8 g tree-1 tapping-1 or g t-1 t-1), IRR 211 (48.8 g t-1 t-1) and IRR 220 (52.0 g t-1 t-1), whereas that using the 1/2S d/3. ET2.5% tapping system, their yields were 63.2 g, 64.3 g, and 66.2 g t-1 t-1, respectively. At four year-old, these clones had girth size of 41.4-51.0 cm, girth increment 9.7-11.6 cm year-1, bark thickness 6.3-7.2 mm, latex vessel rings number 6.8-7.0, and diameter of latex vessels 23.75-26.57 mm. All of the clones were moderately resistant to Colletotrichum, Oidium and Corynespora leaf fall diseases. This study suggests that IRR 207, IRR 208, IRR 211 and IRR 220 rubber clones are suitable for commercial stake holders and the recommended tapping system is 1/2S d/3.ET2.5%.