The land between row of immature rubber period has a potential to produce sorghum.

No abstract

The Land between row of immature rubber period has a potential to produce sweet sorghum. This sorghum is one of high value commodities for food and energy security due to its wide adaptation. The objective of this research were to study the effect of rubber+sorghum intercropping system on the growth of immature rubber trees and to study some agronomic parameters of sorghum and production of sweet sorghum as rubber intercrops. The experiment was conducted at the Sembawa Research Station from June to October 2013. The experiment was carried out as a single factori using Randomized Block Design with three replications. The treatment were 3 varieties of sorghum i.e: Pahat, Kawali and Mandau. Observation of rubber trees was conducted using simple random sampling method, comparing the rubber trees growth of sorghum intercropping system with the rubber trees growth of monoculture system. The results showed that sorghum had a positive effect on the growth of rubber tree IRR 118. Furthermore, fresh stem weight (37.11 t/ha), juice yield (1.80 t/ha), and grains yield (2.69 t/ha) of sweet sorghum Kawali higher than that of the varieties tested. The Kawali has a high potential to produce a biofuel because it had a highest fresh stem weight and juice content.

Estimation model of rubber (Hevea brasiliensis) tree volume compiled pursuant to one independent variable of stem girth. This study aimed to develop a model of mathematical equations to estimate the volume of rubber trees of clones GT 1, PR 255, PR 261, and the combined clones. The experiment was conducted at the Sembawa Research Station, South Sumatra. Sampling was purposive. The results showed that the volume of rubber tree clones of GT1, PR255, PR261 and mixed clones affected by stem girth at breast height and affected by clone.The model of PR255 clone volume, VPR255=0.5827G1.7182 (R 2 =95.6%), klon GT1 VGT1=0.5818G1.0352 , (R 2 =97.8%), klon PR261 VPR261=0.5651G 0.6471 (R 2 =93.5%) and the mixed clones, V=0.5806G 0.5696 (R 2 =98.6%). At replanting time, rubber wood has a potential used for sawn timber, plywood, veneer and MDF raw materials. The biggest utilization of rubber wood is for MDF raw materials, because in MDF processing all parts of the trees can be utilized.Keywords: Clone, hevea brasiliensis, stem girth, and volume estimation ABSTRAK Model penduga volume pohon karet (Hevea brasiliensis) disusun berdasarkan satu peubah bebas lilit batang. Penelitian ini bertujuan menyusun model persamaan matematis untuk menduga volume pohon karet jenis klon GT 1, PR 255, PR 261, dan klon gabungan. Penelitian dilaksanakan pada areal peremajan karet di Kebun Percobaan Balai Penelitian Sembawa, Sumatera Selatan. Pengambilan sampel pohon dilakukan secara purposive. Model penduga volume pohon karet klon GT1, PR255, PR261, dan klon gabungan dipengaruhi oleh lilit batang setinggi dada dan dipengaruhi oleh jenis klon. Model penduga volume klon PR255, VPR255=0,5827G 1,7182 (R 2 =95,6%), klon GT1 VGT1=0,5818G 1,0352 (R 2 =97,8%), klon PR261 VPR261=0,5651G 0,6471 (R 2 =93,5%), dan klon gabungan, V=0,5806G 0,5696 (R 2 =98,6%). Pada saat peremajaan, kayu karet memiliki potensi untuk digunakan dalam industri kayu gergajian, kayu lapis, veneer, dan bahan baku MDF. Pemanfaatan kayu karet terbesar adalah untuk bahan baku MDF, karena pada pengolahan MDF semua bagian pohon dapat dimanfaatkan.Kata kunci: Hevea brasiliensis, klon, lilit batang, dan pendugaan volume

To establish rubber plantations smallholders in South Sumatra, Indonesia, plant materials are planted in polybags fi lled with top soil media from the local area. Good quality media is very important to ensure optimal growth of the rubber planting materials. The availability of top soil has become increasingly limited. In order to fulfi ll the need of planting media, cocopeat, which is available in abundance in the area, can potentially be an alternative to top soil. Cocopeat can potentially be used alone, or in combination with other type of media. In this study, cocopeat was mixed with soil at several mixture ratios to determine the best formula of cocopeat based planting media for rubber planting material. The study was conducted from August 2016 to January 2017 in the Nursery of Sembawa Research Centre Experimental Field, Palembang, South Sumatra, Indonesia. A completely randomized design was employed with six combinations of cocopeat and soil, replicated three times. This study showed that the best mixture ratio is 80% cocopeat and 20% soil, whereas 100% soil or 100% cocopeat is not recommended. The use of cocopeat as planting media should be followed by balanced fertilization in order to provide nutrients that are not available in cocopeat.