Fertilizer application on mature rubber trees is sometimes neglected especially when the rubber price is low. The experiment to demonstrate the effect of fertilizer on rubber yiled was conducted for two years. The treatments impose were control, without fertilizer application, fertlizer application with straight fertilzer with general recommended dose and fertlizer applicakan with NPK tablet where the nutrient content were as much as 75%, 50%, 20% and 15% comapred with straight fertilizer. The experiment showed that the yiled was similar between control and fertilizer appplication during the first year observation, but at the secon year, continued fertilizer application gave better yield compared with control. The renewal bark thickness was also better in fertilizer appplication compared with control. The NPK tablet as much 75% Straight fertilizer gave he highest yield. This meant that NPK tablet is more efficent taken up by rubber tree comapred with straight fertilizer.

The best rubber planting materials are needed to build the best rubber plantation. Humic acids could be used to improve the growth of rubber planting materials. Humic acid plays a role as a hormone-like substance. This research was aimed to determine the optimal concentration of foliar application of humic acid in order to enhance the growth of rubber tree planting materials. This research was arranged in a completely randomized block design with five treatments and four replicates. The treatments were the concentrations of humic acids, i.e. 0; 250; 500; 750; and 1,000 ppm. Observations were made on rubber tree diameter, plant height, shoot and root biomass, and nutrient content of leaves and the stem. The results showed that foliar application of 1,000 ppm of humic acids could enhance the growth of rubber tree planting materials. Foliar application of 500 -1,000 ppm of humic acids could increase K content of the stem. The effects of foliar application of humic acids were more apparent in the root part than in the shoot part.

Rubber is an important commodity for Indonesia. Currently, a problem encountered in the propagation of rubber planting materials is the availability of ideal soils with optimum nutrition as the planting medium. Peat can be used as a growing medium but it still has weaknesses such as high level of acidity and poor in nutrient content. This study was aimed to assess the performance of rubber budded stump grown on modified potting medium and applied with different forms and rates of fertilizers. The nursery experiment consisted of 17 treatments and arranged in a randomized complete block design. After rubber nursery stage, the performance of the rubber budded stump were also monitored in the field for 10 months. Results showed that mixture of peat and soil with the application of recommended rate of solid or liquid fertilizer produced rubber budded stump with bigger stem diameter and taller plants. The potting medium stimulated early root development which led to higher nutrient uptake. These budded stump also performed better in field, showed higher leaf nutrient concentration after 6 months and produced bigger stem diameter after 10 months.

Low prices of rubber has been a serious problem to rubber smallholders in Indonesia. Rubber-based intercropping systems offers a practical solution to this issue and increasing overall productivity of intercrops, for example upland rice and maize. This study reviewed the suitable spatial arrangements in rubber planting to long term impact based intercropping systems. A field experiment was established in a smallholder rubber plantation in Tanah Laut Regency, South Kalimantan with area of 50 ha. Two planting patterns of rubber PB 260 clone were tested: (1) single row planting pattern (SR) by 6 m x 3 m, and (2) double row planting pattern (DR) by 18 m x 2 m x 2.5 m. The experiment showed that girth of rubber trees in the SR system at the first tapping year was slightly larger than in DR system, even though statistically it was not significant. The latex yield per tree of SR and DR systems were similar, however, latex yield per hectare of SR system was higher than DR system due to a higher tree population in SR system. The DR system was technically suitable for long term intercropping, because when rubber tree can reached 8 to 9 years old and light penetration was more than 80% at distance from the rubber row. The total area required for rubber, upland rice and maize grown in monoculture to produce an equivalent of a one hectare of rubber-upland rice-maize intercrop is 1.87. This means the intercropping has an advantage compared to monoculture.

Rubber is one of the economically important tropical trees that produces natural rubber, an essential industrial raw material in Indonesia. In general, rubber can grow well in areas with 1,500 - 3,000 mm rainfall per year that evenly distributed round the year. During the dry season, water availability is reduced so that water becomes a limiting factor for the growth and production of the rubber tree. This paper aimed to determine minimum soil water content that must be maintained to prevent the reduction of PB 260 rubber production based on field water balance. This research was carried out at the Indonesian Rubber Research Institute Experimental Field, South Sumatra, Indonesia, between 2014 to 2019. This experiment used PB 260 clone which was planted in 2001 using a 6 x 3 m plant spacing. Soil analysis showed that the Sembawa had a clay loam soil texture. The measured parameters were latex production (kg per ha per year), rainfall, and evapotranspiration (mm). The results from our six years of study showed that rubber production always decreased when soil water content started to decline below field capacity (33.7 %, or equal to 337 mm with 1m depth of root zone).

Sistem tanpa olah tanah dan cover crop telah banyak diterapkan di beberapa perkebunan karet di Indonesia, namun pengaruhnya terhadap pertumbuhan tanaman belum diketahui. Penelitian ini bertujuan untuk mengetahui perubahan sifat fisik tanah dan pertumbuhan tanaman karet TBM akibat pengolahan lahan dan penggunaan legume cover crop (LCC). Penelitian dilaksanakan pada bulan November 2011- Januari 2015 dengan menggunakan rancangan percobaan split plot dengan 2 faktor. Faktor utama adalah sistem olah tanah (tanpa olah tanah/TOT) dan olah tanah/OT), sedangkan anak petaknya yaitu jenis cover crop (tanpa cover crop/TCC), Mucuna bracteata/MB), dan gulma alami/GA). Pengamatan meliputi parameter pertumbuhan tanaman karet dan sifat fisik tanah. Hasil penelitian menunjukkan bahwa LCC (MB dan GA) mengubah agregat tanah, bobot isi, dan porositas total tanah.  Pada umur 26 BST pertumbuhan tanaman karet pada perlakuan MB dan GA berbeda nyata dibandingkan kontrol.

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.

Low prices of rubber has been a serious problem to rubber growers in Indonesia. Rubber-based intercropping systems offers a practical solution to this issue and increasing overall productivity, for example by growing upland rice and maize between the rubber tree rows. This study was aimed to determine the suitable spacing in rubber planting to facilitate long-term rubber-based intercropping systems. A field experiment was established in a smallholder rubber plantation in the Tanah Laut Regency, South Kalimantan with area of 50 ha. Two planting patterns of rubber clone PB260 were tested: (1) single row planting pattern (SR) by 6 m x 3 m, and (2) double row planting pattern (DR) by 18 m x 2 m x 2.5 m. The experiment showed that the girth of the rubber trees with the SR system at the 1st tapping year was slightly larger than that in the DR system, even though statistically it was not signifi cant. The latex yield per tree of SR and DR systems were similar, however, latex yield per hectare of SR system was higher than the DR system due to a higher tree population in the SR system. The DR system was technically suitable for long term intercropping, because when the rubber tree reached 8 to 9-year-old, the light penetration was > 80% at distance of about 4 m from the rubber tree rows. Economically, DR system can increase the added values for rubber farmers because it allows long term intercropping. Rubber-based intercropping with DR system is suitable to be applied, especially by smallholders, with a marginal benefi t cost ratio of around 2.07. Keywords: Hevea, intercropping system, rubber planting pattern, spatial arrangement