POTENCY AND MANAGEMENT OF ORGANIC MATERIALS IN RUBBER PLANTATION IN INDONESIA
Plant nutrient management, especially organic materials is one of the interesting topics to be studied more deeply in rubber tree plantation. The price of rubber tends to decrease every year. It encourages the planters to utilize organic materials as fertilizer substitute agent. Organic materials have a function to improve the physical, chemical, and biological characteristic of soil.
Organic materials, besides from the plantation (in situ) such as weeds, cover crops, and twigs, but itâ€™s also be sourced from outside the plantation (ex situ) such as compost from oil palm industry. Litter potency from legume cover crop of Mucuna bracteata (Mb) in immature rubber plant area as soil organic material is big enough that is 2â€“7 ton/ha/year or 2,5-7 times higher than conventional cover crop. Furthermore, potency of nutrient returns to soil from Mb biomass amount 250,98 kg/ha N; 9,08 kg/ha P2O5; 72,5 kg/ha K2O; and 11,95 kg/ha MgO. The existence of cover crop in immature rubber plant interrows also affect to uniformity of rubber plant, the number of mature rubber, and bark thickness better than conventional cover crop.
Waste of oil palm industry such as empty fruit bunches and oil palm frond (OPF) also very potential to be used as organic material source to rubber plant. The number of rubber fine roots which is sized < 1 mm in diameter increased up to twice compared with a rubber plant without oil palm empty fruit bunches application. CEC value, C-organic and N, P, K, Ca, Mg content were reported also increased significantly. OPF is agricultural waste that have high lignin and cellulose and with an appropriate composting management become potential to produce manure compost on day 75. In Immature rubber plant, dose of 20 ton/ha increased soil porosity and decreased in bulk density compared plant without compost of OPF application. The treatment of 20 % compost + 80 % subsoil significantly increased the root dry weight of rubber plant seedling and also increased pH, CEC, C-Organic, P, K, Ca, and Mg soil content. Application of organic matter in plantation can be combined with â€œrorakâ€ (small blocked ditches). This condition causes the water plant needs can be fulfilled in dry season hence fertilizer application will be more efficient and nutrient uptake better.Keywords: Hevea brasiliensis, organic matter, nutrient, Mucuna bracteata, compost