Reforestation by direct seeding of Gmelina arborea using seed briquettes: Composition, size and site preparation, and sowing date

Abstract

Direct seeding is a promising technique for reforestation, but it has been poorly studied in tropical forests. The research aims to assess the briquette composition, size and site preparation, and sowing date on the seedling survival and early growth of Gmelina arborea direct seeding at 12 months in Parung Panjang, Bogor. The briquette was printed using some materials, i.e., soil, compost, charcoal, lime and tapioca as a glue, and tested in a greenhouse to obtain the optimal seed germination. The complete randomized design was used to assess the optimum seed briquette composition on germination parameters in the greenhouse, while a randomized block design was used to assess the eight combinations of briquette sizes and site preparation techniques on the seedling survival and growth. The briquette composition of soil 10%, compost 45%, rice husk charcoal 35%, lime 5%, and tapioca 5% resulted in the best germination capacity (78.5%) and other germination parameters. Gmelina arborea seed briquette, which had the size of diameter 5 cm and thickness 3 cm sowed by land clearing and briquette burial, showed the highest seedling survival (56.8%) and growth (seedling height 120.32 cm and diameter 15.92 mm) compared to other sizes. The sowing date also significantly influenced the survival of direct seeding. The application on the early-middle rainy season (the middle of December) was optimal for direct seeding because of the stable rainy frequency in Parung Panjang, Bogor. This study supports the use of direct seeding of the species being studied, but the methods could be improved to include a more significant number of species.