Improving the success of direct seeding through the application of seed briquettes, aquasorb, and sowing time: case studies on Ceiba pentandra, Enterolobium cyclocarpum, and Calophyllum inophyllum

Abstract Direct seeding, a planting technique that has long been applied in restoring degraded land and forest, is often doubted to be successful due to many constrains, both biotic and abiotic. This study aims to increase the success of direct seeding through the application of seed briquettes, aquasorb treatment and determining the right sowing time for three forest tree species, i.e. Ceiba pentandra, Enterolobium cyclocarpum, Calophyllum inophyllum. This study used a randomized block design with two factorials (seed treatments and sowing dates) in each species. Seeds were sown in three blocks in the field according to the sowing time treatments. Each treatment consisted of 10 sowing plots in one block and 5 seeds or seed briquettes in each sowing plot. The results showed that direct seeding when the rain starts to stabilize (ST-2) supported by the use of seed briquettes and the addition of aquasorb was able to increase seedling survival, height and root collar diameter of all tested tree species. In general, seed briquettes and the addition of aquasorb provided better seedling survival and growth compared to direct seeding using untreated seeds. C. inophyllum gave higher seedling survival compared to the other two species indicating that this species is very prospective for direct seeding applications due to its high adaptability.