Using Hawaii's Locally Produced Organic Material to Improving Quality of Vegetable Seedlings

Vermicompost, coconut coir, and thermophilic compost based growing media were evaluated as alternatives to peat for vegetable transplant production. Four greenhouse trials were conducted using eggplant (Solanum melongena var. esculentum) and pak choi (Brassica rapa var. chinensis). Media were: peat:perlite (9:1 v/v)= (P); Peat amended with 0.7 grams CaCO©ý/liter of medium= (PAM); coconut coir= (C); thermophilic compost= (TC); vermicompost= (VC); P, PAM, C with weekly applications of soluble N-P-K (19-19-19) synthetic fertilizer= (PS), (PAMS), (CS); P:VC, PAM:VC, C:VC, TC:VC at rates of (75:25, 50:50 and 25:75 v/v); P, PAM, C, TC, P:TC (50:50 v/v), TC:VC (50:50 v/v) amended with tankage at rates of 5, 10, 12, 15, 20, and 25 grams per liter of medium; P with weekly applications of soluble organic fertilizer comprised of fish emulsion N–P–K (5–1–1) and seaweed extract N–P–K (0.10–0.10–1.5) = (PO). The physical and chemical properties of media were determined and the effect of treatment on tissue nutrient content and seedling growth were evaluated. The total pore space and water holding capacity of the peat and vermicompost used in our study were not significantly different from each other. The pH, EC, nutrient content and C/N ratio of vermicompost was more ideal for seedling growth than that of peat and amendment of peat with vermicompost improved growing media chemical properties. Amending peat, coconut coir and thermophilic compost with vermicompost increased seedling shoot tissue nitrogen content and seedling shoot dry weight, with the greatest shoot dry weights obtained from 100% vermicompost. Thermophilic compost amended with tankage up to a rate of 15 g/L of medium also increased seedling tissue nitrogen content and seedling shoot dry weight relative to the control and was the most cost effective media comprised 100% of local materials.