Effect of Coconut Fiber Proportions in Substrate on Germination and Early Growth of Carnegiea gigantea

Carnegiea gigantea (saguaro cactus) is an indigenous species of the Sonoran Desert that grows at a very slow rate. As it has a vital role in the ecosystem and there is growing interest in cultivating C. gigantea as an ornamental environmental plant, optimization of germination and establishment of C. gigantea seedlings is very important. The substrate used during the early growth of C. gigantea seedlings is very important to provide adequate amounts of water, aeration and root development. The experiment documented here compares the effects of two different coir ratios added to the substrate on seed germination rates and early growth of C. gigantea seedlings. Five treatments including T0 (0% coir), T1 (25% coir), T2 (50% coir), T3 (75% coir) and T4 (100% coir), were subjected to seed germination testing on standard sandy loam soil. Seeds were grown under controlled conditions in a greenhouse. Monitoring of the germination percentage, seedling height, root length, and infection levels was done over a period of 90 days. Results indicated that T2 (50% coir) had the best overall performance; T2 had the highest average germination rate (84%) and average seedling height as well as the most root development. T1 (25% coir) also performed much better than the control. T4 (100% coir) performed poorly on account of lack of drainage, excess moisture retention and highest level of fungal infections leading to poor germination (40%) and weak seedlings. It can be concluded that a 50:50 mixture of coconut coir and sandy-loam substrate provides the best balance of moisture retention and aeration needed for successful propagation of C. gigantea. When used in the right amounts, coconut fiber is a sustainable and effective substrate material for growing desert cactus.