This article is from ECHO Asia Note #19

In a tropical setting, growing seedlings can be a difficult task. A major factor of concern for nursery production is water-logging (Zhu, 2007). During the rainy season, oversaturated soils can effectively suffocate root systems of a seedling by restricting flow of oxygen and other important minerals (Forcella, 2000). Nursery plants potted in dense soils are more prone to the negative effects of water-logging. Traditionally, the incorporation of materials such as perlite and vermiculite into potting mixtures helps to combat soil compaction and facilitate drainage. However, both perlite and vermiculite can be restrictively expensive for growers, especially resource constrained growers, like many of those with whom you work.

Nursery research from recent years has focused on finding viable, sustainable, low-cost alternative materials for potting mixes, often utilizing waste products of other industries such as: wood shavings, municipal compost, rice hull, and coconut coir (Arenas, 2002; Meerow, 1994; Ahmad et al., 2012). Rice hulls and coconut coir, which are plentiful in Asia, have the potential to effectively minimize risk for water-logging while replacing an expensive input such as perlite or vermiculite. Coir material has a high water-holding capacity within its fibers and good drainage through the pore space it creates in a substrate. Rice hull is an abundant byproduct of the rice milling industry and ubiquitous in tropical settings. Like coir, it creates pore space in mixtures needed for appropriate drainage and does not degrade quickly over time. Together, these two materials are promising low-cost alternatives to peat in nursery potting mixtures.