Rice Husk as a Growing Media

We have a lot of exciting aquaponics projects at work here in Cambodia. We have experimental grow beds at the Tuk Vil farm, where we are testing KEM (Khmer Effective Microorganisms) in sustainable aquaponics systems to see how their presence alters the rate of growth of plants. The grow beds are all identical in their set up: they each have a cement pot of about 40 fish underneath, which feeds water in a circuit that flows from the container up to the bed itself where the seeds are planted in gravel.

Gravel is the first growing medium we used as an alternate for soil. Since gravel does not absorb water, it improves the flow of the system while allowing plants to take in more water for themselves. However, it is expensive to buy and transport gravel, making this option less accessible for villagers who typically live on less than one dollar per day. Since our aquaponics systems are meant to act as interventions for this population, other, more accessible and sustainable mediums became necessary to find. Luckily, we have recently had a breakthrough here at Community First in the discovery of a new growing medium that is locally available in abundant quantities and for almost no cost. It also already exists in all the villages that we are working in. This new growing medium is rice husk.

Rice husk, the exterior to rice, is the outermost layer of the rice paddy grain, and it is separated from the rice husk in the milling process. Cambodia is one of the largest exporters of rice in the world, meaning that this resource is already in the villagers’ hands, quite literally. Once it is dried out it can be used as fertilizer, but also as a growing medium in and of itself. Our own experiments using aquaponics systems with the rice husk instead of gravel have shown that plants grow considerably faster in the rice husk than in either gravel or soil. Rice husk barely absorbs any water, nor does it rot. This means it does not have to be replaced often, and water can filter through the rice husk to the plants’ roots more efficiently. This also means that water does not have to be brought through the system as often, which saves both water and electricity.

We are currently conducting growing experiments at the Community First lab, growing tomatoes and pineapple in the rice husk medium. In just a few weeks, we have watched tomato vines grow several inches; this is a much faster rate than observed in both gravel and soil grow beds. Combined with the KEM that we are currently testing at Tuk Vil, we hope to see great improvements in growing speed and therefore crop yield, by using only all natural enhancing methods. Keep on the lookout for more formal updates about our breakthroughs and findings coming soon!