Smoked Rice Hulls as Planting Medium for Seedlings

Reprinted with permission from Asian Vegetable Research and Development Center, P.O. Box 205, Taipei

A planting mix for seedlings must promote good growth and provide sufficient nutrients, water and air to the plant roots.

Ordinary rice hulls make a poor material for this purpose, but smoked rice hull is an excellent one. The benefits of smoked rice hull are: it provides a bacteria and fungus-free material, it has good water-holding ability, it holds its shape for a long time, and it can supply nutrients to the plant.

Smoked rice hull (or husk) is fairly easy to prepare if you

follow the simple steps outlined.

1.  Materials needed are a metal or tile pipe 10 centimeters in diameter and 1-1.5 meters in length, some mediumsize stones or bricks, charcoal, and a quantity of dry rice hull.
2.  Position the pipe upright atop the stones or bricks. You may use the stones or bricks to support the pipe.
3. Place charcoal around the base of the pipe, and start burning it. The pipe will maintain a source of air to the burning charcoal. This will provide an even distribution of heat among the rice hulls when they are added. 
4. Once the charcoal is burning, place some dry rice hull around it. Do not put too much hull at once; add the hull slowly at short intervals as the charcoal burns and the heap heats up.
5. When the rice hull begins to blacken, the charcoal is hot enough to build a mound of dry rice hull around the pipe. Continue adding hull until it reaches the top of the pipe.
6. Let natural carbonization take place; the rice hulls should not be allowed to burn but only carbonize.
7. Watch the process closely. The outside of the pile will change from a yellowish color to brown and then to black. Once the outside of the mound turns black the carbonization process is complete.
8. Spread the smoked rice hull on the ground to cool for 2 to 3 hours. Also get rid of any materials that have turned to ash by washing.
9. To keep the pH at the proper level, mix 1 g of calcium superphosphate for each liter of smoked rice hull.

Now the smoked rice hull is ready for use as a planting medium to grow seedlings.