Abstract
The effects of a rice husk charcoal (RHC) covering on the growth, nitrogen uptake and post-transplant growth were investigated in lettuce plug seedlings under organic fertilization during the cool season. The RHC covering had no effect on the medium temperature. However, the growth and amount of nitrogen uptake were greater in seedlings when the medium was covered by RHC than when it was covered by vermiculite or left uncovered. Growth immediately after transplanting was more rapid in the RHC seedlings than in the other two seedling groups. The head fresh weight at harvest was about 20% higher in the RHC seedlings than in the other seedling groups. The nitrogen concentration in the seedlings increased with increasing RHC volume, but there was no significant relationship between the RHC volume and the seedling growth. A mixture of RHC with medium at equal volumes promoted less seedling growth and nitrogen uptake compared with those with RHC covering alone. The benefits of RHC covering were lost when we shielded the surface of the medium with aluminum foil wrapped in a paper towel.
