Biochar is increasingly used as an amendment to improve agricultural soil functions and plant growth. However, the effect of biochar application on plant growth can be different due to high variability in the quality of biochar. In this study the effect of different types of biochar application on the growth of lettuce (Lactuca sativa L.) was assessed in a pot experiment over two period of cultivation in greenhouse. The biochar were produced from four different feedstocks biomass [Vinyard (Vitis vinifera L.), Tomato (Solanum lycopersicum L.), Banana (Musa) and Carnation (Dianthus caryophyllus. L.)] by slow pyrolysis at 300°C and 500°C temperatures and were used to amend the soil. The experiment was design in randomized complete block with five replications and 9 treatments. The treatments included the Control, VB300, TB300, BB300, CB300, VB500, TB500, BB500 and CB500. The trial consisted of a total of 45 pots (4 agricultural waste × 2 pyrolysis temperature × 5 replications) + 5 controls). Two (2) tons da-1 (80 g-1 10 kg-1 pot-1) of biochar was applied with a basic application of fertilizers NPK (18-18-18) and calcium oxide (CaO). The biochar treatments were found to increase plant height and number of leaves in the second cropping cycle in comparison to no biochar treatments. The application of Tomato (TB300) and Banana (BB500) biochar significantly increased plant height by 15.2% and 10.2% respectively. The greatest increase due to biochar additions was found in the soils with tomato biochar treatment and the least increase was found in the soils without biochar application (Control). The second cropping season appeared to be better in terms of yield and quality parameters than the first season. As a result, in this study revealed that a variation in the temperature of pyrolysis does not impact lettuce growth, and recommends a long-term incubation period for further effect of biochar applications on crops.

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