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The objective of this study was to investigate the efficacy of chicken manure and biochar on productivity of green oak lettuce under acid soil field conditions. The experiment was arranged in a randomized complete block design with 4 replications (plot) for 2 harvesting times. Six treatments included (1) control (no add fertilizer and biochar), (2) application of fertilizer according to the Agricultural Service Center (ASC) practice: chemical fertilizer (30 kg/rai rates of 16-16-16 and 46-0-0) and 2,000 kg/rai rates of cow manure, (3) application of 2,000 kg/rai rates of chicken manure, (4) application of 2,000 kg/rai rates of chicken manure and 500 kg/rai rates of biochar, (5) application of 2,000 kg/rai rates of chicken manure and 1,000 kg/rai rates of biochar, and (6) application of 2,000 kg/rai rates of chicken manure and 1,000 kg/rai rates of biochar at 1st harvesting time and application of only 2,000 kg/rai rates of chicken manure at 2nd harvesting time. The result revealed that the highest yield of green oak lettuce was shown under the application of 2,000 kg/rai rates of chicken manure and 500 kg/rai rates of biochar that were 2,380 and 3,390 kg/rai for the 1st and 2nd harvesting time, respectively. Moreover, they provided the highest economic value average form 2 harvesting times that was 77 baht/kg.
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