<![CDATA[Pakcoy (Brassica rapa L.) is a horticultural commodity with high economic value, yet its productivity still fluctuates. This has encouraged the use of marginal soils such as Ultisols, which have less optimal physical and chemical properties. Biochar derived from livestock waste, such as that from chickens and goats, has the potential to be applied as a ultisoll soil amendment. This study aimed to determine the appropriate dosage of livestock manure Biochar that provides the best growth response of pakcoy (Brassica rapa L.) Nauli F1 variety on Ultisol soil. The research was conducted from March to July 2025 at an experimental field located on Krajan Hamlet Street, Sirnabaya Village, East Telukjambe, Karawang, West Java 41361. The method used in this research is the Experimental Method of Randomized Block Design (RAK) with a single factor with 7 treatments and 4 replications.. The treatments included: Control/No Biochar (P0), Chicken Manure Biochar 20 tons/ha (P1), Chicken Manure Biochar 15 tons/ha (P2), Chicken Manure Biochar 10 tons/ha (P3), Goat Manure Biochar 20 tons/ha (P4), Goat Manure Biochar 15 tons/ha (P5), Goat Manure Biochar 10 tons/ha (P6). The research results were analyzed using the F-test and further tested with the Duncan Multiple Range Test (DMRT) at the 5% significance level. The analysis showed that the application of livestock manure Biochar had a significant effect on the growth of pakcoy (Brassica rapa L.) variety Nauli F1 grown on Ultisol soil. The P1 treatment (Chicken Manure Biochar at 20 tons/ha) resulted in the highest values for plant height (25,12 cm), number of leaves (19,4 strands), and stem diameter (9,17 mm). Based on the research results, the application of chicken manure Biochar at a dose of 20 tons/ha was effective as a soil amendment for Ultisol and has the potential to enhance pakcoy growth sustainably]]>
