Mustard (Brassica juncea L.) is a plant that can live in various places, both in the highlands and lowlands. The productivity of mustard plants in South Kalimantan in 2012 was 2.88 tons ha^-1, in 2013 it was 2.79 tons ha^-1 and in 2014 it was 2.68 tons ha-1 which showed a decrease in mustard production each year. This is because the soil in South Kalimantan itself is included in the ultisol soil which has insufficient or less fertile nutrient content. These problems need to be addressed by adding organic matter. Banana weevil has local microorganisms and contains microorganisms that decompose organic matter that can improve soil nutrients. The banana hump contains 2.2 C/N, 0.09 ppm Fe, and 800 ppm Mg. These chemical elements are very influential on the vegetative growth of plants, especially the formation of leaves. This study used a one-factor completely randomized design with five treatments with four replications so that there were 20 experimental units. Parameters observed in this study were plant height, leaf width, number of leaves, and wet weight of mustard plants.  This research was conducted to determine the best concentration of liquid organic fertilizer (POC) on banana weeds on growth and yield of mustard plants. Based on the results of statistical research, this study showed that banana weevil LOF had a significant effect every week after planting on plant height, leaf width, number of leaves, and wet weight of plants. In the wet weight, LOF administration with a concentration of 200 ml + 800 ml water was able to increase the wet weight by 21.70 g compared to without LOF administration.