ASIAN JOURNAL OF AGRICULTURE Volume 2, Number 2, December 2018 E-ISSN: 2580-4537 Pages: 39-43 DOI: 10.13057/asianjagric/g020201 Short Communication: Volcanic ash utilization as planting medium of curly lettuce with charcoal husk and urban waste compost as soil amendment NITISAPTO MULYONO ♥ , AZWAR MAAS, BENITO HERU PURWANTO, PUTU SUDIRA Laboratorium Agrohidrologi Jurusan Tanah, Universitas Gadjah Mada. Jl. Flora 1 Bulaksumur, Sleman 55281, Yogyakarta, Indonesia. Tel. +62-274- 901221, Fax.: +62-274-55128. ♥ email: nitisapto@ugm.ac.id Manuscript received: 26 April 2018. Revision accepted: 12 October 2018. Abstract. Mulyono, Maas A, Purwanto BH, Sudira P. 2018. Short Communication: Volcanic ash utilization as planting medium of curly lettuce with charcoal husk and urban waste compost as soil amendment. Asian J Agric 2: 39-43. During a volcanic eruption, volcanic ash spreads over an extensive area, causes environmental disturbances, and thus, should be disposed afar from settlements. On the other hand, volcanic ash is useful in urban areas where pot-planting is often lack soil medium. However, the utilization of volcanic ash as direct planting medium has many obstacles due to its characteristics such as the acidic, nitrogen nutrients rareness, compressed and dull to water. Hence, to be ready to use, it should be improved by using soil amendment. This study used charcoal husk combined with compost as the soil amendment. The purpose of this study was to use the volcanic ash as the planting medium, by obtaining a proper dose of volcanic ash and the soil amendments for the growth and yield of curly lettuce. The experimental design applied in this study was the complete randomized design (CRD) with three replications. The first factor was the 5 levels of charcoal husk (on volcanic ash) doses, namely 0.30; 0.40; 0.50; 0.60; and 0.70. The second was the ratio between the media and the 3 levels of urban waste compost doses, namely: 3:1; 2:1 and 1:1, resulting in 5 x 3 total combinations with three replications. The plant growth and yield data results were analyzed by using the variance analysis and continued with Duncan Multiple tests (Duncan Multiple Range Test). The results showed that when used as the sole planting medium, the volcanic ash could not support the growth of lettuce plants. The evidence was shown from the same size and weight of the curly lettuce after the age of 35 days (5 g/plant). The utilization of husk and urban waste compost treatment showed significant growth rise. The combination of volcanic ash and soil amendments showed that the best effect on the growth and yield of curly lettuce was from M3K3 treatment at the dose of 25% volcanic ash, 25% charcoal husk and 50% urban waste compost (60 g/plant). Keywords: Charcoal husk, curly lettuce, municipal waste compost, volcanic ash INTRODUCTION Indonesia is susceptible to volcanic eruptions. However, one of the useful eruption products is the volcanic material. It contains valuable soil nutrient. The volcanic ash layers on soil surface make the soil to experience rejuvenation and weathering process where new soil layer establishes with the help of water and organic acids. They increase the cation concentration (Ca, Mg, K and Na) in the soil up to 50% than the original condition. Also, it functions as ameliorant that will hold nutrient supply degradation because it contains more complete compositions than lime, macro, and micro nutrient, as well as neutralization power to 40% acidity which equals to CaCO3 ( Subiksa et al. 1997; Fiantis 2006). The use of volcanic ash as the planting medium has several constraints, which is its rapid sedimentation and hardening when exposed to water. Such condition causes difficulty for the root development resulting in withering and death. One of the efforts to improve such physical condition of the volcanic ash is by utilizing biochar, a substance with high carbon concentration . Adding biochar to the soil can increase the C concentration and water retention and improve nutrients in the soil (Lehman and Joseps 2009; Gani 2009). Besides being used as the soil amendment material, rice husk is potentially useful in composting process and nutrition, as well as sustaining N within the composting process when added with rice husk (Theba et al. 2012). Husk characteristics include light weight (0.20 g/cm 2 ), coarse (consequently, with high air circulation), high water resistance and can reduce disease influence, especially bacteria. According to Djatmiko (Purnamasari 2008) charcoal husk added to a planting media will decrease the weight/volume of the planting media, rapidly increase the drainage pore space and slowly decrease the drainage pore. Carter et al. (2013) obtained a result where the use of charcoal husk would increase the plant and root biomass, the plant weight and the number of leaf within all plant cultivation in comparison to without charcoal husk treatment because its addition increased the soil pH and CEC (Cation Exchange Capacity). Besides biochar, volcanic ash requires additional nutrient intake from both inorganic and organic fertilizer. This study emphasized more on the use of organic fertilizer from urban waste compost. It comes from large amount of organic wastes produced by households. Usually, the