Abstract—The increments of aromatic structures are widely used to monitor the degree of humification. Compost derived from mix manures mixed with agricultural wastes was studied. The compost collected at day 0, 7, 14, 21, 28, 35, 49, 77, 91, 105, and 119 was divided into 3 stages, initial stage at day 0, thermophilic stage during day 1-48, and mature stage during day 49-119. The change of highest absorptions at wavelength range between 210-235 nm during day 0- 49 implied that small molecules such as nitrates and carboxylic occurred faster than the aromatic molecules that were found at wavelength around 280 nm. The ratio of electron-transfer band at wavelength 253 nm by the benzonoid band at wavelength 230 nm (E 253 /E 230 ) also gradually increased during the fermenting period indicating the presence of O-containing functional groups. This was in agreement with the shift change from aliphatic to aromatic structures as shown by the relationship with C/N and H/C ratios (r = - 0.631 and -0.717, p< 0.05) since both were decreasing. Although the amounts of humic acid (HA) were not different much during the humification process, the UV spectral deconvolution showed better qualitative characteristics to help in determining the compost quality. From this study, the compost should be used at day 49 and should not be kept longer than 3 months otherwise the quality of HA would decline regardless of the amounts of HA that might be rising. This implied that other processes, such as mineralization had an influence on the humification process changing HA’s structure and its qualities. Keywords—Compost maturity, UV spectroscopy, humification, humic acid I. INTRODUCTION OMPOSTS derived from mix manures and agricultural wastes are useful as they help reducing the agricultural wastes and utilizing them to improve soil quality. Although it is lower cost when compared to chemical fertilizers, there are some inherent problems. One of them is the quality of the compost as the types of raw materials are different every time of mixing [1]-[4]. Therefore, the confidence of farmers to apply the varieties of compost is questionable. Samples were sieved through 2 mm mesh and kept frozen for further analysis N. Sanmanee is with the Department of Environmental Science, Faculty of Science, Silpakorn University, Nakorn Pathom, Thailand 73000 (phone: +6634-219-146; fax: +6634 273-047; corresponding author e-mail: nsanmanee@yahoo.com). K. Panishkan, is with the Department of Statistics, Faculty of Science, Silpakorn University, Nakorn Pathom, Thailand 73000 (e-mail: kamolcha@su.ac.th). K. Obsuwan is with the Department of Biology, Faculty of Science, Silpakorn University, Nakorn Pathom, Thailand 73000 (e-mail: kulanart@hotmail.com). S. Dharmvanij is with the Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand 10330 (e-mail: sirichai.d@chula.ac.th). To gain the high profit in compost application in the field, several indices are used to assess the quality of compost, such as color, odor, temperature, C/N ratio, H/C ratio including the humic acid quantity. However, in last decade these parameters were considered insufficient to evaluate the degree of compost maturity [1]-[2], [4]. To better understand the evolution of humic substance structures, the parameters related to the quality of humic structures such as spectroscopic measurement were employed [1]-[2]. The wavelength range between 200- 220 nm indicates the small molecules such as nitrate and carboxylic that most likely appear in the humification process faster than the aromatic or unsaturated molecules at longer wavelength (280 nm, etc) [1]. The absorbances at 253 (E 253 ) and 230 (E 230 ) nm represents the electron-transfer band and benzonoid band. Both are related to each other as the increasing of E 253 is greatly affected by the degree of substitution in the aromatic ring [2]. Therefore, the higher ratio of E 253 /E 230 helps to determine the degree of possible nature substitution. It also indicates the presence of O- containing functional groups on the aromatic ring such as hydroxyl, carbonyl, and ester groups [2]. In this study, the compost derived from mix manures and agricultural wastes was used to evaluate the compost maturity. The samples were collected along the fermenting period—day 0, 7, 14, 21, 28, 35, 49, 77, 91, 105, and 119 and were further analyzed for humic characteristics. II. MATERIALS AND METHODS Compost derived from mix manure—bat, chicken, pig and cow mixed with chopped Leucaena leucocephala de Wit, bran of rice, dolomite, molace, fish fermented juice, and micronutrients for 2.13, 8.5, 17, 17, 10.63, 25.5, 10.63, 2.3, 2.13, and 4.25% , respectively. The samples were collected during fermenting period at day 0, 7, 14, 21, 28, 35, 49, 77, 91, 105, and 119. General parameters such as pH, temperature, odor, and texture were monitored to help in determining the compost maturity stage. The humic acid (HA) was extracted after the method of International Humic Substance Society (IHSS) [5]. Carbon (C), hydrogen (H), and nitrogen (N) were analyzed using Perkin Elmer 2004 CHN analyzer. The spectroscopic measurements were done by Jasco UV- Spectrophotometer model V-530. Statistical analyses were calculated using SPSS program. . N. Sanmanee, K. Panishkan, K. Obsuwan, and S. Dharmvanij Study of Compost Maturity during Humification Process using UV-Spectroscopy C World Academy of Science, Engineering and Technology International Journal of Agricultural and Biosystems Engineering Vol:5, No:8, 2011 448 International Scholarly and Scientific Research & Innovation 5(8) 2011 scholar.waset.org/1307-6892/12741 International Science Index, Agricultural and Biosystems Engineering Vol:5, No:8, 2011 waset.org/Publication/12741