Abstract
Aluminum Detoxification by Humic Substance Extracted from Compost of Organic Wastes (S Winarso, E Handayanto and A Taufiq): Humic substance could control the activity of metal as well as exchangeable aluminum (Alexch) on acid soil. The humic substance extracted from compost of agricultural waste is rarely conducted. The objective of research was to evaluate the effect of humic substance concentration and sources to pH and Al suspension. The research had been conducted in the Soil Laboratory of Agricultural Faculty of Jember University from April to July 2009. The humic substance used in these researches was extracted from compost of rice straw (RS), soybean straw (SS), cassava starch solid waste (CSSW), and empty bunch of oil palm tree (EBOPT). The humic substance concentration treatments were 0, 10, 20, 30, 40, 50, 75, 100, 150, 200, 250, and 300 ppm. Result of the analysis showed that characteristic of humic substance was difference depending on the source material used. The humic substance extracted from SS contain total base cations (K, Na, Ca, Mg) higher (1.17%) compared with CSSW (1.07%), OPT (0.87%), and RS (0.69%). While the humic substances extracted from RS contain total organic acid (Acetic, Fumeric, cetoglutamic, Sucsinic, Propionic, Butiric, Ocsalic, and sitric acid) higher (157 ppm) compared with EBOPT (129 ppm), SS (115%), and CSSW (108%). Among these organic acids, acetic acid was highest concentration (> 34.51% of total acid). The addition of humic substance increased pH and decreased aluminum concentration of the suspension. The higher pH increment and Al concentration reduction took placed in the suspension treated with humic substance from SS compost. The correlation between decreasing Al concentration with humic substance concentration which explained chelation was higher (r = 0.97) than decreasing Al concentration with increasing pH which explained precipitation (r = 0.93). Based on these research results, it can be concluded that humic substance extracted from agricultural waste have a good prospect as a soil ameliorant to increase soil pH, detoxify soil aluminum, and increase soil P availability on acid soil.
Highlights
Previous researches showed that humic substance affect soil characteristic, water, and environment
The objective of the research was to evaluate the effect of humic substance addition, that was extracted from compost of rice straw, soybean straw, cassava starch solid waste and oil palm tree, to pH and Al suspension
The results indicated that Al chelation and precipitation by humic substance originated from some agricultural wastes compost can be used to control metal element on land metal-contaminated
Summary
Previous researches showed that humic substance affect soil characteristic, water, and environment. The role of humic substance in the soil that affect or control the metal activities and other pollutant (like pesticide) were studied by previous researchers, for example Cu (Karlsson et al 2008), Uranium (Singhal et al 2006), Hg and Pb (CruzGuzma et al 2003), and pesticide (Li et al 2003). Aluminum (Al) content in the soil is very high, but the solubility is very low. The Al solubility will increase as the soil acidity increase (Lindsay 1979). High Al concentration has a negative effect on plant root growth, and potentially retard nutrient absorbtion, like Mg (Sverdrup and Warfvinge 1993)
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