Oxygen Containing Functional Groups of Humic Acid of Soil Organic Matter

In an incubation study for 120 days by adding seven organic materials viz, paper sludge, farmyard manure, saw dust, rice husk, groundnut shell, wheat straw and rice straw to six representative soils of Rajasthan from Udaipur, Bhilwara, Ajmer, Pali, Kota and Bharatpur, the functional groups viz. total acidity, carboxyl, phenolic hydroxyl, alcoholic hydi oxyl, total hydroxyl, carbonyl and methoxy groups were determined in humic acid extracted from the soil at various stages of incubation. Materials showing higher contents of carboxyl, carbonyl and phenolic hydroxyl, and low contents of alcoholic hydroxyl and methoxy groups indicated a higher stage of humification. At later stages of humification, the nature of soil was observed to contribute more to the quantity of functional group rather than the nature of organic material added.