The Soil Humin Carbon and its Indication of Humification

The soil under mixed evergreen forest contains more organic carbon than that from the other sites and follows the order: mixed evergreen forest soil > deciduous forest soil > natural grassland soil > deforested cultivated soil. Soil humin carbon follows the same order as soil organic carbon. The quantity of dilute alkali soluble soil humic carbon is greater than that of soil humin carbon. Dilute alkali soluble soil humic carbon follows the same order as soil organic carbon. The average value of soil humin carbon per 100 g of soil organic carbon follows the order: natural grassland soil > deforested cultivated soil > deciduous forest soil > mixed evergreen forest soil. The ratio of dilute alkali soluble soil humic and dilute alkali insoluble soil humin carbon shows almost parallel E₄/E₆ values of dilute alkali soluble soil humic substances; the higher its value the lower the degree of humification. The inverse value of this ratio is always less than one for all soils and is also one of the best indicators for the study of humification of soil organic matter. A high value of the inverse ratio indicates high degree of humification. The average value of the ratio between alkali soluble soil humic carbon and soil humin carbon follows the order, mixed evergreen forest soil> deciduous forest soil > deforested cultivated soil > natural grassland soil. The soil organic matter under natural grassland is highly humified due to higher value of inverse ratio. The average value of the inverse ratio follows the reverse order of that ratio. The soil under natural grassland shows the maximum average value of the inverse ratio which indicates highest degree of humification.