Relationship between organic carbon and optical characteristics of sandy soils receiving long term organic matter
1992
Patcharee Saenjan | Ketsuda Dejbhimon (Khon Kaen Univ., Khon Kaen (Thailand). Faculty of Agriculture. Dept. of Soil Science)
Study on the relationship between organic carbon and optical characteristics of sandy textured soils receiving various long-term organic materials was carried out with 19 soil samples from Northeast Thailand. They were analyzed for total carbon, total humus and measured for optical density (OD) of their NaOH-soluble humic substance at the wavelength of 400 and 600 nm. In addition, ratio of colour and total humus (RF), humification degree (delta log K) and humic-substance extraction coefficient (EC) of the soil samples were calculated. Subsequently, the relationships between total carbon, total humus and other variables were computerized. It was found that total carbon of Surin paddy, forest and pasture soils with returned organic matter has increased. Turning forest and pasture land to upland crops such as cassava and sorghum resulted in decline of soil carbon. relationship was not found for paddy soils. Relationships between total humus and OD400, OD600 and RF values of the whole soil samples were found to be linear, and all of the mentioned relationships gave high correlation coefficients of 0.80. Moreover, range of delta log K of paddy soils was higher than pasture soils indicating lower humufication degree in paddy soils. RF values of the soils decreased with the increase in delta log K on an exponential scale.
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