Relationship between organic carbon and optic characteristics of sandy soils receiving long-term organic matter
1993
Patcharee Saenjan | Ketsuda Dejbhimon | Sathaporn Paiboonsak (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 sample 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 between total humus and total carbon of pasture soils was found to be linear while this 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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