| Sumario: | Seven surface soils from Colombia were analyzed directly (field-fresh), after drying at 40°C and after giving it the temperature treatments at 105°C, 300° and 500°C in order to study the effect of temperature upon soil characteristics. The pH values increased up to 1.5 units on heating to 500°C. The carbon and nitrogen content decreased to minimal values, specially after 500°C, the temperature of 300°C, that is common on burning the plant residues , would induce a loss of aproximately 200 kgN/ha in these soils. Burning of organic matter liberates P as H2PO4- wich then reacts to form calcium, iron and aluminum phosphates in soils. The increase in the water soluble cations was a very significant, and occurred parallel to the decrease in their reserves as exchangeable cations.
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