Clay-organic complexes in a Polish loess soil

Complexes formed between clay and soil organic matter are important for carbon sequestration and for soil physical quality. Here, we use samples of loessial soil from South-East Poland to explore the phenomenon of complexing in loess. Soil samples were collected from a single catchment 8 years after the introduction of strip tillage and their compositions were characterized by traditional methods. Complexing was characterized in terms of the content of non-complexed clay which was estimated in two ways: firstly, by measurement of the content of readily-dispersible clay (which was assumed to be the non-complexed clay); and secondly, by calculation using algorithms that had been developed and evaluated previously. The calculations were based on the concept that, at carbon saturation, the clay/organic carbon mass ratio is equal to n. The calculations were done with a range of values of n. It was assumed that the correct value of n was that which gave the greatest coefficient of correlation between the measured values of clay dispersion and the predicted values of non-complexed clay. For the loess used, the optimum value was n = 14.