The nature of soil organic matter affects sorption of pesticides.: 1.: Relationships with carbon chemistry as determined by 13C CPMAS NMR spectroscopy

The structural composition of soil organic matter (SOM) was determined in twenty-seven soils with different vegetation from several ecological zones of Australia and Pakistan using solid-state CPMAS C-13 NMR. The SOM was characterized using carbon types derived from the NMR spectra. Relationships were determined between K-oc (sorption per unit organic C) of carbaryl (1-naphthyl methylcarbamate) and phosalone (S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-ylmethyl O,O-diethyl phosphorodithioate) and the nature of organic matter in the soils. Substantial variations were revealed in the structural composition of organic matter in the soils studied. The Variations in K-oc values of the pesticides observed for the soils-could be explained only when Variations in the aromatic components of SOM were taken; into consideration. The highly significant positive correlations of aromaticity of SOM and K-oc values of carbaryl and phosalone revealed that the aromatic component; of SOM is a good predictor of a soil's ability to bind such nonionic pesticides.