SUMMARYPrevious solution13C n.m.r. studies of soil organic matter have been confined to isolated humic or fulvic acid fractions. A study of 10 crude alkaline extracts from five New Zealand topsoils has now shown that such purification is unnecessary. Spectra were not noticeably broadened by co‐extracted iron in concentrations up to 2 mg cm−3. Optimized pulse parameters were similar to those reported for a solution of a purified humic acid. Relaxation results support a generalized model for humic material, in which aromatic structures, carbohydrates, amino acids and polymethylene chains are linked together to form flexible macromolecules. Relative contributions from each component varied from soil to s