Title: Nitrogen and organic matter of volcanic ash soils of Santa Bárbara Association in Chile
Abstract: Abstract Santa Bárbara association is a group of Andosols widely distributed on the western foothills of the Andes Mountains in the Central Valley of Chile from about 36° to 40° south latitude. The soils of this association may be divided into two groups—south and north—by the characteristics of soil organic matter, although they are much alike in morphology. The line of demarcation between the groups lies at about 38° south latitude. The potential nitrogen fertility or , the content of easily decomposable organic nitrogen is greater in the south soils than in the north soils of which humic matter is at a more advanced stage of humification, as compared with that of the south soils. Dry summers have caused the north soils to lessen in their potential nitrogen fertility and to stimulate humification of organic matter, altering the organic matter in quantity as well as in nature. It is evident that the analysis of soil organic matter is an effectual measure for the characterization of Andosols, and hence for the classification of the soils. It is very probable that a considerable water erosion has occurred in the soils of this association, transporting the fine soil particles from the mid-slope to the foot of the hills.