The most important agricultural soils in Chile are those onglnatíng from volcanic ash. The rclationship between sorne of the physical and chemical charactcristics of (he soils of the Central Valley, between the provinccs of Linares and Chiloé, has been studied in this tri al. In Chile, the following soils are considered to originate fronl volcanic ash: trumaos (developed from uew ashes under good drainage), ñadis (developed from new ashes under poor drainagc conditions), and red clay soils (developed from old ashes under good drainage eonditions). 262 samples of surface soils from the provinces oI Linares, Río-BiD, Osorno, Llanquihue and Chiloé, and 57 samples of complete soil profiles of trumao and ñadis from the provinces oI Valdivia, Osorno and Llanquihue were analyzed. From the results, obtained, the following points were discussed: a) VARIATIONS IN CONTENT UF ORGANIC MATTER. Content of organic matter increases as rainfall increases, and this in turn, increases exchangeable hydrogen, extractable aluminum by Margan extraction, fixatioIl capacity of phosphorus in the soil, and total catian exchange capacity; pH decreascs as organic matter incrcases. b) VARIATIOKS IN WElGHT OF VOLUME. Valucs of valume weight are very Iow, generally not higher than 0.7, and the highest figures eorrespond, in the majority of cases, to surface samples. c) PHOSPHORUS FIXATION. The fixation curves of surfacc soils indicate that the higo hest fixation is related to high contents of organic matter and extractable alumiIlum by Morgan extraction. From an analysis oí a prafile of the Corte Alto series, in which organic malter ,vas eliminated, it was seen that the fixation of phosphorus increased with the destruction of organic matter, and fixation value was the sarne throughout the profile. On trcating the soíl with caleium hydroxide, in order to measure the pH changes in phosphorus fixation, it was seen that no changes took place in thc powcr of fixation of phosphorus as a result of the |
ChileanJAR
