Significance of loess addition in relation to andic soil properties of volcanic ash soils

Abstract

Sixty two soil-loess combinations using 2 loess samples from China and 6 volcanic ash soils from Japan were studied to determine the contribution of loess to some of the chemical properties of Andisols. Prior to mixing- the loess with the soil samples, CaCO3was removed by pretreating the loess samples with a sodium acetate buffer solution. The various chemical criteria evaluated included the phosphate retention (PR) values, amount of oxalate-oxalic acid extractable aluminum (Alox)+1/2 oxalate-oxalic acid extractable iron (Feox), and fluoride pH. These chemical properties were selected due to their importance as diagnostic criteria in Andisol classification. There was an inverse relationship between the PR values and amounts of loess added while a direct relationship was detected between the PR values and the amounts of volcanic ash soils. A level of more than 60 to 70% loess incorporation was critical to attain PR values above 85%. On the other hand, approximately less than 30 to 40% loess incorporation was necessary to obtain Alox+1/2 Feox values above 20 g kg−1. A negatively significant correlation was observed between the percentage loess and Alox+1/2 Feox (g kg−1) values while there was a positively significant correlation between the amount of volcanic ash soils and the latter. The significance of loess addition to 6 allophanic volcanic ash soils in relation to Andisol classification was discussed. © Taylor & Francis Group, LLC.