Comparative Assessment of the Effects of Soil Carbon and Nitrogen Amendment on Subsurface Soil pH, Eh and Sulfate Content of Acid Sulfate Soils

Abstract

The harmful impacts of acid sulfate soils (ASS) on various ecosystems are diverse and management of the impacts needs ecosystem-specific strategies. The importance of subsurface soil carbon and nitrogen for amelioration of sulfuric soil and curtailing of sulfidic soil oxidation as an option for ASS management was investigated in this study. The results showed the mechanisms involved in amelioration of sulfuric soil and curtailing of sulfidic soil oxidation were dependent on amendment and the microbial ecology the resources were capable of supporting microbial metabolism. Glucose as a single nutrient source capable of engaging a few soil microbes was ineffective in ameliorating the sulfuric soil, compared to complex organic matter, which is a source of multiple nutrients and is capable of engaging a diversity of soil microbes. Addition of complex organic matter effectively ameliorated the sulfuric soil and prevented sulfidic soil oxidation. The alkalization processes was limited by resource availability and the processes ceased as resources got depleted. Polynucleotide analysis of at least one group of sulfate reducing bacteria (SRB, Desulfovibrio) showed that the concentrations of these polynucleotides is high when availability of resources is high and decreases as the resource is limited over time. A three-fold increase in RNA and a ten-fold increase in DNA concentrations of the target SRB were measured in soil amended with organic matter and incubated for four weeks; after six weeks, they decreased.