The influence of high application rates of polyacrylamide on eubacterial structural diversity in an agricultural soil
Book Chapter
Entry, JA, Mills, DE, Jayachandran, K et al. (2012). The influence of high application rates of polyacrylamide on eubacterial structural diversity in an agricultural soil
. 55-71.
Entry, JA, Mills, DE, Jayachandran, K et al. (2012). The influence of high application rates of polyacrylamide on eubacterial structural diversity in an agricultural soil
. 55-71.
Anionic polyacrylamide (PAM) is a linear, water soluble anionic polymer. The formulation used in this study has a molecular weight of 12 to 15 Mg mole-1 and is widely used for erosion control and water quality protection. There has been an issue whether this formulation could possibly have negative effects on soil microbial diversity by altering microbial binding to soil particles or to one another and thus restricting their mobility and role in C and nutrient cycling To explore this possibility, we conducted an eight year study annually applying ultra high rates (more than two orders of magnitude higher than recommended application rates) of PAM to soil and then monitored impacts on soil eubacterial diversity. In July and August, we measured active soil bacterial and fungal biomass and microbial diversity in soils receiving 0 (control), 2691 and 5382 kg active ingredient (ai) PAM ha-1. Active microbial biomass in soil was 27-48% greater in the untreated control than soil treated with 2691 or 5382 kg ai PAM ha -1. Active bacterial biomass in soil was 20-30 % greater in the control treatment than in soil treated with 2691 or 5382 kg ai PAM ha -1 in August, but not July. Active fungal biomass in soils was 30-50% greater in the control treatment than soil treated with 2691 or 5382 kg ai PAM ha -1 in July, but not August. Amplicon length heterogeneity polymerase chain reaction (LH-PCR) DNA profiling was used to access the eubacterial diversity, richness, and evenness in an agricultural soil that received 0 (control), 2691 and 5382 kg active ingredient (ai) PAM ha-1. LH-PCR profiles showed no discernible change in the soil microbial diversity, richness, and evenness due to either of the PAM treatments at any sampling time. We found that although soil receiving these massive PAM application rates and prolonged exposure may reduce active bacterial and fungal biomass, those reductions were not consistent, varying with sampling date. Furthermore these massive application rates did not substantially or consistently affect eubacterial structural diversity, richness or evenness in this agricultural soil.
