Potential legacy effects of biofuel cropping systems on soil microbial communities in southern Wisconsin, USA

Chao Liang,Randall D Jackson,Gregg R Sanford,Teri C Balser

doi:10.4236/as.2011.22019

Abstract

Soil microbial community structure is clearly linked to current plant species composition, but less is known about the legacy effects of plant species and agricultural management practices on soil microbial communities. Using microbial lipid biomarkers, we assessed patterns of community-level diversity and abundance at depths of 0 - 10 and 10 - 25 cm from three hay (alfalfa/orchardgrass) and two corn plots in southern Wisconsin. Principal components analysis of the lipid biomarkers revealed differential composition of the soil microbial communities at the two depths. Despite similar abundance of fungi, bacteria, actinomycete, protozoa, and total microbial lipids in the hay and corn at 0 - 10 cm, community structure differed with a significantly higher absolute abundance of arbuscular mycorrhizal fungi and gram-negative bacteria in the hay plots. No significant microbial lipid mass differences were detected between the two management regimes at 10 - 25 cm, but the proportional dominance of bacterial gram type differed with depth. These results indicate the potential for legacy effects of annual and perennial cropping systems management on microbial community composition and suggests the importance of considering past land-use when initiating long-term agroecological trials.

Highlights

Concern about ecological sustainability has stimulated interest in describing the structure and function of soil microbial communities, and in understanding how they are affected by past and current land use [1,2,3]
In the corn site by depth, we found no significant differences in pH value, cation exchange capacity (CEC), total C, total N or organic matter (OM) contents
The corn monoculture did not have significant chemical and physical differences between the 0 - 10 cm and 10 - 25 cm soil layers compared with the relatively distinct layers in the alfalfa/orchardgrass hay field. We reason that this stems from the fact that corn management includes tillage while the hay systems do not

Summary

Introduction

Concern about ecological sustainability has stimulated interest in describing the structure and function of soil microbial communities, and in understanding how they are affected by past and current land use [1,2,3]. Land use management often alters plant species composition and soil properties, which exert selective pressures on soil microbial taxa via differences in the quantity and quality of organic inputs and altered microbial competition for soil nutrients [8,9]. These selective pressures can play a key role in shaping the in situ composition of microbial communities [2,10,11,12]. This is manifested by the effect of crop rotation - increasing microbial diversity, which can alleviate pathogen load and reduce weed and insect populations compared to continuous monocultures [9,16]

Methods

Results

Conclusion