Worldwide soil degradation is a growing problem, influencing both natural and agroecosystems. Soil amendments are one way to relieve soil degradation. To combat degradation, soil amendments are gaining attention. Given their high soil fertility, organic matter, and water holding capacity, adding dredged sediments to poor soils could greatly benefit agricultural production. However, herbaceous plant species often have difficulty establishing on dredged material because of low nutrient availability, inhibitory levels of toxins, unsuitable moisture conditions, and a lack of microorganisms capable of ameliorating these characteristics. The use of a cover crop may mitigate these complexities by increasing the abundance, diversity, and function of beneficial soil microorganisms. In order to understand how dredge sediment shifts these communities when applied in an agricultural setting, we examined changes in dredge sediment microorganism communities due to the application of a winter cover crop (winter rye: Lolium perenne) by comparing plots planted with the cover crop and left fallow through the winter. We haphazardly collected ten soil samples from each plot, before and after planting of the cover crop and after the final corn harvest. We recovered bacterial and fungal DNA from these plots and compared the resulting communities using a combination of univariate and multivariate statistics.
Results/Conclusions
Both plots exhibited different microorganism communities after a full growing season but the presence of the cover crop increased the abundance of beneficial microorganisms compared to the plot left fallow. Both fungal and bacterial communities exhibited this pattern such that guilds associated with beneficial functions were more abundant then guilds associated with saprobic or pathogenic activity. These shifts in microorganism community structure echo patterns seen for fields grown with cover crops but without a soil amendment, emphasizing the potential for dredged sediments to be used in combination with a cover crop. This work represents an important step in quantifying the benefits of cover crop usage in conjunction with dredged material for enhancing crop production. The use of dredged material as an agricultural amendment in nutrient poor soils is becoming more common worldwide but little is known about the response of microorganisms to these amendments. Knowledge regarding the role cover crops play in stimulating these organisms is particularly lacking. Outcomes from this research represent important steps in filling knowledge gaps regarding the potential for dredged sediments to be used as soil amendments. Soil is a non-renwable resource so methods which revitalize degraded soil are vital for ensuring agricultural production worldwide.