Soil Microbiology and Prairie Restoration

Period: January 30, 2005 – April 15, 2010
Contact: Stephen Anderson, Robert Kremer
Organization: the University of Missouri and USDA-Agricultural Research Service
Funding Source: Prairie Fork Trust

Objectives: The proposal will provide educational experiences related to soil and environmental monitoring and conservation. Specifically, learning experiences about soil quality at PFCA will be provided by using an on-site “soil quality test kit” to characterize several important soil properties through practical demonstration and hands-on training of students and practitioners. The outcome of these experiences will be an increased awareness of participants of how land use and management affects sustainability of the soil resource by assessing soil quality and an increased knowledge to help people better conserve and sustain our natural resources and the environment.

The specific emphasis area of “Soil microbial characteristics/soil history at PFCA” is addressed in this proposal using standard research methods to address microbiological and physical attributes of soil quality on land undergoing prairie restoration compared to native prairie and cultivated fields.

Our previous research at PFCA (Kremer & Anderson, 2004 Progress Report) demonstrated that soil quality measurements based on soil enzyme activity, physiological and molecular characteristics, and selected physical traits (water-stable aggregation, saturated hydraulic conductivity) differentiated soils managed as established, native prairie, restored prairie, cool-season grassland, or cultivated crops. However, trends in the data suggested that the sites studied at PFCA were early in the transition to a true prairie in which grass vegetation is the dominant influence on the soil properties. This was especially evident for water-stable aggregates, porosity, and microbial diversity where these properties still reflected the former agroecosystem under row-crop cultivation. Because the major influence on microbial activity and water relations in prairie ecosystems is based on the extensive network of roots that develop under warm-season grasses, we propose to closely examine selected soil properties as these interact with grass roots at sites under various stages of restoration relative to a native prairie site.

The information generated from our proposed study will be important in understanding the extent and rate at which the restoration process is progressing toward soil properties and microbial communities characteristic of established prairie ecosystems. This information can then be used to develop adjunct management practices to improve and perhaps hasten transition to acceptable grass establishment and growth during restoration.

The effectiveness of prairie restoration practices on the soil environment can be evaluated using soil quality assessments. Soil quality is the capacity of a soil to function within an ecosystem to sustain plants and animals, resist erosion, and reduce negative impacts on water and air resources (Karlen et al., 1997). Soil quality assessment can indicate changes in both the ability of a soil to optimize plant growth and to maintain its structural and biological integrity. Restoration and maintenance of soil quality is highly dependent on organic matter, an array of soil organisms and biological activity, plant growth and rooting traits, and improved physical and chemical characteristics including water infiltration, macropores, aggregate size and stability, and bulk density. Considerable effort has been directed at correlating soil management practices with soil quality in agroecosystems. Most assessments of soil quality are comparative and made with reference to a baseline level, which is generally an undisturbed area such as uncultivated grasslands (Gregorich et al., 1994; Jordan et al., 1995; Saviozzi et al., 2001). In all these studies, native grassland soils exhibited higher soil quality attributes including soil organic carbon, soil enzyme activities, microbial biomass respiration, and aggregate stability compared to soils in agroecosystems. However, native or restored prairies have rarely been the focus for assessments of soil quality or studies of microbial biology and ecology. Indeed, natural grassland ecosystems are considered the best benchmark for understanding soil sustainability yet potential key indicators of grassland health and soil quality are not fully understood (Piper, 1999). Even less information is available on contribution of interacting soil properties on root function in establishment of prairie ecosystems. Limited work has recently established that healthy, fibrous roots with abundant mycorrhizal colonization are the driving force in aggregate stabilization, root growth, and balanced nutrient cycling by microorganisms in stabilizing restored tallgrass prairies on formerly disturbed (cultivated) land (Jastrow et al., 1998). Thus re-establishment of the perennial cover of grasslands on former cropland will not only reduce soil erosion but also increase C inputs due to development of dense root biomass and lead to increased microbial diversity and activity (Kuske et al., 2002; Piper, 1999). Reducing or eliminating annual tillage and establishing native perennial grasses and forbs will increase soil carbon, which will increase microbial activity and improve soil structure through increased aggregate stabilization.

Project Resources:

Soil Microbiology Presentation