soil physical, microbial enzyme, and molecular characterization of native prairie and agricultural...

Soil Physical, Microbial Enzyme, and Molecular Characterization of Soil Physical, Microbial Enzyme, and Molecular Characterization of Native Prairie and Agricultural EcosystemsNative Prairie and Agricultural Ecosystems

S.H. Anderson, R.J. Kremer, and N. MungaiS.H. Anderson, R.J. Kremer, and N. MungaiDepartment of Soil, Environmental & Atmospheric Sciences, University of MissouriDepartment of Soil, Environmental & Atmospheric Sciences, University of Missouri

USDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, MissouriUSDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, Missouri

Soil Physical, Microbial Enzyme, and Molecular Characterization of Soil Physical, Microbial Enzyme, and Molecular Characterization of Native Prairie and Agricultural EcosystemsNative Prairie and Agricultural Ecosystems

S.H. Anderson, R.J. Kremer, and N. MungaiS.H. Anderson, R.J. Kremer, and N. MungaiDepartment of Soil, Environmental & Atmospheric Sciences, University of MissouriDepartment of Soil, Environmental & Atmospheric Sciences, University of Missouri

USDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, MissouriUSDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, Missouri

Materials and Methods (cont.)Materials and Methods (cont.)Additional soil samples were taken and essayed for Additional soil samples were taken and essayed for energy transformation enzymes (dehyrogenase); energy transformation enzymes (dehyrogenase); nutrient mineralization enzymes for C (β-nutrient mineralization enzymes for C (β- glucosidase), P glucosidase), P (alkaline phosphatases), and N (β-(alkaline phosphatases), and N (β- glucosamidase); soil glucosamidase); soil

microbial diversity by a C microbial diversity by a C substrate utilization substrate utilization assay; and COassay; and CO22 respiration. respiration.

Total soil DNA was extracted, quantified, and Total soil DNA was extracted, quantified, and subjected subjected to amplification (polymerase chain to amplification (polymerase chain reaction, PCR) with reaction, PCR) with known, primer DNA to detect known, primer DNA to detect various bacterial various bacterial genotypes. Different DNA genotypes. Different DNA sequence combinations sequence combinations resulting from PCR were resulting from PCR were separated on a gel matrix using separated on a gel matrix using electrophoresis, electrophoresis, visualized as a series of bands visualized as a series of bands distributed over the distributed over the matrix. The series of bands obtained matrix. The series of bands obtained from from separating the DNA fragments resulted in separating the DNA fragments resulted in genetic genetic profiles that characterized microbial profiles that characterized microbial communities.communities.

ResultsResults Soil bulk density was 32% lower for the native prairie Soil bulk density was 32% lower for the native prairie site (TP) compared to the sites with a history of site (TP) compared to the sites with a history of tillage (RC, PF-NP, CRP; Table 2).tillage (RC, PF-NP, CRP; Table 2).

Water-stable aggregates were 10 times higher for the Water-stable aggregates were 10 times higher for the TP site compared to the RC site. The CRP and TP site compared to the RC site. The CRP and restored prairie sites had values at 72% of the TP restored prairie sites had values at 72% of the TP site site (Table 2).(Table 2).

Saturated hydraulic conductivity values were over 35 Saturated hydraulic conductivity values were over 35 times higher for the native prairie (TP) compared to times higher for the native prairie (TP) compared to the continuously cropped site (RC), and 2.5 times the continuously cropped site (RC), and 2.5 times higher compared to the restored sites (PF-NP, PF-higher compared to the restored sites (PF-NP, PF- SL, SL, CRP; CRP; Table 2). This was attributed to the Table 2). This was attributed to the greater greater number of macropores (> 1 mm in effective number of macropores (> 1 mm in effective diameter) diameter) for the native prairie site.for the native prairie site.

Soil enzyme activities were consistently highest for TP Soil enzyme activities were consistently highest for TP and PF-SL sites (Table 3), reflecting the close and PF-SL sites (Table 3), reflecting the close relationship of SOM levels with microbial activityrelationship of SOM levels with microbial activity..

Enzyme activity values were generally lowest for soil Enzyme activity values were generally lowest for soil under continuous cropping (RC) likely due to low under continuous cropping (RC) likely due to low SOM SOM and water-stable aggregates (Table 3).and water-stable aggregates (Table 3).

PF-NP soils were lower in dehydrogenase, PF-NP soils were lower in dehydrogenase, glucosaminidase, and phosphatase, which may be a glucosaminidase, and phosphatase, which may be a reflection of different microbial communities and reflection of different microbial communities and possible different SOM qualitypossible different SOM quality.

Soil DNA content agreed closely with other indicators Soil DNA content agreed closely with other indicators of soil quality (SOM, glucosidase) that are associated of soil quality (SOM, glucosidase) that are associated with microbial activity.with microbial activity.

The site with the highest number of bands from The site with the highest number of bands from molecular analysis of extracted soil DNA, TP with molecular analysis of extracted soil DNA, TP with 20, 20, appears to have the greatest bacterial diversity, appears to have the greatest bacterial diversity, while while soil from RC with 10 bands had the lowest soil from RC with 10 bands had the lowest diversity. diversity. Soil from the PF and CRP sites had band Soil from the PF and CRP sites had band numbers numbers ranging from 12 to 16, suggesting that this ranging from 12 to 16, suggesting that this ‘intermediate’ level of diversity is a characteristic ‘intermediate’ level of diversity is a characteristic response of soil undergoing restoration to its response of soil undergoing restoration to its original original bacterial community.bacterial community.

The relationship of soil organic matter (SOM) to The relationship of soil organic matter (SOM) to biological activity is illustrated by strong biological activity is illustrated by strong correlations correlations between soil DNA (representing the between soil DNA (representing the bacterial bacterial community) and water stable aggregates community) and water stable aggregates (r(r2 2 = 0.82) and = 0.82) and glucosidase activity (representing glucosidase activity (representing SOM decomposition; SOM decomposition; rr22 = 0.83). = 0.83).

Table 1.Table 1. Characteristics of ecosystems at study sites. Characteristics of ecosystems at study sites.

Study Site Study Site CodeCode Management SystemManagement System VegetationVegetation

Tucker PrairieTucker Prairie TPTP Uncultivated nativeUncultivated native Native, warm seasonNative, warm seasonprairie.prairie. grasses and forbs.grasses and forbs.

Prairie Fork – NewPrairie Fork – New PF-NPPF-NP Row crops until 1993,Row crops until 1993, Little bluestem, Little bluestem,

PrairiePrairie native grasses and native grasses and side-oats side-oats gramma,gramma,

legumes since 1994.legumes since 1994. Indian grass.Indian grass.

Prairie Fork – SiriceaPrairie Fork – Siricea PF-SLPF-SL Same as PF-NP.Same as PF-NP. Same as PF-NP withSame as PF-NP withLespedezaLespedeza infestation ofinfestation of

lespedeza.lespedeza.

Centralia-CRPCentralia-CRP CRPCRP Managed as CRP sinceManaged as CRP since Cool season grassesCool season grasses1990, no fertility.1990, no fertility. and forage legumes. and forage legumes.

Centralia-Row CropCentralia-Row Crop RCRC Rotation since 1990, highRotation since 1990, high Soybean (2003), Soybean (2003), fertility, minimum tillage.fertility, minimum tillage. corn (2004).corn (2004).

IntroductionIntroduction

Evaluation of critical soil properties is essential in Evaluation of critical soil properties is essential in assessing the restoration of degraded prairies and old assessing the restoration of degraded prairies and old cultivated fields to ecosystems that resemble native cultivated fields to ecosystems that resemble native prairies. Restoration and maintenance of soil quality is prairies. Restoration and maintenance of soil quality is highly dependent on organic matter (SOM), an array of highly dependent on organic matter (SOM), an array of soil organisms and biological activity, and improved soil organisms and biological activity, and improved physical characteristics including water infiltration, physical characteristics including water infiltration, macroporosity, aggregate stability, and bulk density.macroporosity, aggregate stability, and bulk density. Soils managed under native ecosystems relative to Soils managed under native ecosystems relative to agricultural row crops often have significant differences agricultural row crops often have significant differences in soil physical and microbial properties. Assessment of in soil physical and microbial properties. Assessment of relationships among these properties may provide useful relationships among these properties may provide useful information in how the physical environment affects information in how the physical environment affects microbial properties.microbial properties.

ObjectiveObjective The objective of this research was to quantify soil The objective of this research was to quantify soil

physical properties and soil enzyme activity, physical properties and soil enzyme activity, physiological and molecular characteristics for native, physiological and molecular characteristics for native, restored, and cultivated prairies. restored, and cultivated prairies.

Figure 1.Figure 1. Sites used for the study (a) Tucker Prairie, (b) Prairie Fork- Sites used for the study (a) Tucker Prairie, (b) Prairie Fork- new prairie, (c) Prairie Fork with sericea lespedeza new prairie, (c) Prairie Fork with sericea lespedeza

infestation, (d) Centralia CRP, and (e) Centralia row crop infestation, (d) Centralia CRP, and (e) Centralia row crop rotation (with corn).rotation (with corn).

b c d ea

Table 2.Table 2. Soil physical and chemical properties. Soil physical and chemical properties.

BulkBulk Water-StableWater-Stable Hydaulic HydaulicStudy SiteStudy Site SOMSOM DensityDensity Aggregates Aggregates Conductivity*Conductivity* PorosityPorosity

%% g cmg cm-3-3 % % mm h mm h-1-1 m m33 m m-3-3

TPTP 7.07.0 0.83d**0.83d** 40.8a 40.8a 671a 671a 0.619a0.619a

PF-NPPF-NP 3.43.4 1.22ab1.22ab 29.4b 29.4b 243b 243b 0.485cd0.485cd

PF-SLPF-SL 3.83.8 1.12c1.12c 28.2b 28.2b 222b 222b 0.521b0.521b

CRPCRP 3.03.0 1.19b1.19b 30.6b 30.6b 285b 285b 0.497c0.497c

RCRC 2.72.7 1.26a1.26a 3.8c 3.8c 17.9c 17.9c 0.473d0.473d

*Geometric means*Geometric means**Means within a column followed by the same letter are not significantly different at P<0.05.**Means within a column followed by the same letter are not significantly different at P<0.05.

Table 3.Table 3. Microbial enzyme activities and DNA content for the sites. Microbial enzyme activities and DNA content for the sites.

Dehydro-Dehydro- Glucos-Glucos- SoilSoilStudy SiteStudy Site genase genase aminidase aminidase GlucosidaseGlucosidase PhosphatasePhosphatase DNADNA

g tpf gg tpf g-1-1 -------------- -------------- g g -nitrophenol g-nitrophenol g-1-1 soil -------------- soil -------------- g gg g-1-1 soil soil

TPTP 320 a*320 a* 160 a160 a 350 a 350 a 1580 a 1580 a 10.310.3

PF-NPPF-NP 190 c190 c 90 c 90 c 325 ab 325 ab 640 cd 640 cd 8.1 8.1

PF-SLPF-SL 250 b250 b 150 ab150 ab 300 bc 300 bc 1180 b 1180 b 7.4 7.4

CRPCRP 260 b260 b 130 b130 b 290 c 290 c 710 c 710 c 8.2 8.2

RCRC 120 d120 d 70 c 70 c 250 c 250 c 400 d 400 d 6.2 6.2

*Means within a column followed by the same letter are not significantly different at P<0.05.*Means within a column followed by the same letter are not significantly different at P<0.05.

Materials and MethodsMaterials and MethodsLand treatments included native, uncultivated Land treatments included native, uncultivated prairie with established warm-season grasses and prairie with established warm-season grasses and forbs; 10-yr-old restored prairie dominated by little forbs; 10-yr-old restored prairie dominated by little bluestem (bluestem (Schizachyrium scopariumSchizachyrium scoparium),), side-oats side-oats gramma gramma ((Bouteloua curtipendulaBouteloua curtipendula), and Indian grass ), and Indian grass ((Sorghastrum nutansSorghastrum nutans);); 10-yr-old restored prairie 10-yr-old restored prairie dominated by sericea lespedeza (dominated by sericea lespedeza (Lespedeza cuneataLespedeza cuneata); ); a 14-yr-old conservation reserve program site with a 14-yr-old conservation reserve program site with cool-cool-season grasses and low density forage legumes; season grasses and low density forage legumes; and a and a site under row crop production with the past site under row crop production with the past 14 years 14 years under a corn (under a corn (Zea maysZea mays)-soybean ()-soybean (Glycine Glycine maxmax) ) rotation cropping system (Fig. 1, Table 1).rotation cropping system (Fig. 1, Table 1).

Sampling sites were located on Mexico silt loam (fine, Sampling sites were located on Mexico silt loam (fine, smectitic, mesic Aeric Vertic Epiaqualfs).smectitic, mesic Aeric Vertic Epiaqualfs).

Relatively undisturbed cores (7.62 cm by 7.62 cm ) were Relatively undisturbed cores (7.62 cm by 7.62 cm ) were sampled from the 0 to 10 cm depth on 12 May 2004; sampled from the 0 to 10 cm depth on 12 May 2004; 3 3 replicate locations with 5 sub-samples per location.replicate locations with 5 sub-samples per location.

Samples were evaluated for physical properties: bulk Samples were evaluated for physical properties: bulk density, pore-size distributions, saturated hydraulic density, pore-size distributions, saturated hydraulic conductivity and water-stable aggregates.conductivity and water-stable aggregates.

SummarySummary

This research demonstrated that soil measurements This research demonstrated that soil measurements based on soil enzyme activity, physiological and based on soil enzyme activity, physiological and molecular characteristics, and selected physical traits molecular characteristics, and selected physical traits (water-stable aggregation, saturated hydraulic (water-stable aggregation, saturated hydraulic conductivity) differentiated soils managed as native conductivity) differentiated soils managed as native prairie, restored prairie, or cultivated land. Results prairie, restored prairie, or cultivated land. Results indicated that sites under restoration to prairie indicated that sites under restoration to prairie vegetation are transitional between native prairie and vegetation are transitional between native prairie and cultivated soils based on combined physical and cultivated soils based on combined physical and microbiological analyses. The use of physiological and microbiological analyses. The use of physiological and molecular analyses of prairie soils yielded new insights on molecular analyses of prairie soils yielded new insights on the complex functional and structural diversity of their the complex functional and structural diversity of their soil bacterial communities, which contribute to the soil bacterial communities, which contribute to the biological characteristics of these soils.biological characteristics of these soils.