Rationale and Objectives
1
C overcrop treatm ent NC WD 2C C 8C C Total FA M E S (nm ol g -1 ) 110 120 130 140 150 N o C over Disk U ndercutter Treatm entx Term ination p = 0.0436 Term ination p = 0.0005 Treatm entp = 0.258 D A 1 Score -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 D A 2 S core -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 2C C D isk 2C C U ndercut 8C C D isk 8C C U ndercut W D D isk W D U ndercut N o C over Rationale and Objectives Many studies have demonstrated microbial community response to individual cover crop species, but the effects of increasing cover crop diversity has received less attention. Moreover, there is increasing interest in conservation tillage strategies for cover crop termination and residue management. The objective of this study was to determine the relative influence of cover crop diversity and termination method on soil microbial community structure in an organic cropping system through the extraction of fatty acid methyl esters (FAMEs). Materials and Methods A split-plot RCBD field experiment was conducted in 2009 and 2010 near Mead, NE in a non-irrigated field. Spring-sown mixtures of 2 or 8 cover crop species were included in a sunflower – soybean – corn crop rotation. Cover crop mixtures were a 1:1 combination of legume and Brassica spp. Cover crops were planted in late-March and terminated in late-May using a field disk or sweep plow undercutter and main crops were planted within one week. Three (2009) or four (2010) soil cores (3.2 cm diameter x 20 cm depth) were sampled aseptically in all experimental units at 45 or 32 days following cover crop termination in 2009 and 2010, respectively. Lipids were extracted from 10 g of soil subsamples and microbial community structure was determined from phospholipid fatty acid methyl esters (FAMEs). Fatty acids were designated as the total number of carbon atoms followed by a colon, the number of double bonds followed by the position of the double bond from the carboxyl end of the molecule and its cis or trans configuration (e.g., C16:1c11). Differences in total FAME biomass (nmol g -1 ) and ratios of FAME peak area to peak area of C16:0 (nmol %) within and among microbial groups were analyzed with ANOVA, while canonical discriminant analysis was utilized to characterize changes in overall soil microbial community structure. Conclusions •FAME microbial biomass was generally greater following termination with an undercutter compared to the disk, especially following the 2 species cover crop mixture •Unmanaged spring weed communities and cover crop termination with an undercutter both led to reduced abundance of FAME biomarkers for actinomycetes •Unmanaged spring weed communities and cover crop termination with a disk both led to reduced abundance of FAME biomarkers for AMF and bacteria •Microbial community structure segregated according to the presence of cover crops (2CC and 8CC) or weeds (WD), and termination method was only important within the 2CC treatment Treatment Practice 2CC Buckwheat or Idagold Mustard, Hairy Vetch cover crop mixture 8CC 2CC + Field Pea, Pacific Gold Mustard, Crimson Clover, Oilseed Radish, Chickling Vetch, Dwarf Essex Rape cover crop mixture WD No cover crop but weedy prior to cover crop termination NC No cover crops or weeds prior to planting main crops Disked Cover crops terminated with field disk Undercut Cover crops terminated with sweep plow undercutter Relative influence of cover crop diversity and residue management on soil microbial community structure Sam E. Wortman, Rhae A. Drijber , and John Lindquist, University of Nebraska – Lincoln Table 2. Mean and standard errors of ratios of FAME peak area to peak area of C16:0 (nmol %) as influenced by cover crop treatment. Figure 1. Effects of cover crop treatment and termination method on total FAMEs (nmol g -1 ) at 45 and 32 days after cover crop termination in 2009 and 2010, respectively. Error bars represent the standard error of the mean. Table 1. Cover crop mixture and termination treatments used in 2009 and 2010. Table 3. Mean and standard errors of ratios of FAME peak area to peak area of C16:0 (nmol %) as influenced by cover crop termination method. Figure 2. Cover crop termination via undercutter (left) and disk (right). NC WD 2C C 8C C B acteria iC 16:0 4.53 (0.08) 4.38 (0.06) 4.56 (0.06) 4.55 (0.06) A ctinom ycetes i10MeC17:0 1.31 (0.08) 1.15 (0.06) 1.36 (0.06) 1.28 (0.06) i10MeC18:0 3.65 (0.28) 3.13 (0.20) 3.79 (0.20) 3.60 (0.20) AM F C 16:1c11 2.59 (0.13) 2.41 (0.10) 2.85 (0.10) 2.69 (0.10) C 18:1c11 4.70 (0.10) 4.42 (0.07) 4.74 (0.07) 4.77 (0.07) C over C rop T reatm ent No Cover Disk U ndercutter B acteria C 17:0 0.736 (0.011) 0.718 (0.006) 0.739 (0.006) A ctinom ycetes 8M eC16:0 1.85 (0.08) 1.88 (0.04) 1.71 (0.04) i10MeC17:0 1.31 (0.08) 1.33 (0.05) 1.20 (0.05) i10MeC18:0 3.65 (0.28) 3.71 (0.16) 3.30 (0.16) a10M eC18:0 0.453 (0.020) 0.467 (0.012) 0.441 (0.012) 10M eC18:0 1.438 (0.028) 1.430 (0.016) 1.468 (0.016) AM F C 18:1c11 4.70 (0.10) 4.56 (0.06) 4.72 (0.06) C over C rop T erm ination M ethod S tandardized coefficientforD A1 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 S tandardized coefficientforD A 2 -1.5 -1.0 -0.5 0.0 0.5 1.0 C 16:1c5 C 17:1c9 i10MeC18:0 a10M eC18:0 C 18:1c11 C 18:1c13 C18:0 cyC 19(9,10) C20:n Figure 3. Discriminant score means for all cover crop x termination treatment combinations (a), and standardized canonical coefficients for FAMEs (b) contributing to the two significant discriminant functions DA1 and DA2.
-
Upload
westbrook-sterling -
Category
Documents
-
view
17 -
download
2
description
Relative influence of cover crop diversity and residue management on soil microbial community structure Sam E. Wortman , Rhae A. Drijber , and John Lindquist, University of Nebraska – Lincoln. Rationale and Objectives - PowerPoint PPT Presentation
Transcript of Rationale and Objectives
Cover crop treatment
NC WD 2CC 8CC
Tot
al F
AM
ES
(nm
ol g
-1)
110
120
130
140
150
No CoverDiskUndercutter
Treatment x Termination p = 0.0436Termination p = 0.0005Treatment p = 0.258
DA 1 Score
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
DA
2 S
core
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
2CC Disk
2CC Undercut
8CC Disk
8CC UndercutWD Disk
WD Undercut
No Cover
Rationale and Objectives
Many studies have demonstrated microbial community response to individual cover crop species, but the effects of increasing cover crop diversity has received less attention. Moreover, there is increasing interest in conservation tillage strategies for cover crop termination and residue management. The objective of this study was to determine the relative influence of cover crop diversity and termination method on soil microbial community structure in an organic cropping system through the extraction of fatty acid methyl esters (FAMEs).
Materials and Methods
A split-plot RCBD field experiment was conducted in 2009 and 2010 near Mead, NE in a non-irrigated field. Spring-sown mixtures of 2 or 8 cover crop species were included in a sunflower – soybean – corn crop rotation. Cover crop mixtures were a 1:1 combination of legume and Brassica spp. Cover crops were planted in late-March and terminated in late-May using a field disk or sweep plow undercutter and main crops were planted within one week. Three (2009) or four (2010) soil cores (3.2 cm diameter x 20 cm depth) were sampled aseptically in all experimental units at 45 or 32 days following cover crop termination in 2009 and 2010, respectively. Lipids were extracted from 10 g of soil subsamples and microbial community structure was determined from phospholipid fatty acid methyl esters (FAMEs). Fatty acids were designated as the total number of carbon atoms followed by a colon, the number of double bonds followed by the position of the double bond from the carboxyl end of the molecule and its cis or trans configuration (e.g., C16:1c11). Differences in total FAME biomass (nmol g-1) and ratios of FAME peak area to peak area of C16:0 (nmol %) within and among microbial groups were analyzed with ANOVA, while canonical discriminant analysis was utilized to characterize changes in overall soil microbial community structure.
Conclusions
•FAME microbial biomass was generally greater following termination with an undercutter compared to the disk, especially following the 2 species cover crop mixture
•Unmanaged spring weed communities and cover crop termination with an undercutter both led to reduced abundance of FAME biomarkers for actinomycetes
•Unmanaged spring weed communities and cover crop termination with a disk both led to reduced abundance of FAME biomarkers for AMF and bacteria
•Microbial community structure segregated according to the presence of cover crops (2CC and 8CC) or weeds (WD), and termination method was only important within the 2CC treatment
Treatment Practice2CC Buckwheat or Idagold Mustard, Hairy Vetch cover crop mixture
8CC 2CC + Field Pea, Pacific Gold Mustard, Crimson Clover, Oilseed
Radish, Chickling Vetch, Dwarf Essex Rape cover crop mixture
WD No cover crop but weedy prior to cover crop termination
NC No cover crops or weeds prior to planting main crops
Disked Cover crops terminated with field disk
Undercut Cover crops terminated with sweep plow undercutter
Relative influence of cover crop diversity and residue management on soil microbial community structureSam E. Wortman, Rhae A. Drijber , and John Lindquist, University of Nebraska – Lincoln
Table 2. Mean and standard errors of ratios of FAME peak area to peak area of C16:0 (nmol %) as influenced by cover crop treatment.
Figure 1. Effects of cover crop treatment and termination method on total FAMEs (nmol g-1) at 45 and 32 days after cover crop termination in 2009 and 2010, respectively. Error bars represent the standard error of the mean.
Table 1. Cover crop mixture and termination treatments used in 2009 and 2010.Table 3. Mean and standard errors of ratios of FAME peak area to peak area of C16:0 (nmol %) as influenced by cover crop termination method.
Figure 2. Cover crop termination via undercutter (left) and disk (right).
NC WD 2CC 8CCBacteria
iC16:0 4.53 (0.08) 4.38 (0.06) 4.56 (0.06) 4.55 (0.06)Actinomycetes
i10MeC17:0 1.31 (0.08) 1.15 (0.06) 1.36 (0.06) 1.28 (0.06)i10MeC18:0 3.65 (0.28) 3.13 (0.20) 3.79 (0.20) 3.60 (0.20)
AMFC16:1c11 2.59 (0.13) 2.41 (0.10) 2.85 (0.10) 2.69 (0.10)C18:1c11 4.70 (0.10) 4.42 (0.07) 4.74 (0.07) 4.77 (0.07)
Cover Crop Treatment
No Cover Disk UndercutterBacteria
C17:0 0.736 (0.011) 0.718 (0.006) 0.739 (0.006)Actinomycetes
8MeC16:0 1.85 (0.08) 1.88 (0.04) 1.71 (0.04)i10MeC17:0 1.31 (0.08) 1.33 (0.05) 1.20 (0.05)i10MeC18:0 3.65 (0.28) 3.71 (0.16) 3.30 (0.16)a10MeC18:0 0.453 (0.020) 0.467 (0.012) 0.441 (0.012)10MeC18:0 1.438 (0.028) 1.430 (0.016) 1.468 (0.016)
AMFC18:1c11 4.70 (0.10) 4.56 (0.06) 4.72 (0.06)
Cover Crop Termination Method
Standardized coefficient for DA1
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Sta
ndar
dize
d co
effic
ient
for
DA
2
-1.5
-1.0
-0.5
0.0
0.5
1.0
C16:1c5
C17:1c9
i10MeC18:0
a10MeC18:0
C18:1c11
C18:1c13
C18:0
cyC19(9,10)
C20:n
Figure 3. Discriminant score means for all cover crop x termination treatment combinations (a), and standardized canonical coefficients for FAMEs (b) contributing to the two significant discriminant functions DA1 and DA2.
