View Full Table | Close Full ViewTable 1.

Summary of soil characteristics in the study area

 
System1 Size fraction, %
Sand Silt Clay Soil type pH
GRE 70.1 16.0 13.8 Sandy loam 5.9
SysA 55.0 23.5 21.5 Sandy clay loam 6.0
SysB 52.8 26.8 20.4 Sandy clay loam 6.2
1GRE: grazing exclusion; SysA: 1 cow/ha stocking rate and 112,000 kg live weight/ha stocking density; SysB: 2.5 cows/ha stocking rate and 32,700 kg live weight/ha stocking density.



View Full Table | Close Full ViewTable 2.

Soil bulk density in pasture soils grazed under 2 management strategies and nongrazed

 
Soil bulk density,1 g/cm
Item GRE SysA SysB
2012 grazing season
    Soil depth, cm
        0 to 5 1.27 1.20 1.25
        5 to 10 1.27 1.20 1.25
        10 to 20 1.57 1.25 1.35
        20 to 30 1.43 1.47 1.44
    SEM 0.05
    Source of variation
        Treatment 0.11
        Depth <0.01
        Treatment × depth 0.11
2013 grazing season
    Soil depth, cm
        0 to 5 1.46 1.57 1.39
        5 to 10 1.46 1.57 1.39
        10 to 20 1.65 1.58 1.62
        20 to 30 1.65 1.59 1.57
    SEM 0.04
    Source of variation
       Treatment 0.14
       Depth <0.01
       Treatment × depth 0.36
1GRE: grazing exclusion; SysA: 1 cow/ha stocking rate and 112,000 kg live weight/ha stocking density; SysB: 2.5 cows/ ha stocking rate and 32,700 kg live weight/ha stocking density.



View Full Table | Close Full ViewTable 3.

Soil organic carbon and total soil nitrogen stocks in pasture soils grazed under 2 management strategies and nongrazed

 
Stock
C:N
Item SOC,1 Mg/ha TSN,2 Mg/ha
Systems3
    GRE 42.0a 3.44a 21.0
    SysA 47.4a 3.95a 18.7
    SysB 63.0b 4.85b 19.4
SEM 3.8 0.2
Source of variation
Treatment <0.01 <0.01 0.06
a,bWithin columns, means without a common superscript differ(P < 0.05).
1Soil organic carbon.
2Total soil nitrogen.
3GRE: grazing exclusion; SysA: 1 cow/ha stocking rate and 112,000 kg live weight/ha stocking density; SysB: 2.5 cows/ha stocking rate and 32,700 kg live weight/ha stocking density.



View Full Table | Close Full ViewTable 4.

Daily greenhouse gas exchange from pasture soils and animal and total C equivalent flux from pasture sites managed under 2 different management strategies and nongrazed pasture sites during 3 grazing seasons

 
Soil emissions,1 kg C·ha−1·d−1
Animal emissions (FCH4cows),2 kg C·ha−1·d−1
Total emissions (Ceqflux),3 kg C·ha−1·d−1
FCO2
FN2O
FCH4soil
Item P14 P24 P14 P24 P14 P24 P14 P24 P14 P24
2011 grazing season
    System5
        GRE
        SysA 10.54 6.07a* 1.16 0.80 −0.18 -0.07 11.35 6.77a*
        SysB 9.74 7.64b* 1.19 1.59 −0.21 0.06* 10.69 9.57b
    SEM 0.41 0.32 0.04 0.64
    Source of variation
        Treatment 0.28 0.07 0.25 0.03
        Period <0.01 0.96 0.02 <0.01
        Treatment × period <0.01 0.08 0.04 <0.01
2012 grazing season
    System
        GRE 8.24 9.13 0.11 0.05 0.01a 0.003 0 0 8.38a 9.18a
        SysA 8.04 8.31 0.44 0.08 0.14b 0.08 3.28 2.26 12.06b 10.75a,b
        SysB 7.11 9.26* 0.31 0.19 0.08a 0.07 4.89 3.43 12.17b 12.73b
    SEM 0.50 0.11 0.04 0.63 0.57
    Source of variation
        Treatment 0.43 0.19 <0.01 0.12 <0.01
        Period 0.15 0.09 0.38 0.03 0.97
        Treatment × period 0.07 0.33 0.51 0.68 0.06
2013 grazing season
    System
        GRE 19.96 8.57a* 0.96a -0.88 0.20 -0.17 20.77a 7.71a*
        SysA 19.72 10.75a,b* 4.75b 0.35* 0.23 0.33b 1.93a 1.61a 26.13a,b 13.40b*
        SysB 21.49 14.97b* 3.23b 0.82 0.26 0.35b 3.26b 6.22b 28.13b 22.49c
    SEM 1.36 0.70 0.18 0.84 1.96
    Source of variation
        Treatment <0.01 <0.01 <0.01 0.02 <0.01
        Period <0.01 <0.01 0.78 0.11 <0.01
        Treatment × period 0.04 0.03 0.02 0.05 <0.01
a–cWithin columns, means without a common superscript differ (P < 0.05).
*Within rows, means without a common symbol differ (P < 0.05).
1FCO2: C equivalent flux of CO2 from the soil. FN2O: C equivalent flux of N2O from the soil. FCH4soil: C equivalent flux of CH4 from the soil.
2FCH4cows: C equivalent flux of enteric CH4 from the cows.
3Ceqflux: net greenhouse gas exchange in terms of C equivalent.
4July 7 to August 3, 2011 (P1); August 13 to 26, 2011 (P2); May 18 to June 10, 2012 (P1); August 21 to September 11, 2012 (P2); May 20 to June 10, 2013 (P1); August 26 to September 17, 2013 (P2).
5GRE: grazing exclusion; SysA: 1 cow/ha stocking rate and 112,000 kg LW/ha stocking density; SysB: 2.5 cows/ha stocking rate and 32,700 kg live weight/ha stocking density.



View Full Table | Close Full ViewTable 5.

Daily greenhouse gas exchange from soil and animal managed under 2 different grazing strategies and nongrazed pasture sites averaged for 3 grazing seasons

 
Item Soil emissions,1 kg C·ha−1·d−1
Animal emissions (FCH4cows),2 kg C·ha−1·d−1 Total emissions (Ceqflux),3 kg C·ha−1·d−1
FCO2 FN2O FCH4soil
System4
    GRE 9.87a 0.25a -0.09a 0 8.88a
    SysA 10.03a 1.56b 0.13b 2.09a 13.96b
    SysB 11.47b 1.17b 0.10b 4.91b 15.34b
SEM 0.66 0.32 0.08 1.09 0.74
Source of variation
    Treatment 0.17 <0.01 <0.01 0.02 <0.01
a,bWithin columns, means without a common superscript differ (P < 0.05).
1FCO2: C equivalent flux of CO2 from the soil. FN2O: C equivalent flux of N2O from the soil. FCH4soil: C equivalent flux of CH4 from the soil.
2FCH4cows: C equivalent flux of enteric CH4 from the cows.
3Ceqflux: net greenhouse gas exchange in terms of C equivalent.
4GRE: grazing exclusion; SysA: 1 cow/ha stocking rate and 112,000 kg LW/ha stocking density; SysB: 2.5 cows/ha stocking rate and 32,700 kg live weight/ha stocking density.