Ensayo

Simulating Soil Organic Carbon Sequestration in Cotton Production Systems with EPIC and the Soil Conditioning Index in the Southeastern USA
Deborah A. Abrahamson, M. Lee Norfleet, Hector J. Causarano, Jimmy R. Williams, Joey N. Shaw, D. Wayne Reeves, and Alan J. Norfleet, Causarano, Franzluebbers
Abbreviations: Abbreviations:
• • • • • • • • • • CT, Conventional tillage CT, Conventionaltillage
220

RESULTS AND DISCUSSION RESULTS AND DISCUSSION
Blackland Prairie
No-tillage bermudagrass corn-cotton rotation No-tillage cotton/cover crop No-tillage corn-cotton rotation

EPIC simulations of soil organic C EPIC simulations of soil organic C Organic C content within the surface 2 m of soil Organic C content within the surface 2 m of soil increased with time in all management systems,increased with time in all management systems, although at a greater rate with NT systems than with although at a greater rate with NT systems than with CT (Figure 2). CT (Figure 2). Within the 2-m profile and averaged across MLRAs, Within the 2-m profile and averaged across MLRAs, the rate of simulated SOC sequestration was greater the rate of simulated SOC sequestration was greater under NTmanagement systems than under CT under NT management systems than under CT (Table 1). (Table 1). There were no differences in the simulated rate of There were no differences in the simulated rate of SOC sequestration or total amount of SOC SOC sequestration or total amount of SOC sequestered among the three NT management sequestered among the three NT management systems. systems.
EPIC Linear rate ofTotal quantity SOC of SOC sequestration sequestration (Mg ha-1 yr-1) (Mg ha-1) -0.03 -1.5 0.39 20.1 0.49 25.5 0.50 35.3 SCI Unit-less relative change -1.07 0.38 0.50 0.80

Soil Organic C (Mg ha -1)0-2m

NT, no tillage NT, no tillage SOC, soil organic carbon SOC, soil organic carbon SCI, soil conditioning index SCI, soil conditioning index EPIC, Erosion Productivity-Impact Calculator EPIC,Erosion Productivity-Impact Calculator (renamed the Environmental Policy Integrated (renamed the Environmental Policy Integrated Climate) model Climate) model WUE, water use efficiency WUE, water use efficiency

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140 Conventional tillage cotton 120

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Coastal Plain
100 No-tillage bermudagrasscorn-cotton rotation No-tillage cotton/cover crop No-tillage corn-cotton rotation Conventional tillage cotton 20

Soil Organic C (Mg ha-1)0-2m

MLRA, Major Land Resource Area. MLRA, Major Land Resource Area.

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Management Systems: Management Systems:
1. 1. 2. 2. 3. 3. 4. 4. Monoculture cotton with conventional tillage Monoculture cotton with conventional tillage (CT) (CT) Cotton/wheatcover under no tillage (NT) Cotton/wheat cover under no tillage (NT) Corn/wheat cover (4-yr)–cotton/wheat cover (4Corn/wheat cover (4-yr)–cotton/wheat cover (4yr) rotation under NT yr) rotation under NT Bermudagrass (Cynodon dactylon L.) pasture (5Bermudagrass (Cynodon dactylon L.) pasture (5yr)–corn/wheat cover (5-yr)–cotton/wheat cover yr)–corn/wheat cover (5-yr)–cotton/wheat cover (5-yr) underNT (5-yr) under NT

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Management system (1) CT cotton (2) NT cotton/wheat cover (3) NT corn/wheat cover–cotton/wheat cover (4) NT bermudagrass–corn/wheat cover– cotton/wheat cover Analysis of variance CT vs NT systems (1 vs 2-3-4) NT ungrazed vs grazed (2-3 vs 4) NT monoculture vs rotation (2 vs 3)

Southern Piedmont100

Soil Organic C (Mg ha -1)0-2m

80

No-tillage bermudagrass - corn-cotton rotation No-tillage cotton/cover crop

--------------------------- Pr > F --------------------------0.03 0.008 F --------------------------0.06 N.A. 0.22 N.A. 0.96 0.04 0.90 0.24 0.11 N.A. 0.21 N.A.

Figure 3. Figure 3.
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Figure 1. Location of the three simulation sites within the Blackland Prairies,...