North Carolina Agricultural & Technical State University The School of Agriculture and Environmental Sciences

Effect of Soil Organic Carbon Level on the Erodibility of a U.S. Piedmont Soil

Jordan Sedlock1, Charles Raczkowski1, Gudigopuram B. Reddy1, Warren Busscher2, Alan Franzluebbers3 & Philip Bauer2,

(1)N.C. A&T State University (2)USDA-ARS, Florence, SC (3)USDA-ARS, Watkinsville, GA

0 15 30 45 60 75 900

1

2

3

4

5

Ru

no

ff,

mm

DT

NTB

0 15 30 45 60 75 900

150

300

450

600

Time, min

So

il L

os

s,

g m

-2

DT

NTB

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 315

20

25

30

35

40

45

50

SOC, % C

K, g

m-2

mm

-1

Y = 42.5 – 5.8xR2 = 0.32*

Introduction

We studied the relationship of SOC content and soil erodibility using a Mecklenburg sandy clay loam (fine mixed, active, thermic, Ultic Hapludalfs) soil that had been managed for 7-years using key agronomic practices, including winter cover cropping, the application of compost and the use of no tillage.

Intensive soil cultivation and high soil erosion has impoverished levels of soil organic carbon (SOC) in the southeastern U.S. Piedmont region. Sound soil management practices that build SOC levels are needed to reduce soil erodibility and restore soil quality.

Objective

Materials & Methods

Materials & Methods

DT, 1.2% C DTB, 1.6% C

NT, 2.2% C NTB, 2.7% C

The soil used was collected in June 2010 from the upper 7.5 cm of treatments (see photos above) in a field study that began in 2003: (i) no tillage summer vegetable planting (NT), (ii) fall applied poultry hatchery compost (11 Mg/ha) + winter rye-clover cover crop + no tillage summer vegetable planting (NTB), (iii) summer vegetable planting after disk tillage (DT) and, (iv) fall applied poultry hatchery compost (11 Mg/ha)+ winter rye-clover cover crop + summer vegetable planting after disk tillage (DTB).

A Norton rainfall simulator was used to apply 75 mm hr-1 intensity rain for 1.5 h on a 1 m2 soil pan adjusted to a 9% gradient.

Relative to other treatments, the gradual increase of NTB runoff (figure below) and soil loss figure above) indicates a more structurally stable soil surface and a lower rate of surface seal formation.

Results & Discussion

Time, min

Contact InformationCharles W. Raczkowski

Tel 336 334 7779Email:

raczkowc@ncat.edu

Treatment

Variable†

SOC%

Total Runoff

mm

Total Soil LossKg/m2

DT 1.2 73a 2.7a

DTB 1.6 62b 2.3b

NT 2.2 65b 1.8b

NTB 2.7 53c 1.2c

Total runoff and total soil loss was lowest in NTB and highest in DT.

Relative to DT, NTB runoff was 27% less and soil loss was 55% less.

†For each variable, treatment means having the same letter in common are not significantly different at the 5% significant level as indicated by Fisher’s Protected LSD test.

Increasing SOC content increased the stability of soil aggregates and decreased surface seal formation rate, runoff, and soil loss.

The regression analysis showed a 14% decrease in soil erodibility with a 1% increase in soil carbon (figure above)