A presentation from the WCCA 2011 conference in Birsbane.

1. Pérez Nieto J, Valdés Velarde E, Reyes Yurame
M, and Rodríguez Lara J
Chapingo University. State of México, México.
Corresponding author: jperezn14@hotmail.com

2. Conservation agriculture can mitigate global warming
by
CO2
N2O
Organic carbon Moderating
and nitrogen greenhouse
sequestration gas emission
CTS involve retaining the residues of previous crops on soil.
Its effects on soil organic carbon and nitrogen sequestration had been known
in the world, however in México, there is limited information about the long-
term (≥10 years) effects.

3. Objective and hypothesis
Objective: to evaluate the effect of three tillage
systems on soil organic carbon (SOC) and soil total
nitrogen (STN) sequestration and properties
associated in MOLLISOL in the Central Valley of
Mexico.
Hypothesis: No tillage (NT) and Minimum tillage (MT) systems would increase
organic carbon and nitrogen concentrations at the soil surface compared with
the effects of Conventional tillage (CT), influencing carbon/nitrogen ratio.
Hypothesis: additionally, this would reflect in higher SOC and STN under NT
and MT than CT, and improve others physical and chemical characteristics of
the soil.

4. Material and Methods
A field experiment was conducted in a Mollisol (Soil Taxonomy)
from 1999 to 2008 at Agricultural Experimental Station of
Chapingo University.
In Central Valley of Mexico.
19o 29’ N, 98 o 53’ W, 2240m altitude.

5. Characteristics of treatments
Treatments Cover with Soil tillage Planting Weed
residues control
(%)
No Tillage > 30 Undisturbed No-till Chemical
(NT) seeder
Minimum > 30 Chisel plowing No-till Chemical
Tillage (MT) seeder
Conventional < 15 Mouldboard No-till Mechanic
Tillage (CT) plowing, seeder and
disking and Chemical
field cultivator
Rotation cropping system:
P. vulgaris or Z. mays in spring and summer cycle.
T. aestivum or A. sativa in autumn and winter cycle.

6. Treatments evaluated
Minimum tillage
(MT)
No tillage
(NT) Conventional
tillage (CT)
Corn (Z. Mays) was planted in spring and summer cycle
2008 in three treatments evaluated.
NT and MT include more than 30% of cover with residues
of previous crops.

7. Soil sample
Treatments were arranged in a Latin-square designs with three replications
in a plot of 46x46m.
Undisturbed soil core samples were collected from five random places in a
central square of 20mx20m.
Soil samples were collected with a hand probe (5.7cm inside diameter x
3.0cm high).
Data were collected in September 2008.
Soil samples were collected at 0-3cm, 15-18cm and 30-33cm of soil depth.

8. Variables evaluated
Variable Measure Method
Bulk density Mg m-3 Dividing mass soil sample by volume
of probe
Organic carbon (C) % Dry combustion using a Perkin Elmer
concentration 2400 Series II
Nitrogen total (N) % Dry combustion using a Perkin Elmer
concentration 2400 Series II
Soil organic carbon (SOC) Mg C ha-1 Multiplying organic C by bulk density
and depth (11cm)
Soil total nitrogen (STN) Mg N ha-1 Multiplying N by bulk density and
depth (11cm)
Carbon/Nitrogen (C/N) Ratio of organic C (%) and N (%)
Volumetric water content (%) Multiplying gravimetric water by bulk
density by 100
Data were analyzed by GLM and Tukey procedures of SAS.
Statistical significance was evaluated at P≤0.05.

9. Results and Discussion
1.6
NT MT CT
Bulk density (Mg m-3)
1.4 a
a
b
a c
1.2
1.0
0-3 15-18 30-33
Soil depth (cm) Plow pan
Soil bulk density was not significantly
influenced (P≤0. 05) by soil tillage
treatments at 0-3cm and 15-18cm soil
depth. Greater bulk density in CT at 30-
33cm, probably due to plow pan
But it was significantly greater in CT resulting from more tillage
than NT and MT at 30-33cm soil operations.
depth.

10. Results and Discussion
40 a NT MT CT
SOC (Mg C ha-1)
30 b
a
20 c a
b
b Retained residues of the previous crops
10 increases SOC at the soil surface.
0 Larger SOC at 22-33cm in CT is probably
0-11 11 22 22-33 associated with higher bulk density
Soil layer (cm) observed, as well as the mix of profile soil by
plow tillage.
SOC was significantly influenced (P≤0. 05)
by soil tillage treatments.
Long-term linear estimated C sequestration
SOC was significantly greater in NT than rates were 4 Mg C ha-1 year-1 greater in NT
MT and CT at 0-11 cm layer. The opposite than CT.
occurred at 22-33cm.
Corresponding long-term C sequestration
At 11-22cm soil layer it was not influenced under MT compared with CT was 2 Mg C ha-1
by treatments.
year-1 greater.

11. Results and Discussion
5
NT MT CT
4 a
STN (Mg N ha-1)
b
3 a
c a
2 ab
b
1
0
0-11 11 22 22-33 The difference between levels of
Soil layer (cm) STN fixed under NT and MT
compared with CT ranged
Similarly to SOC, STN varied between 0.72 and 1.44 Mg N ha-1.
significantly with treatments at the
surface soil layer and at 22-33cm.
Linear estimated N sequestration
Retained residues of the previous by conservation tillage systems
crops on the soil increases N over the 10 years was from 72 to
cycling and soil N content. 144 Kg N ha-1 year-1.

12. Results and Discussion
25 a
15
Volumetric water content (%)
NT MT CT
20 ab
12 a a
Carbon/nitrogen ratio
a b
a a 15
9 b
b b
6 10
NT MT CT
3 5
0 0
0-3 15-18 30-33 0-3 15-18 30-33
Soil depth (cm) Soil depth (cm)
Other characteristics like volumetric
The C/N ratio of the soil also was water content also was influenced by
influenced by soil tillage treatments at soil tillage treatments at the surface
the surface soil layer after ten years. soil layer after ten years.
It was significantly greater in NT than It was significantly greater in NT and
MT and CT at 0-11 cm layer. At the other MT than CT at 0-11 and 15-18 cm soil
layers it was significantly the same. depth. At 30-33cm it was significantly
the same.

13. In summary
Thank you for your attention