Martha Mamo

1. Martha Mamo1, Jeff Bradshaw1, Richard Ferguson1, Kent Eskridge1, Kenneth Evans1, John Guretzky1, Karla Jenkins1, Walter Schacht1, Jerry
Volesky1, Patrick Wagner1, Sean Whipple2, Anita Wingeyer3, Haishun Yang1
1University of Nebraska-Lincoln; 2ISK Biosciences Corporation, MO, 3Instituto Nacional de Tecnología Agropecuaria, Entre Ríos, Argentina
Change in grazing density can influence dung
distribution patterns, with potential impacts on the
abundance and frequency of dung beetles
populations and nutrient cycling in grazing systems.
The distribution and subsequent decomposition of
dung pat across the landscape are some of the many
processes of nutrient cycling in managed grazing
systems. We hypothesize that the rates of
decomposition and/or incorporation of nutrient pulses
under specific grazing strategies are regulated by
the spatial and temporal distribution of these
pulses, thus affecting nutrient cycling and nutrient
use efficiency in rangelands.
Grazing Management Effect on Micro- and Macro- Scale Fate of C and N in Rangelands
Rationale & Hypothesis
Materials and Methods
Site Description
Research was conducted at the University of
Nebraska-Lincoln, Barta Brothers Ranch
(42°13'28.65"N, 99°38'19.17"W) on subirrigated,
sandy to fine sandy loam soils in the Valentine series.
Sub-objective 1: Evaluate nutrient pulses’ size and
quality in relation to grazing strategies
• Treatments: Low stocking density and high stocking
density grazing
• Litter collected monthly during grazing & nongrazing
periods
Sub-objective 2: Abundance and diversity of dung
beetles across grazing strategies
• Dung beetles collected using pitfall trap
• Five grazing strategies
Sub-objective 3: GHG flux and soil N
• 20 cm diameter pats from 1.5 L of homogenized
beef cattle manure placed directly on the ground
(BEETLE), inside a wire-mesh exclusion cage (NO
BEETLE), and a no dung treatment (CONTROL).
• The 3 treatments were arranged in a repeated
measurement RCB with 8 blocks and replicated
during grazing season (sequential June and July
2014).
• Gas samples were taken at 1, 2, 3, 7, 10, 14, 21,
28, and 56 days after placement (DAP).
• Soil samples at 0-10 and 10-20 cm depths taken
below dung pat at 1, 3, 7, 14, 28, and 56 DAP.
Results
This project was supported by Agriculture and Food Research Initiative Competitive Grant Program no.
2013-67019-21394 from the USDA National Institute of Food and Agriculture. We would like to thank Pam
Sutton, Jon Soper, Heidi Hillhouse, Matt Judkins, Erin Hatch, Torie Lindsey, Carolyn Fox, and Jenna
Beckman for their assistance in field and laboratory work..
• Treatment was significant for CO2-C flux
but not for N2O-N and CH4-C fluxes
• CO2-C flux was highest in NO BEETLE
TRT 5 out of the 9 sampling dates.
• There was no consistent trend in GHG flux
when pat was covered to exclude dung
beetles and flux was similar between NO
BEETLE and BEETLE TRTs.
• June CO2-C flux was most often highest
from NO BEETLE treatment
• July peak N2O-N flux occurred at later
DAP in BEETLE compared to control and
NO BEETLE.
Dung Beetle Simpson's Diversity Index:
Acknowledgement
Project Framework
CHG Flux:
Field experiment sensors and treatments
*addressed on this poster
Treatment
Simpson's
Diversity
High density (Mob) 2.84
Once-Over Rotation 2.77
Twice-Over Rotation 2.69
Continuous 1.36
Non-Grazed Hay 1.46
Non-Grazed Control 1.60
• 760 individual beetles collected in
2014
• Significantly higher dung beetle
diversity in rotational grazing
compared to continuous grazing or no
grazing.
• Differences were not significant
between low density and high density
rotation.
Production of Litter and Standing Dead:
• Av. standing dead dry matter
was 1333 kg ha-1
• Av. litter dry matter production
was 2631 kg ha-1
• Annual (4/2014-3/2015),
production of dead plant material
was similar between grazing
strategies
June Experiment
Days After Application
0 10 20 30 40 50 60
CH4-CFlux,mgm-2d-1
-3
-2
-1
0
1
2
3
Pre-experiment flux
N= 24
July Experiment
Days after Placement
0 10 20 30 40 50 60
CH4-CFlux,mgm-2d-1
-3
-2
-1
0
1
2
3
Pre-experiment flux
N= 24
July Experiment
Days After Placement
0 10 20 30 40 50 60
N2O-NFlux,mgm-2d-1
0.0
0.2
0.4
0.6
0.8
1.0
Pre-experiment Flux
N= 24
June Experiment
Days After Placement
0 10 20 30 40 50 60
N2O-NFlux,mgm-2d-1
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
4.0
6.0
Pre-experiment flux
N= 24
Soil N, 0-10 cm depth:
Dung beetle trap set-up
June Experiment
Days After Placement
1-Day
3-Days
7-Days
14-Days
28-Days
56-Days
NH4-N,mgkg
-1
0
10
20
30
40
50
60
NO BEETLE
BEETLE
CONTROL
June Experiment
Days After Placement
1-Day
3-Days
7-Days
14-Days
28-Days
56-Days
NO3-N,mgkg
-1
0
50
100
150
200
NO BEETLE
BEETLE
CONTROL
June Experiment
Days After Placement
1-Day
3-Days
7-Days
14-Days
28-Days
56-Days
NH4-N,mgkg
-1
0
200
400
600
800
1000
1200
NO BEETLE
BEETLE
Dung N:
Grazing Strategy Pasture size
(ha)
Number of
pastures
High Density
(Mob)
6.8 2
Low Density
(4PR1)
0.6 8
Dung beetle
species
recovered at
research site
• Treatment (NO BEETLE vs. BEETLE) was
not significant for soil NH4-N and NO3-N
• Soil NH4-N was higher under dung pat
only at days 7 and 28 days, while soil
NO3-N peaked at 7 days after dung pat
application and decreased after 14 days.
Initial Dung NH4-N: 424 + 22
• Treatment (NO BEETLE vs. BEETLE) and sampling
dates were significant for dung NH4-N
• Dung NH4-N in BEETLE treatment was higher than
NO BEETLE (429 vs. 355 mg kg-1)
• Dung NH4-N followed the trend of
Days 3 > Days 7=Days 56 > Day 1=Days 4 =Days 5
• While dung NH4-N peaked at Days 3, soil NH4-N
peaked at Days 7 indicating a lag in the movement
of dung NH4-N into soil. Dung NH4-N increase in
Days 56 likely associated with rain event at Day 55.
Precipitation and Air Temp., 10 June - 13 August
Arrows indicate sampling dates for GHG and/or soil-dung
Days After Placement
0 10 20 30 40 50 60
Precipitaion,mm
0
5
10
15
20
25
30
35
AverageAirTemp.,
o
C
0
5
10
15
20
25
30
35
GHG sampling chambers