G. Sanjari, H. Ghadiri, C. Ciesiolka
Research Institute of Forests and Rangelands, Tehran, Iran
School of Environmental studies, Griffith University, Australia
Department of Natural Resources and Mines, QLD, Australia
Short term intensive rotational grazing in native pasture: Effects on
soil nitrate and extractable P
Outline
IntroductionCurrajong project
Location and climate Grazing treatments Soil analysis Results
Soil Organic Carbon and Nitrogen
Soil nitrate and extractable P Sheep camp results
Conclusion
Introduction
Livestock industry is of main sources responsible for downstream water pollution
Introduction (continue)
• The maximum concentration of nitrate allowed in drinking water is 10 mg/L.
• For aquatic life, nitrate level more than 4 mg/L considered as pollution problem
• Biological growth can be stimulated when Dissolved reactive P (DRP) exceeds 0.01 mg/L
Standards for the pollutants
In soil solutions:
In water:
• Environmental concern arise when the nutrient level in soil profile exceed 160 kg/ha for nitrate and 330 kg/ha for available P
Introduction (continue)
Grazing behavior and animal waste concern in native pasture
• Recycle 75 – 85% of forage they consume• Don’t graze pasture uniformly• Distribute deposits mainly around food
and water troughs, under shades, along fence lines, etc
Grazing animals:
Outcomes of a continual grazing:• Imbalanced distribution of nutrients• Nutrient depletion across paddocks• Low pasture productivity• Animal camp site development and
environmental concern on water contamination
Sheep Camp
Introduction (continue)Grazing practices affect soil health and water quality
Continuous grazing (large paddock) • Increasing runoff and soil loss and low
productivity• Grazing animals are free to congregate• Encourages animal camp development
Rotational grazing (small paddocks)• Includes rest periods for pasture recovery
after grazing operations• Better runoff and soil loss control• Discourages animal congregation• More balanced distribution of animal
wastes
Currajong case study
Short term Intensive Rotational Grazing (SIRG) vs. yearlong Continuous Grazing (CG)
• Organic Carbon (SOC)• Organic Nitrogen (SON)• Nitrate-Nitrogen• Extractable P
Soil parameters:
the data
Queensland
Murray Darling Basin
CurrajongLocation:
Property of CurrajongSoutheast Queensland
31%
69%
Dry Season
Wet season
Oct
MarApr
Sep
Currajong study (continue)
Climate
Long term annual: 645 mmRainfall:
Soil:Up to 50 cm in depthBrown to dark clay loam
Vegetation:Open Eucalypt woodland withunderstorey of perennial grass species
Dominant species: Dichanthium sericem
Methods: Stocking properties36
530
3658
036
630
3668
036
730
3678
036
830
3688
036
930
3698
037
030
3708
037
130
3718
037
230
3728
037
330
3738
037
430
3748
037
530
3758
037
630
3768
037
730
3778
037
830
3788
037
930
3798
038
030
3808
038
130
3818
038
230
3828
038
330
3838
038
430
3848
038
530
3858
038
630
3868
038
730
3878
038
830
3888
0
02468
101214161820
Continuous grazing Short intensive rotational grazing
Sto
ck
ing
ra
te
DS
E/H
DDH- Number of dse days per hectare over the whole study period; ‡- Means ± 1SD; SR- Stocking rate
Grazing Grazing periods Rest periods SR DDH Treatments (days) (days) (dse/ha) dse.day/ha
Short intensive rotational 14 ± 9‡ (101 ± 60)‡ 12.6 ± 6 ‡ 3608
Continuous 365 0 1.6 ± 0.2 3529
Currajong study (continue)
Currajong study (continue)
Methods: Soil analysis
Soil Organic Carbon:Rapid wet oxidation (Walkley and Black)
Soil Organic Nitrogen:Semimicro Kjeldahl procedure (Bremner 1996)
Nitrate and Ammonium:2 M KCL solution extraction (Bremner Keeney 1966), auto analyzer (Lachat 2001)
Extractable P0.5 M NaHCO3 Orthophosphate extraction(Colwell 1963), colorimetric procedure (Murphy and Riley 1962)
Currajong study (continue)
Results: SOC & SON (treatments)
20.0
22.5
25.0
27.5
30.0
SO
Cto
n ne/
h a
Short intensiverotational grazing
Continuousgrazing
Notgrazed
2001 2006
ns
ns
ns
p<1
1.6
1.8
2.0
2.2
2.4
SO
Nto
nn
e/h
a
Short intensiverotational grazing
Continuousgrazing
Notgrazed
2001 2006
ns
nsns
p<29
p<25
Results: SOC & SON (sub-treatments)
Currajong study (continue)
SO
Nto
nne/
ha
C1 C2 C3 C4
3.0
2.5
2.0
1.5
1.0
Short intensiverotational grazing
Continuousgrazing
2001 2006ns
ns
ns
ns
p<18
C1 C2 C3 C420.0
24.0
28.0
32.0
SO
Cto
nne/
ha
Short intensiverotational grazing
Continuousgrazing
2001 2006
*p<10
ns
ns
n
1.5
3.0
4.5
6.0
NO
3-N
Kg/
ha
0.0
2001 2006
Short intensiverotational grazing
Continuousgrazing
Notgrazed
Currajong study (continue)
Results: Nitrate & Extractable P
Ammonium concentrationIn grazing exclusion:
2001 4.56 mg/kg
2006 13.69 mg/kg
0
10
20
Ext
rac
tab
leP
Kg
/ha
2001
2006
Short intensiverotational grazing
Continuousgrazing
Notgrazed
Currajong study (continue)
Results: Nitrate & Extractable P (continue)
0
400
800
1200
1600
2000
0 268 683 1047 1367 1737 1824
May 01 Days May 06
Massofresiduekg/ha
Short intensive rotational grazing
Continuous grazing
1000
1500
2000
2500
3000
3500
May 01 Feb 02 Mar 03 Mar 04 Feb 05 Feb 06 May 06
Date of samplingH
erb
age
mas
skg
/ha
Rotational grazing
Continuous grazing
Increase in herbage mass
Increase in Residue
Currajong study (continue)
Results: Nitrate & Extractable P (Sheep camp effects)
100
10
1
0.1
0.010 100 200 300 400 500
1000
100
10
1
0.1
Distance from sheep camp (m)
NO3 2001
PO4 2001
PO4 2006
NO3 2006
PO4concentration(kg/ha
in0-10
cm)
NO3concentration(kg/ha
in0-10
cm)
Sheep camp vegetation:
Couch grassAgropyron repense (L.) P.Beauv
Couch grass regrowth:
Herbage massKg/ha DM
Rest perioddays
2650 26
3685 60
Soil analysis:
NitrateKg/ha
PhosphateKg/ha
2001 126 222
2006 17.6 79.3
Thresholds 160 330
Results: Nitrate & Extractable P (Sheep camp effects)
Currajong study (continue)
Water analysis: Sampled on 22/01/06
NO3-N (Mg/L) 0.143 0.189 0.133 0.100
DRP (Mg/L) 0.062 0.013 0.137 0.141
Time (min) 6 15 25 34
Water analysis:Sampled in 2001
NO3-N 3.4 Mg/L
DRP 2.5 Mg/L
Conclusion
Continuous grazing encourages animal aggregation to develop camp sites with large deposits of animal wastes raising alarm for downstream water contamination
In the study area we found the above threat could be easily the case at regional scale with more camp site development under continuous grazing
Short period Intensive Rotational Grazing (SIRG) in the native pasture, modified the aggregation behavior of animals, leading to a major decrease in soil nitrate and extractable P concentrations
The rotational grazing provides an environmentally oriented pasture utilization giving a more forage production over continuous grazing