How Useful Is Spur

1
How Useful Is Spur?

• Richard Teague
• Joelyn Foy
• TAES Vernon

2
Presentation Outline

• How can we be of more value?
• How well does SPUR perform in the southern great
  plains?
• How we are using SPUR
• Where are we aiming?

3
TO BE OF MORE VALUE Need to Provide

• Information to allow critical assessment of
  inputs to outputs
• Calculate cost of doing and NOT doing
• Results must be applicable beyond the site, time
  and circumstances of trials
• Results must be collated
• Results at relevant scales

4
Combines
SPUR2.4

• Spur2 (Hanson Baker 1992)
• Spur91 (Carlson Thurow 1992)
• Century (Parton et al 1992)

5
Linkages Within
SPUR 2.4
6
SPUR2.4
Model corroboration against field data at
applicable scale is essential
7
SPUR 2.4
SINGLE SOIL
8
3-Year Water Balance (1986-1988)
obs SPUR2.4
Rain (mm) 1955 1955
Runoff (mm) 33 66
ET (mm) 2003 1857

Deep Perc (mm) 21 49
Soil water (mm) 16 17
Sediment (kg/ha) 749 286
9
Soil Water to 100cm
(1988-1989)
25
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10
11
12
months
10
Soil Water
Herbaceous and Mesquite
1000 800 600 400 200 0
Soil Water Content (mm)
Data SPUR-91
1986 1987
1988 1989 Year
11
Soil Organic Matter
5000
4000
3000
2000
(g m-2)
1000
0
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
YEAR
EST SOM
SPUR-91
CENTURY
(Burke et.al. 1989)
one-comp
three-comp
est SOM f(temp,ppt,silt,clay)
12
Annual C3 grass
Total Aboveground
Biomass
20
15
10
(g m-2)
5
0
1
2
3
4
5
6
7
8
9
10
11
12
Months
Data
SPUR91
SPUR2.4
13
C3 Winter grass Live
Aboveground Biomass
(g m-2)
14
C4 Shortgrass Live
Aboveground Biomass
(g m-2)
15
C4 Mid grass Live Aboveground
Biomass
(g m-2)
16
Animal Weights
SPUR 2.4
Cows R2.951
Calves R2.984
17
SPUR 2.4
Cow-calf production
Mean
cow wt
calf ww
milk
kg
obs
467
264
5.44
sim
480
263
5.40
18
SPUR 2.4
Cow-calf production
Mean
REPL
CONC
CROP
Per cow
Per acre

kg
obs
15
92
83
219
16
sim
28
92
226
16
77
19
SPUR 2.4
MULTIPLE SOILS
20
Throckmorton Experimental Ranch
Heavy Continuous (HC)
Moderate Continuous (MC)
Merrill 4 pasture, 3 herd (DR)
21
Proportion of Soil Seriesby Treatment
22
Total Standing Crop
using means by month
g m-2
MC HC DR
MC HC DR
Live
LiveDead
23
C4 Shortgrass
g m-2
MC HC
MC HC
Live
LiveDead
24
C4 Mid-grass
g m-2
MC HC
MC HC
Live
LiveDead
25
C3 Wintergrass
g m-2
MC HC
MC HC
Live
LiveDead
26
C3 Annual grass
g m-2
MC HC
MC HC
Live
LiveDead
27
Weaning Weight per Cow(across all treatments)
kg
Herefords (1961-1978)
Charolais/Black-Baldy (1979-1989)
28
Weaning Weight per hectare(across all
treatments)
kg/ha
Herefords (1961-1978)
Charolais/Black-Baldy (1979-1989)
29
Weaning Weight (by Treatment)
kg
Herefords (1961-1978)
Charolais/Black-Baldy (1979-1989)
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Weaning Weight Per Hectare(by Treatment)
kg/ha
MC
HC
DR
Mean
MC
HC
DR
Mean
Herefords (1961-1978)
Charolais/Black-Baldy (1979-1989)
31
Doing Well!

• Soil moisture
• Live standing crop across all species
• Calf growth and weaning weight
• Animal production within treatments
• Animal production across all treatments

32
Need to improve

• Standing crop sensitivity to potential soil
  differences
• Standing crop sensitivity to stocking rate
• Supplementation
• N cycling

33
How we are using
SPUR2.4

• Enhance understanding of experiments
• Assess management strategies
• Decision aid tool

34
Landscape or
Ranch scale
Shallow Clay (vx)
Loamy Bottomland (Bot)
Clay loam (TcB)
35
Needs

• Ranch scale research

• accounting for differences on the ground

• Decision aid tool

• to calculate stocking rate

• for a given soil mix

• and range condition

36
SPUR 2.4
Future Development

• Improve hydrology

• Spatial capability

• Brush growth and dynamics

• Wildlife habitat

• Field data on SOM

• Different locations

37
SPUR2.4

• TAES Vernon