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CONSERVATION PRACTICES TO INCREASE RESILIENCY
Making sure we can handle the extremes!
Carolyn Olson, Ph.D.90th Annual Outlook Forum February 20-21, 2014
SOIL MANAGEMENT AND SOIL HEALTH
FACTORS AFFECTING RESILIENCY
Inherent Soil Properties texture
mineral content
Dynamic Properties Water Holding Capacity
Organic Matter Content
Soil Moisture
Soil Temperature
Images Courtesy Purdue University
July 2012
September 2012
GOOD SOILS = GOOD YIELDS
Mean NCCPI
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Co
un
ty Yield
(g m
-2)
180
200
220
240
260
280
300
320
340
KentuckyIowaNebraska
Kentucky(Double crop)Y = 131.187 + 187.458X. r2 = 0.72***
Soybean yields across Iowa, Kentucky, and Nebraska
SOIL WATER BALANCE
Soil Water
Precipitation
irrigation
Evapotranspiration (ET)
Runoff
Drainage
= -
Inputs Losses
Corn Water Use 2000
Day of Year
100 120 140 160 180 200 220 240 260 280
Wate
r U
se (
mm
)
0
100
200
300
400
500
600
Clarion Spring N (100 kg/ha) Webster Spring N (100 kg/ha)Clarion Fall N (200 kg/ha)Webster Fall N (200 kg/ha)
Organic Matter (%)
0 1 2 3 4 5 6 7
Ava
ilab
le W
ate
r C
onte
nt
(%)
0
5
10
15
20
25
30
35
Data Points Sand, AWC = 3.8 + 2.2 OMSilt Loam, AWC = 9.2 + 3.7 OMSilty clay loam, AWC = 6.3 + 2.8 OM
WATER IS REQUIRED FOR GRAIN PRODUCTION
Corn Water Use Efficiency
Water Use (mm)
200 300 400 500 600 700 800 900
Yie
ld (
kg h
a-1)
8000
10000
12000
14000
16000
18000
20000
22000
24000
26000
28000
Water deficitneed 5 inches more water to grow 300 bu corn
EVAPOTRANSPIRATION
ET = Soil water evaporation + Plant transpiration
Energy Input
(Net radiation)
Water Vapor
Gradientf (temp, vapor
pressure)
Windspeed
Gradient
Soil Water Availabilit
y
Components of ET
Potential ET (how much could evaporate) vs Actual ET (how much does)
Rate-limitation
PROJECTED CHANGE IN NORTH AMERICAN PRECIPITATION
BY 2080-2090
PRECIPITATION CHANGES
Change in seasonality Change in intensity Change in frequency Change in regional distribution
IMPLICATIONS
Soil water availability will become more variable because the input will be more variable
How do we manage soil water when the supply has an increased variation
Wet SpringHot Summer
Wet SpringCool Summer
Dry SpringCool Summer
Dry SpringHot Summer
CLIMATE PROJECTION:WETTER SPRING, HOTTER SUMMER
Iowa climate projection is average May-June rainfall and July-August temperature using 9 downscaled climate scenarios, spanning 3 GCMs and 3 emissions scenarios.
Training period for downscale method is 1960-1999.
Data Source: Stoner et al. (2013)
CLIMATE PROJECTION:FEWER WET SUMMERS, MORE HOT SUMMERS
Iowa climate projection is average May-June rainfall and July-August temperature using 9 downscaled climate scenarios, spanning 3 GCMs and 3 emissions scenarios.
Training period for downscale method is 1960-1999.
Data Source: Stoner et al. (2013)
TEMPERATURE CHANGES
Warmer temperatures increase ET demand through vapor pressure deficit
Warmer temperatures will increase the rate of water use inducing agricultural drought more quickly
OBSERVATIONS
Tillage increases the soil water evaporation rate
Yield differences among soils within a field is related to organic matter content and soil water holding capacity
Water use patterns within a field cause “drought” stress to occur in every year
Organic Matter (%)
0 1 2 3 4 5 6 7
Ava
ilab
le W
ate
r C
on
ten
t (%
)
0
5
10
15
20
25
30
35
Data Points Sand, AWC = 3.8 + 2.2 OMSilt Loam, AWC = 9.2 + 3.7 OMSilty clay loam, AWC = 6.3 + 2.8 OM
BENEFITS OF CONSERVATION AGRICULTURE
Short-term Reduce soil water
evaporation Increase infiltration
of rainfall or irrigation events
Reduce the overall of evapotranspiration rate if plants are grown in standing stubble
Long-term Increase the soil
water holding capacity through improved organic matter content
Increase water availability to the crop
Increase rooting depth
RESILIENCY STRATEGIES
Conservation practices focused on dynamic soil properties such as improving soil organic matter and water holding capacity - broadly, soil health Conservation tillage Cover Crops Residue
Management
No Till
Conventional
CONSERVATION PRACTICES Can’t make it rain any more often and at the
optimum time to have best yield Will increase the ability of the soil to capture
more water, reduce the evaporation rate from the soil surface, and increase water availability to the crop
Over the long-term will increase the capacity of the soil to store more water and make water available to the plant
Will increase the overall resiliency of the cropping system to withstand climate stresses (variable precipitation and temperature extremes)