Nutrient Transport in Soils and the Landscape:
Follow Water!
Henry Lin
Dept. of Crop and Soil Sciences, Penn State University
[email protected]
Daniel Gimenez
Dept. of Environmental Sciences, Rutgers University
OUTLINES
• Land Use Impacts on Soil Hydraulic
Properties & Their Seasonal Changes
• Wastewater Spray
Urban Environment
Irrigation
in
• Universal Preferential Flow in the
Subsurface
Anthropocene
• A new geological epoch in which humankind has
emerged as a globally significant, and potentially
intelligent, force capable of reshaping the face of
the planet (Clark et al., 2004).
Contaminant Fate in the Environment
-- The “mystery” of the soil zone?!
..?
Root
zone
Water Table
Vadose zone
Ground water
Septic
tank
Leaching of
fertilizers &
pesticides
on farmlands
Chemical
spill
Landfill
leaching
Leaking
petroleum
tank
Toxic Shallow
waste well
dump
Intermediate
zone
“Active Zone”
(Critical Zone)
(fresh water)
Capillary
fringe
Confining unit
Aquifer
(saline water)
Pumping
well
(Modified from
Fetter, 1993)
Abandoned
well
When, where, how fast, and how much contaminants
coming from the overlying vadose zone?
Land Use Impacts on Soil Hydraulic
Properties & Their Seasonal Changes
Genoform
Phenoform
Land Use/Management Options
Forest
(1)
Pasture
(2)
Surface Soil
Control
Section
Subsoil
Cropland
(3)
Urban
(4)
1, 2, 3, 4, 5, or …
…
Dynamic Properties
(Use-dependent)
Inherent Properties
(Use-invariant)
(Modified from Grossman et al., 2001)
Soil Bulk Density (Mg/m3):
Scale bar:
Quartz 2.65, concrete 2.05, water 1, pinewood 0.7
• Histosols: 0.1-0.7
• Uncultivated (forest) loamy A: 0.8-1.2
• Cultivated clay and silt loams: 0.9-1.5
• Cultivated sandy loams and sands: 1.2-1.7
• Root penetration limitation: ~1.65
• Fragipans: 1.7-2.0
• Compacted glacial till: 1.9-2.2
(Source: Brady & Weil, 2004)
Subsoil compaction is a serious form of soil degradation
Adjacent cropland
soil of same series
Highly compacted
urban soil
2nd Inch Infiltration Rate (inch/hour)
1000.00
Series1
Series2
100.00
Series3
10.00
1.00
0.10
0.01
0.50
0.70
0.90
1.10
Bulk Density (g/cm^3)
1.30
1.50
1.70
Bulk Density and Land Use
Baseline:
forest soil
Conversion from forest to cultivated land and pasture resulted in 16.9±2.2%
and 9.5±2.1% increases in bulk density (n=78), respectively.
Murty et al. 2002. Global Change Biology 8, 105-123.
Steady-state Infiltration Rate
at 0 Supply Potential ( m m/s)
350
y = 428.13e -0.5424x
300
R2 = 0.9485
250
200
150
100
50
0
Restored
pasture
Native
Pasture
Soybean
Oat
Land Use
Pre-development
Agriculture
TX Study
Urban
(Lin, 1995)
Seasonal Changes of Surface Soil Hydraulic Conductivity
Hydraulic Conductivity (cm/hr)
100.00
Glenelg
At 6 cm tension
At 0 cm tension
10.00
1.00
0.10
0.01
GeCSpring
04
GeCFall 04
GeCFall 05
GeCSpring
06
GePSpring
04
GePFall 04
GePFall 05
GePSpring
06
GeUSpring
04
GeUFall 04
GeUFall 05
GeUSpring
06
GeWSpring
04
GeWFall 04
GeWFall 05
GeWSpring
06
• Urban soil K values generally decreased as compared to
other land uses, though spatial variability existed;
• There are obvious seasonal changes in soil K values in all
Cropland
Pasture
Urban
Woodland
land uses;
• Soil type, land use,
and their interactions are statistically
Spring 2004 – Spring 2006
PA Study (Zhou et al., 2008)
significant in influencing soil K values
Bulk Density vs. Soil Permeability, Ocean County, NJ
Ocean County Soil
Conservation District, NJ
(Courtesy of Chris Smith)
Ocean County Soil
Conservation District, NJ
(Courtesy of Chris Smith)
Bulk Density, Ksat and Land Use
Series Freehold – sandy loam
0
20
20
40
40
Depth (cm)
Depth (cm)
0
60
Golf course
Forest
Agriculture
80
60
80
100
100
1.0
1.2
1.4
1.6
1.8
2.0
0
20
40
Bulk density (g cm-3)
80
100
120
140
100
120
140
-1
Ksat (mms )
Series Quakertown – clay loam
0
20
20
40
40
Depth (cm)
Depth (cm)
0
60
60
Trees (recently planted)
Trees (well established)
Agriculture
80
60
80
100
100
1.0
1.2
1.4
1.6
-3
Bulk density (gcm )
1.8
2.0
0
20
40
60
80
-1
Ksat (mms )
• Macropore generation: physical, chemical, biological,
anthropogenic
• Some macropores are temporally stable, others are not.
Pore Radius Ranges:
5%
5%
< 0.06 mm
7%
0.06-0.125 mm
9%
0.125-0.25 mm
0.25-0.5 mm
4%
0.5-0.75 mm
0.75-1.5 mm
55%
16%
> 1.5 mm
Contribution to Total Water Flux
by Different Pore Radius Ranges
Heavy Rains
Temporal dynamics of infiltration rates
Example from a Large Database
• Rawls et al. (1998) presented average Ks values for selected
textural classes, each at low and high levels of BD.
1000
Ks (mm/hr)
100
10
1
Low BD
High BD
0.1
0.0
0.1
0.2
0.3
0.4
Effective Porosity (cm3cm-3)
0.5
Example from a Large Database
• A more clear picture of the effect of increases in BD on Ks is
achieved by plotting the ratio of high/low Ks and effective
porosity values for each textural class:
0.9
0.8
Ks,c / Ks
0.7
0.6
0.5
0.4
0.3
0.1
0.2
0.3
0.4
0.5
Eff Porc / Eff Por
0.6
0.7
0.8
Surface Sealing and Crusting
• Surface seal: dispersed clays clog soil pores
• Crust: when surface seal dries up
• In arid and semiarid regions, soil sealing and
crusting can have disastrous consequence because
high runoff losses leave little water available to
support plant growth
• To minimize such a problem, keep vegetative or
mulch cover, improve management of soil organic
matter, use soil conditioners
(Doerr et al., 2007)
Soil Hydrophobicity (Water Repellency)
(Bachmann et al, 2007)
Soil hydrophobicity can enhance
overland flow particularly after
wildfire as seen here in a burnt
Eucalypt forest in Australia
(photo: courtesy of Rob Ferguson)
Soil hydrophobicity can enhance
preferential flow (as indicated by
a tracer in this sandy soil),
leading to accelerated
contaminant transfer
(photo: courtesy of L.W. Dekker)
Wastewater Spray Irrigation in
Urban Environment
SGL
Irrigation Field
Astronomy
Irrigation Field
University
Wells
W
W
W
W
W
18” Pipe
Campus
State College
Treatment Plant
Soil Changes after 40 years of Wastewater Irrigation
IRRIGATION RATE OF 2” PER ACRE PER WEEK
• 2” PER WEEK * 52 WEEKS
PER YEAR
=104 INCHES
• MEAN ANNUAL
RAINFALL
=38.35 INCHES
________________
TOTAL = 142.35”/YEAR
RAIN FOREST ≥ 140”/YEAR
Bulk Density in the Landscape
(Walker and Lin, 2007, Catena)
Saturated Hydraulic Conductivity
(Walker and Lin, 2007, Catena)
pH changes
over time
(Walker and Lin, 2007, Catena)
Organic Matter Content Changes
(Walker and Lin, 2007, Catena)
Different Colors of Water: Quality of Water
White Water

Brown Water
Blue Water
Black Water
Green Water
Universal Preferential Flow
in the Subsurface
Preferential Flow at the Landscape Scale
-- Surface Flow
(Hillel, 1998)
The Challenge!
(From: Hillel, 1998)
Soil structure is critical for water flow!!!
Moderately well drained soil showing depth to water table in the summer.
In winter and early spring water table would be about two feet from soil surface.
Loysville series, Snyder co.
Three Common Types of Preferential Flow
Macropore Flow
Mud
cracks
Fine
sediment
Fine sediment
Infiltrating
water front
Finger Flow
Infiltrating water front
Coarse
sand
Fine
sand
Funnel Flow
Fine sand
Coarse sand lens
(From: Fetter, 1993)
Fine sand
Infiltrating
water front
Peds
Horizons
Roots
Animals
Microbes
…
Heterogeneity
Tonguing in
a Spodosol
Positive
Feedbacks
Plinthite in
an Alfisol
Non-uniform
Flow Drivers
Interpedal Pore
Desiccation
Crack
Preferential Flow
Macropore
Flow
Finger
Flow
Funnel
Flow
Hydrophobicity
Through
Flow
…
Root Channel
Worm Hole
Dual-Flow Regimes
Like a “hare and
tortoise” race
• Macropores:
Episodic, rapid spurts,
gravity-driven
• Micropores:
Slow,
generally
continuous
(at
variable rates), driven
by hydraulic gradients
that
are
variably
directed
Two Flow Regimes
Piston Flow
Preferential Flow
(Curtsey of Chris Graham, 2009)
Observable Networks Aboveground
C
B
A
Lightning network
Leaf vein network
D
Dry soil cracking network
Landscape drainage network
Hidden Networks Belowground
E
Preferential flow network
G
F
Root branching network
Mycorrhizal fungi network
H
Earthworm borrowing network
How Hot Spots Occur?
(From: McClain et al., 2003)
(From: McClain et al., 2003)
N Cycling Research
• Flowpath consequence on the Nitrogen Cycle
• Biogeochemistry
• Hydrology
Open Water
How do flowpaths affect solute abundance,
nitrogen cycling & nitrate export?
Matrix Flow
Macropore Flow
Nitrate Flushing- Rapid transport of nitrate
from nutrient rich surface soils
NO3- NO3NO3- NO3NO3NO3- NO3NO3NO3NO3NO3-
Mechanisms1. Rise and fall of transient water table that
leaches nutrients from surface soils
2. Activation of rapid flowpaths allow nitrate
to travel unabated from nutrient rich
surface soils to ground & surface waters
NO3NO3-
Ground Water
Nitrate Flushing- Rapid transport of nitrate
from nutrient rich surface soils
Precipitation
NO3- NO3NO3- NO3NO3NO3- NO3NO3NO3NO3NO3-
Rapid Flowpaths
NO3NO3-
Mechanisms1. Rise and fall of transient water table flushes
nutrient-rich surface soils
2. Activation of rapid flowpaths allow
nitrate to travel unabated from nutrient
rich surface soils to ground & surface
waters
Nitrate Flushing- Rapid transport of nitrate
from nutrient rich surface soils
Precipitation
MechanismsRapid Flowpaths
NO3- NO3NO3- NO3NO3NO3NO3NO3NO3NO3NO3NO3NO3-
1. Rise and fall of transient water table flushes
nutrient-rich surface soils
2. Activation of rapid flowpaths allow
nitrate to travel unabated from nutrient
rich surface soils to ground & surface
waters
Pay serious attention to:
Preferential Flow!
Electrifying take-off?!
SUMMARY
Land Use Impact on Soil Function:
Urban is the “champion”
Wastewater spray irrigation:
Can that be “sustainable”?
Universality of preferential flow:
Don’t ignore subsurface “superhighway”