hanson salinity control.ppt · measuring soil salinity ec of saturated extract (ece collect soil...
TRANSCRIPT
Blaine HDepartment of Land, Air
University of Cabrhanson@u
ansonr and Water Resourceslifornia, Daviscdavis.edu
Where Do Salts in theSoil Come From?
Irrigation waterUpward flow from a saline,tableFertilizers
, shallow water
Salinity ‐ Total Dissolv
CalciumMagnesiumSodiumChlorideSulfateBicarbonate/carbonateMinor ‐ nitrate, potass
ved Salts (TDS)
esium
Electrical Conductivity
Measure of the ability of aThe larger the salt concent
Doubling the concentration
Units of ECmillimhos per centimeter ‐mmicromhos per centimeter ‐decisiemens per meter ‐ dS/
y (EC)
a solution to conduct electricitytration, the larger the ECn does not double the EC
mmhos/cm‐μmhos/cm/m (equals mmhos/cm)
TDS (ppm) = K x EC (dS/m
Generalized K = 640: EC less than 5 dS/mK = 800: EC more than 5 dS/
San Joaquin Valley DrainaK = 740: EC less than 5 dS/mK = 840:EC between 5 and 1K = 920: EC greater than 10
Santa Maria ValleyK = 740
m, mmho/cm)
m/m
age Waterm 10 dS/m dS/m
Measuring soil salinity
EC of saturated extract (ECeCollect soil samples with deptDry the soil and then grind itAdd distilled water until the sExtract the solution from the ECe can be related to crop tol
Soil EC expressed as a 1:1, 1Monitor soil salinity over timeNot very useful for assessing s
e)th in the root zone
oil is saturated soil with a vacuum extraction apparatuserance values
1:5, or 1:10 soil/water ratios e soil salinity impact on crop yield
Leaching
Leaching ‐ process of applying imoisture depletion to flush saltwater percolates below the rooLeaching fraction – actual perceinfiltrated water that percolateLeaching requirement ‐ percentbelow the root zone needed to threshold soil salinityLeaching fraction should excee
irrigation water in excess of soil t from the root zone. Excess ot zone carrying the salt with it.entage of the applied or es below the root zonetage of applied or infiltrated maintain soil salinity at the
d leaching requirement
Salt distributions in soil p profile: well‐drained conditions
0 2 4
Dep
th (f
eet)
0
1
2
3
4
Soil salinity with de
ECi = 2 dS/mLeaching Fraction = 12%
ECe (dS/m)
6 8 10 12
epth
Furrow irrrigation
Surface drip irrigation (
Soil water
%
(ECi = 1.5 – 2.0 dS/m
Soil salinity
ECe(dS/m)
Subsurface drip irriggation (ECi = 2 dS/m)
Salt distributions in soil pgroundwater conditions
profile: saline shallow
5.2 8.1
EC of Shallo
0
2
4
6
8
10
12
14
16EC
e of
Soi
l (dS
/m)
Dep0-1 1
Effect of salinity of sh
10 13 25
ow Groundwater (dS/m)
pth Interval (feet)1-2 2-3 3-4 4-5
hallow groundwater
EC
0 2 4 6
Dep
th (f
eet)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
No leach
No Leaching
e (dS/m)
8 10 12 14 16
hing
Factors affecting soil salisaline shallow groundwa
Depth to shallow groundwSalinity of shallow groundIrrigation water salinityAmount of applied waterLocation of drip line relativSoil type
nity with drip irrigation under ter conditions
waterdwater
ve to plant row
Drip
Dri
Dri
Localized leaching around drip lines
p line
ip line
ip line ECi = 0.3 dS/mECgw = 8‐11 dS/mGW depth = 6 feet
ECi = 1.1 dS/mECgw = 9‐16 dS/mGW depth = 2‐3 feet
ECi = 0.3 dS/mECgw = 5‐7 dS/mGW depth = 2‐3 feet
ECe
SummaryWell‐drained soil profile
Soil salinity near surface – irrigSoil salinity at deeper depths –
Saline shallow groundwater conSoil salinity near surface – irrigSoil salinity at deeper depths –salinity, leaching fraction?
Drip irrigationSmall levels of soil salinity neaSalinity increases with horizondecreasesHigh salinity levels midway betSalt accumulates above buried
ation water salinity– irrigation water salinity, leaching fraction
nditionsation water salinity– irrigation water salinity, groundwater
r drip lines ‐ highly concentrated leachingntal distance from drip line ‐ leaching
tween drip lines ‐ little or no leachingd drip lines ‐ no leaching
Controlling root zone soil
Objective: reduced or maintain soil salinity at values equal to or less than the threshold soil salinityKey principle: apply sufficient water to leach salt from the root zone
l salinity
Vegetable Crops
ECe (dS/m)
0 1 2 3 4 5 6 7
Rel
ativ
e Yi
eld
(%)
0
20
40
60
80
100
120
Strawberry (1.0)Lettuce (1.3)Broccoli (2.8)Tomato (2.5)Celery (1.8)
Almond
ECe (dS/m)
0 1 2 3 4 5 6 7
Rel
ativ
e Yi
eld
(%)
0
20
40
60
80
100
120
A = 1.5 dS/m
Thresholdsoil salinity
Types of leaching
ContinuousMaintain soil salinity at a mReduction in infiltration ratcontinuous leachingDrip irrigation
PeriodicPeriodic leaching to reduce acceptable levelPre‐plant irrigationFurrow, flood, sprinkle, drip
ore or less constant levele over time may limit opportunities for
accumulated salts in the soil to an
p
Effect of leaching frac
E
0 2 4 6
Dep
th (f
eet)
0
1
2
3
4
ction (well‐drained soil)
ECi = 2 dS/m
Ce (dS/m)
8 10 12 14 16
Leaching fraction = 7 %Leaching fraction = 18 %
EC
0 2 4 6 8
Dep
th (f
eet)
0
1
2
3
4
Effect of irrigation water safraction (well‐drained soil)
Ce (dS/m)
10 12 14 16 18 20
EC i = 2 dS/m, LF = 12%ECi = 4 dS/m, LF = 13%ECi = 4 dS/m, LF = 20%
alinity and leaching
Leaching under saline sh
No subsurface drainageShallow soil profile duegroundwaterCareful irrigation watePeriodic leaching for fusprinkle irrigation (pre‐Continuous leaching –
allow groundwater conditions
e systemse to saline shallow
r managementurrow, flood, and ‐plant irrigation)drip irrigation
Periodic leaching – shalloconditions
ObjectiveReturn fall soil salinity leveReplenish fall soil moisture
Pre‐plant irrigationLeaching – apply about 1 iof soil to be leached after moisture depletion
ow ground water
ls to spring levels depletion
nch of water per foot replenishing any soil
Controlling soil salinity u
Highly concentrated leachwetting patternsPre‐plant irrigation (sprinksubsurface drip irrigationEffect of drip line placemesalinity
Drip line and plant row locathe root zoneDrip line and plant row locaproblems
nder drip irrigation
hing near drip lines due to localized
kle irrigation) – may be required for
ent on root distribution and soil
tions coincide – concentrated leaching in
tions offset – may have salinity control
Surface drip irrigation; saline irrigation wa
4 6 8 10 12-10
-8
-6
-4
-2
April
Drip Lin
4 6 8 10 12 1Distance Across B
-12
-10
-8
-6
-4
-2
July
Dep
th (i
nche
s)
Drip Lin
Soil Salinity (ECe in dS/m)
No leaching under drip irrigation
Leaching under drip irrigation
ater; no shallow ground water
2 14 16 18
0.00.51.01.52.02.53.03.54.04.55.05.56.0
ne
14 16 18 20 22Bed (inches)
ne
ECe
Pre‐plant irrigation‐ subsurface drip irrigatioon
-30 -20 -10 0 10 20 30-30
-20
-10
0
-30 -20 -10 0 10 20 30-30
-20
-10
0
-30 -20 -10 0 10 20 30-30
-20
-10
0
Distance from plant row (inches)
Dep
th (inc
hes)
Soil water patterns
Drip line
Drip line
Drip line Drip line
Plant row
61014182226303438Wet
Dry
-20 -15 -10 -5 0 5 10 15 20
-30
-25
-20
-15
-10
-5
A
-20 -15 -10 -5 0 5 10 15 20
-30
-25
-20
-15
-10
-5
Dep
th (i
nche
s)
B
-15 -10 -5 0 5 10 15 20Distance from plant row (inches)
-30
-25
-20
-15
-10
-50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9High
Low
Root patterns
Drip line
Plant row
Effect of amount of applied water of surface drip irrigation
Note: as the leaching fraction increaslow‐salt soil increases.
f volume of low salt soil under
ses, the amount of relatively
Effect of amount of applied water of subsurface drip irrigation
f volume of low salt soil under
Effect of amount of applied water of surface drip irrigation – computer sim
f volume of low salt soil undermulation study
0 10 20 30 40 50 60 70-100
-90-80-70-60-50-40-30-20-10
0
0 10 2-100
-90-80-70-60-50-40-30-20-10
0
0123456789101112
0.3 dS/m
Distance f
Dep
th (c
m)
Drip line
Effect of irrigation water salinity
EC soil water
20 30 40 50 60 70 0 10 20 30 40 50 60 70-100-90-80-70-60-50-40-30-20-10
0
1.0 dS/m 2.0 dS/m
from drip line (cm)
Recommended salinity control pracof processing tomatoes under salinconditions
Sufficient localized leaching must oprofitable yields Seasonal water applications shouldevapotranspiration (ET) to providereduce water table response to irrigUse relatively low salt irrigation wadS/m) Irrigation frequency – daily to 2 to 3Periodic leaching of salt accumulatnecessary with sprinklers for standDrip system should be designed foline) Periodic system maintenance mustdrip lines, which will reduce the loc
ctices for subsurface drip irrigation ne, shallow groundwater
occur near drip lines to maintain
d be about equal to the seasonal sufficient localized leaching and to gationater (ECi equal to or less than about 1
3 times per week. ted above buried drip lines may be d establishment r high uniformity (DU>90% along drip
t be performed to prevent clogging of calized leaching
Estimating leaching fract
No entirely satisfactory mAssumptions used in somemay not fit field situations
tions
method existse methods s
Water balance approach
MeasurementsAmount of applied water (ACrop evapotranspiration (ET
Leaching fraction = 100 xField‐wide average leachinSeasonal or irrigation leacSome parts of the field mamay receive less due to noAppropriate for sprinkle, fMay underestimate leachi
AW)T) – CIMIS, other
x (AW – ET) ÷ AWng fractionching fractionay receive more leaching while others on‐uniformity of applied water flood, and furrow irrigationng fractions for drip irrigation
Year LeachingFraction
(%) DI
1999 0 2000 22 2001 0
BR1 1999 0 2000 0 2001 1
DE 2000 17 2001 9
BR2 2002 0
Water balance leaching fraction under drip irrigation
-25 -20 -15 -10 -5 0 5 10 15 20 25-25
-20
-15
-10
-5
Dep
th (i
nche
s)
B
0.511.522.533.544.555.566.577.5High
Low
Distance from drip line (inches)
Drip line
ECeLocalized leaching around drip line
Computer simulations (HYDRUS‐2D): wfraction and actual leaching fraction for
Applied water(% of
potential ET)
Watbalanleachfract
(%60 080 0100 0115 15
Notes:●Applying an amount of water equal to irrigation efficiency = 100% for drip irrig●High irrigation efficiency under drip irrsevere deficit irrigation conditions●This behavior is due to the wetting patand can not be avoided
water balance leaching r drip irrigation
terncehingion
%)
ActualLeachingfraction
(%)
7.717.324.5
5 30.9
the ET does not result in anation, as is commonly assumedrigation occurs only for
ttern around drip lines
Estimate leaching fractio
Measure root zone soil salMeasure irrigation water EUse leaching charts to detAssumptions
Root distributionSteady‐state leaching
on from soil salinity data
inity (Ece) ECtermine leaching fraction
1 0.5 1 1.5 2 2.5
EC of Irriga
0
1
2
3
4
5
6
7
8
9
10A
vera
g e R
o ot Z
o ne
E Ce
(dS/
m)
Leaching Fraction
Convention
LF = 7.5%
3 3.5 4 4.5 5 5.5 6
ation Water (dS/m)
n = 5% 10%
20%
30%
40%
50%
nal Irrigation
%
1 0.5 1 1.5 2 2.
EC of Irri
0
1
2
3
4
5
6
7
8
9
10A
vera
ge R
oot Z
one
ECe
(dS /
m)
High Freq
5 3 3.5 4 4.5 5 5.5 6
gation Water (dS/m)
Leaching Fraction = 5%
10%
20%
30% 40%
50%
quency Irrigation
Is the calculated leachingg fraction sufficient?
Measure soil salinity
Sample soil in the root zonIndividual samples – identify
Cost considerationsInformation on variability
Composite samples – samplLower costNo information on variability
Sampling strategiesSystematic – sample on a gridRandom
Compare root zone soil saspecific cropMonitor soil salinity over t
ne and measure the ECefy zones of high salinity
le in zones of high salinity
d
linity with threshold values for a
time
Monitor soil salinity over
Periodic sampling in the roContinuous monitoring wisensorsMonitor in zones of high swithin a fieldConcerns
Sufficient samples to reduceLittle or no variability over tsamples
r time
oot zone with soil samplesith soil moisture/salinity
alinity at several locations
e effect of soil variability time in laboratory processing of
Publication No. 3375anrcatalog.ucdavis.edu