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  • Practical ways to improve water quality

  • Salinas/Castroville area ditches, creeks and sloughs Average of 2005-07 monthly sampling of 11 sites

    W t lit M t E d 2005 2007Water quality parameter

    Measurement unit

    Exceedance threshold

    2005-2007 monthly average

    NO3-N PPM > 10 25 PO4-P PPM > 0.5 0.63 Algae % survival > 110 228

    Turbidity NTU > 50 587 Water toxicity % survival < 80 27y Sediment toxicity % survival < 80 24

  • Source of nutrients ?Source of nutrients ? Fertilizer Well water

  • What soluble nutrient load does vegetable field runoff carry ?

    In 13 Salinas Valley trials …

    PPM NO3-N PO4-PNO3-N PO4-P

    Low 1 0.1 High 48 2 1High 48 2.1 Mean 12 0.7

  • How about drain tile effluent ?How about drain tile effluent ?

    2002-04 drain tile sampling in the Salinas Valley

  • Why is drain tile effluent so high in NO3-N? all NO3-N is in the soil solution

    Relationship of soil NO3-N to soil solution NO3-N :

    Soil NO3-N NO3-N in soil solution (PPM) (PPM) Sandy loam Clay( ) y y

    10 50 30

  • In 13 Salinas Valley field trials runoff turbidity ranged from 200 - 4,600 NTU

  • Bottom line : Any water escaping from a vegetable field is likely to exceed

    t lit t d d f ll t twater quality standards for one or more pollutants

    What can be done ? Treat the water to remove pollutants Reduce the application of materials that can move in water Reduce the volume of water that leaves the field

  • Water treatment :

    Consistently reduce sediment loss Minimally effective for soluble nutrients May conflict with microbial food safety practices

  • Water treatment :

    PAMPAM

  • Water treatment :

    PAM

    Highly effective for sediment removal Relatively inexpensive, can be automated Inconsistently effective at reducing soluble nutrients

  • Most practical solution is to limit the volume of runoff or leachate …

    … and drip irrigation is the ideal tool

  • Crop water use can be predicted by canopy size and ETo :

    80

    100

    ov er

    40

    60

    80

    t c an

    op y

    co or

    le ttu

    ce

    0

    20

    1 2 3 4 5 6 7 8 9 10

    Pe rc

    en t fo

    1 2 3 4 5 6 7 8 9 10

    Weeks after planting

  • Irrigation requirementIrrigation requirement can be predicted by canopy size and ETo :

    100 120

    T o

    40 60 80

    rc en

    t o f E

    T fo

    r l et

    tu ce

    0 20

    1 2 3 4 5 6 7 8 9 10

    Pe r f

    Efficient seasonal drip irrigation volume ≈ 80 – 120 % of ETo

    Weeks after planting

  • 250ie d

    Drip irrigation management varies greatly among growers :

    150

    200

    250

    ET o a

    pp li

    rip

    50

    100

    150

    ea so

    na l E

    w ith

    d r

    Ideal zone

    0

    50

    1 2 3 4 5 6 7 8 9 10 11 12 13 14% o

    f s e

    Commercial field

    Drip-irrigated lettuce fields in the Salinas Valley

  • 250lie d

    Consequences of excessive irrigation :

    150

    200

    ET o a

    pp l

    dr ip

    50

    100

    50

    ea so

    na l E

    w ith

    d

    Ideal zone

    0

    50

    1 2 3 4 5 6 7 8 9 10 11 12 13 14% o

    f s e

    Commercial field

    Assume early summer conditions northern Salinas Valley locationAssume early summer conditions, northern Salinas Valley location, sandy loam soil :

    If field 5 applied 5 inches of water with drip, h fi ld 14 li d 10 i hthen field 14 applied 10 inches

    If soil is 10 PPM NO3-N, field 14 lost > 50 lb N/acre in leaching !

  • Long irrigation intervals ruin drip irrigation efficiency :

    In drip-irrigated celery fields …

    8

    10 ys

    io

    ns

    4

    6

    ra ge

    d ay

    n irr

    ig at

    2

    4

    A ve

    r be

    tw ee

    n

    0 1 2 3 4 5 6 7 8 9

    Field

  • Long irrigation intervals lead to heavy individual applications :heavy individual applications :

    1.5

    2

    ch es

    io n

    Light soil Heavy soil

    0 5

    1

    er ag

    e in

    c er

    ir rig

    at

    Maximum for efficient irrigation

    0

    0.5

    1 2 3 4 5 6 7 8 9

    A ve pe efficient irrigation

    1 2 3 4 5 6 7 8 9

    Field

    Above this maximum range the leaching fraction becomes significant !

  • What constitutes efficient fertigation ?

    30

    20 25 30

    up ta

    ke / w

    ee k)

    5 10 15

    et tu

    ce N

    lb

    / ac

    re

    90 - 120 lb N/acre at harvest

    0 1 2 3 4 5 6 7 8 9 10

    W k ft l ti

    Le (l

    Weeks after planting

  • 20 25 30

    pt ak

    e w

    ee k)

    10 15 20

    tu ce

    N u

    p / a

    cr e

    / w 90 - 120 lb N/acre

    at harvest

    0 5

    1 2 3 4 5 6 7 8 9 10

    Le tt

    (l b

    Weeks after planting

    40

    20

    30

    N u

    pt ak

    e re

    / w

    ee k)

    180 - 220 lb N/acre

    0

    10

    20

    C el

    er y

    N (l

    b / a

    cr 180 220 lb N/acreat harvest

    0 1 2 3 4 5 6 7 8 9 10 11 12

    Weeks after transplanting

  • 2007 lettuce fertigation trials :

    FieldFieldField Lettuce Lettuce Lettuce

    typetypetype Soil NOSoil NOSoil NO333---N at startN at startN at start of fertigation (PPM)of fertigation (PPM)of fertigation (PPM)g ( )g ( )g ( )

    111 headheadhead 202020 222 headheadhead 272727 333 romaineromaineromaine 212121

  • 2007 lettuce fertigation trials :

    Reference evapotranspiration Drip irrigation Field (ETo , inches) applied (inches)

    1 6.2 4.9 2 6 5 4 72 6.5 4.7 3 2.4 2.8

  • 60 80

    ga tio

    n cr

    e)

    field 1

    12 f

    0 20 40

    25 30 35 40 45 50 55 60 65

    N fe

    rt ig

    (l b/

    ac 127 lb N fertigated

    25 30 35 40 45 50 55 60 65

    Days after planting

    153 lb N fertigated40 60 80

    ga tio

    n cr

    e)

    field 2

    153 lb N fertigated

    0 20 40

    25 30 35 40 45 50 55 60 65

    N fe

    rt ig

    (l b/

    ac

    67 lb N f ti t d

    25 30 35 40 45 50 55 60 65

    Days after planting

    60

    80

    at io

    n re

    )

    field 3

    67 lb N fertigated

    0

    20

    40

    N fe

    rt ig

    a (l

    b/ ac

    r

    25 30 35 40 45 50 55 60 65 Days after planting

  • 80n field 1

    Reduced N treatment created by eliminating some N fertigation :

    0 20 40 60

    N fe

    rt ig

    at io

    n (l

    b/ ac

    re ) field 1

    x x 0

    25 30 35 40 45 50 55 60 65

    Days after planting

    N

    80n field 2

    0 20 40 60

    N fe

    rt ig

    at io

    (l b/

    ac re

    ) field 2

    x x

    0 25 30 35 40 45 50 55 60 65

    Days after planting

    N

    80

    n field 3

    20

    40

    60

    N fe

    rt ig

    at io

    (l b/

    ac re

    )

    x 0

    25 30 35 40 45 50 55 60 65 Days after planting

  • Results :

    lb N / acre Mean

    plant wt Crop N uptake

    Field Treatment total fertigated (lb) (lb / acre)Field Treatment total fertigated (lb) (lb / acre) 1 Grower 169 127 2.29 98

    Reduced N 92 50 2.31 91

  • Results :

    lb N / acre Mean

    plant wt Crop N uptake

    Field Treatment total fertigated (lb) (lb / acre)Field Treatment total fertigated (lb) (lb / acre) 1 Grower 169 127 2.29 98

    Reduced N 92 50 2.31 91

    2 Grower 171 153 2.16 103 Reduced N 64 46 2 27 101Reduced N 64 46 2.27 101

  • Results :

    lb N / acre Mean

    plant wt Crop N uptake

    Field Treatment total fertigated (lb) (lb / acre)Field Treatment total fertigated (lb) (lb / acre) 1 Grower 169 127 2.29 98

    Reduced N 92 50 2.31 91

    2 Grower 171 153 2.16 103 Reduced N 64 46 2 27 101Reduced N 64 46 2.27 101

    3 Grower 115 67 1.92 102 Reduced N 67 19 1.81 87

    Conclusion : given careful irrigation, a modest level of N fertigation is sufficient

  • What will efficient fertilization do to water quality ? Reduced N application limits potential N lossReduced N application limits potential N loss

  • What will efficient irrigation do to water quality ? N concentration of runoff or leachate might increase but

    concentration x volume = load

    N concentration of runoff or leachate might increase, but environmental load will decrease substantially

  • What will efficient irrigation do to water quality ? N concentration of runoff or leachate might increase but

    concentration x volume = load

    N concentration of runoff or leachate might increase

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