• Bob Hutmacher, Extension Specialist • Shafter REC and West Side REC

SDI versus Furrow Decisions –Some Considerations

• Best practice or choices not necessarily the same over time as water availability, equipment costs, labor costs and environmental conditions change

• Competition for less stable water supplies, potentially more salinity, trace element, and shallow groundwater issues all can come into play

Does research or local evidence suggest you will get a yield response? If the answer is “yes”, how much additional yield and what is it worth?How well the system will work depends in part on soil type, slope, groundwater depth, other factors – will it work for the combined conditions you have?How much savings in water or fertilizer or other inputs are expected and needed to justify costs?Installation and design costs for the system ?

Annual operating costs for system? Labor and expertise available for installation, maintenance and mgmt.?Longevity required to make system cost-effective, and how does that influence installation & maintenance costs?Compatibility of the system with crop rotation plans?How willing are you to change mgmt practices?

Presence of soil layers influencing water movement and placement of systemHow deep place system to limit problems with gophers and insects, impacts on tillage depth and system longevityWater quality issues / filtration and water treatment needs for systemRelative costs of annual repairs to system

Water costs & energy costs for pressurization – are water costs and potential savings a significant concern? Are energy sources available at reasonable cost to run the system?where will salts, trace elements accumulate, will there be new approaches and information needed to manage for suitable longevity?

Capabilities of systems: With subsurface systems, can improve water delivery to plants even in soils where soil physical or chemical characteristics make water infiltration difficult … improve application uniformity and plant responseCan reduce evaporation and runoff losses if managed and designed properly for soil typeIn areas with aeration/anoxia problems, can put on water/nutrients in small amounts at a time that limit extent and duration of saturated zonesCapability to apply water/nutrients frequently, avoid even short term deficits (might only be important if plants/yields or quality are responsive)

Capabilities of systems: On uneven or sloping terrain where other surface water delivery methods would be difficult, well-designed drip systems can greatly improve irrigation water delivery to the root zone and uniformity of applicationsWhere depth of soil for rooting is very limited, sdi or drip can be used to meet water and nutrient needs through frequent, small applications (helpful with hardpan, shallow soils due to shallow gw, soil chemistries, etc.)

Question to ask:Is ability to save significantly on applied water a vital part of the equation? Do you need savings due to limits on water availability? Impacts on water cost?

Ability to deliver water savings depends on:soil factors as well as irrigation system choicesExperiences of many has shown a very large range in actual water savings (soil types, inefficiencies of prior systems, crop sensitivity to stress, ability to judge water needs to avoid deep percolation losses all can impact ACTUAL SAVINGS)

Cotton Lint Yields (lbs / acre)

Year1-SDI Year 1-Furrow

Year 2- SDI Year 2-Furrow

Good Soil 1704 1738 1613 1608

Poor Soil 1637 1445 1517 1325

Net Water Applied (inches)

Good Soil 24.1 41.8 26.3 38.5

Poor Soil 22.9 45.9 25.7 41.1

*sandy loam soils / poor =nonuniform, declining infiltration rates, variable root development

Shafter REC(sandy loam soil, declining soil surface infiltration, mod.-low rooting depth)

When use LWP toavoid mod. stress:Largest savings (up to 30%+) consistently on non-uniform ground, variable infiltration soils (yield responses similar in these cases)

West Side REC(clay loam, good intake characteristics, potential for deep rooting)

When use LWP toavoid mod. stress:water savings generally low (<5 to 10%) depending on uniformity of irrigation (yield responses similar)

timing and type of fertilizer materials can be important placement of fertilizers / consider impacts of system placement relative to plant rows, application frequency on opportunity for root uptake with less mobile nutrients such as P or K, depth of drip line relative to root growth can impact availability at times Same can be true with perennial crops several years down the line example: in some alfalfa work, we had problems delivering K effectively to an established, drip irrigated crop with high yields & high K uptake – how get adequate nutrients to active part of plant root zone? follow-up plant (or soil) evaluations to: (1) assess adequacy at key periods, and; (2) avoid excess and waste

If use shallow placement of tapes, must be really aware of potential to pinch off flow by use of any heavy equipment (tire traffic, implements, etc.) that crosses line of placementThis is especially an issue if the soil moisture is conducive to packing of the soil Personal experience with this last year due to my neglect!

No-till or reduced tillage part of the plan?If placed deep enough or planned around, MI can be managed to produce drier soil, fewer weeds, and less need for tillage? Depending on system placement, emitter output, and how operated, can also develop more and different weed issues due to sustained higher surface soil water contents?

Does the system need to provide all irrigation (including germination moisture) or can you go with a second system (ex: sprinklers - for seeding, transplants or for leaching?)Impacts on choices and continued use of some chemicals / herbicide materials - some of which work best or even require activation with moisture to be fully effective

how well do automated components of systems perform (filters, injectors, valves, controllers, etc.)?Consider experience of those you work with – relative payoff in time savings vs. complexity in repairs, who can do repairs, required mgmt time?Multiple growers or managers have noted that it isn’t good to “over-automate” if it leads to impression that you can stay out of the field and not check out performance, problems and crop progressIn the past, mixed results with some automation and non-wired controls but improvements always coming

Where are the roots?

What is the effective rooting volume and how does it change when you change systems or management?

-3

-2.4

-1.8

-1.2

-0.6

00 0.5 1 1.5 2

ROOT LENGTH DENSITY (cm/g)

DEP

TH I

N S

OIL

(m

)

SDI

LPS-06

Furrow

Late irrigation start & deficit irrigation restricted rooting even at WSREC

* This just a “Snapshot” of what is there at a specific time!

45 30 15 0 15 30 4545

30

10

HORIZONTAL DISTANCE (cm)

DEP

TH (c

m)

Soil Water Content Grid - Trt 100/80/60 - 8/18/06

32-3727-3222-2717-2212-17

Drip lateral Plant row

Water distribution patterns have great potential to impact where roots develop

1500

1800

2100

2400

2700

3000

550 650 750 850 950

EVAPOTRANSPIRATION (mm)

YIE

LD (

kg/h

a)

year 1year 2year 3

700 mm = 27.5”(applied + soil water use) Deficit irrigation

options

SOME SIGNIFICANT CONSIDERATIONS IN DECISIONS

TO LOOK AT DRIP:

(1) Crop(s) you intend to grow

(2) How responsive crops are to changes in water & nutrient availability and management

CROP RESPONSES TO MINIMIZING WATER OR NUTRIENT STRESS (multiple studies, multiple crops)

• if adequate nutrients provided, multiple studies demonstrate higher, more “even” growth rates with minimal stress mgmt. & at applications close to full Etc levels

• impacts of ability to avoid water & nutrient stresses is to sustain:

• new shoot growth (fruiting site and leaf area production)

• limit critical losses of root uptake ability/growth at key times

• in some crops, sustained & high dry matter production is the goal … in others, managing balance of growth & fruit and quality can be more complicated

OPINION: more efforts will be needed to see which types of irrigation systems or mgmt. best-suited to getting the best crop responses out of deficit irrigation

Example: Sonora Chile Pepper Evaluations (New Mexico) – Las Cruces

YIELDS - 25 PERCENT

FERTILIZER COSTS – 26 PERCENT

OTHER CHEMICALS – 18 PERCENT

CAPITAL COSTS – 47 PERCENT

FIXED COSTS – 19 PERCENT

SEED COSTS – 20 PERCENT

OVERALL NET OPERATING PROFIT – 12 PERCENT

Subsurface versus Furrow Irrigation of Alfalfa – some comments(1990’s USDA-ARS study in Imperial Valley, CA)

Bob Hutmacher, Claude Phene, Richard Mead, David Clark, Susan Vail, Merle Peters, Carl HawkPete Shouse, Terry Donovan, Jack Jobes, Joanne FargerlundBob SwainDick KershawImperial Irrigation DistrictDean Currie

Imperial Valley Research Center Imperial Valley Conservation Research Center Committee

Table 1. Treatment descriptions in Alfalfa SDI versus furrow irrigation studies (1991-1997) – Imperial Valley (Hutmacher et al., USDA-ARS)

Irrigation treatments

Drip Lateral Spacing (in.)

Number of beds per plot

Bed Width (inches)

SDI-Ram 40 8 40

SDI-Ram 80 4 80

SDI-Rootguard 40 8 40

SDI-Rootguard 80 4 80

Field Lysimeter (SDI Rootguard)

40 2 40

Furrow – 40” beds

- 16 40

- Difference between 1991-1992 versus 1993-1997 setup was in drip lateral depth of placement (0.4 m vs. 0.63 to 0.7 m)- Soil type was heavy clay, with potential surface infiltration and aeration issues

Table 2. Irrigation water quality characteristics - Alfalfa SDI versus furrow irrigation studies (1991-1997) – Imperial Valley (Hutmacher et al., USDA-ARS)

Electrical conductivity (average) = 1.15 to 1.3 dS/m

pH = 7.4 to 7.9

Boron = 0.13 to 0.31 mg/L

SAR range about 5.5 to 7

Subsurface Drip versus Furrow Alfalfa Studies – Imperial Valley, 1991-1997 (USDA-ARS)

Phase I of trial (0.4 m drip line depth) – 1991 to 1992Original intent was to let lysimeter control SDI irrigation (avoid stress even during regrowth period)Problem was surface wetting of small but significant areas that impacted harvest equipment Water applications scaled back to 25-50% crop Etc during few days pre-harvest through bale removal

Phase II of trial (0.7 m drip line depth) – 1993 late to 1997

o Deeper installation depth prevented applied water from coming to surface

o Fewer observed leaks, less rodent damage

o Changed salinity patterns and surface soil drying & cracking

o No phased-back irrigations required at harvest with deeper installationj

Applied Irrigation Water in alfalfa SDI versus furrow trial – Imperial Valley(USDA-ARS Fresno)

0

400

800

1200

1600

2000

2400

WA

TER

APP

LIC

ATI

ON

S (m

m)

1991-part

1992-part

1994 1995 1996

SDI-40SDI-80FurrowLysimeter

* Upper limit on furrow irrigation amounts was determined by height of beds and care to avoid aeration issues and plant “scalding” – ground shanked to improve water entry following each harvest

Alfalfa Forage Yields in alfalfa SDI versus furrow trial – Imperial Valley(USDA-ARS Fresno)

0

4

8

12

16

20

FOR

AG

E Y

IELD

S (T

/acr

e)

1991-part

1992-part

1994-part

1995 1996

SDI-40SDI-80Furrow

•Forage yields were corrected to uniform moisture content

• 1991, 1992, 1994 represent partial years (establ. 4/91, termin. 9/92, establ. 3/94)

+23% +18%+17%

+27%

+14%

Subsurface versus Furrow Irrigation of Alfalfa –some comments(1990’s USDA-ARS study in Imperial Valley, CA)

Salinity Accumulation IssuesDifferent mgmt approach required for drip versus furrow (furrow pushed salts to bed center, SDI patterns more complicated) Patterns develop within months in high ET locationDeal with accumulations or eventually problems developAn option we evaluated was to deal with salt accumulations by winter sprinkler applications in both furrow and SDI (worked well in evening out saline “hot spots” in upper root zone) – extra cost but could impact yields and yield declines over time

Subsurface versus Furrow Irrigation of Alfalfa –some comments(1990’s USDA-ARS study in Imperial Valley, CA)

Summary Comments:WUE increases (yld/mm ET) of about 20% with SDI compared with furrow (this soil, this site)>WUE due to yield increases, not reductions in applied water, ETLimited rooting due to water application patterns, soil characteristics resulted in some fertility issues, apparent K responsesIn Phase II, deeper depth allowed continued water applic. during harvest and regrowth, faster regrowth ratesShort furrow run lengths make furrow fairly efficient and uniform, but counterbalanced by lighter, more frequent irrigations needed in this soil to avoid “scalding” and aeration problemsMay be more opportunities for water savings in soils where intake uniformity with flood or furrow is more variable As usual, system and mgmt costs need to be balanced against water availability and costs

Some good sources of information on MI design and/or mgmt. available from many sources:

Companies International groups (FAO, others) University of USDA resources, such as:

UC Water Mgmt Handbook Series (Hanson, Schwankl, Grattan, and Pritchard) Cal Polytechnic SLO (Burt et al.) CSUF-Center for Irrigation Technology

Drip systems offer capabilities to deliver water and nutrients in a flexible, on-demand wayNot all crops (in research trials or grower fields) respond economically to minimizing short-term water or nutrient stress (a particular capability of well-managed drip systems)

The above statement is less true when you push crops more to the limits and try to get higher and higher yields out of moderate size, “manageable” plants