Apopka, FL – May 2008

Irrigation scheduling methods and tools: Enhancing efficiency of water and

fertilizer deliveryKelly Morgan, Michael Dukes, and Lincoln Zotarelli

2008 Best Management Practices Workshop

• Florida: biggest citrus producer and second biggest U.S. vegetable producer

• Vegetable & Citrus: produced on sandy soils with poor water & nutrient holding capacity

Introduction

Vegetable & Citrus Irrigation

Average annual total of 207,700 acres planted with vegetables and 741,000 acres of citrus between 1998 and 2006 (NASS/USDA, 2008)

• Florida: biggest citrus producer and second biggest U.S. vegetable producer

• Vegetable & Citrus: produced on sandy soils with poor water & nutrient holding capacity

• Landscapes: largest single state in home construction in recent years

Introduction

Municipal Water Use• Population served by public supply

5.4 million 197017 million 200420 million 2020 (est.)

• 15% U.S. new home construction in FL• + ~1,000 people/day• Most new homes in FL include

irrigation• ~60% household water use for

irrigation• High quality landscapes and low water

holding capacity

• Florida: biggest citrus producer and second biggest U.S. vegetable producer

• Vegetable & Citrus: produced on sandy soils with poor water & nutrient holding capacity

• Landscapes: largest single state in home construction in recent years

• Conventional irrigation management: inadequate to ensure optimal resource use and to minimize nutrient leaching

• Use of technological innovations:enhance production efficiency provide local growers with a competitive edge reduce environmental impacts

• Research priorities: Lack of precise information on crop water & nutrient status excessive water & fertilizer use

Introduction

Month

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Irrig Water Req - Turf 8 inch RZPrecip ETc

Automatic Irrigation Control Systems used in FloridaAuthor/year Crop Automatic Irrigation

Control System (AICS)Research Findings

Smajstrla and Locascio, 1996

Tomato Switching tensiometers Reduced irrigation requirements of tomatoes by 40% to 50% without reducing yields compared to fixed schedule (3 to 5 timesper/week

Smajstrla and Koo, 1986 Citrus Switching tensiometers Efficient use to schedule irrigation application based on soil water potential. Maintenance and periodic inspections are required.

Dukes et al., 2003 Pepper Time domain transmission (TDT)

Use of 50% less irrigation water, similar yields compared to a daily based on Class A pan evaporation irrigation method

Nogueira et al., 2003 Sweet corn Time domain reflectometry(TDR)

Permits the control of the water application showing potential for automatic irrigation management

Dukes and Scholberg, 2005 Sweet corn TDR Up to 11% of reduction in water use using AICS with subsurface drip irrigation compared to sprinkler irrigation without affecting yields

Munoz-Carpena et al., 2005 Tomato switching tensiometers/ granular matrix sensor

Switching tensiometers at the 15 kPa set point resulted to up to 73% reduction in water use when compared to the control

Dukes et al., 2006 Pepper Dielectric sensor 50% of reduction in water use compared to manually irrigated once a day, similar yields

Munoz-Carpena et al., 2008 Tomato TDT Savings up to 74% in water use compared to the fixed time irrigation; 61% of savings compared to the evapotranspiration based water application

Zotarelli et al., 2008 Zucchini TDT Reduction in water use by 30-80% compared to the single daily fixed time irrigation, significant reduction in N leaching, increase in yield and N use efficiency

Zotarelli et al. 2008, In press

Tomato TDR Irrigation water savings superior to 67% compared to the control, yield increment of 11-26%

Tensiometers

GranularMatrix

TDR

Capacitance Sensors

RadioTelemetry

• Vegetable Crops – shallow root zone, high valued crops, water conservation – sensor-based systems

• drip irrigation –high potential for acceptance due to control systems used.

• Seepage irrigation –potential for use limited to monitoring only since system control is coarse.

• Citrus – Perennial, deeply rooted• Microsprinkler irrigation – systems

becoming automated to reduce labor requirements and improved water and nutrient use efficiencies.

Soil moisture sensor irrigation reduction compared to 2 d/wk seasonal adjustment & no rain sensor◦ 70-90% during normal to rainy conditions◦ 15-40% during dry conditions◦ 50% on cooperating residential homesRain sensors (MiniCLIK) irrigation reduction compared to 2 d/wk seasonal adjustment & no rain sensor◦ 15-35% under normal rainfall conditions◦ 10-20% under dry conditionsET controller irrigation reduction compared to 2 d/wk seasonal adjustment & no rain sensor◦ Depends on time of year◦ 9-60% predominantly dry conditions

Sensor Based Irrigation Control

Soil Moisture Sensor

Day30 31 1 2 3 4

Fixed Time (2h)

Day30 31 1 2 3 4

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VWC 25-55cm

Irrig

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• Types: • On-demand irrigation• Bypass irrigation

24 hrs 3 days 7 days

Effect of irrigation on solute displacement(injecting dye in fertigation lines)

soil sensor based

irrigation

fixed time irrigation schedule

40 cm

+95 cm

• Uniformity of water application also drives the uniformity of the fertilizer application

• Irrigation system needs to be completely pressurized before the fertigation begins

• Fertilizer used must be completely soluble in water, and pass through the filters

• Injecting N fertigation towards the end of the irrigation cycle may also prevent immediate N displacement below crop root zone

Application uniformity

drip tape atcenter of the bed

dry soilat side of the bedwet soil

Photo: L. Zotarelli

Photo: M. Dukes

• Studies on young trees (<6 yrs) have found highest yields

• Leaf N values were generally higher per unit of applied N in the fertigated plots indicating more efficient uptake

• Most efficient method probably due to optimal placement and multiple applications

• Groundwater loading of nitrate-N was lower using fertigation

• Studies on mature trees (>8-10yrs) found no significant interaction between rate and method

• Reuse Type• Landscape Irrigation 44%• Agricultural irrigation 19%• Ground water recharge 16%• Industrial activities 15%• Wetland 16%

Florida DEP, 2005

• Conserv II, provides reclaimed water for agricultural irrigation

• Delivers approximately 35.1 million gals. of reclaimed water per day, 57% used for irrigation • 10,035 acres of citrus

groves, • 7 foliage and landscape

nurseries, • 2 tree farms, • 3 ferneries,• 2 golf courses.

• ET provides reference measure of water use based on plant water demand

• Scalable for specific crop, growth stage, climate, and season of year

• ETc = ETo * Kc

• Citrus – Perennial, deeply rooted• Microsprinkler irrigation• systems becoming automated to

reduce labor requirements• improved water and nutrient use

efficiencies. • Proportion of reference ET

varies by time of year and soil moisture.

• ETc = ETo * Kc * Ks

Irrigation scheduling school/demonstration projects◦ Guidelines for automatic (sensor based) irrigation control◦ Demonstration of soil moisture automated irrig. control

(vegetable, citrus & landscape)◦ ET based irrigation scheduling toolsFertilizer/irrigation◦ Assessment of fertilizer application methods◦ Nutrient distribution uniformity at various fertilizer rates◦ Development of electrical conductivity (EC) probesField scale use of irrigation technologies◦ Number and placement of sensors◦ ET and Kc values under drip and mulched systemsUse of reclaimed water for irrigation◦ Food safety◦ Nutrient management◦ Water quality (irrigation & groundwater)

Future research priorities