2008 Best Management Practices Workshop Irrigation scheduling methods and tools: Enhancing efficiency of water and fertilizer delivery

Transcription

1 2008 Best Management Practices Workshop Irrigation scheduling methods and tools: Enhancing efficiency of water and fertilizer delivery Kelly Morgan, Michael Dukes, and Lincoln Zotarelli Apopka, FL May 2008

2 Introduction Florida: biggest citrus producer and second biggest U.S. vegetable producer Vegetable & Citrus: produced on sandy soils with poor water & nutrient holding capacity

3 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)

4 Introduction 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

5 Municipal Water Use Population served by public supply 5.4 million million 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

6 Introduction 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

7 10 8 Irrig Water Req - Turf 8 inch RZ Precip ETc Depth (inches) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

8 Automatic Irrigation Control Systems used in Florida Author/year Crop Automatic Irrigation Control System (AICS) Smajstrla and Locascio, 1996 Research Findings Tomato Switching tensiometers Reduced irrigation requirements of tomatoes by 40% to 50% without reducing yields compared to fixed schedule (3 to 5 times per/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%

9 Granular Matrix Capacitance Sensors TDR Tensiometers Radio Telemetry

10 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.

11 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 homes Rain sensors (MiniCLIK) irrigation reduction compared to 2 d/wk seasonal adjustment & no rain sensor 15-35% under normal rainfall conditions 10-20% under dry conditions ET controller irrigation reduction compared to 2 d/wk seasonal adjustment & no rain sensor Depends on time of year 9-60% predominantly dry conditions

12 Sensor Based Irrigation Control Types: On-demand irrigation Bypass irrigation Soil Moisture Sensor Fixed Time (2h) 0.20 Irrigation (mm) VWC (0-25cm) VWC 25-55cm Volumetric water content (v/v) Day Day 0.00

13 Effect of irrigation on solute displacement (injecting dye in fertigation lines) 24 hrs 3 days 7 days soil sensor based irrigation 40 cm fixed time irrigation schedule +95 cm

14 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

15 Application uniformity Photo: M. Dukes wet soil dry soil at side of the bed drip tape at center of the bed Photo: L. Zotarelli

16 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

17 Reuse Type Landscape Irrigation 44% Agricultural irrigation 19% Ground water recharge 16% Industrial activities 15% Wetland 16% Florida DEP, 2005

18 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.

19 ET provides reference measure of water use based on plant water demand Scalable for specific crop, growth stage, climate, and season of year ET c = ET o * K c

20 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. ET c = ET o * K c * K s

21

22 Future research priorities 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 tools Fertilizer/irrigation Assessment of fertilizer application methods Nutrient distribution uniformity at various fertilizer rates Development of electrical conductivity (EC) probes Field scale use of irrigation technologies Number and placement of sensors ET and K c values under drip and mulched systems Use of reclaimed water for irrigation Food safety Nutrient management Water quality (irrigation & groundwater)