ET and Deficit Irrigation Approaches in Cotton

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1 ET and Deficit Irrigation Approaches in Cotton Daniel Munk University of California Cooperative Extension Fresno

2 Current Issues State water supply- increasing water for environmental, municipal and recreation uses. (Delta Smelt and Friant- Kern Compromise) The water molecule is quickly becoming the newest California endangered species Harry Cline Demand for food and fiber production continue

3 ET Daily (inches Daily / Weekly Cotton ET 2.5 Cut-Out First Flower 2.0 ET(weekly) Defoliation ET(daily)* First Square Sep 23-Sep 16-Sep 9-Sep 2-Sep 26-Aug 19-Aug 12-Aug 5-Aug 29-Jul 22-Jul 15-Jul 8-Jul 1-Jul 24-Jun 17-Jun 10-Jun 3-Jun 27-May 20-May 13-May 6-May 29-Apr 22-Apr Data from DWR Bulletin ET Weekly (inches)

4 Water Management Options Scale dependent District and regional Field and farm scale

5 Field and Farm Options 1. Seasonal contributions

6 Field and Farm Options 1. Seasonal contributions 2. Residual soil moisture

7 Field and Farm Options 1. Seasonal contributions 2. Residual soil moisture 3. Modify cropping system/selection

8 Field and Farm Options 1. Seasonal contributions 2. Residual soil moisture 3. Modify cropping system/selection 4. Deep well availability

9 Field and Farm Options 1. Seasonal contributions 2. Residual soil moisture 3. Modify cropping system/selection 4. Deep well availability 5. System type (DU)

10 Field and Farm Options 1. Seasonal contributions 2. Residual soil moisture 3. Modify cropping system/selection 4. Deep well availability 5. System type (DU) 6. System performance- design & maint. (DU)

11 Field and Farm Options 1. Seasonal contributions 2. Residual soil moisture 3. Modify cropping system/selection 4. Deep well availability 5. System type (DU) 6. System performance- design & maint. (DU) 7. Crop irrigation scheduling and imposing deficits

12 Why Consider Deficit Irrigation? Depending on commodity, water costs and availability, DI can be an economically sound option Keep land in production Provide more beneficial use on remaining acreage

13 What is Deficit Irrigation? From a crop production standpoint From a physiological perspective Cotton ET will increase as applied water increases to a point Cotton production increases with increasing water applied?

14 How does irrigation influence yield? Crop Water Response What impact does irrigation have on economics?

15 Yield response to applied water Yield Applied Water

16 What is Deficit Irrigation? Yield Deficit Irrig. (water stress) Peak Yield Destructive (anaerobic) Applied Water

17 Regulated Deficit Irrigation (strategic) Uses knowledge of crop phenology and physiology to determine timing of deficits Makes use of existing deficit irrigation databases to gauge time x intensity relationships and estimate economic impacts on production and quality

18 UCCE Irrigation Management Guidelines Minimum water stress during prebloom period Modest water stress during effective bloom Late flower water use < 0.32 in./day Best opportunity to deficit irrigate is post cutout -15, -18 bars Acala s Limit (-20) -16, bars Pima s Limit (-22)

19 Midday LWP Hanford Sandy Loam 22.0 Leaf Water Potential (-bars) y = 0.67x R 2 = Days After Irrigation

20 WSREC Irrigation Trials - Acala , 2002, and 2006 Yield (pounds of lint/acre) y = x R 2 = Cumulative Leaf Water Potential

21 WSREC Irrigation Trials Acala 2000 Pounds of Lint per Acre y = x x R 2 = y = x x R 2 = Cumulative Leaf Water Potential

22 Water Applied and Cotton Yield (5 years), Furrow Irrigated Cotton WSREC 2200 SJV Pima Yield (pounds of Lint per Acre) Water Applied (acre inches)

23 Changing System Efficiencies 2200 Yield (pounds of Lint per Acre) Elevated Water Use Efficiency SJV Pima Standard Furrow System Water Applied (acre inches)

24 Increasing Plant Water Deficits Field Geography Isolated (texture, salinity) Widespread Plant Effects Xylem Veg. Growth Fruit Retention (fruit & quality losses) High Water Potential Low Water Potential Nutrients Diminishing Nutrient Transport ET VPD Transient Reductions Stomatal Closure Ps Light & Temp. Minor Declines Injury of Ps Apparatus

25 Consider Earliness Effects 10 Nodes Above Cracked Boll NI 7/10 5" 7/10, 8/7 10" 7/2, 7/30, 8/24 15"

26 Potential Problems with Deficit Irrigation Quality: length Length , 96, and 97 WSREC Irrigation Trials y = x R 2 = y = x R 2 = y = x R 2 = ' WS Irr. 96' WS Irr. 97' WS Irr Pounds of Lint/Acre

27 RDI Benefits and Challenges Energy and resource efficiencies increased Some production uncertainties remain Potential for reductions in groundwater contamination Long term consideration for future buildup of soil solutes, need for managing salts

28 Applying a Deficit Approach Assess water and commodity costs Evaluate weak links; soils, system, soils x system Where will water savings go? Start conservatively and plan Start early season & build stress w/ each irrigation Reasonable expectations expect quality impacts to begin as yield declines beyond 15%

29 Thank you cottoninfo.ucdavis.edu

30 Thank You Meeting Sponsors Agri-Valley Irrigation Netafim Irrigation Watson Ag. Irrigation CIT Agricultural Pump Efficiency Program

31 Question Preirrigation Needs Residual Moisture Rooting depth at first irrigation Alternate Furrow Reduced run length

32 Economic Yield Response Curve Yield Y = ax 2 + bx + c Rational Use Zone Lower Limit Upper Limit Applied Water

33 Why Deficit Irrigate? Can have minimal impacts on yield Can have predictable impacts on yield Not always your best option but can be a useful tool

34 Improving WUE Decreasing variability of water uptake Limiting deep percolation Decreasing Evaporation Increasing reliability of a scheduling system

35 Diurnal Variation of LWP (-Bars) Furrow Acala Maxxa7/ :00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 AM 1:00 PM 2:00 PM 3:00 PM

36 Time-Stress Response to Soil Water Availability 22.0 Leaf Water Potential during a 27 Day Period 20.0 Leaf Water Potential (-bars) Sandy Loam y = 0.67x R 2 = 0.93 Clay Loam y = 0.396x R 2 = Days After Irrigation

37 Transpiration and Water Stress Daily Transpiration Water Stress

38 Why Consider Deficit Irrigation? Production Losses Crop quality Is deficit irrigation predictable? Risk management decisions (cost benefit)

39 Irrigation Scheduling Plant Water Status Emphasis Leaf water potential - Pressure chamber Leaf temperature and canopy spectra IRT, ground and aerial spectral data including NDVI

40 Yield and vegetative growth response to applied water 2200 Yield (pounds of Lint per Acre) Plant Height (in.) Water Applied (acre inches)

41 Approximate amount of water needed to bring selected soil textures to field capacity Available soil water remaining (%) Loamy Sand Sandy Loam Silt Loam and Clay Loam Sandy Clay and Silty Clay At field capacity

42 Poorly Drained Soils Optimum Irrig. Schedule Yield Applied Water

43 How much? Retain ability to monitor changes in pump performance Water meters, depth to groundwater, drawdown

44 Irrigation Scheduling Soil / Water Balance Emphasis Knowledge of crop ET ETc = ETo X Kc (DWR s CIMIS program) Knowledge of crop growth including plants underground hydraulic system Water holding capacity of the soil Allowable depletion of root zone

45 Overview Current issues Cotton water requirements Plant responses to water applied Considerations in deficit irrigation

46 Evapotranspiration Rates for Several Irrigated Crops (Acre Inches) Jan Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec. Total Alfalfa Cotton Corn Wheat Barley Lettuce * * * * 8

47 What is Deficit Irrigation?

48 Farms: Dealing with Change Implement short and long term Planning Evaluate all options

49 Est. Rooting Depth based on Soil Moisture Extraction 1-Jun 8-Jun 15-Jun 22-Jun 29-Jun 6-Jul 13-Jul 20-Jul 27-Jul 3-Aug 10-Aug 17-Aug 24-Aug 31-Aug 7-Sep 14-Sep Rooting Depth (cm) Percent Clay Content Munk et. al. 1997

50 Thank You Meeting Sponsors Agri-Valley Irrigation Netafim Irrigation Watson Ag Irrigation CIT Agricultural Pump Efficiency Program