Regulated Deficit Irrigation

Regulated Deficit Irrigation ofTart CherryDr. Brent Black and Kylara PapenfussPlants Soils and Climate DepartmentUtah State University

Overview• What is Regulated Deficit Irrigation?• Why try it in tart cherries?• A summary of the tart cherry RDI project• 2007 and 2008• 2009

Regulated Deficit Irrigation• Deficit ≡ less coming in than going outdeficit irrigation ≡ intentional drought stress• Regulated ≡ specific timing and severity• Why?• Save water• Induce some type of favorable crop response

Regulated Deficit Irrigation (RDI)• Grape• Fruit quality• Color• Sugar• Flavors• May reduce fruit size!Kriedemann and Goodwin

Regulated Deficit Irrigation (RDI)• Grape• Fruit quality• Canopy managementHigh irrigation - AugustLow irrigation - AugustWample and Smithyman, 2002

RDI for Tart Cherry?• Water savings• Reduced shoot growth?• Improved fruit quality

RDI for Tart Cherry?• Water savings.• Reduced shoot growth?• Improved fruit quality.• Improved tree health.

Regulated Deficit Irrigation• Deficit ≡ less coming in than going outirrigation deficit = intentional drought stress• Regulated ≡ specific timing and severity• When?• How Severe?

Growth Stages – fruit developmentTukey and Young (1939)

Tart Cherry Project• Commercial orchard inSantaquin (planted 1994)• Micro-spray irrigation system

TreatmentsFlow Rate (gph)@ 33 psiInches/Irrigation(12 hours)7.7 0.512.2 0.815.6 1.019.9 1.325.8 1.7

o o oo o oo o oo o oo o oo o oo o oo o oo o oo o oo o oo o oPlot size• Each treated area was 3 rows by 12 trees.• Observations made on the middle 10trees.• Treatments started at pit hardening.• A full tank of fruit for each plot wastracked through harvest and processing.

How stressed is the tree?• Mid-day day stem water potential

2007 - 2008• RESULTS

Mid-day day stem water potential

Fruit quality172716200720082620072008Soluble solids concentration (%)15141312Chroma (color intensity)25242322110 20 40 60 80 100 120Irrigation applied (% of control)210 20 40 60 80 100 120Irrigation applied (% of control)

Trunk injury

Return bloom

Early Conclusions on RDI• No negative effect on yield.• Some reduction in fruit size, but only in themost severe treatments.• Fruit color and sugar content increased.• Severity of trunk injury was reduced.• No reduction in bloom or fruit doubling.• Significant water savings.• Moderate levels of RDI appear to be beneficial.

2009• Strong flower bud initiation• Good winter bud survival• Lack of spring frost damage• Good pollination weather• No available thinning options• The crop load “Perfect Storm”

Yield

Undersized fruit

Packout

Trunk injury

Tree Death

Return bloom?Fruit doubling?• Stay tuned - Spring 2010

What happened?

Mid-day day stem water potential

Final Conclusions on RDI• Effects of RDI on yield, fruit size, quality, andtrunk strength could be beneficial in light- andmoderate-crop years (2007, 2008).• In heavy crop years like 2009, maintainingoptimum soil moisture is critical (don’t t needimposed stress)

Final Conclusions on RDI• How do you maintain optimum soil moisture?• Monitor

Final Conclusions on RDI• How do you monitor tree stress?• Mid-day day stem water potential?• Equipment ($3,000)• Gas cylinder• Equilibration time• Time of day

Future Research• More simple methods for consistently determiningtree stress?• Are the fruit quality changes consistent anduseful?• What is the long-term plant health effects of RDI?• Reduction in accumulated trunk injury?• Negative side effects?

Acknowledgements• Kylara Papenfuss• Marc Rowley• Cherry Hill Farms• Payson Fruit Growers• Funding sources• USHA-Research Committee• NRCS-CIGCIG• UDAF-Specialty Crop Block Grant