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Improving Irrigation Efficiency in Pears – Case Studies

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by Tianna DuPont, WSU Extension; Lee Kalcsits, WSU Horticulture; Troy Peters, WSU Extension

Hot summers and recent issues with cork spot in D’Anjou pears highlight the need for a better understanding of how irrigation timing and frequency, in conjunction with good calcium programs, can affect tree growth, productivity, and fruit quality in pears. As part of a larger project which includes research into optimum irrigation timing and quantity for pears we have identified several common challenges to irrigation in pears. Lack of sufficient irrigation; uneven pressure and distribution due to hills; irregular water distribution across the block due to old, inappropriate or malfunctioning equipment; sandy soils with low water holding capacity; heavy soils with limited drainage; insufficient or excess watering due to inability to time water applications; and/or system inefficiencies can all limit growers ability to achieve optimum irrigation. The following case studies highlight common problems and the results of irrigation upgrades designed to address these challenges.

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Caudle Irrigation Efficiency Case Study 1

Long Irrigation Efficiency Case Study 2

CASE STUDY 1 Caudle ORCHARD
Improving Irrigation Efficiency


Hot summers and cork spot in D’Anjous can be a significant challenge in Central Washington. Cork spot is responsible for an estimated $7 to $8 million dollarsi in losses to Anjou production every year. In 2017, cork spot accounted for approximately 33% of Anjou culls. Irrigation frequency and timing, as well as good calcium programs can affect tree growth, productivity and fruit quality in pearsii. Fruit size is also critical for high returns.

SITE CHALLENGES

• Run-off
• Small fruit
• Inability to conduct tractor work when sloping field stays wet.
• Lack of uniformity, variable weak trees

Figure 1 Standard system created run-off in order to maintain sufficient moisture at the top of the slope.

STANDARD SYSTEM

Impact sprinklers (Rainbird) on 36 foot by 36 foot spacing. Growers generally run 1 row at a time skipping a row as they go across the field and return taking 9 days to irrigate the five-acre field.

NEW SYSTEM

R10 micro sprinklers were installed every row on a 20 by 20 foot spacing in a five-acre field encompassing one half of the sloped field in spring 2018.

GROWER OBSERVATIONS

“Zero run off in the new system.”

“Leaf color was more uniform.”

“Before the quickest we could water was 9 days. Now if we want to we can water the whole block in 2 days (20 lines at a time).” = more flexibility “If we need to push water it is a lot easier.”

“Good to have less water more often.”

IMPACT ON WATER USE

Soil moisture record from 2019. The soil in the standard system tended to stay too wet.

IMPACT ON TREE STRESS

Tree water limitation is measured by using a pressure chamber to measure leaf water potential. Water within the plants moves through a network of cells (xylem) that act like pipes carrying water from the roots. When the soil dries and the roots cannot keep pace with evaporation from the leaves the water in the plant becomes under tension. Tension over 1.2 mpa is considered too high.

Water limitation measured by leaf water potential was lower in the upgraded block (0.79 to 1.13 mpa on July 17, 2018) compared to the standard block (0.81 to 1.7 mpa).

Tree water stress for 2018 (left) and 2019 (right).


 

 

 

 

 

 

 

 

 

IMPACT ON FRUIT QUALITY

In 2018 the packout for the upgraded block was 95.6% compared to 92.7% for the standard system resulting in 23 vs 22 packs per bin. In 2019 the packout for the upgraded block was 92.1% compared to 93.7% in the standard block. 20% of the culls in the standard block were due to small fruit, and 8% to cork in the standard block compared to 10% to small fruit and 14% cork in the upgraded block.

Fruit quality packs per bin

IMPACT ON FRUIT SIZE

In 2018 and 2019 fruit size was more uniform in the upgraded block compared to the block irrigated using the standard system.

The upgraded block had more large fruit which impacted returns. Returns were estimated using average by fruit size from the Washington State Tree Fruit Association for Sept 2019 and January 2018 (months fruit was packed). Using the average price per box per size class (90s:$22.48; 100:$19.37; 110:$18.21; 120-:$21.88) revenue per acre in the upgraded block was $17,703 compared to $17,011 for the standard system in 2018.   In 2019 assuming prices per box of 90s+:$29.7; 100: $27.2; 110:$25.5; 120+:$23 revenue per acre was $23,482 in the upgraded block compared to $21,248 in the standard.

Fruit size in 2018 (top) and 2019 (bottom).

Returns per acre based on block packs and fruit sizes from a 56 bin run. Assumes 40 bins per acre.


 

CASE STUDY 2 LONG ORCHARD
Improving Irrigation Efficiency


Hot summers and cork spot in D’Anjous can be a significant challenge in Central Washington. Cork spot is responsible for an estimated $7 to $8 million dollarsi in losses to Anjou production every year. In 2017, cork spot accounted for approximately 33% of Anjou culls. Irrigation frequency and timing, as well as good calcium programs can affect tree growth, productivity and fruit quality in pearsii. Improved irrigation systems can target water to the crops increasing water use efficiency.

SITE CHALLENGES

  • Severe cork.
  • Did not pick block in 2017 due to 80% cork.

Figure 1. Project site Long Orchard Flowery Divide Rd Cashmere WA.

Figure 2.  Cork is a challenge at this site.

STANDARD SYSTEM

Impact sprinklers (Rainbird and R2000) on 24 foot by 20 foot spacing. Grower generally runs irrigation weekly during the growing season using 12 to 24 hr sets.

Figure 3. Rainbird sprinklers (left) and R2000 sprinklers (right).

UPGRADE

Sentec soil moisture sensors were installed in April 2019. Irrigation in 2019 in the ‘upgrade’ block was done according to soil moisture needs rather than a standard schedule.

Figure 4. Sentec irrigation sensor installed April 2019.

IMPACT ON WATER USE

Figure 5. Soil moisture stayed above the full point (field capacity) for most of the season in the standard irrigated block compared to between refill and full in the block where Long irrigated according to soil moisture sensor readings.

 

IMPACT ON FRUIT QUALITY

Figure 6. Fruit quality information from commercial packout from 2019 fruit packed 12/31/2019.

iThis value was estimated using cull analysis and pack out data from packinghouses representing 33% of the pear industry

iiRaese et al. (1982).

Thank you to collaberators Larry and Renee Caudle, Brandon Long, Erica Bland, Aaron Hargrove, Bob Gix; Sandy Letzing, Cascadia Conservation District, Chet Walker, S&W Irrigation

Thank you to in-kind support from

Wilbur Ellis

ITC

Sentek

Thank you to funding from

Bonneville Environmental Foundation

 

 

 

Washington Fresh Pear Committee

 


 

Additional Information

 

Irrigation Sensors with Jac LeRoux – Improving Irrigation Efficiency in Pears Virtual Field Day

Cost Share Availability – Irrigation Efficiencies Virtual Field Day

Long Case Study Improving Irrigation Efficiency in Pears

Improving Irrigation Efficiency in Pears Caudle Case Study

 

Washington State University