Don McMoranAgriculture and Natural Resources

Extension EducatorWSU Skagit County Extension

Irrigation to combat silver scurf in Potatoes

Skagit Valley Agriculture

• 113,821 acres farmable– Small plots of land

• Climate– Maritime– 32 inches of rainfall

• Major crops– Potatoes– Seed Crops– Small Fruit Crops– Flower bulbs and nursery

Acreage

• 1968- 537 acres of potatoes in Skagit County.

• 2007- 13,250 acres of potatoes in Skagit County

Irrigation need

Crop Water Use in Northwestern Washington

0

1

2

3

4

5

6

7

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Rai

n a

nd

ET

(in

ches

) Potato Crop Water Use

Precipitation

Irrigation of Potatoes

• Irrigation has increased from 0 to ~15,000 acres in Skagit County alone.

• Reel Big Gun

Big Gun Evaluation- Farmer A

Farmer B

Farmer C

Farmer D

du rep1 du rep 2 avg du

Farmer A 0.143628 0.035256 0.089442

Farmer B 0.191481 0.135309 0.163395

Farmer C 0.776256 0.728672 0.752464

Farmer D 0.802552 0.802552

Average 0.478479 0.381968 0.430224

Boom Type Carts

Energy Comparisons

Big-gun Boom Big-gun BoomFuel Cost/Season 2,585$ 723$ 9,435$ 2,462$

Cost/acre-in 2.59$ 1.02$ 9.44$ 3.49$

Electric Diesel

WSU NWREC – Drip Irrigation in Potatoes Trial- Incubating Silver Scurf in Storage

Silver Scurf seed ranking

30 tuber analysis• Silver scurf severity 1.4%• Silver Scurf Incidence 70%• Common scab

Cultivating and Chemigation- 45 DAP

Irrigation Scheduler mobile

Great looking trial

Harvest

WSU NWREC Yield

Non-irrigated Vertisan 45 DAP Vertisan 60 DAP Quadris 45 DAP Quadris 60 DAP Reel Big Gun16

16.5

17

17.5

18

18.5

19

19.5

20

20.5

Avera

ge y

ield

per

plo

t (t

ons)

Washing and preparation for Storage

WSU NWREC results – size categories

Non-ir-rigated

Vertisan 45 DAP

Vertisan 60 DAP

Quadris 45 DAP

Quadris 60 DAP

Reel Big Gun0

5000

10000

15000

20000

25000

30000

A'sB'sC'sNo. 2's

Avera

ge y

ield

per

plo

t

Evaluation

Silver Scurf

Non-irrigated Vertisan 45 DAP Vertisan 60 DAP Quadris 45 DAP Quadris 60 DAP Reel Big Gun0

2

4

6

8

10

12

14

16

Silver

scurf

severi

ty (

% p

ota

to a

ffecte

d)

Conclusion

• Farmers in Skagit County can improve irrigation on big gun irrigation by trying to cover less ground per set and irrigating at night, after daytime winds die down.

• Boom type irrigators do a better job of irrigation and use less energy but are not as convenient to use.

• Drip irrigation uses the least amount of energy and has the highest start up costs. Adding fertigation, chemigation and other practices will be required to encourage farmers to make the switch to energy efficient irrigation practices in western Washington.

Special Thanks

• Washington State Potato Commission• Washington State Department of Agriculture• Western Washington Agriculture Association• Clear Water Supply• Skagit Farmers Supply• WSU NWREC• Viva Farms• Skagit County

Questions/Comments

Don McMoran Agriculture and Natural Resources Extension

Faculty County Director

WSU Skagit County Extension 11768 Westar Lane, Suite A

Burlington, WA (360) 757-7136

dmcmoran@wsu.edu