Water Use of Southern Highbush Blueberry

Jeff Williamson Horticultural Sciences Department

IFAS, University of Florida

Pine Bark Culture

Pine Bark Culture• Bark beds are

currently one of the common methods for growing SHB.

• Pine bark increases organic matter, decreases soil pH, maintains N in NH4 form.

Before planting

Newly planted blueberry field on pine bark beds in Florida

Newer system – bark incorporated into soil with ground cloth and drip irrigation

Bark beds Bark incorporated into soil

Incorporated bark with ground clothPine bark increases organic matter, decreases soil pH, maintains N in NH4 form,

Examples of SHB production systems

While overhead irrigation is still needed for freeze protection, most new plantings are low-volume, usually drip

or drip with ground cover.

Excavated Blueberry Plant Root system was only a few inches deep

The bark bed and root system was easily separated from soil with very few roots located in the underlying soil

Soil depth (inches)

Soil treatment Percent of total roots

0 to 3.5 Bark bed 44

Bark incorporated 46

4 to 7.0 Bark bed 37

Bark incorporated 45

7.5 to 10.5 Bark bed 19

Bark incorporated 8

Blueberry roots at three soil depths for two soil treatments

Plant water potential during the fruit ripening period - 2010

OBJECTIVES• The objective of this

study was to evaluate plant drought stress during the final stages of fruit development of blueberry grown in several soil management systems without irrigation.

• Predawn and solar noon plant water potential of ‘Emerald’ SHB was measured with a pressure chamber during a dry period of fruit development and no irrigation was applied.

MATERIALS AND METHODS

5/10 5/11 5/12 5/13 5/14 5/15 5/16-800

-600

-400

-200

0Drought - Predawn 2010

Incor.+Mulch.

Bed

Incorpor.

Soil

Date

kilo

pasc

als (

kPa) b

b

a

b bb

a

b

ab

b

a

ab

Irrigation was shut off

5/10 5/11 5/12 5/13 5/14 5/15 5/16-2000

-1800

-1600

-1400

-1200

-1000

Drought - Solar Noon + 2 hours 2010

Incor.+Mulch.

Bed

Incorpor.

Soil

Date

kilo

pasc

als (

kPa)

bb

a

b

ab

b

aab

bb

a

b bb

a

bbb

a

b

abb

a

ab

Irrigation was shut off

Preparing holes for lysimeters

Bark or soil/bark mixture added

Transplanting blueberry plant

Plant positioned above lysimeter December, 2009

June, 2011

December, 2011

Treatment

June 2010

Aug 2010

June 2011

After pruning

Dec. 2011

Dec 2012

Soil

B 2.36 1.64 3.73 2.03 2.45 3.52

B+S 2.03 1.85 3.08 2.05 2.35 3.57

Irr. freq.

1x/day 2.11 1.64 3.26 2.05 2.32 3.32

2x/day 2.27 1.86 3.55 2.03 2.48 3.77

Plant canopy volume (yd3)

Treatment 2011 2012

Soil

Bark 17.7 11.3

B+S 15.3 10.2

Irrigation

Once/day 16.6 8.9

Twice/day 16.6 12.5

Berry yield (lbs./plant) in 2011 and 2012

Jan* Feb* Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

0.5

1

1.5

2

2.5

Gal

lons

.pla

nt-1

.day

-1

Monthly means + SE of daily water use of mature ‘Emerald’ southern highbush blueberry plants averaged across treatments and years from April, 2010 to Sept. 2012. *Means for one year due to complications from overhead irrigation for freeze protection.

Daily plant water use of mature ‘Emerald’ blueberry plants by month averaged across treatments and years.

16-Apr 1-May 16-May 31-May 15-Jun 30-Jun 15-Jul 30-Jul0

0.5

1

1.5

2

2.5

Mean

Gal

lons

/pla

nt/d

ay

Pruned

Harvest

Jan* Feb* Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Overall means

Cro

p co

effic

ient

(Kc)

Monthly Kc means + SE for mature ‘Emerald’ southern highbush blueberry plants averaged across treatments and years from April, 2010 through September, 2012. Kc values are based on 3 ft. in-row by 10 ft. between row plant spacing (1452 plants/a.). *Mean for one year due to complications from overhead irrigation for freeze protection. Mean annual Kc = 0.65.

Monthly crop coefficients (Kc) for mature ‘Emerald’ blueberry plants Averaged across treatments and years from April, 2010 to Sept. 2012

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

gal/day 625 1452 2091 2265 2875 2643 2846 3151 2686 1888 1496 842

gal/month 19,375

40,656

64,821

67,950

89,125

79,290 88,226

97,681

80,580 58,528

44,880

26,102

Estimated per acre water use of mature ‘Emerald’ blueberry plants at 3’ by 10’ spacing (1452 plants/a)

Yearly water use = 757,214 gal. per acre or 27.88 acre-inches in the planted field. Assuming 4 ft. wide beds with 10 ft. row spacing≈ 69.71 inches in the row bed (area with root system).

Conclusions• Southern highbush blueberry plants are shallow-rooted

and drought susceptible. 80+% of roots were in the top 7 inches of soil.

• Frequent, light, irrigations are needed during the growing season.

• Bark, applied as either a bed or incorporated into the soil reduced drought stress.

• Regardless of soil treatment, plant water stress increased significantly after 3 days without irrigation.

Conclusions• Monthly averages for daily plant water use of mature ‘Emerald’ blueberry plants

ranged from about 0.6 gal/day (winter) to over 2 gallons/day (mid to late summer).

• Water demands increased rapidly in the spring (March) and peak water demands occurred during the late stages of fruit development (late April and May) and in mid to late summer (July – Sept.). Maximum monthly averages

≈ 2.0 – 2.25 gal./plant/day. • Monthly averages do not reflect the day to day variation in water demand which

is heavily influenced by weather and can be considerably greater or less than the monthly averages.

• Summer pruning significantly reduced plant water use for 3 to 4 weeks until plant canopies were re-established.

• Kc values can be used with reference ET to determine general water requirements. Soil moisture monitoring devices along with a knowledge of rooting depth, distribution, and soil water holding characteristics are useful when developing irrigation schedules.

Acknowledgements

Southwest Florida Water Management District Florida Blueberry Growers Association

Luis Mejia, graduate student, Horticultural Sciences Department, IFAS, UF Bradley Ferguson, graduate student, Horticultural Sciences Department, IFAS, UF

Paul Miller, former biologist, Horticultural Sciences Department, IFAS, UFEric Ostmark, biologist, Horticultural Sciences Department, IFAS, UF

Thank You!

Questions?