Beyond Skogholm Cotoneaster: Performance of Hydrangea, Azalea, Juniper and

Spirea in a clay amended substrate.

Jim Owen, Jr., Stuart L. Warren, Ted E. Bilderback, and Joseph P. Albano

NC STATE UNIVERSITY

The last three years…

Develop management practices and production systems to improve nutrient and

water use efficiency to minimize nutrient leaching/runoff

Our Objective

Finding the Balance

NUTRIENTS

ENVIRONM

ENT IRRIGATION

SUBSTRATE

ContainerContainer

Finding the Balance

NUTRIENTS

ENVIRONM

ENT IRRIGATION

SUBSTRATE

ContainerContainer

Our Approach

To engineer a pine bark-based soilless substrate to increase water and nutrient efficiency.

Industrial Mineral Aggregates

The last three years… Mineral aggregate particle size

Small (24/48 mesh)• ≥ 100,000 gal H2O growing acre-1 season-

Calcined 24-48

4 - 20

Pine bark

Sand

The last three years… Mineral aggregate particle size

Small (24/48 mesh)• ≥ 100,000 gal H2O growing acre-1 season-

Mineral temperature pre-treatmentCalcined clay

• P - 62% effluent decrease • NH4 ≈ 50% effluent decrease

Calcined 24-48

4 - 20

Pine bark

Sand

The last three years… Mineral aggregate particle size

Small (24/48 mesh)• ≥ 100,000 gal H2O growing acre-1 season-

Mineral temperature pre-treatmentCalcined clay

• P - 62% effluent decrease • NH4 ≈ 50% effluent decrease

Mineral amendment rate11% by vol.

Calcined 24-48

4 - 20

Pine bark

Sand

The last three years… Mineral aggregate particle size

Small (24/48 mesh)• ≥ 100,000 gal H2O growing acre-1 season-

Mineral temperature pre-treatmentCalcined clay

• P - 62% effluent decrease • NH4 ≈ 50% effluent decrease

Mineral amendment rate11% by vol.

Reduce P and water inputs by 50%

Calcined 24-48

4 - 20

Pine bark

Sand

The last three years… Mineral aggregate particle size

Small (24/48 mesh)• ≥ 100,000 gal H2O growing acre-1 season-

Mineral temperature pre-treatmentCalcined clay

• P - 62% effluent decrease • NH4 ≈ 50% effluent decrease

Mineral amendment rate11% by vol.

Reduce P and water inputs by 50%

Calcined 24-48

4 - 20

Pine bark

Sand

Equivalent or increased growth of Skogholm cotoneaster

Beyond Skogholm cotoneaster

Beyond Skogholm Cotoneaster

Randomized Complete Block Design Taxa (14 L containers)

Hydrangea macrophylla ‘Nikko Blue’Spiraea x Bumalda ‘Goldflame’Rhododendron (Carla hybrid) ‘Sunglow’Juniperus conferta ‘Blue Pacific’

Substrate (11% amendment rate)Clay: calcined 24/48Sand (8 pine bark:1 sand)

Beyond Skogholm Cotoneaster Cultural practices

17-5-10 six month CRFMicromax and dolomiteCyclically micro-irrigated – 0.2 LFGrown for 100 days

Data analysisRoot and shoot dry massSubstrate physical properties

StatisticsDry mass - AVOVASubstrate - MANOVA

• Wilks’ Lambda

Plant growth

0

2

4

6

8

10

12

14

Azalea Hydrangea Juniper Spirea

ClaySand

Ro

ot

dry

wei

gh

t (g

)

Taxa

ABNS

NS

P ≤ 0.10

NS

Plant growth

0

10

20

30

40

50

60

70

80

Azalea Hydrangea Juniper Spirea

ClaySand

Sh

oo

t d

ry w

eig

ht

(g)

Taxa

AB

BA

NS

NS

P ≤ 0.10

Plant growth

Clay Sand

Clay Sand

100+ days after initiation

Sunglow azalea

Nikko blue hydrangea

Substrate Physical Properties

AB0

20

40

60

80

100

Clay Sand

Per

cent

vol

um

e

Pine bark amendment

80% total porosity83% total porosity

H0: clay = sandP = 0.02

Substrate Physical Properties

AB0

20

40

60

80

100

Clay Sand

Pe

rcen

t vo

lum

e

Pine bark amendment

80% total porosity83% total porosity

24% air space

59% container capacity

24% air space

56% container capacity

H0: clay = sandP = 0.02

Substrate Physical Properties

AB0

10

20

30

40

50

60

Clay Sand

Per

cent

vol

um

e

Pine bark amendment

56% CC59% CC

H0: clay = sandP = 0.02

Substrate Physical Properties

AB0

10

20

30

40

50

60

Clay Sand

Pe

rcen

t vo

lum

e

Pine bark amendment

56% CC59% CC

35% available

water

24%unavailable

water

31%available

water

25%unavailable

water

H0: clay = sandP = 0.02

Substrate Physical Properties

AB0

10

20

30

40

50

60

Clay Sand

Pe

rcen

t vo

lum

e

Pine bark amendment

56% CC59% CC

35% available

water

24%unavailable

water

31%available

water

25%unavailable

water

≈ ½ L per 5 gal container

H0: clay = sandP = 0.02

Industry SignificanceGrowth effect of clay amendment is

taxa specific.

Thanks….

FNRI

Columbia River Gorge, OR

Particle size distribution

sand clay

> 6.3mm2 mm0.71 mm0.5 mm0.25 mm0.106 mmPan

Sieve size

Pine bark amendment (11% by vol.)

58%40%less than 0.5 mm

42%less than 0.5 mm

greater than 0.5 mm

60%greater than

0.5 mm

Additional Research dogwood – Cornus florida ‘Cloud Nine’ sweetbay magnolia – Magnolia virginiana willow oak – Quercus phellos sourwood – Oxydendrum arboreum

Water and nutrient (N & P) budgets

Particle size distribution

sand clay

> 6.3mm2 mm0.71 mm0.5 mm0.25 mm0.106 mmPan

Sieve size

Pine bark amendment (11% by vol.)