Adding Clays to Pine barkPotting Substrates

Jim Owen, Stu Warren & Ted Bilderback

Department of Horticulture ScienceNorth Carolina State University

FERTILIZER

SUBSTRATE

IRRIGATION

ContainerContainer

Managing the Container System

Narrow border/filter strips are helpful, but not letting nutrients out of the pot saves money and protects watersheds

Amending Container Substrate With Clay

Amending Container Substrate With Clay24/48 4/20

EXPERIMENTAL SUBSTRAES

Treatment Substrate

8PB:1SAND Industry Standard

OD 5/20 LVM Pine Bark + 8% 5-20 mesh LVM

OD 4/20 RVM Pine Bark + 8% 4-20 mesh RVM

OD 24/48 LVM Pine Bark + 8% 24-48 mesh LVM

OD 24/48 RVM Pine Bark + 8% 24-48 mesh RVM

Root and Shoot Dry Weights

0

0.5

1

1.5

2

2.5

8PB:1SAND OD 5/20 LVM OD 4/20 RVM OD 24/48 LVM OD 24/48 RVM

Treatment

Volume (L)

Irrigation Water Consumed Leachate

A BC

C

BBC

C

A

CB

B

AB

BC CD D

Irrigation Partition

Irrigation water applied, plant use, water leached (L) over 112 days to maintain a 0.20 leaching fraction for Cotoneaster in pine bark substrates amended with 8% clay

Water Applied Plant Use (Evapotranspiration)

Leached

Cumulative Irrigation Applied

Cumulative amount of water (L) applied to maintain a 0.2 leaching fraction on Cotoneaster grown in pine bark substrates amended with clay.

Cumulative Phosphorus Loss

Cumulative amount of phosphorus lost over 112 days from 3.7 gal containers pine bark substrates amended with clay to grow Cotoneaster while maintaining a 0.2 leaching fraction.

Total phosphorous leached (mg) per container over 112 days to maintain a 0.20 leaching fraction while growing Cotoneaster spp. In pine bark substrates amended with 8% clay.

Cumulative Phosphorus Loss

Cumulative Ammonium Loss

Cumulative amount of ammonium lost over 112 days from 3.7 gal containers pine bark substrates amended with clay to grow Cotoneaster while maintaining a 0.2 leaching fraction.

Significance to the Industry

• 100,000-200,000 gallons of WATER / A bed space– Significant Drought & Water Conservation Impacts

• 67% less Phosphate leached from containers– Watershed protection

• Equivalent Growth to Pine bark:Sand

Adding Clay to pine bark potting mixes may help keep the Monsters out of irrigation supplies and watershed protection.