NCSU Horticulture Substrates Lab Hydration Index
 

Substrate and Treatments

  • 60% Peat: 30% Vermiculite: 10% Perlite
  • 0 WA: no wetting agent
  • 2 lb G: 2 pounds granular wetting agent per cubic yard
  • 5 oz L: 5 ounces of liquid wetting agent per cubic yard

Results

  • The control (no wetting agent) took 6 - 7 irrigations to wet to the levels of the wetting agent treatments
  • The wetting agent treatments absorbed similar amounts of water at the first and all subsequent irrigations
  • There was a slight difference between samples treated with granular vs liquid materials

Hydration Test

Hydration Index

Calculation: (Average of PourThru 1, 2, & 3) / PourThru 10

PourThru
0 WA
2 lb G
5 oz L

.

Water Retained for each PourThru
1
75
116
128
2
96
118
130
3
103
119
132
4
110
121
133
5
113
122
133
6
116
122
134
7
118
123
134
8
121
123
135
9
123
124
136
10
124
124
136
Index
0.73
0.95
0.96

Notes

  • Hydration Index (HI) provides a single number for wettability
  • HI compares initial wettability with the maximum water held by the sample
  • Most substrates with wetting agents have HI's > 0.90
  • An HI of 0.80 or higher indicates that the potting soil should hydrate sufficently

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