Re: Volumetric vs Gravimetric

[Len Ornstein]

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Jason:

On the other hand, what the crop cares about is water potential, not 
soil water content, so the low sensitivity of a tensiometer to large 
water content changes near field capacity poses no threat to the 
crop. But when the water potential starts to dive, even if the change 
in water content is small, you better start to irrigate!

Len Ornstein Ph. D.

>Dear Tom:
>
>From water release curve you will find that in low soil moisture region, a
>small change in volumetric soil water content would lead to a large change
>in soil water potential, and vice versa. In other words, the sensitivity is
>high for the instrument that measures water potential in low soil moisture
>region, however in high moisture region, their sensitivity is much lower
>than those measuring water content.
>
>Jason Sun Ph.D.
>
>ESI Environmental Sensors Inc
>100-4243 Glanford Avenue
>Victoria, BC
>Canada, V8Z 4B9
>
>Tel: 250-479-6588
>Fax: 250-479-1412
>e-mail: jason@esica.com