Plant health – Campbell Scientific Sentek TriSCAN® Manual v 1.2a User Manual

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TriSCAN Manual Version 1.2a

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soil fertility is indicated at 30 cm depth than at all others. This is indicative of previous cropping history and
fertilizer applications.

Figure 6. Example of EC distribution uniformity in a potato field

Due to the specific nature of each site in terms of irrigation system, cultivation practice and fertilizer
application method, it is inappropriate to give prescriptive advice on tube placement. Placement should
however be representative and consistent. General guidelines, for commonly used systems, and principles
of sample site selection follow:

For sprinkler systems, it is preferable to use two access tubes per site, placing one into an area receiving
average precipitation and the other into an area of perceived need.

Under centre pivot irrigation,, two or more access tubes should be installed if the distribution uniformity tests
show significant variation between booms..

For high pressure rain guns, measure the water application pattern under different wind conditions to ensure
that you don’t pick an area of extremely low or high water application.

Installation of access tubes in drip irrigation crops needs consideration of the extent of the ‘wetting onion.’
Use at least two access tubes to monitor soil moisture of drip irrigated crops to measure the lateral spread of
water.

In furrow irrigated fields, avoid installing access tubes too close to the head ditch or where tail water from the
irrigation may back up the furrows and give unrepresentative readings. Consider also installing an access
tube in the middle of the field to measure the depth of irrigation there.

Plant health

Select a site next to an average sized, healthy plant representative of the irrigation management unit (macro
zone). Avoid:

•

Stunted or sick plants

•

Unusually large plants

•

Spots where plants are missing

General guidelines for key crops follow:

•

In field crop and vegetable production, ensure that the probe is inserted within the actively growing
root zone.

•

In orchards, use two access tubes to monitor the site. Place one access tube under the canopy of a
tree and another outside the canopy. Again take care to select a site that represents dynamic data
trends (root activity).

Crop: Potato
Irrigation: Centre Pivot
Water DU = 79.1%
Salinity DU = 86.9% (10cm),
85.4% (30cm), 91.2% (50cm).