Delmhorst Instrument KS-D1 - Manual (Page 9)

8
HOW TO USE IRRIGATION
CHARTS
Irrigation charts are provided with each instrument.
Additional charts are available on order. Regular use
of the charts helps in planning irrigation.
All readings should be recorded using a line of different
identity to indicate the readings of each particular block.
As readings are made and recorded, a curve of soil moisture
changes will result. By extending the slope of the lines, it
will be possible to see well in advance when the soil moisture
will reach the level at which irrigation is required. In
addition, the chart will also indicate how much water is
needed to restore the moisture to field capacity.
For example, assume that irrigation should be applied when
a block planted at 18” and yielding a reading of 63, indicates
roughly 1.5 in terms of bars tension. Soon after irrigation,
this block may read 96; a few days later (without irrigation
or rainfall) it may read 88; the next day 80. If these three
readings are plotted on the irrigation chart, and a line
extended through them, it is possible to project the time
at which the 1.5 bars tension level (or irrigation point) will
be reached; in this case it would be less than three days.
NOTE: The gypsum blocks must be soaked in water for
1 hour and allowed to dry as soon as received.
This wetting-drying cycle will improve their
uniformity. Before planting the blocks, they
should be soaked again for 2 to 3 minutes to
improve contact with the soil.
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