6 of 12
METER READING GUIDELINES
Soil Type No Irrigation Irrigation Danger Zone
Required to be Applied Insufficient
Soil Moisture
Fine 80-100 60-80 Below 60
Medium 88-100 70-88 Below 70
Coarse 90-100 80-90 Below 80
The above guidelines are determined by the fact that different soils have a
different capacity to hold and release moisture to the plants.
Fine textured ones (clay soils) store a larger amount of water, but they also hold
a larger amount of residual water than do coarse textured (sandy soils). In the
overall picture, clay soils hold more available moisture than sandy soils. Loam
and sandy loam-type soils fall in between.
For these reasons, irrigation in sandy loam is normally applied at higher meter
readings than in clay loam soils, since available moisture can be used up more
rapidly by the plants and dry climatic conditions in sandy loam.
There is an optimum range of moisture for optimum plant growth. Over irrigation,
which tend to prevent adequate root aeration and possibly lead to root rot, can be
prevented with proper irrigation scheduling. This entails recording and observing
soil moisture meter readings, recording of rainfall, knowledge of the soil and of
the crops involved.
A grower with a good understanding of soil moisture meter readings and of all the
other factors playing a role in plant growth will, in a short time, be able to
establish his own guidelines for optimum irrigation scheduling in relation to his
soil(s), crop and climate.
