ēKo Pro Series User’s Manual
Page
95
Doc. # 7430-0710-01 Rev. C
Heavier clay soils store much more water than sandy soils. But even more important, the plant
cannot readily extract all of this stored moisture, only the “available” portion. The general rule of
thumb is that irrigation should commence before reaching 50% of the “available” portion being
depleted.
Figure 8-1
shows the soil moisture tension at the 50% level of available moisture.
Assuming a medium type soil, this 50% level would occur at about 60-70 centibars. While
determination of the proper irrigation point is largely dependent on soil type, also consider the
crop and irrigation method. Sensitive crops may require irrigation sooner; less sensitive crops
may not need water until later. Surface irrigation may allow you to apply water much more
rapidly than a drip system, thus you need to consider how quickly your system can react in order
t o a v o i d m o i s t u r e s t r e s s ( S e e
F i g u r e 8 - 2 ) .
Figure 8-2. Graph showing when to irrigate
8.1.6 Determining “How Much” To Irrigate
Record keeping and experience with the crop, soils and irrigation method are essential with any
good management system. With Watermark sensors properly placed in both the top (e.g. 12”)
and bottom (e.g. 24”) of the crop root system, readings will tell whether it is the shallow or deep
moisture which is depleted. If the shallow reading is 60 and the deep reading is 10, then apply
enough water to rewet the top 12”. If the readings are reversed, with 40 for the shallow and 60
for the deep, twice as much water may be needed.
8.2 eS1201 Ambient Temperature and Humidity Sensor
The eS1201 Temperature/Humidity sensor measures relative humidity and air temperature.
These readings are also used to calculate dew point. The sensor enclosure protects the sensor
from mechanical damage, and a membrane filter protects the sensor elements from dust, dirt, and
water spray. The housing includes a cable strain relief.
