Irrigation—Principles & Practices
Part 1 – 236 | Unit 1.5
the average ETo rate then we can easily determine
an approximate weekly rate of irrigation for most
crops —when in full canopy—typically grown in
small-scale diverse systems.
For example if our average ETo is about .15
inches per day then we would need to apply roughly
1 inch per week of irrigation water to a crop in full
canopy.
ETo .15” per day times 7 days per week = 1.05”
There are many other considerations to take into
account when making irrigation decisions, includ-
ing soil type, crop type, time of harvest, and irriga-
tion system application uniformity, but the “water
budget” method of irrigation rate calculation does,
when used properly, provide a basis for sound deci-
sion making in small-scale farms and garden—es-
pecially when used in conjunction with the “feel”
method.
Supplement 2: Overview of the “Water Budget Approach”