Irrigation 101 - Revisited

This is a correction to some mathematical errors in the Irrigation post of a year ago.  In some of the calculations I used gallons rather than inches.  And I did not adjust the figures for sandy soil.  So here are the corrected tables:


Duration of irrigation (in minutes) for plants in sandy soil

                       grass          perennial           shrub          tree    
sprinkler             18                 37                   73             116
rotor                   36                 72                 144            228
bubbler               0.3                0.6                  1.2            1.9
soaker hose         18                 36                   72            114
1/2" dripline       30                 60                  120           190
1/4" dripline       36                 72                  144           228

This table assumes there are enough sprinklers, bubblers, emitters, etc. to cover the area that needs to be watered.  If not, multiply the figure by the number of square feet each bubbler, emitter, etc. needs to cover.
For soil that is loam, multiple each figure by 1.5.
For soil that is clay, multiply each figure by 3.


Frequency of irrigation (times per month) for plants in sandy soil.

                        grass         perennial        shrub         tree

cold                  10.5               5.3                 3              1.5        
mild                  26.4             13.5                6.6           4.2
hot                    36                 18                  9              5.7

For soil that is loam, divide each figure by 1.5.
For soil that is clay, divide each figure by 3.

Note -- These tables are for plants that need normal amounts amounts of water (called "regular" in the Sunset Western Garden Book).  The frequency of watering will need to be adjusted for plants needing "little", "moderate", or "abundant" amounts of water.