Irrigation Scheduling for Citrus—User's Guide for IScitrus
IS002 Quick Answer
R. L. Snyder, Biometeorology Specialist
Department of Land, Air and Water Resources
University of California
Davis, CA 95616, USA
N.V. O'Connell, Farm Advisor
UCCE Tulare County
Ag Bldg Co Civic Ctr
Visalia, CA 93291, USA
Copyright - Regents of the University of
California
Created
- July 2000
Last
Revision –July 2001
Introduction
IScitrus is an Excel program that helps
users to determine an irrigation schedule based on evapotranspiration. To
obtain a copy of program, click on IScitrus. There are two worksheets and four charts in
the program. Each of the worksheets and charts are opened by clicking on a
worksheet or chart name at the bottom, left-hand part of the screen. The
irrigation schedule is computed in the worksheet named "Schedule".
Historical ETo and rainfall data are entered into the
directory "HETo". The first chart has the
name "NA" for a plot of the cumulative ETc
and net applications during the season. The second chart has the name
"ET" and it shows a plot of the daily ETo
and ETc rates during the season. The third chart
"CET" shows the cumulative ETo and ETc plots for the years. The fourth chart "Kc" is
a plot of the annual Kc curve.
Historical Data
When the program is started, open the HETo worksheet.
Then enter the 12 monthly average ETo values in inches
per day in the appropriate cells in column B. These data can be found in the ETo zone map for
Entering Data
DU is an Excel program for
calculating distribution uniformity and the mean application rate of drip and
micro-sprinkler irrigation systems. The companion program ‘DUm’ is the metric version of the same program. To
use the DU or DUm
programs, you must collect some data from the irrigation system that you are
trying to evaluate. Then enter the following information into the ‘Input’
worksheet. In cells B2 and B3, enter a block number and the date for
record keeping. The flow rates from the emitters can be made
in ounces or in milliliters for a pre-selected rate of time. Enter the measurement
time interval in seconds into cell G2. Based on experience, a measurement
time interval of 15 seconds works well for typical micro-sprinklers used for
citrus. In the cell below, enter either "O" for measurements in
ounces or "M" for measurements in milliliters (cell G3). In the
cell G3, enter the number of emitters per acre for the DU program. Enter
the emitters per hectare in the DUm program.
Then enter the measured flow rates into the table in cells B7 through
P26. Row (hose) numbers are listed across the top and emitter numbers are
given along the left-hand side. Entering the data in the correct order
helps to identify problem emitters in your system. A sample entry table
for a system with 121 emitters per acre (299 emitters per hectare) is shown
below. Sample flow rates in milliliters per 15 seconds were entered for nine
emitters on each of six hoses (rows). The flow rate in milliliters
per 15 seconds would also be entered into the DUm
(metric) program. Note again that the flow rate can also be input in
ounces per 15 seconds if ‘O’ rather than ‘M’ is input for the volume
measurement in the DU program.
Results
The worksheet named
"Output" contains the results of the calculations. The emitter
flow rates, converted to gallons per hour per emitter, are shown in the main
body of the sample table below. The total number of samples, the number
of low quarter samples, the overall mean flow rate (gph
per emitter), and the mean of the low quarter are shown above the sample flow
rate data for each row (hose of emitters). The results for all of
the emitters, are shown in column A. Above the
flow rate data, the distribution uniformity percentage (DU%)
and mean application rates in inches per hour and gpm
per acre are provided. The overall mean DU% and application rates are
given in column A.
Collecting Flow Data
The schematic below shows the
laterals and hoses for a typical system. Flow measurements should be
taken from a minimum of about 20 emitters. Be sure to measure the flow
from emitters from hoses at both the upper and lower end of the lateral.
Take one measurement near the riser and one near the end of each hose.
Collect at least two measurements equally spaced between the riser and the end.
