Peterphrastus

The ”Schedule” dialog provides a summary of the evapotranspiration calculations required to determine landscape irrigation needs. To see a definition of the parameters, click on the heading text. The calculations involved are beyond the scope of this document. However, a brief explanation of some parameters is warranted. The schedule is color coded for each growth stage. A code legend is at the lower left of the dialog.

• ETo is the daily reference crop evapotranspiration calculated from the most accurate weather data available to RHS.
• P-RO is daily precipitation minus runoff. This is rain corrected for surface runoff and canopy effect. If no rain gauge is attached, it is not possible to calculate runoff as this is a realtime event. If rain data is collected from a weather service, P-RO could be high.>
• E is daily evaporation from the soil surface.
• ETc is daily crop evapotranspiration. This is ETo multiplied by Kc. Kc is calculated from the basal species coefficient, density coefficient and microclimate coefficient.
• RAW is readily available soil water based on the current root depth and corrected for management allowed deficiency.
• DP is deep percolation. If the amount of irrigation and rain exceeds the soil water holding capacity, it will percolate below the root zone.
• Dec is corrected ending depletion. When this amount exceeds RAW, an irrigation event is signaled.
• NIN is net irrigation needed as of midnight.

There are a number of buttons on the ”Schedule’ dialog. They perform the following functions. Care should be exercised in using some buttons.

• Simulate generates a schedule with simulated P-RO events. The original schedule is not affected.
• Unlock allows days before today to be recalculated. This is useful if changes to soil or crop parameters have been made and it is desirable to reflect these changes from the startup date. The historical schedule will be replaced.
• Recalculate resets P-RO (precipitation minus runoff) and NIbd (net irrigation at beginning of day) to zero for days from today to the end of the schedule. This can be used to apply crop and soil parameter changes going forward while retaining past schedule values.
• Recalc all resets P-RO (precipitation minus runoff) and NIbd (net irrigation at beginning of day) to zero for all days.
• Reinit sets Dee (ending evaporation), Dec (ending soil depletion) and NIN (net irrigation needed) to zero for yesterday’s date. This can be useful if mechanical problems with equipment occurred or it is desirable to artificially restart the schedule while retaining historical data.
• Reset resets P-RO (precipitation minus runoff) and NIbd (net irrigation at beginning of day) to zero for all days.