Probe for Windows: Scheduling whole season

Predictions about soil moisture requirements for the remainder of the season area are calculated

The predictions are only done if 'season scheduling' is chosen on ProbeMenu/Update or ReadingsMenu/Scheduling.

ProbeMenu/Update allows the data to be saved to the database for reports or export to MS.Access.

Example

The calculations are done in 1-day increments.

The value of RZ1 is calculated from...

RZ1 = Previous_RZ1 + ApplicationRate + Rain - CropWaterUse (DWU)

RZ1 is the total amount of water (mm) in the active root zone.

Application Rate is the effective amount of irrigation applied (mm) per day.

Rain is the effective amount of rain (mm) in the day.

Crop Water Use is the amount of water used by the crop, per day.

Losses from through-drainage, surface run-off and evaporation are the differences between delivered and effective amounts.

If RZ1 after a rainfall is above the full point it is cut back to the full point; the excess is excluded in the calculation of total effective rain.

Non-drip sites

Daily application rate is zero.
If RZ1 falls to the lower limit an irrigation is assumed to take place.
Required effective amount = UPPERAMT - LOWERAMT.

Drip sites

Application rate is the daily effective delivered rate
Rate is re-calculated every 7 days (DRIPDAYS).
At the end of each 7 day period the amount required to reach the next 'Target' is calculated.
TargetAmount = ( UPPERAMT + LOWERAMT ) / 2
Required effective amount = CropWaterUse * 7 + RZ1 - TargetAmount.
Assumed that the amount will then be delivered on a daily basis.

Crop water use

Crop water use (DWU) = Evaluate(SiteDWUFormua) * K-Soil Correction

Site DWU Formula

Allows for variation as a function of date - dwu details
Can also include both ET and canopy terms e.g. blenheim.et * shiraz.ca
Can also be a function of soil moisture status relative to full/refill/pwp (but see k-Soil below).

K Soil Correction

Adjusts DWU depending on the current value of RZ1 relative to FULL and REFILL.

1 = FULL; 0 = REFILL; -0.1 = 10% of (FULL - REFILL) below refill.

Adjustment factor and constant assumed to be dependant on soil type, so the correction factors are saved in a 'KS' file.

e.g. the file SAND.KS (below)

    ------------------------
  Relative, Factor, Constant
       1.0,    3.0,        0
       0.0,    1.0,        0
      -0.1,    0.8,        0
      -0.2,    0.0,        1
    ------------------------

Will adjust the value of dwu depending on the value of soil moisture relative to FULL and REFILL...

RZ1 below..	and above..	Corrected DWU
	FULL	DWU = 3*DWU (through-drainage)
FULL	REFILL	DWU = DWU (normal)
REFILL	10% below REFILL	DWU = 0.8 * DWU (some stress)
10% below REFILL	20% below REFILL	DWU = 1 mm/day (high stress)

A KS file can also be used to allow for through-drainage when RZ1 is above FULL.

Lower and Upper limits

The Upper and Lower limits are the required maximum and minimum values of RZ1.

Allow for varying upper and lower limits to be entered as a function of date.
Values can be specified in either...
absolute mm relative to FULL or REFILL
or relative to FULL and REFILL (or PWP).

Rain

Predicted rainfall scenarios can be used.

GD Note: 'Scenarios' saved in PRWIN2.INI; rainfall data in 'RA' or weather file.

Rainfalls 'senarios' are in files, with date and amount in mm.
Actual weather station output files can be used.
A 'Low' scenario could be generated by analysing rainfall records for the area, over many seasons, and selecting (or generating) a 'low probability' year.
A 'minimum' amount can be specified.
Predictions for different rainfall scenarios are saved separately in table 'SCHEDULE'.

Total amounts required for whole season

The effective amount required at each irrigation is calculated as above

Totals for the season are calculated and saved in table SCHEDULE

The required delivered amount = EffectiveAmount * FACTOR4 (to allow for losses in system)

Total volume required (kl) is calculated from TotalDelivered * Wet Area

Wet Area = Area * ( RowSpace / WetWidth )

The calculated crop water use, corrected for K-Soil, is totalled and saved.

Fields in table SCHEDULE - available for GPT, SPT or RPT formulas.

Field	Description
SeasonID	Identifier for season (join to YEARS.ID)
SiteID	Identifier for site (join to SITES.SITE)
RainScenarioID	Identifier for rainfall scenario.
SEFFIRRI	Total mm that will be effective.
SDELIVIRRI	Total mm required to be delivered.
SNUMIRRIS	Total number of irrigations.
STOTALVOLUME	Total volume required in Kl (mm * WetArea).
SEFFRAIN	Total effective rain (delivered less wastage from over full point)
SDELIVRAIN	Total rain from scenario (less amounts below lower limit)
SNUMRAINS	Total number of rainfalls used in scenario.
STOTALDWU	Cumulative total crop daily water use.

MS Access can be used to generate summary reports across all farms in a region

Details about each individual gain (irrigation) is saved in table SCHDETAIL. These fields are not available in Prwin, but can be used in Access to re-create the season simulation.

Field	Description
SeasonID	Identifier for season.
SiteID	Identifier for site.
RainScenarioID	Identifier for rainfall scenario.
DATE	Date of gain
GAINTYPE	2=Irrigation' 3=Rain; 4= EndOfDripPeriod; 15=EndofSeason
EffectiveAmount	Effective gain (mm)
DeliverAmount	Amount that should be delivered (mm)
UpperAmount	Calculated value of Upper formula
LowerAmount	Calculated value of Lower formula
DWU	Calculated value of crop water use
KS	KSoil correction factor used
LowestRZ1	Value of RZ1 just before the gain
HighestRZ1	Value of RZ1 just after the gain

Predicting next irrigation

The next irrigation is calculated with various options

RDI Factor

Only used to correct the DWU used to predict the next irrigation, but not subsequent irrigations.

e.g. Amount required = DWU * Evaluate(RDIFactor) * 7.