FAO-56 Irrigation in Binette: Understanding the Guidance

A tool to monitor irrigation for your plants

Binette combines information about your plants with weather data to provide irrigation advice. The App Store and Google Play listings describe this monitoring and the use of the FAO-56 water balance model.

The benefit is having a reference that accounts for crop development and recorded inputs. The displayed water reserve remains an estimate: Binette does not measure your soil’s moisture with a sensor. Compare this reference with your observations in the garden.

From weather to watering amount: four distinct concepts

ETo represents the reference climatic demand. Binette retrieves daily ETo data provided by Open-Meteo, which corresponds to a well-watered grass surface and is based on the FAO Penman-Monteith method. This is not yet the requirement for your vegetable. Provider’s definition

ETc estimates crop evapotranspiration. The basic relationship is ETc = ETo × Kc, where Kc is a coefficient linked to the crop and its growth stage. In the manual, this relationship describes standard conditions without water limitations. Binette’s engine uses crop parameters and an estimated growth stage, adding its own adaptations. FAO, equation 56 and conditions

The balance tracks an estimated root zone reserve. The model updates a water deficit based on evapotranspiration, the rainfall taken into account and recorded irrigation. The capacity of this reserve depends on assumptions about the soil and roots. A reserve percentage in the app describes the state of this calculated reservoir, not a measured soil moisture percentage. The FAO manual also distinguishes between calculating ETc and the water balance needed to decide on irrigation. FAO, water balance

The recommended dose reflects a model decision. It depends on the calculated deficit, the triggering threshold, and Binette’s quantity rules. It may be capped and rounded. It is therefore not simply the day’s ETc to replace, nor a measure of the volume your plants’ roots will absorb.

To explore these distinctions further, consult our explanation of the FAO-56 method.

Key data in Binette’s calculations

The calculation uses the selected crop, its monitoring dates, weather data for the plot, and the irrigation you have recorded. Mulching events may also modify the model’s assumptions. Record your irrigation to ensure it is included in the monitoring.

Weather data comes from a service, without a weather station installed in your garden. Open-Meteo specifies that the grid cell used may be a few kilometres from the requested coordinates. Localised showers or conditions under cover may therefore differ from the data used. Open-Meteo, coordinates and variables

Soil type, root depth, and initial soil moisture are not all known through measurement. The engine then uses assumptions or fallback values. For a planting entered in the app after it was planted, the model may assume it was properly watered before monitoring began: it does not reconstruct your actual actions.

How to use a recommendation

1. Check the plant and its dates. An error in the crop or planting date can alter the estimated growth stage and water reserve.
2. Read the unit alongside the quantity. A dose in L/plant applies to each plant; a dose in L/m² applies to an area. These values are not directly interchangeable. A depth of 1 mm over 1 m² equals 1 litre. FAO, units
3. Compare the advice with field conditions. Examine the soil in the root zone and account for actual rainfall received. The practical irrigation guide details this observation.
4. Record the irrigation applied. Enter the date and quantity in the recommended unit. An unrecorded irrigation event can make the water balance less representative of your garden.

What the FAO-56 reference does not guarantee

Crop coefficients, the effect of mulching, rainfall infiltration, and volume conversions require modelling choices. The manual itself provides for adaptations to practices and small areas. Citing FAO-56 therefore does not imply FAO endorsement of Binette or full validation of each dose for the vegetable garden. FAO, adaptations and small areas

Depending on the app workflow and the data available, some weather gaps may be filled using local climate normals. These are seasonal estimates, not the actual rainfall received. If data remains insufficient, the maintenance irrigation recommendation may be unavailable; however, a separate establishment recommendation may still be available. The absence of a recommendation does not, in itself, prove that the soil contains sufficient water.

Use this guidance to structure your observations, then adjust irrigation based on soil moisture and plant condition.