Environmental & Climate

Humidity Deficit & Crop Steering

Humidity deficit in g/kg (the Dutch grower standard) with vegetative/generative/exhaustion steering and air-exchange limits.

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What it does

A humidity deficit and crop steering calculator that reports humidity deficit (HD) in grams of water per kilogram of dry air. It also shows HD in g/m³ and VPD for cross-reference.

When to use it

Use it to classify current conditions as generative, neutral, vegetative or exhaustion and to find a maximum HD for a given air-exchange rate. The thresholds are adapted from Godfried Dol (2020) and are meant as a starting point to tune to your crop and stage.

How it calculates

Saturation vapor pressure from the Magnus-Tetens equation: es = 0.6108·exp(17.27·T ÷ (T + 237.3))
Air pressure from elevation: 101.325 × (1 − 2.25577e-5 × elevation)^5.2559
Humidity ratio (g/kg) = 1000 × 0.62198 × e ÷ (P − e). HD = saturation humidity ratio − actual humidity ratio.
Steering bands: generative ≤ 3, neutral 3 to 5, vegetative 5 to 8, exhaustion > 8 g/kg. Maximum HD = min(20, 40 ÷ air exchanges per hour).

What you enter

Air temperature(°C)
Relative humidity(%)
Elevation(m)
Air exchanges(per hour)

What you get

Humidity Deficit(g/kg)
Steering class
Recommended maximum HD(g/kg)
Humidity deficit, volumetric(g/m³)
Vapor pressure deficit(kPa)
Actual moisture (GH) (g/kg)
Saturation (AH = GH + HD) (g/kg)

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