From now on, MIYO calculates evapotranspiration and offers another option for irrigation control.

🌱💧 What is Evapotranspiration? 💧🌱

Evapotranspiration describes the water cycle in the soil in and out of the root zone, which in gardens includes approximately the top 20 cm of the soil layer. This cycle is determined by several processes. 🌍

👉 Precipitation: The most important source of water supply.
👉 Evaporation: The evaporation of water at the soil surface.
👉 Transpiration: The loss of water through the leaves of plants.
👉 Percolation (Infiltration): Water penetrates the soil and moves from the upper soil layers (root zone) to deeper layers. This is crucial for replenishing groundwater reservoirs. Too little infiltration due to soil compaction and sealing? Then precipitation flows off on the surface and is not available for plants or for refilling groundwater reservoirs.

The right balance of these processes is essential for healthy plant growth, stable ecosystems, and the fight against climate change.

Evaporation

Factors influencing evaporation (in parentheses the approximate share of the factor in total evaporation. Since the factors influence each other alternately, the exact share depends on the respective overall situation):

• 🌞 Sun intensity/cloudiness (~30–50%): strong sunlight increases evaporation.

• Wind speed (~20–30%): increases the release of water into the air.

• 💧 Humidity (~10–25%): dry air absorbs water more easily.

Transpiration in plants occurs through the open stomata (pores) of the leaves and serves several vital functions that go far beyond compensating for water loss:

• Cooling: heat energy is released

• Nutrient transport: Water conduction function through the negative pressure generated by transpiration. This allows dissolved minerals to move from the soil through the roots to the leaves.

• Stabilization of cell pressure, which is important for the stability of plants.

• Photosynthesis: water is released at the stomata, but CO2 is also absorbed.

Factors influencing transpiration:

The factors influencing transpiration are similar to those affecting evaporation, primarily sunlight intensity, temperature, wind, as well as air and soil moisture. Additionally, a very important factor is the plant species, as each plant is differently adapted to heat and dryness.

Heat-resistant plants generally have small, often thick or hairy leaves and deep roots. Examples include many herbs such as lavender, rosemary, sage, thyme, as well as yarrow and stonecrop. 

In contrast, many types of vegetables have high transpiration rates. For example, tomato, zucchini, pumpkin. Most types of lawn grass transpire a lot, but also hydrangeas with their many large leaves.

The MIYO calculation of evapotranspiration

The MIYO calculation of evapotranspiration is based on the Penman-Monteith model, which is the most important reference model worldwide. The calculation incorporates weather data from the internet, soil parameters recorded during garden setup, as well as the sensor measurement parameters (soil moisture and sunlight intensity).

What are typical evapotranspiration values

Typical evapotranspiration values in Central Europe in spring and autumn are between 1 and 2 mm per day. In midsummer, 8 mm/day is not unusual. 1 mm corresponds to 1 l/m², meaning the amount of water lost from a 500 m² garden ranges between 500 l and 4,000 l per day. If your irrigation does not adjust accordingly, both your plants and your wallet will suffer. 

A conventional irrigation controller is overwhelmed by this task and inevitably leads to constant over- and under-watering. The intelligent MIYO irrigation provides a solution by keeping an eye on evapotranspiration for you and always adjusting the watering to the current conditions. Curious? Also new now is the demo mode in the app. Simply download it from the app store (for iOS and Android) and get to know the smart MIYO features.