How do plants absorb water?

Every plant is unique and has its individual water needs. These change with the weather, season, soil type, and location. Plants absorb water and nutrients through their roots, especially in the zone where most fine roots are located. In the garden, these fine roots are usually found at a soil depth of 10–60 cm (depending on the plant). Of course, there are plants that root many meters deep, but this is usually not relevant for gardens.

Why is the root zone important for irrigation?

• Water absorption: Plants absorb water through their fine roots
• Nutrient availability: Nutrients in the soil are only absorbed in dissolved form. Therefore, the root zone must be sufficiently moist so that nutrients can dissolve and be reached by the roots.
• Soil properties: The storage capacity, drainage, and air circulation in the root zone determine how much water is available to the plants before the soil becomes dry or waterlogging occurs.
• Plant growth: Dryness or waterlogging in the root zone can inhibit root growth and make the plant susceptible to stress. Balanced moisture is therefore essential.

At the root of a young Swiss chard plant, you can clearly see how quickly roots grow:

Soil consists predominantly (>90%) of mineral components of different grain sizes and a proportion of organic substances (<10%).

Mineral components and their grain sizes

The mineral components of the soil are divided according to their grain size:

Sand: Grain size: 0.063–2 mm

Silt: Grain size: 0.002–0.063 mm

Clay: Grain size: < 0.002 mm

In practice, almost only mixed forms occur, which are called loam. The classification is done using the soil triangle, which shows the mixing ratios. For example:

Sandy loam: 60 % sand, 30 % silt, 10 % clay

Clay loam: 35 % clay, 40 % silt, 25 % sand

1. Sandy Soils

Organic Material Content: 1–2 %

Description: Sandy soils have a low capacity to store organic material because they have a small surface area and poor nutrient retention. Organic substances decompose and leach out more quickly.

Water Retention:

Low fertility

Low water retention capacity, rapid water loss

Improvement needed by adding humus or compost

Plants often have access to water only for a short time

Suitable Irrigation: Frequent but small water applications to maintain surface moisture.

2. Silty Soils

Organic Material Content: 2–4 %

Description: Silty soils have a medium structure that allows moderate storage of organic material. They promote even decomposition of organic matter.

Characteristics:

Good water retention capacity

Medium fertility

Susceptible to erosion by wind and water, so mulch or organic cover layers are recommended

Suitable Irrigation: Even irrigation with moderate amounts

3. Loamy Soils

Organic Material Content: 3–6 %

Description: Loamy soils offer the best mix of water retention, nutrient availability, and decomposition rate. They promote the buildup and storage of humus.

Characteristics:

Suitable Irrigation: Medium-sized water applications at longer intervals. Flexible, generally tolerates both longer dry periods and a lot of water well.

4. Clay Soils

Organic Material Content: 2–5 %

Description: Clay soils store organic substances well due to their fine particles, but slow air exchange can inhibit decomposition, especially in waterlogged conditions.

Characteristics:

Suitable Irrigation: Longer, slow irrigation with small amounts of water to achieve even moistening.

5. Peat Soils (Special Case)

Organic Material Content: 30–90 %

Description: Peat soils consist mainly of organic material because decomposition is greatly slowed under water-saturated conditions.

Characteristics:

Very high water retention capacity

Low in nutrients because organic substances hardly decompose

Extremely low in oxygen, therefore mostly unsuitable for agriculture

Valuable CO2 storage

Two central terms in the soil water balance are field capacity and the wilting point.

1. Field capacity
   Field capacity describes the maximum amount of water the soil can store after rain without excess water draining away.
2. Wilting point
   The wilting point is the state when the soil contains so little water that plants can no longer absorb water and begin to wilt.

The range between field capacity and wilting point is available as water for plants and is called plant-available water.

Relationship between soil type and field capacity

The following overview table shows the field capacity, the wilting point, and the plant-available water (PAW) for different soil types. The values are averages as they depend on factors such as organic content, soil structure, and compaction:

Organic substances, such as dead plant material, roots, and microorganisms, are called humus. Humus is constantly decomposed by microorganisms in the soil and thus converted into plant nutrients.

• Humus improves water retention, soil structure, and nutrient availability.
• Organic substances contribute to the formation of macro- and micropores, which are important for water and air circulation.
• Soils with high humus content can store more plant-available water.

• Consider soil type: Sandy soils often require more frequent but smaller amounts of water, while clay soils tolerate larger, less frequent water applications. With MIYO, all irrigation parameters can be set based on specifications and individually adjusted to the garden's needs if necessary.
• Monitor evapotranspiration: MIYO calculates the evapotranspiration precisely for each irrigation zone based on measured and transmitted data. This way, the irrigation exactly compensates for water losses through evaporation and transpiration. You can find more information here.
• Optimize irrigation timing: Watering early in the morning before it gets hot reduces water loss through evaporation. The afternoon is also an option. Avoid watering in the evening or at night, as prolonged moisture on leaves can promote the growth of fungal diseases. In the MIYO app, you can adjust the times for each day with just a few clicks.
• Drip irrigation: This method delivers water directly to the plant roots and minimizes losses through evaporation.
• Mulching: reduces evaporation and ensures that water stays longer in the root zone.
• Avoid overwatering: Waterlogging causes severe and long-term damage to plants and soil and should therefore be avoided at all costs. The easiest way to do this is with a smart MIYO irrigation system. Irrigation controllers with fixed intervals should definitely be avoided, as they inevitably lead to constant over- or underwatering.
• Adjust irrigation intervals to the plant: Shallow-rooted crops benefit from more frequent watering. Deep-rooted plants need water less often but in larger amounts to moisten the deeper layers. These parameters can be easily adjusted to the plant's needs in the MIYO app.
• Measure soil moisture: Soil sensors or simple digging tests can help monitor moisture in the root zone and avoid overwatering or drought stress.
• Increase water holding capacity: Organic matter (e.g., humus) in the root zone improves water retention and increases the amount of plant-available water.

The water needs of your plants depend on their type, location, and weather and soil conditions. All these factors are taken into account by MIYO when irrigating your garden.

Here's how to proceed

• Divide your garden into irrigation zones. Areas with similar water needs can usually be grouped into one zone. Later changes and reassignments of Sensors and valves are easy to perform with MIYO.
• To save water, it is best to plant plants with similar water needs in one area. The Sensor should be placed at a representative spot in this area. Targeted water supply, e.g., drip irrigation, is more economical than irrigating large areas, e.g., with sprinklers. Irrigation should be designed so that the area is evenly supplied.
• MIYO can irrigate either purely time-controlled or with soil moisture measurement. Even when irrigating with soil moisture measurement by the Sensor, you can enter time windows during which irrigation can take place. In the irrigation settings, you can set the lower and upper moisture limits. To achieve natural fluctuations and save water, make sure to set the moisture limits far enough apart. Usually, irrigation is not needed every day.
• Consideration of rain and rain forecasts can be optionally set for both time-controlled and sensor-controlled zones. 
• You make adjustments to irrigation based on the water consumption of the plants in the irrigation settings of the zone in the MIYO app. There are no universal guidelines; the values must be determined individually for plants and garden. Besides the type of plants, location, sun orientation, wind exposure, type of planting, and soil condition of the garden should also be considered. The more drought-resistant a plant is, the lower the lower limit of soil moisture measured by the MIYO Sensor can be set. Thanks to the numerous adjustment options, the intelligent MIYO irrigation can be adapted equally well for flowers and vegetables as for lawns and trees.
• Use mulch: If you apply a layer of mulch around your plants, it helps retain soil moisture by reducing evaporation. Mulch also helps suppress weed growth, regulate soil temperature, and improve soil structure in the long term.

MIYO is the best guarantee for optimal water supply to your garden and for avoiding overwatering. Adjustments to the growth phases of the plants or observations of plant health are easily done on your phone.