Understanding water movement in soil for vineyard success

Bringing improved water-use efficiency to vineyards, drip irrigation has added a lot of value to the wine grape industry. As technology improves and our knowledge expands it will continue to do so. With increased pressure on agriculture to use fewer resources, the fundamental challenge remains: how can we maximise grape quality while using less water? The answer lies beneath our feet—understanding how water moves through soil is key to scheduling irrigation effectively and ensuring optimal vine performance.

Soil Insights

Each soil type has unique characteristics that affect water movement. Factors such as infiltrability, hydraulic conductivity, water retention, and porosity determine how water is absorbed, distributed, and stored in the soil profile. These factors impact the answer to the important question: What affects water distribution in soil?

• • Infiltrability is the rate at which water can penetrate the soil, or in other words, the ability of the soil to absorb water at the surface and allow it to move in the soil. If irrigation exceeds infiltration capacity, water spreads horizontally on the soil surface resulting in puddles or run-off and increasing evaporation losses and the risk of shallow root zones.
  • Hydraulic conductivity is the water’s potential to move in soil or how quickly water moves through soil. It is a measure of the soil’s ability to move water through its pores under a hydraulic gradient. This is influenced by the soil’s texture, structure and pore size. Furthermore, the wetter the soil, the more easily water flows; in dry conditions, water infiltration slows down significantly.
  • Water retention depends on soil texture—clay retains more moisture than sandy soils, which drain quickly.
  • Porosity affects oxygen availability in the root zone. While soil should retain moisture, excessive saturation displaces oxygen, limiting root respiration and nutrient uptake.

Saturated Circles

When crops are drip irrigated, the water is delivered in one spot, and we rely on the soil’s physical ability to distribute the water. A wetted bulb or saturated circle form under the dripper. Your soil’s physical characteristics and the delivery rate of the dripper will determine the dimensions of this circle.

Remember, roots require oxygen to grow and take up water and nutrients. It is therefore important that there is balance between the water and air that fills soil pores. As water infiltrates soil, it replaces air in the pores. In drip irrigation this creates a gradient between low and high oxygen levels in the soil. 

Balancing Water Distribution

Optimal irrigation demands understanding the soil, the irrigation system, the crop and local climatic conditions. “Efficient irrigation provides the tools for precise crop management. It’s about timely, need-based water delivery and integrating all influencing factors to manage the crop based on phenological stages for optimal production. A holistic approach is necessary where all data and impacting factors are integrated.

However, the reigning idea that drip irrigation must be ‘understood’ in order to manage it successfully places, draws skewed emphasis. It is about understanding how water moves in soil. This may be difficult to explain or learn theoretically, but often easy to illustrate. We must dig profile pits after active irrigation or do water distribution test before system planning, all the forces that affect water movement changes from theoretical concepts to some­thing you have seen in action. A lot happens in an orchard or field, the more you understand the effect water can have as tool for optimal production, the better you can use it.

Flow and infiltrability

Drippers with higher deliver rates displace more air faster, creating variation in the soil’s oxygen levels and leading to lower uptake of water. Drippers with lower delivery rates allow for better hydraulic conductivity without rapidly reducing the levels of oxygen in the root zone. An ideal point of balance between water and oxygen, at which plants will thrive, exists for each soil. When we irrigate, our aim is to manage the root-zone with precision in order to maintain the perfect soil-water-oxygen balance.

A low infiltrability rate combined with a high flow rate will lead to very wide horizontal distribution, but very shallow vertical distribution. This is often when you see ponding, high run-off and shallow root-zones. By lowering the delivery rate, distribution is more uniform with balanced horizontal and vertical water distribution and a more balanced oxygen level.

Lower flow rates make the necessary balance possible by achieving good infiltration on moist soils. The forces of gravity and capillary action become more equal and soil/ water/air ratios can be kept more constant throughout the wetted area.

To conclude our thoughts around flow rates, infiltrability rates and soil characteristics, here are three of the many lessons Team Netafim has learned through experience in orchards, vineyards and beyond:

• Higher delivery rates in sandy soils tend to create deep but narrow wetted zones, often leading to water loss beyond the root zone.
• Lower delivery rates promote better capillary action, allowing water to spread more evenly and ensuring balanced root-zone hydration.
• Compacted soils alter water movement by restricting infiltration, causing water to pool horizontally above compaction layers, potentially suffocating roots.

Click here to read more about lower flow rate concept and lessons from other industries.

Holistic Success

Vineyard success will depend on everything from soil preparation to harvesting practices, it will depend on important decisions the farmer and the experts he consults will make, and it will depend on many factors beyond the farmer’s control. Two of the many impacting factors of success in a drip-irrigated vineyard is dripline selection and irrigation scheduling. Dripline selection is about selecting a quality dripline with suitable features and specifications to do the job at hand.

Click here to read more about dripline selection.

Scheduling, as is about understanding all impacting factors and integrating these in a holistic approach. By monitoring soil moisture trends and using tools such as profile pits or neutron probes, growers can adjust irrigation duration and frequency to optimize soil moisture without over-saturating the vines.

To achieve the best results, wine grape farmers should embrace a data-driven approach:

• Use soil moisture sensors to track trends rather than relying on guesswork.
• Regularly inspect dripper performance to ensure consistent water delivery.
• Adjust irrigation scheduling based on weather patterns, soil moisture levels, and vine requirements.
• Leverage modern irrigation technology to automate precise water and nutrient delivery.

Click here to read more about irrigation scheduling.

Impactful Insight

Effective irrigation is not just about applying water—it’s about understanding how it moves through soil. By adopting a tailored, soil-conscious irrigation strategy and applying this strategy with quality precision irrigation equipment, wine grape farmers can produce high-quality grapes while conserving water. The more we align irrigation with soil movement dynamics, the greater our ability to enhance both sustainability and profitability in the vineyard.