RETENTIS® in the focus of science: How our lignin-based hydrogel helps young vines withstand summer stress
Summary: Young vines are particularly sensitive during dry periods because their root system still has to colonize the soil. Two studies by Frioni et al. (2024, 2025) show that RETENTIS®, an organic lignin-based hydrogel, measurably improves soil hydrology—and that this improvement translates directly into plant responses. In the trials, plant-available water increased significantly, water status remained more stable under drought stress, root biomass increased, and yield in the pot trial rose by 26 percent. The 2025 paper also provides a concrete profitability calculation, with break-even already within the first two years after planting.
Key facts at a glance
Soil physics and water availability
- More plant-available water: Increase of 48% compared with the control.
- 75% higher field capacity: Increase from 24% to 42%.
- Maximum available water: Expansion of the usable storage in the root zone from 23% to 34%.
Plant physiology and yield
- Stress tolerance: More stable water status with about +0.25 MPa in stem water potential at the critical point before re-irrigation.
- Growth boost: +12.4% root fresh mass and, in the field after two years, up to +25% more leaf area.
- Yield increase (pot trial): Increase from 3.5 kg to 4.4 kg per vine, which corresponds to about +26%.
- Photosynthesis: After re-irrigation, higher assimilation was measured; for the organic hydrogel about +8 µmol m⁻² s⁻¹ compared with the control.
- Sugar content (TSS): In the 2025 study, treated vines showed a slightly lower sugar content. This effect is not a quality disadvantage; it is linked to the higher yield and improved berry hydration. Target sugar levels can still be managed precisely through harvest timing and yield management.
The results highlight an important physiological principle: Under drought stress, sugar in berries often rises primarily because growth and transpiration collapse early. With RETENTIS®, water status and photosynthesis remain stable for longer, supporting a more balanced development between yield and ripeness.
Understanding the pF curve: Why RETENTIS® doesn’t just hold water, but makes it plant-available
A central part of the 2024 study is the so-called pF curve, or water retention curve. For practitioners, this is the decisive chart because it answers the most important question: Can the vine actually take up the stored water at the crucial moment?
The curve links two quantities. First, soil water content, i.e., how much water is present in the soil. Second, soil water potential, which describes how strongly that water is bound. The more negative the potential, the more energy the plant must expend to extract water. That’s exactly why not every additional amount of water is automatically an advantage. What matters is the share that lies within the range where roots can take up water efficiently.
What you can read directly from the pF curve
- Rightward shift of the curve: With RETENTIS®, more water is present in the soil at the same water potential. This means the soil stays longer in a range where water uptake is realistic for the vine.
- Field capacity increases strongly (+75%): Water content at field capacity rises markedly; in the data this corresponds to about 0.24 g water per g soil in the control and about 0.42 g water per g soil with RETENTIS®.
- Wilting point shifts: Water content at the permanent wilting point also increases, from about 0.01 to 0.08 g water per g soil. This shows that part of the water is more strongly bound, but the gain in field capacity clearly outweighs this.
- The AWC zone becomes wider: This is the practical core. Available water—the difference between field capacity and wilting point—increases by 48% in the study. That translates into valuable additional days of hydration during a heat wave.
RETENTIS®: The sustainable choice for professionals
As the manufacturer of RETENTIS®, we deliberately rely on a lignin base. Lignin is a plant structural polymer and therefore a raw material from renewable sources. In the 2025 study, the organic hydrogel is described as an option that is particularly attractive in the context of ecological requirements, whereas environmental aspects are more frequently discussed in the technical debate around purely synthetic polymers.
At the same time, the studies deliver an important practical point: RETENTIS® doesn’t convince through a laboratory record, but through its performance in soil. In the 2024 work, water uptake of the lignin-based material remains stable across rewetting cycles—an essential factor throughout the establishment phase. In the 2025 work, effects on water status, gas exchange, and growth are confirmed—exactly where it matters in the vineyard.
A look at the lab number—properly put into context
In the 2024 study, the maximum water uptake of the lignin-based hydrogel is 9.19 g water per g polymer. This is not a beaker-bench comparison contest, but an indication that RETENTIS® can reliably absorb water and—together with the soil—translate it into improved water availability. This translation is shown precisely by the pF curve and the increase in AWC.
Profitability: ROI according to Frioni et al. (2025)
An investment in a vineyard has to pay off. The 2025 study provides a concrete model calculation based on practical assumptions and a planting density of 3,000 vines per hectare.
Practical takeaway: The study authors describe that the application can shorten the unproductive phase after planting because vines are more vigorous and fill the trellis system faster. This is where the economic leverage comes from—fewer losses, faster development, earlier yield.
Scientific terms explained simply
- Field capacity (FC): The amount of water remaining in the soil after gravitational water has drained—practically the upper storage point. FC is around −0.03 MPa → pF ≈ 2.5. In very sandy soils, FC is sometimes set slightly higher, e.g., around −0.01 MPa → pF ≈ 2.0
- Permanent wilting point (PWP): Water content at very strongly bound water, typically at −1.5 MPa (pF 4.18); below this, water uptake becomes extremely difficult.
- Plant-available water (AWC): The difference between field capacity and wilting point—i.e., the usable water reserve for the plant.
- Stem water potential: A vine stress indicator; the less negative it is, the better the water supply.
- Photosynthetic assimilation: The rate at which the plant converts CO2 into sugar—a direct indicator of growth and performance.
- Degrees Brix (TSS): Sugar content of grapes; slight decreases at higher yields and better water supply are physiologically plausible and—depending on wine style—may even be desirable.
