The Adler Agro strategy improves fresh weight retention in lettuce under water deficit

Lettuce trial results: key effects observed

Figure 1. General view of the potted romaine lettuce trial under greenhouse conditions.

Adler Agro has completed an agronomic trial in romaine lettuce under greenhouse conditions during the 2026 growing season. The aim of the trial was to evaluate the performance of the rooting biostimulant Root, comparing it with a commercial reference product and an untreated control without rooting biostimulant application, under two irrigation levels. The lettuce trial results showed a favorable response to the Adler Agro strategy, particularly under reduced irrigation conditions, where Root achieved the highest mean fresh weight and showed a greater ability to maintain above-ground growth compared with full irrigation conditions.

Objective and trial design

The objective was to determine the effect of Adler Root on lettuce development and its ability to maintain growth under conditions of reduced water availability.

The trial included 36 plants, grown individually in pots with peat-based substrate, using a factorial design consisting of 3 treatments × 2 irrigation levels × 3 replicates × 2 plants per replicate.

Two irrigation conditions were evaluated:

• 100% irrigation: 4 L/h drippers.

• 50% irrigation: 2 L/h drippers.

The trial lasted 20 days from transplanting to the final evaluation.

Treatments evaluated 

• Adler Agro: application of Root at a dose equivalent to 5 L/ha, corresponding under the trial conditions to 10 mL of product per plant and application.

• Commercial reference: application of a commercial rooting product at a dose equivalent to 2.5 L/ha, corresponding to 5 mL of product per plant and application.

• Control: crop management without rooting biostimulant application.

A total of 200 mL of solution per plant was applied in all treatments, with two applications carried out during the trial.

Variables analyzed

• Fresh weight of the above-ground part: determined individually for each plant at the end of the trial.

• Response to reduced irrigation: comparison of fresh weight obtained under 50% irrigation with that achieved under 100% irrigation.

• Visual observation of the root system: comparative assessment of root development among treatments.

The strong adhesion of the substrate made complete extraction of the root system difficult and resulted in the loss of some fine roots. For this reason, no quantitative comparisons of the root system were performed, and the observed differences were assessed visually only.

Figure 2. Layout of the agronomic trial.

Productive response according to water availability

Figure 3. Lettuce plants.

The fresh weight of the above-ground part showed a different response depending on the treatment and irrigation level.

Under 100% irrigation, mean values were similar among treatments: 79.0 g per plant with Adler Root, 75.8 g with the commercial reference, and 81.8 g in the control. Under these conditions, the control showed the highest mean value, although differences among treatments were small.

When water supply was reduced to 50%, the response changed. Adler Root achieved the highest mean fresh weight, with 74.7 g per plant, compared with 67.8 g for the commercial reference and 70.7 g for the control.

In relative terms, under reduced irrigation Adler Root showed a fresh weight:

• 5.7% higher than the control.

• 10.1% higher than the commercial reference.

These results indicate a more favorable response of Adler Root when the crop was subjected to lower water availability.

Figure 5. Mean fresh weight of the above-ground part of plants subjected to 50% irrigation in the three treatments evaluated.

Greater fresh weight retention under reduced irrigation

Figure 6. Lettuce plants.

To assess the ability of each treatment to maintain growth when water supply was reduced, the fresh weight obtained under 50% irrigation was compared with that recorded under 100% irrigation.

Adler Root retained 94.5% of fresh weight, while the commercial reference retained 89.5% and the control 86.4%.

Therefore, the reduction in fresh weight when irrigation was reduced was lower in the Adler treatment. This represents a difference of +5.0 percentage points compared with the commercial reference and +8.1 percentage points compared with the control in fresh weight retention.

This response shows that the Adler Root strategy allowed the plants to retain a greater proportion of above-ground biomass when water availability was reduced by half.

Figure 7. Percentage of fresh weight retained under 50% irrigation compared with 100% irrigation for each treatment.

Visual observation of the root system

Figure 6. Representative images of the root systems of the Adler Root, commercial reference and control treatments under 50% irrigation conditions.

At the end of the trial, a visual assessment of the root system was also carried out using representative plants from the different treatments.

In the images obtained under 50% irrigation conditions, a greater development and volume of the root system can be visually observed in plants treated with rooting products compared with the control, with this response being particularly noticeable in the Adler Root treatment.

However, the strong adhesion of the substrate made complete root extraction difficult and caused the loss of some fine roots during the process. For this reason, the root system comparison is considered exclusively visual and not quantitative, and these observations were not used to establish statistical differences among treatments.