In the Seville region (Benacazón), Spain, SGS Institut Fresenius conducted an independent field study on open-field tomato cultivation in 2023. The goal was to examine how the use of water-retaining granules affects yield and fruit quality when the irrigation volume is significantly reduced. The results show that, under the test conditions, water requirements could be significantly reduced without any decline in yield or fruit quality compared to full irrigation.
Experimental Setup
- Crop: Field-grown tomatoes, variety H1015.
- Location: Southern Spain, warm, dry climate with typical irrigated farming.
- Partner: SGS Institut Fresenius, an independent, officially recognized testing organization.
- Products: Polygrain water-retaining granules, applied once to the planting hole when planting.
Two groups of areas were created
- Control plots: Tomato cultivation using the standard irrigation regimen (100% water).
- Experimental plots: Tomato cultivation using identical management practices, but with a water reservoir in the root zone and a significantly reduced irrigation volume.
Variety, planting density, fertilization, and plant protection were the same in both groups—the only difference was in the volume of water and the use of the granules.
Irrigation Regime
- Reference: Irrigation at the usual level throughout the entire growing season.
- Experimental plots: Reduction in irrigation volume and the number of irrigation applications, resulting in a total water supply per season that was approximately 45–52 % below the reference level.
This simulated a cost savings scenario that is relevant in practice under water restrictions or rising costs.
Plant Condition and Cultivation Practices
During the trial period, it became apparent that the use of the granules caused no visible damage to the plants. The stands on the plots with reduced irrigation volumes remained healthy and did not differ noticeably in appearance from those on the fully irrigated plots. Crop management could be carried out without any adjustments to the product; application at planting was unproblematic.
Thus, the reduction in water did not lead to additional symptoms of stress as long as the water reservoir in the soil remained intact.
Experimental Results
- Yield: On plots with approximately 45–52 % less irrigation water, the total tomato yield was at a comparable level to that on the fully irrigated reference plots. No significant decline in yield was observed. Variations between treatments fell within the usual range; no clear trend toward lower yields with less water was evident.
- Quality: The quality parameters examined (including sugar content/Brix, fruit size, and percentage of marketable produce) in the experimental plots were within the range observed in the reference plots.
There was no evidence of quality losses beyond normal seasonal fluctuations.
Conclusion
For agricultural operations, this study clearly demonstrates the following for tomato cultivation: Under the conditions tested, water savings of approximately 45–52 % of the previous irrigation volume are possible without a significant decline in yield or fruit quality compared to full irrigation.
This results in significant cost savings on water and irrigation, particularly in systems with expensive water rights, high energy costs, or limited water availability.
