Strawberries perform best when the roots can breathe and the root ball doesn’t change “mood” every hour. In substrate cultivation, this is achieved with a medium that combines sufficient air pores and easily available water. Coco can fulfill this role if properly formulated and carefully managed. Literature on soilless systems highlights two key points: high aeration with good drainage without losing water reserves, and quality control of the coco itself, which can bring residual salts and vary between batches (Noguera et al., 2003; Evans et al., 1996).
Coco is not uniform: pith, chips, and fiber contribute different properties to the substrate. Fine pith retains more water, while chips and coarse fractions open pores and improve oxygen availability for the roots. Long fiber contributes little to rehydration and retention, so excess fiber complicates management. For this reason, a pith range of 0.5–2.0 mm usually works as a base, removing fractions smaller than 0.2 mm, which reduce aeration and increase the substrate’s bulk density (Konduru et al., 1999; Londra et al., 2018).
Water–Air Curves: The Compass for Irrigation
Understanding the water–air curve is crucial. Easily available water is that which the substrate releases between 10 and 50 cm tension; the buffer capacity between 50 and 100 cm cushions demand peaks; and the point where water volume equals air volume indicates whether the medium breathes while hydrating. With more fine pith, the reserve increases, but usable air decreases; with coarser fractions, air increases, but irrigation must be more frequent to maintain hydration during the plant’s peak activity hours. In strawberries, this balance is critical, as oxygenated roots and stable water determine fruit quality and firmness (Durand et al., 2023).
Designing Coco-Only Mixes
Working solely with coco allows modulation of air and water by combining fine pith with coarser coco fractions. The choice depends on climate and the irrigation system:
- In humid climates or greenhouses with highly reactive irrigation, it is advisable to increase the coarse fraction to avoid waterlogging and maintain oxygen, while ensuring that easily available water does not drop too low. This requires a high level of technology in the crop; there is little inertia, and neither over- nor under-watering is acceptable.
- In dry climates or with longer irrigation windows, the fine fraction increases water reserves, always keeping fines <0.2 mm to preserve macropores. However, high temperatures reduce dissolved oxygen, and roots respire more at higher temperatures. Aeration is critical.
Container shape also influences outcomes: the shorter the substrate column, the lower the total aeration. Deeper pots allow better root oxygenation, translating technical adjustments into uniform growth and consistent fruit (Rivera-del Río et al., 2015; Palencia et al., 2016).
Water, Salts, and Structural Stability
Some coco batches contain residual Na⁺ and K⁺, requiring washing with fresh water and sometimes buffering with calcium nitrate before starting the crop. The advantage of coco over other media like peat is its excellent rehydration and water retention capacity with high lignin content, ensuring structural stability throughout the cycle. In practice, shrinkage >5% should be avoided, as it can affect roots and complicate daily management.
Controlling drainage, EC, and pH is not bureaucracy; it is the tool that allows correction of salt accumulation before it impacts vigor and yield. Thus, strawberries in coco achieve irrigation patterns that synchronize water, air, and nutrients, ensuring firm fruit and continuous harvests (Durand et al., 2023; Konduru et al., 1999).
Practical Observations
Studies in protected structures show that the substrate explains much of the variation in biomass, crowns, and leaf area. The success of working with “coco-only” mixes lies in selecting the correct particle size and coordinating it with irrigation: coarser fractions require more pulses and shorter pauses; finer fractions need longer pauses to reoxygenate the substrate and prevent hidden water accumulation. This approach ensures that roots receive constant oxygen and stable water, regaining control over daily crop management.
References
- Noguera, P. et al. (2003). Influence of particle size on physical and chemical properties of coconut coir dust as container medium.
- Evans, M.R.; Konduru, S.; Stamps, R.H. (1996). Source variation in physical and chemical properties of coconut coir dust.
- Konduru, S.; Evans, M.R.; Stamps, R.H. (1999). Coconut husk and processing effects on chemical and physical properties of coconut coir dust.
- Londra, P.; Paraskevopoulou, A.; Psychoyou, M. (2018). Hydrological behavior of peat- and coir-based substrates and their effect on begonia growth.
- Durand, S.; Jackson, B.E.; Fonteno, W.C.; Michel, J.-C. (2023). Quantitative description and classification of growing media particle morphology through dynamic image analysis.
- Rivera-del Río, R. et al. (2015). Alteration of physical properties of substrates and accumulation of nutrients in strawberry hydroponic systems.
- Palencia, P. et al. (2016). Investigating the effect of different soilless substrates on strawberry productivity and fruit composition.
