Blueberry is a fine-rooted crop, lacking root hairs, that thrives under low pH, low-salinity solutions, and precise water management. For this reason, container and soilless substrate systems have become established in areas where soils are not ideal. These systems combine peat, coco, and perlite with controlled fertigation; technical literature recognizes them as a valid approach for commercial production when the goal is to control pH, salts, and maintain root zone stability (Kingston et al., 2017; Retamales & Hancock, 2012).
The plant defines its “comfort zone” at pH 4.5–5.5 and favors ammonium over nitrate nitrogen. It also maintains lower foliar concentrations of macronutrients than other fruit crops, implying modest nutritional requirements and high sensitivity to salt accumulation in the wet root zone. In practice, this means that decisions on water quality and drainage are as important as the fertilization recipe.
Why Coco and How to Mix It
Coco offers good aeration and water retention, and its structure is relatively stable over time. However, origin and processing alter its chemistry and physics: there are batch-to-batch variations affecting residual salts, cation exchange capacity (CEC), and water behavior; this justifies washing and conditioning coco before planting (Konduru et al., 1999; Noguera et al., 1997).
Mixing coco with perlite opens macropores and improves oxygen, but reduces easily available water reserves. Studies show that too much perlite can reduce growth, not due to nutrition but due to changes in substrate hydraulics. The operational conclusion is simple: adjust texture according to climate and available water; more air in humid climates or intensive irrigation, more retention if your operation has long irrigation windows.
Besides balancing fine and coarse particles for a proper air/water ratio, container height is a crucial factor. More fine particles retain more water at the bottom of the container, affecting roots, while the upper profile may not dry excessively. Conversely, more coarse particles increase air throughout the profile; although the bottom receives air quickly after irrigation, the top may become too dry for root development. Finding and maintaining this balance over multiple years is not easy.
Water and Salinity: Managing Quality from the Start
In many production areas, irrigation water contains NaCl and bicarbonates/carbonates, requiring salinity management strategies. Coco allows this to be managed with a proper washing plan and EC control, especially when reverse osmosis is unavailable. Studies clearly recommend diagnosing water and planning salt management from day one. If drainage EC rises, early correction involves reducing concentration and increasing the drainage fraction during peak demand hours. These small adjustments prevent losses in vigor and quality. They must be minor, as this crop does not tolerate abrupt changes (Machado et al., 2014; Kingston et al., 2020).
Sensitivity to salts is confirmed even when they come from fertilizer: ammonium sulfate reduced root and shoot growth as EC increased, reinforcing the need to keep the system in low and stable ranges.
Substrate Physics and Irrigation Management
Coco particle size and its combination with other components determine the air–water balance and the root ball’s response to each irrigation. Fine fractions close macropores and increase retention, slowing system response; coarse fractions and perlite open pores and accelerate gas exchange, but require more frequent pulses to maintain hydration.
Coco also interacts with ammonium (NH₄⁺) through adsorption, affecting nitrogen availability dynamics. Understanding this interaction helps explain crop responses and avoids excess in the initial formula. In practice, this translates into measured pulses and pauses allowing reoxygenation, especially in large pots. Elevating containers and avoiding water films beneath the pot prevents cold and anoxic zones.
During establishment, decisions on substrate preparation and pre-fertilization should be conservative. Studies show that pre-plant fertilization in coco can increase microbial respiration without improving young plant establishment, favoring nutrition via controlled fertigation.
Practical Comparisons and Final Recommendations
Container blueberry trials indicate that peat and coco are suitable as substrate bases, while high bark levels can affect growth. At lower pH with more peat, foliar tissues remain within acceptable ranges, though hypoxia risk increases if frequent washes are needed. Coco-based systems showed easier water drainage due to better aeration and greater stability over time.
The final takeaway is clear: blueberry in substrate works when the system is designed around the plant’s needs—low pH, low salts, and high oxygen. Coco fits if washed and conditioned, mixed thoughtfully to achieve the air–water balance required by the climate, and irrigation is measured according to demand with attention to drainage EC. Literature agrees: water quality and substrate physics explain much of the outcome, and growth responds more to water and oxygen than to overcorrections in fertilization (Heller et al., 2022; Muñoz et al., 1993).
References
- Kingston, P.H.; Scagel, C.F.; Bryla, D.R.; Strik, B.C. (2017). Suitability of sphagnum peat moss, coir, and Douglas fir bark as soilless substrates for container production of highbush blueberry.
- Kingston, P.H.; Scagel, C.F.; Bryla, D.R.; Strik, B.C. (2020). Influence of perlite in peat- and coir-based media on vegetative growth and mineral nutrition of highbush blueberry.
- Machado, R.M.A.; Bryla, D.R.; Vargas, O. (2014). Effects of salinity induced by ammonium sulfate fertilizer on root and shoot growth of highbush blueberry.
- Heller, C.R.; Nunez, G.H. (2022). Preplant fertilization increases substrate microbial respiration but does not affect southern highbush blueberry establishment in a coconut coir-based substrate.
- Retamales, J.B.; Hancock, J.F. (2012). Blueberries (2nd ed.).
- Konduru, S.; Evans, M.R.; Stamps, R.H. (1999). Coconut husk and processing effects on chemical and physical properties of coconut coir dust.
- Noguera, P.; Abad, M.; Noguera, V.; Puchades, R.; Maquieira, A.; Martínez, J. (1997). Physical and chemical properties of coir waste and their relation to plant growth.
- Kithome, M.; Paul, J.W.; Kannangara, T. (1999). Adsorption isotherms of ammonium on coir.
- Muñoz, C.; Soto, R.; Valenzuela, J. (1993). Effect of chemical and physical potting media characteristics on growth of container-grown rabbiteye blueberries.
