Adoption pathways of hydroponic blueberries – optimised fertiliser practices and economic viability

How do the economics of hydroponics compare with the economics of standard blueberry practices?

Research into the economics of growing crops typically includes the initial capital cost and the ongoing maintenance costs of the growing method. The normal cost inclusions for capital are land and infrastructure and ongoing maintenance are labour, water, energy, fertiliser and weed and pest control. Comparing blueberry bush yield per hectare enables hydroponic growing method economics to be compared with soil growing method.

Analysis of the costs of hydroponic growing typically includes capital costs such as greenhouses, heating and cooling infrastructure and water recycling systems. The use of a netted outdoor environment open to the weather for both field and hydroponically grown blueberries in this research created a more equivalent economic comparison regime. Literature on research of the costs of open field netted hydroponic growing method used in this research could not be located.

Purchase or leasing of land on which to grow blueberries is a significant cost. Eck and Childers (1966, p.142), referring to the blueberry growing industry in the USA in the 1960’s, observes that “as the national demand for blueberry fruit increases, lands ideally suited for blueberry production will become increasingly more difficult to obtain. Consequently, the trend must be toward the use of less ideally suited lands which may require the use of special soil management practices”. He was referring to the practice of mulching however this observation is relevant to all blueberry growing practices.

The cost and lack of suitable land motivates farmers to grow “more food with less earth” (Vydra, 2017, p.39). More plants can be grown hydroponically on a hectare than when grown in soil. “In southern Australia there are 2000 to 2100 plants per hectare. Each plant produces 8-10 kg of fruit. Full production does not occur until year five” (Wilk & Simpson, 2015, p.2). When grown hydroponically it is possible to increase the density of the plantings/containers. Reduction of plant spacing and row spacing can enable up to 11,854 plants per hectare however 7173 plants per hectare is probably more realistic (Fang, Nunez, da Silva, Phillips & Munoz, 2020, p.5). The hydroponic trial at Tuckerberry Hill takes up 800 square meters (100m by 8m). During this research there were 900 plants being grown hydroponically in this area. This has been reduced to 600 plants as the rapid vegetative growth led to overcrowding which presented access difficulties. This planting density is equivalent to 8,500 plants per hectare. High density planting may reduce light penetration and therefore impact on photosynthesis. Also, restriction of airflow may increase the potential for fungal infections and pest infestations. Ease of access for pruning, plant management and picking may also be compromised (Fang et al., 2020).

At Tuckerberry Hill, field grown blueberries require capital to be outlaid on initial soil preparation that includes weed control, ripping, mounding, and mulching. Wilk and Simpson (2015) have researched these costs for northern NSW and southern Australia. The southern Australia costs are of interest to this study. Their research assumes that the soil is suitable for blueberry growing and only requires minor pH adjustments by the application of Sulphur. Modification of less suitable soil for growing blueberries in the field is a significant cost. Adding gypsum, peat moss, and mulch to improve the soil yet maintain acidity is costly and needs to be repeated each year at Tuckerberry Hill.

Hydroponic growing of blueberries under netting requires different capital inputs than field growing. Pots, substrate, ground covering, and run-off water capture infrastructure are the major costs incurred.

Soil type is an important variable in growing blueberries. Low pH soils enable blueberry plants to take up the required iron for healthy growth. Michel, Beya-Marshall, Rombola, Pastenes, and Covarrubias, (2019, p.118) report that solving iron deficiency in soils by acidifying the soil can have detrimental impacts on microbial biomass and mycorrhizal fungi populations.

In their 2018-2022 strategic investment plan the Australian Blueberry Growers Association, (2018, p.6) comments that “Traditionally blueberries have been grown in the soil and exposed to the elements. However, in recent years there has been a substantial increase in the use of protective tunnels or netting together with hydroponic (out of the soil) production which is most likely to continue into the future. These new production systems help to protect blueberry crops from adverse weather conditions, while simultaneously, allowing for improved productivity and consistency of fruit quality.” The desire to expand blueberry production into hydroponic growing methods is thus widely recognised however very little public research is available for scrutiny to assess the method for comparative economic advantage.

In the Tuckerberry Hill trial both field and hydroponically grown plants were under the same protection – bird and hail netting. The plants were therefore subject to the same rain, temperature, and sunlight conditions. Therefore, the cost or impact of protective netting is not regarded as a variable in this trial. Research articles relevant to this trial - growing blueberries hydroponically under netting - have not been located by the researchers as hydroponically grown blueberries are more normally located in tunnels or greenhouses. While netting does not provide the advantage of longer growing seasons and increased climatic controls that plastic or glass coverings provide, netting does not incur the increased management and infrastructure costs of plastic coverings.

Field grown and hydroponic grown pest control costs are similar eliminating snails, caterpillars, and elephant weevils as they appear in the orchard. Snail bait is used for snail control in both growing methods. They are also removed by hand.

Weed control in the field and hydroponic blueberries is by hand. Adjoining paddocks weed control is achieved by herbicides such as Slasher or Roundup – depending on the time of year.

Heavy soils and waterlogging of the Tuckerberry Hill site has led to Phytophthora stunting stem and root growth. The use of drip irrigation has compounded this problem (Yeo, Sullivan, Bryla, & Weiland, 2016). Using substrate in place of soil with hydroponically grown blueberries eliminates the labour and costs of overcoming such root borne disease (Mann, 2015, p.41).

What is the impact on fruit production quantity and quality of increased nutrient solutions for hydroponic blueberry productions?

The finding by Parks, Jarvis, Simpson and Morris (2019) that “Little information has been developed on blueberry hydroponic nutrition” describes a trial design for the Clean Coastal Catchments (CCC) initiative by the NSW DPI to address the use of fertiliser by the blueberry industry. Research that has been conducted however has been for purposes other than determining nutrition requirements of hydroponically grown blueberries. Despite this lack of research focused on hydroponics, there is research that refers to the nutritional requirements of hydroponic blueberries and the impact of higher concentrations of nutrients and beneficial fungi.

Eck and Childers, (1966, p.140) “Greater amounts of nitrogenous fertilizer must be used to obtain good plant growth when mulches … are used.” However, this observation may not be transferable to hydroponically grown blueberries. Substrates used to grow blueberry bushes hydroponically are very different to the mulch that is applied to the mounds in which field blueberries are grown.

Parkes (2015, p.3) observes that blueberries “generally have a lower nutritional requirement than other fruit trees”. Investigation of increased nitrogen application on blueberry bush health and fruit yield was carried out by Ethret et al in 2014. The study also compared fertigation with broadcasting as a method of fertilisation. Ehret et al (2014, p.1) “fertigation produced more shoot growth and greater yields with less N than with broadcast applications of fertiliser.” This research study also found that an increase in N application rate did not have an immediate impact on the yield of a blueberry plant. The increase in yield occurred in subsequent years with fertigation having a greater impact than broadcast fertilisers. Our research study did not investigate a comparison of the method of application of fertiliser however it is noteworthy as hydroponic application of fertilisers have used fertigation throughout the life of the plants in the trial whereas the field blueberries have been fertilised by both fertigation and broadcast fertiliser applications.

“Southern highbush … has been shown to take up significantly more ammonium than nitrate in a soil medium (Poonnachit and Darnell, 2004) in Parks, 2015 p.3. Iron uptake, essential for healthy growth in blueberries, is increased in ammonium uptake and decreased in nitrate uptake (Poonnachit and Darnell, 2004, p.404). Optimum concentrations of ammonium and nitrate was not included in this research.

Recent research by Fang et al (2020, p.10) commented that “Additional research is necessary to determine optimum nutrient application rates and timing for container-based blueberry productions”. They have added the observation that “fertility recommendations for soil-based production might not cross over appropriately to container-based systems.”

Growing conditions for field blueberries has investigated the role played by beneficial fungi that assists the roots to take up nutrients. Mann (2014, p.22) postulates that “in hydroponic systems with good feeding programs these fungi may not be necessary as the plants are being administered exactly what they require.” The fungi that she refers to are Mycorrhizae and Trichoderma. Additionally, Trichoderma occurs naturally in coir substrates.

Parks (2015, p.28) reports that “containerized blueberries have been shown to benefit from inoculation with mycorrhizal fungi.” However, increased fertiliser application reduces this benefit (Scagel, 2005, p.792). Additionally, higher concentrations of nutrients in leaves may limit “growth, potential production efficiency and crop quality” in container nursery production (Scagel, p.793).

Research into the quality of hydroponically grown blueberries has not been located. Many questions remain unanswered such as – how does hydroponic production impact shelf life of blueberry fruit? Does hydroponically fruit taste different to field grown fruit in the areas of sweetness, berry taste and mouthfeel?

Quite simply more research is required into all areas of hydroponic blueberry production. Growers need some certainty of their production practices prior to investing their capital and transferring their production from field to hydroponic growing methods.

Australian Blueberry Growers Association, (2018). Australian blueberry industry. Strategic investment plan 2018-2022. www.abga.com.au

Eck, P. & Childers, N.F. (Eds.). (1966). Blueberry culture. New Brunswick, NJ: Rutgers University.

Ehret, D.L., Frey, F., Forge, T., Helmer, T., Bryla, D.R., & Zebarth, B.J. (2014). Effects of nitrogen rate and application method on early production and fruit quality in highbush blueberry. Canadian Journal of Plant Science 94, 1-15.

Fang, Y., Nunez, G.H., da Silva, M.N., Phillips, D.A., & Munoz, P.R. (2020).  A review for southern highbush blueberry alternative production systems. Agronomy 10, 1531, 1-15.

Mann, N. (2014). Compendium for the report on: “Intensive berry production using greenhouses, substrates and hydroponics. Is this the way forward?” Nuffield Australia Farming Scholars, Project 1415.

Mann, N. (2015). Intensive berry production using greenhouses, substrates and hydroponics. Is this the way forward? Nuffield Australia Farming Scholars, Project 1415.

Michel, L., Beya-Marshall, V., Rombola, A.D., Pastenes, C., & Covarrubias, J.I. (2019). Evaluation of FE-heme application or intercropping for preventing iron deficiency in blueberry. Journal of Soil Science and Plant Nutrition 19, 117-126.

Parks, S. (2015). Bringing blueberries into protection. Practical Hydroponics & Greenhouses. September. Sydney, NSW: Department of Primary Industries.

Parks, S., Jarvis, J., Unsworth, D., Simpson, M., & Morris, S. (2019). CCC blueberry fertigation pot trials September 2019. Sydney, NSW: Department of Primary Industries - Clean Coastal Catchments (CCC) initiative.

Poonnachit, U., & Darnell, R. (2004). Effect of ammonium and nitrate on ferric chelate reductase and nitrate reductase in Vaccinium species. Annals of Botany 93, 399-405.

Scagel, C.F. (2005). Inoculation with ericoid mycorrhizal fungi alters fertiliser use of highbush blueberry cultivars. HortScience 40 (3), 786-794.

Vydra, J. (2017). More food, less earth: investigating emerging methods to grow more horticulture produce with less space and fewer inputs. Nuffield Australia Farming Scholars, Project 1623.

Wilk, P., & Simpson, M. (September 2015). Blueberry establishment and production costs. Primefact 133, 4^th ed. Wollongbar, NSW: Wollongbar Primary Industries Institute.

Yeo, J., Sullivan, D., Bryla, D., & Weiland, J. (March 30, 2016). Fighting phytophthora in blueberries.  American Fruit Grower News. Retrieved from