Nutripool: a new capillary fertigation system for pot-cultivation of Phalaenopsis orchidsABSTRACT
Phalaenopsis orchids are among the most important crop in the floriculture industry. There is a demand for sustainable cultivation systems, more adaptable to climate extremes and use fewer resources. This study aimed to demonstrate the suitability of a new cultivation system, called Nutripool. The objective of this system is to maintain the fertigation nutrient solution in a large plastic container. The pot containing the substrate and the plant is inserted into this container, which keeps the nutritive solution in direct and continuous contact with the substrate, utilizing capillary action of the substrate for fertigation. We studied different substrates, with presence or absence of stone layer, aiming to improve Phalaenopsis orchid cultivation in this system. The substrates used were sphagnum moss, charcoal fines, coconut fiber, polyurethane foam and commercial substrate based in pinus bark and coconut chips. Finally, Nutripool system was compared with conventional overhead fertigation. The use of sphagnum moss proved to be the best for the cultivation of Phalaenopsis under Nutripool system. Sphagnum presented good water-holding capacity (101%), reduced rate of water mass loss, stable pH (5.7-6.5) and electrical conductivity (1.5-1.65 mS/cm), which resulted in best vegetative (4.8 leaves/plant and 19.6 cm of leaf length) and reproductive (80% plants with inflorescences and >10 flowers/plant) development of Phalaenopsis. Using sphagnum as substrate, Nutripool proved to be a better cultivation system than conventional overhead fertigation. The results also demonstrated significant water and fertilizer savings using Nutripool system, using only 25% water and fertilizers compared with conventional overhead fertigation.
Keywords:
pot flower; water; substrate; fertilizers; new technology; sustainable floriculture
Resumo
As orquídeas do gênero Phalaenopsis são uma das culturas mais importantes na floricultura mundial. Há uma demanda por sistemas de cultivo sustentáveis, mais adaptáveis a climas extremos e que utilizem menos recursos. Este estudo teve como objetivo demonstrar a adequação de um novo sistema de cultivo, denominado Nutripool, no cultivo de Phalaenopsis. O objetivo deste sistema é manter a solução nutritiva de fertirrigação em um recipiente de plástico de maior volume, no qual o vaso contendo o substrato e a planta é inserido neste, o que mantém a solução contendo água e nutrientes em contato direto e contínuo com o substrato de cultivo. Foram estudados diferentes substratos, com ou sem a presença de uma camada de pedra, com o objetivo de avaliar a viabilidade e melhoria do cultivo de orquídeas Phalaenopsis. Os substratos utilizados foram esfagno, carvão vegetal, fibra de coco, espuma de poliuretano e um mix comercial de casca de pinus e chips de coco. Finalmente, o sistema Nutripool foi comparado ao sistema convencional de cultivo utilizando a fertirrigação por cima dos vasos. O substrato esfagno foi aquele que demonstrou o melhor desempenho no cultivo de Phalaenopsis, utilizando o sistema Nutripool. Entre as características observadas desse substrato estão: boa capacidade de retenção de água (101%), perda de massa de água mais lenta, maior estabilidade do pH (5,7-6,5) e condutividade elétrica (1,5-1,65 mS/cm), o qual resultou no melhor desempenho no desenvolvimento vegetativo (4.8 folhas/planta e 19.6 cm de comprimento de folha) e reprodutivo (80% de plantas floridas e >10 flores/inflorescência) das plantas de Phalaenopsis. O sistema Nutripool utilizando o esfagno como substrato provou ser um sistema melhor para o cultivo de Phalaenopsis, comparado ao sistema convencional utilizando a fertirrigação por cima dos vasos. Os resultados também demonstraram uma economia significativa de água e fertilizantes com o uso do sistema Nutripool, utilizando somente 1/4 da água e dos fertilizantes utilizados em sistemas convencionais de fertirrigação.
Palavras-chave:
flor de vaso; água; substrato; fertilizantes; nova tecnologia; floricultura sustentável
Global agriculture has seen a notable new technology evolution in cropping systems. The same applies to the production of flowers and ornamental plants. This sector is experiencing rapid expansion in cultivated areas, increased productivity, and improved plant quality as producers adopt new technologies in response to increased demand for flowers (Wani et al., 2023), global expansion of production and trade, and consequent market globalization (Gabellini & Scaramuzzi, 2022). In this context, it is important to highlight technologies that promote the sustainability, particularly regarding the efficient use of natural resources. These technologies aim to address the sector's primary challenges, including increased production costs, climate change, and the need to adapt to abiotic stressors (Gruda et al., 2019; Cardoso & Vendrame, 2022).
Orchids are among the most commercially important flowers in the world. They belong to one of the largest angiosperm families, Orchidaceae. An estimated 35,000 species are spread throughout the world, in addition to at least 100,000 hybrids (Iiyama et al., 2024). The Phalaenopsis genus is the main representative of the global production chain, accounting for 70-80% of the entire orchid market (Tiwari et al., 2024). Phalaenopsis orchids have a monopodial growth habit and fleshy distichous leaves. The success of this Phalaenopsis orchid's cultivation and commercialization, is due to technologies of breeding, ease cultivation and high resistance to transportation, and its flowers have an excellent shelf life after commercialization, enabling long-distance transport and increasing the chances of retail sale (Hsu et al., 2018; Iiyama et al., 2024). However, the cultivation of flowers, such as Phalaenopsis orchids, is still considered highly dependent on natural resources, substrate quality, and pesticide use (Pereira et al., 2021).
A current trend in flower cultivation systems is the use of substrates made from industrial waste products, such as coconut fibers and chips, and pine bark. These substrates are generally lightweight and have high drainage capacity (Faria et al., 2018). This method of cultivation, which involves using substrates with high drainage capacity in increasingly compact pots, meets the demands of today's florists and consumers (Thakur et al., 2023). Unfortunately, it also results in wasted water and fertilizer applied via irrigation, which increases water consumption and production costs (Mathers et al., 2005). This reduces the efficiency of the cultivation system and can result in environmental contamination surrounding the cultivation areas. Reducing the use of water and fertilizers and making them more efficient is indeed one of the greatest challenges of modern floriculture (Wendimu, 2021; Zhang et al., 2024).
Therefore, improving flower and ornamental plant cultivation systems is essential for more economical and environmentally sound production that meets sustainability criteria (Darras, 2020). This contributes to more efficient irrigation and fertilization management and reduces waste of water and fertilizers (An et al., 2021).
In flower cultivation, the use of sustainable technologies in production systems is growing, such as rainwater reservoirs collected from greenhouses' roofs in conjunction with efficient, precise irrigation systems. Subirrigation methods, in which plants receive water from the bottom up through capillary action between the water layer in the soil and the substrate/plant in the pot, provide plants with greater water availability and minimize episodes of water deficit or stress. The goal of this system is to minimize water consumption and increase floriculture productivity (Ferrarezi et al., 2015).
In this sense, it is important to simplify and improve the flooding system so that its benefits can be realized at a reduced cost. In this way, we propose a system that is based on capillary irrigation in a simple, practical way. This system uses a larger container placed just below growing pots, leveraging the capillary force of the substrates to allow water to reach the upper parts of the pot and contact with the roots. We simplified the system by partially and constantly immersed in the substrate in the pots, eliminating the need for complex pressurization and depressurization systems. The system incorporates fertilizers (fertigation), supplying a nutrient solution instead of water alone. We initially called this system as Nutripool because it mimics a small pool containing water and fertilizers where the growing pot, substrate, and roots are partially immersed. Capillary irrigation methods were developed and have been used recently in floriculture (Semananda et al., 2018, Quevedo-Nolasco et al., 2023), showing the potential of this technique to provide water and fertilizers in floriculture industry.
Our main hypothesis is that Nutripool capillary fertigation method is a viable and more sustainable technique for pot Phalaenopsis orchid cultivation, but this depends on the use of correct substrate with high capacity of capillarity. Considering the multiple factors involved, their interactions in cultivation, and the need for a viable system for orchid cultivation, this study aimed to evaluate the viability of this new system. The study primarily focused on experimenting with different substrates available on the global market and their potential to deliver nutrients to plants. Additionally, the study examined the performance of this system in cultivating Phalaenopsis orchids, which are among the most important products in world floriculture.
MATERIAL AND METHODS
Location and plant material used in cultivation
The experiment was carried out in a climate-controlled greenhouse with a maximum and minimum temperature of 18°C and 28.5°C and high relative humidity (50-90%). The Photosynthetic Photon Phlux Density (PPFD) ranged from 40-50 μmol/m2/s at 11:00 AM. The experiment was conducted for 12-months, from the transplantation of seedlings to the pots until one complete cycle to obtain flower plants. The greenhouse's roof was protected with agricultural diffuser plastic and shaded from 60% of the natural light intensity using an aluminum-colored shading screen. The greenhouse was located at Araras, the state of São Paulo, coordinates, 22°18’28.13”S and 47°22’56.12”W.
The Phalaenopsis seedlings used in the experiment were hybrid progeny from the Phalaenopsis Lianher Happy Dancer × Phal. PH501. Although genetic variability exists in progeny, their use in experiments related to cultivation systems may be beneficial because it reduces excessively genotype-dependent responses. Thus, the responses from plants derived from one progeny could be more broadly attributed to the genus, considering there are over a thousand registered Phalaenopsis hybrids on the market. The seedlings were first obtained from in vitro germination of seeds and cultivation, until to obtain plantlets containing 2-4 leaves, with at least one live with minimum 3-cm length, and two roots. The plantlets were acclimatized in plastic cell trays using peat and rice husk as substrate.
In order to reduce the variability in the progeny used, 50 seedlings of this progeny were selected that had similar vegetative characteristics, such as number of leaves and size of individuals, and these were transplanted individually into transparent plastic pots with a 15 cm diameter mouth and capacity of 1 liter substrate. The pots had 3 holes at 2,5-cm height from the bottom of the pot, to allow more contact between the substrate and the nutrient solution (Figure 1).
Experimental design and treatments
The experimental design was a completely randomized 2 x 5 factorial, where the first factor refers to the stone-layer in the pots, with or without stone layer (1,5-2,5 cm diameter), by using 2,0-2,5 cm layer from the bottom of the pot, and the second factor refers to five different types of the substrates: Agrolink® (Artur Nogueira, Brazil) washed fine coconut fiber; charcoal fines; Orquídea (Vida Verde®,Mogi-Mirim, Brazil) substrate (composed of pine bark, coconut chips and charcoal); Polyurethane foam, and sphagnum moss. Individual pots containing one plant each were used as repetition for the experiment, totalizing five repetitions per treatment.
Nutripool sub-irrigation system used for fertigation of Phalaenopsis orchid culture. Both pots have 1 liter capacity, 9 cm height (nutrient solution pot) and 13,5 cm height (cultivation pot). Araras, Universidade Federal de São Carlos, 2022.
Based on information related to the nutritional requirements of the Phalaenopsis genus (Anthura®, 2024), a nutrient solution was prepared containing the final nutrient concentrations: Calcium Nitrate (Ca(NO3)2 0.48 g/L, potassium nitrate (KNO3) 0.66 g/L, magnesium sulfate (MgSO4) 0.21 g/L, monoammonium phosphate (NH4H2PO4) 0.28 g/L, and a mix of chelated micronutrients 25 mg/L (Apex mix®, Apex Agro, Valinhos, Brasil). The concentrations (g/L) of each macronutrient in solution were: 0.75 NO3; 0.04 NH4 +; 0.25 K+; 0.23 PO4 3; 0.117 Ca2+; 0.08 SO4 2 and 0.021 Mg2+.
After preparing the nutrient solution, the pH (Seven Compact, Mettler, Switzerland) and EC (Groline HI98318, Hanna, Romania) values were measured. The solution was adjusted to maintain a pH between 5.0 and 5.5 and an EC between 1.0 and 1.2 mS/cm, as recommended previously (Anthura, 2024).
Next, 400 mL of the prepared nutrient solution was added to the transparent, 1-liter container located below the pot used for cultivation. The potted plants were placed in these containers, so that the substrate was partially immersed in this solution and initiating the exchanges between the substrate used in the treatment and the nutritive solution in the larger container. The nutrient solution was changed only every 28 days or when the volume of nutritive solution was less than 50 mL in the larger container. Using this parameter, we observed that since 50 mL or less are present in larger container, the substrate presents constant high humidity, especially in higher capillarity substrates. The nutrient solution was completely replaced by removing the remaining volume of the previous solution and adding 400 mL of a new solution with the same formula into the major containers.
After the vegetative development period, 6-months after planting, when the plants began producing inflorescences, a new nutrient solution was prepared called flowering nutrient solution, maintaining a pH of 6.35 and an EC of 0.97. To meet the demand for the most of macro and micronutrients, 1.0 g/L of the PlantProd® fertilizer (Brantom, Canada) with the formulation 20-20-20 + Fe (0.1%), Mn (0.1%), Zn (0.1%), and Cu (0.05%) + Mo (0.02%) was used. 0.2 g/L of magnesium sulfate (Synth®, Barueri, Brazil) was used as magnesium and sulfur source and 0.5 g/L of the biofertilizer called Algen (Oceana®, Maranhão, Brazil), based on fossilized seaweed Lithomanium, was used as calcium source (32%). For each pot and container set, 500 mL of the flowering nutrient solution was used. Then, the plants in the flowering phase were inserted back into the Nutripool system containing the flowering nutrient solution.
A control treatment, utilizing conventional overhead fertigation, was maintained under the same cultivation and crop management conditions as the experiment to evaluate and compare the vegetative development of plants grown in the Nutripool system versus the conventional cultivation system. The analysis includes only the substrates that resulted in flowering under Nutripool fertigation conditions, compared with the overhead fertigation using pinus mix substrate (pinus bark, coconut chips and charcoal).
Determination of water-holding capacity and substrate density
For each substrate, the WHC (water-holding capacity) and density were determined based on the Normative instructions nº17 (MAPA, 2023), adapted and modified, as follows, for practical evaluation in substrates used for cultivation: three pots containing 250 mL of each substrate used in the experiment were saturated with water for three consecutive days, wetting the substrate abundantly until completely saturated. After 3 days, the pots were left to drain the excessive water for two hours, until all the water not adhering to the substrate was drained. At this point, the moist substrate was weighed on an analytical balance with a precision of two decimal places. The pots containing these substrates were then kept in a drying oven at a temperature of 40°C for 12 days, at which point the dry substrates were weighed again to determine the mass of the dried substrate. From the difference in values between the moist and the dry substrate, the mass of retained water in the substrate was calculated, and the WHC was calculated by dividing the mass of water by the weight of the dry substrate, multiplied by one hundred, with the WHC value presented as a percentage. Density was obtained by dividing the mass of the dry substrate by the volume of 250 mL of each substrate and displayed in g/L.
Determination of irrigation lamina and nutritive solution waste by overhead fertigation
Aiming to calculate the volume of water applied or irrigation lamina, Phalaenopsis orchids were grown in a commercial substrate, corresponding to the use of pine bark, coconut chips, and charcoal 3:3:1 (Vidaverde®, Mogi Mirim, Brazil), at a density of 40 plants per square meter. The conventional irrigation system used overhead irrigation by micro-sprinklers with a flow rate of 450 L/h and a reach range of 7.0 meters. The growing conditions were the same as those described for the Nutripool subirrigation system, corresponding to the same greenhouse. Sampling of the water applied by the overhead irrigation, as well as water losses due to substrate drainage or irrigation outside the pot area, was carried out on a bench measuring 1.2 m wide by 3.0 m long and 0.80 m high. Water sampling was performed by randomly distributing 5 pots with an internal diameter of 11 cm at the mouth along the bench. Similarly, five identical pots were placed on the greenhouse floor, directly below the growing bench, to collect the sum of the nutrient solution drained from the pot and that applied outside the collection area of the pots by overhead irrigation. The volume was collected every 7 days and until 28 days of cultivation. The calculation of the applied water depth, obtained from the volume applied and collected by the pot, was converted to liters/square meter or liters per pot to facilitate comparisons with the Nutripool subirrigation system.
Evaluations and statistical analysis
This experiment evaluated the exchanges and the physical/chemical characteristics between the nutrient solution and the substrate-plant system. This evaluation included changes in pH and EC throughout cultivation, as well as the time it took for the substrates used to retain and lose water. The influence of this system on the vegetative and reproductive development of Phalaenopsis was also assessed.
To better understand the dynamics between the nutrient solution and the substrates used in the experiment, data on the nutrient solutions (pH, EC, and water volume) were collected weekly, during 10 months of cultivation (March to January) in Araras, Brazil. These samples consisted of the measurements using all the volume of the solution remained in the pot containing the nutrient solution and each pot from each treatment individually. Based on the data of 10 months of cultivation, each one of 28-days of exchange between substrate and nutritive solution, we presented the mean pH and EC values at 0, 7, 14, 21 and 28 days of the nutritive solution remained in the larger pot. Water retention and water mass loss over time of the substrates were also recorded.
Vegetative development, after 6-months in each treatment, was analyzed using plant diameter, leaf number, leaf length and width, and chlorophyll a, b, and a+b levels, measured by a Falker Chlorophyll Meter (CFL001, Falker, Brazil). Flowering was assessed when the plants had at least three fully open flowers. We evaluated the percentage of plants that produced inflorescences and flowers, the length of the floral stem (inflorescence), the number of flowers, and the length and width of each flower.
The data obtained from the experiment were tested by analysis of variance (ANOVA), and their means were compared using the Tukey test, with a significance level of 5%, using the R or Jamovi statistical software. For percentage of plants with inflorescence, we used the Exact Test of Fisher and means were compared by Bonferroni Test at 5% probability. An additional analysis was realized comparing only treatments that complete flowering using Nutripool (Sphagnum, Charcoal and Pinus mix) with the conventional fertigation system using Pinus mix as substrate. The volume of water consumption from the Nutripool solution and the water mass loss by substrates were submitted to correlation analysis and the coefficient of correlation were tested using Pearson’s correlation test at 5% probability. Aiming to confirm the normal distribution of all the data there were used Shapiro-Wilk test at 5% probability.
RESULTS
Analysis of pH, electrical conductivity (EC) and water-holding capacity (WHC) of the substrates
The pH values were influenced by the substrate, the presence or absence of stone layer, and the interaction between these factors (p<0.01). Using the stone layer, the most alkaline pH was observed with charcoal fines (pH 8.5), followed by polyurethane foam (pH 7.6), a commercial substrate composed of pine, coconut, and charcoal (pH 7.3), sphagnum moss (pH 7.2), and washed coconut fiber (pH 6.0). For substrates without a drainage layer, the following order was observed: charcoal fines (pH 8.3) > polyurethane foam (pH 8.0) > sphagnum moss (pH 7.5) > commercial substrate composed of pine, coconut, and charcoal (pH 6.0) > washed coconut fiber (pH 5.7). The charcoal fines and washed coconut fiber substrates had higher pH values in the presence of the drain; the other substrates had higher pH values in its absence.
In decreasing order, the EC values (dS/cm) of the substrates were as follows: washed coconut fiber (EC = 0.57 and 0.70) > charcoal fines (EC = 0.15 and 0.37) > sphagnum moss (EC = 0.09 and 0.05) > commercial pine substrate, coconut and charcoal (EC = 0.04 and 0.05) > polyurethane foam (EC = 0.01 and 0.01).
Except for pinus bark mixture, that presented the lowest water-holding capacity (WHC) of 50.6%, these values of the most substrates presented high WHC with emphasis on polyurethane foam (846%), followed by sphagnum moss (101%) and charcoal fines (93.2%). The density of each substrate was: 0.17 g/m3 (Pinus bark mix); 0.18 g/m3 (Charcoal): 0.04 g/m3 (Polyurethane foam), 0.41 g/m3 (Sphagnum moss) and 0.44 g/m3 (coconut fiber).
pH and EC of the solution during the substrate-nutrient solution interaction and volume of nutritive solution absorption
The pH used for preparing and applying the nutrient solution to the cultivation pots was 6.4-6.5. For most substrates, there was a decrease in pH of nutritive solution over the 28 days of exchange between the substrate and nutritive solution, except for the charcoal-based substrate, in which the pH increased from 6.5 at the time of solution addition to approximately 7.5 shortly after 14 days of cultivation, remaining at that level until the 28th day (Figure 2A). The substrate that resulted in the largest and fastest decrease in pH was the mixture containing pine bark, coconut chips and charcoal with a pH of 4.6 at 28 days of exchange between the substrate and nutritive solution. The other substrates resulted in milder reductions, with final values ranging from 5.35 to 6.3 (Figure 2A). Furthermore, the effects of stone layer in the pH allowed us to conclude that the drainage layer maintained the pH value closer to that of initial fertigation solution.
For all substrates, the EC values of the nutrient solution tended to increase until the 21st day of cultivation, rising from an initially adjusted 1.5 mS/cm, with the highest value being 2.2 mS/cm with the use of washed coconut fiber (Figure 2B). However, from day 21 to day 28, a tendency towards reduction or stabilization of EC was observed, with the lowest value observed in the washed coconut fiber substrate (2.2 mS/cm to 1.4 mS/cm), while the others resulted in intermediate values (1.5-1.8 mS/cm) (Figure 2B). The substrates that resulted in more stable EC values, with and without drainage, was the mixture of pine bark, coconut chips, charcoal and the sphagnum moss, with no statistical difference for the presence of stone layer.
pH (A), Electrical conductivity (B) volume of nutritive solution (C) consumed and substrate water mass loss (D) in different substrates, during each cycle of exchange between the nutritive solution and substrate. The values represent the means of 10 months of cultivation period. *All r-values were significant at 5% probability by Pearson’s correlation test. Araras, Universidade Federal de São Carlos, 2022.
In all substrates, there was a decrease in volume and, consequently, an increase in the consumption of the nutrient solution according to the cultivation time (Figure 2C). The washed coconut fiber (327 mL/pot) and sphagnum moss (284 mL/pot) substrates were those with the highest consumption of nutrient solution at 28 days of cultivation.
The water mass losses curve was obtained for each substrate used in the Nutripool system (Figure 2D). The objective was to determine if water was transferred to the substrate by capillarity, and if the substrate type or drainage system affected water-holding. This was based on periodic measurements of pot mass and calculations of substrate water mass loss. The sphagnum and washed fine coconut fiber substrates had the highest moisture holding percentages and remained moist the longest during the 12-days evaluation period. The polyurethane foam, despite its high-water retention capacity (846%), resulted in low volume of nutritive solution consumed (Figure 2C) and rapid water mass loss within the first two days of cultivation (Figure 2D), showing no or few capillarity action of this substrate. This occurred due to the large size of each foam, with presence of a large number of macropores, which hindered interaction between the substrates and the Nutripool solution. Interestingly, despite having a larger particle size than sphagnum moss and coconut fiber, the charcoal fines resulted in a similar water mass loss to that of sphagnum moss, remaining moist for a longer period (Figure 2D). No phytosanitary control was required during the experimental period.
Vegetative and reproductive development of Phalaenopsis plants under different substrates
The main effects observed in the experiment was attributed to the substrate on the vegetative and reproductive development of Phalaenopsis plants, while stone layer showed effect only on diameter of longest leaf, with best response using the stone layer (Table 1). Therefore, we analyzed the simple effects of the substrate for the most analyzed variables.
The sphagnum moss substrate produced the highest means for all analyzed parameters: the length and diameter of the largest leaf, the number of leaves. These results differed statistically from those of the other substrates (Table 1, Figure 3).
Vegetative development of Phalaenopsis orchid hybrids cultivated under different substrates and using the Nutripool system of cultivation along 10-months: Cha: charcoal fines; Sph: sphagnum moss; PB;CC;Cha: pinus bark + coconut chips + charcoal (3:3:1); CF: washed coconut fiber; PF: polyurethane foam. Bars = 10 cm. Araras, Universidade Federal de São Carlos, 2022.
The major effects in chlorophyll contents were also attributed to the substrate. The sphagnum moss substrate resulted in the highest index of Chlorophyll a (35.7), b (18.3) and total (56.9) (Table 1). The charcoal substrate produced similar index of chlorophyll a (35.7) and total (49.0), but differs from Sphagnum in index value of Chlorophyll b (13.4). The lowest values for chlorophyll content in the leaves were obtained in the coconut fiber substrate, while Polyurethane foam and Pinus bark mixture presented intermediary to low values.
The highest percentage of plants that produced inflorescences were obtained using sphagnum moss, independently of the stone layer, and in the commercial substrate containing the mixture of pine bark, coconut chips and charcoal. Plants with limited vegetative development in polyurethane foam and washed coconut fiber substrates presented low percentage of plants that formed inflorescences (20%), but did not complete flowering by precocious abortion of flower buds. Intermediary flowering percentages (40-60%) were observed using charcoal and in the mixture of pine bark, coconut chips and charcoal. Due to the absence of flowering in some treatments, we analyzed in details the reproductive development in the next subsection considering only the substrates that flowered, and compared with conventional fertigation system performance (Figure 4).
Nutripool system performance compared to conventional fertigation
In this subsection we compared the treatments using the Nutripool system that completed flowering, such as using the substrates sphagnum, charcoal and pine bark mix substrates, compared to the conventional cultivation system using fertigation in a pine bark mix substrate (Figure 4).
The results showed that the Nutripool system associated with the sphagnum substrate achieved the best cultivation performance, yielding a higher number of leaves (Figure 4A), longer inflorescences (Figure 4F), and higher number of flowers per plant (Figure 4G) than all other treatments, including fertigation systems using pinus bark mix substrate. The pine bark mix substrate showed better vegetative performance and adaptation to the fertigation system, showing higher number of leaves (Figure 4A), length of the longest leaf (Figure 4B) and total chlorophyll content (Figure 4D) compared with the same substrate under Nutripool subirrigation system, possibly due to its larger particle size and reduced capillary capacity. No differences among treatments were noted for flower diameter (Figure 4H).
Nutritive solution quantification demonstrated that conventional overhead fertigation uses around 1.2 L of nutritive solution per pot along 28 days. Using Nutripool system, only 0.4 L/plant of nutritive solution was used, saving 800 mL per plant per month of nutritive solution (water and fertilizers). If compared with nutritive solution consumed by the Sphagnum moss, the best substrate used for Nutripool system, only 0.28 L/plant was effectively consumed by Phalaenopsis orchids. The most part of these difference between Nutripool and overhead irrigation was due to drainage of solution or solution applied out of the target by overhead irrigation. The estimates showed that 48 to 76% of total nutritive solution applied overhead is wasted by the drainage of the substrate or was applied out of the target, between the pot-spacing.
Vegetative (A-D) and flowering performance (E-H) of Nutripool compared with plants cultivated under conventional fertigation system. *Different letters in columns for each variable means significative difference among substrate treatments using Tukey’s test at 5% probability or using Exact Test of Fisher (for E plants with inflorescence (%)). Araras, Universidade Federal de São Carlos, 2022.
DISCUSSION
The effects of substrate and stone layer in Phalaenopsis pot-development
In our study, the substrate types had major effects on the effectiveness of Phalaenopsis cultivation in the Nutripool system, with minor or specific effects of stone layer in the development of pot Phalaenopsis orchids. During the 10-month cultivation period, the sphagnum moss substrate promoted adequate vegetative development, achieving the highest values for leaf diameter and length, leaf number and chlorophyll a, b, and total levels (Table 1; Figure 3). This improved vegetative performance also resulted in better reproductive performance, with longer inflorescences and a greater number of flowers per plant (Figure 4).
Physico-chemical factors such as pH (5,3-6,5) and EC stability (1,52-1,55) along the cultivation period, the high capillary action demonstrated by the greater transference of volume solution from the Nutripool container to the substrate (Figure 2), and the slow loss of water mass (Figure 2D), with a longer maintenance time of the solution in the sphagnum moss, visible by the high humidity in the substrate along all the cultivation period, were the predominant characteristics to explain the good results obtained with this substrate. According to Anthura® (2024) the EC (1.0-1.2 mS/cm) and pH (5.2-6.2) is ideal for fertigation purposes of commercial cultivars of Phalaenopsis. However, some authors proposed that this EC is not universally standard and could be adjusted according to environmental and cultivation conditions of Phalaenopsis (Cho et al., 2020, 2022). Cho et al. (2020) reported that EC of 2.0, instead of 1.0, lead to longer spikes and number of flower buds, and also to increases or similar values of water use efficiency (WUE) of plants. These results agree with actual results about the ideal range of pH promoted by sphagnum, and intermediary values of EC (1,0-2,0) recommended for Phalaenopsis cultivation.
Polyurethane foam showed the highest water-holding capacity among all substrates tested, with 846%. This high WHC was due the lowest density (0.04 g/dm3) and characteristics of sponge of this substrate. Despite this high percentage of WHC, this substrate had the fastest water mass loss, associated with lower absorption volumes of the Nutripool solution, suggesting a low capacity of this synthetic substrate to translocate water by capillarity. Sphagnum moss and charcoal substrates had the second and third highest WHC, 101% and 93.2%, respectively. These substrates had high consumption of the Nutripool solution and slower water mass loss, demonstrating greater capillary strength. Charcoal also resulted in similar performance to Sphagnum moss for chlorophyll a and total, but are inferior to Sphagnum moss for the most of all other variables analyzed (Table 1).
The plants in sphagnum moss did not exhibit any symptoms of pests or diseases that could be associated with keeping the roots constantly moist. Also, no symptoms of nutrient deficiency were observed in plants grown using the Nutripool system with sphagnum moss as the substrate. Furthermore, this substrate retained the most moisture throughout the growing season, with minimal water loss and nearly complete absorption of the nutrient solution in the largest Nutripool container. These results agree to An et al. (2021) with cultivation of hybrid Cymbidium orchids, that reported that substrates with larger particle sizes, such as tree bark, require up to eight times more water and fertilizer to maintain a similar matric water potential as finer substrates with reduced particle size. Using finer substrates increased the efficiency of water and nutrient use without causing diseases associated with higher humidity. These conclusions partially reinforce those of actual study with Phalaenopsis, particularly when using sphagnum moss. Sphagnum moss resulted in better utilization of the nutrient solution applied by the Nutripool system and superior vegetative and reproductive development of Phalaenopsis plants. These results are also consistent with those of Lichty et al. (2015), who found that sphagnum moss promoted the highest water-holding and performance of Miltassia Shelob Tolkien orchids compared to other conventional orchid substrates. The same authors also reported that higher proportions of sphagnum moss mixed with redwood bark resulted in better plant growth performance using different irrigation frequencies.
Conventional overhead fertigation vs Nutripool capillary fertigation
Micro-irrigation methods are the most widely used and efficient method of applying water to floricultural species, especially when considering water savings through reduced waste. Overhead irrigation by micro-sprinkler or drip irrigation remains the most common methods for cultivating plants in protected environments, including flower production (Shen et al., 2018; Singh et al., 2020). Overhead micro-sprinkler irrigation has additional advantages beyond providing water, as these irrigation methods create a microclimate that increases relative humidity and decreases air temperature. This alleviates periods of stress caused by high temperatures and/or low relative humidity (Liu et al., 2021). However, although micro-irrigation systems, especially micro-sprinkling are effective and practical they can present problems such as high implementation costs and the need for pure water to avoid clogging micro-pipes (Teztezlaf, 2017).
Under the same growing conditions used for the experiment with the Nutripool system, the conventional overhead irrigation system demonstrated high water loss rates, near to 48% of all the nutrient solution applied according to the results obtained in actual study with Phalaenopsis cultivation. These results showed that even in systems considered efficient, such as micro-sprinkling, they can also waste water and fertilizers, especially when cultivating potted flowers, with spacing between the pots, and when using substrates with a large particle size and high drainage power, such as pinus bark, coconut chips and other those used for potted orchids. In fact, a large portion of the applied water does not remain in the substrate and is leached (Hoskins et al., 2014; An et al., 2021). Considering the need to reduce waste in water and fertilizer use, as well as reduce costs and increase the effectiveness of irrigation and fertilization in floriculture, Videnov et al. (2021) proposed the use of irrigation-associated software to enhance the performance and efficiency of water applications. This study proposes a low-cost alternative system to optimize the use of water and fertilizers.
In the experiment using actual Nutripool capillary fertigation system, 400 mL of nutrient solution was used per container at the beginning of cultivation, providing continuous access to water and nutrients for 28 days, eliminating the need for additional overhead irrigation. According to Floricultura (Floricultura BV, 2021, one of the world's leading companies in Phalaenopsis cultivation technology), conventional Phalaenopsis cultivation requires an average of 15 liters of water per square meter per week, totaling just over 60 liters per square meter of cultivated area per month. We confirm that near values, ≡13.0 liters per square meter per week, was reported using the conventional overhead fertigation under the same conditions of greenhouse used for Nutripool study. Thus, for a 6 × 12 m (36 m²) bench with 1.800 Phalaenopsis plants (50 plants/m2), a conventional fertigation system would require 2.160 liters of water per bench per month or 1.2 liters of nutrient solution per plant. Replacing the conventional system with the Nutripool sub-irrigation system and adding 400 mL of nutrient solution per pot per month would result in a nutrient solution consumption of 720 liters per month for the same 1.800 plants on the same bench. Therefore, using the Nutripool system would result in an average savings of 800 mL of nutrient solution per plant per month. Considering an 18-month growing cycle, this equates to 14,4 liters of nutrient solution savings per plant. However, if the only water used over 28 days was counted by using sphagnum substrate (284 mL/plant), which resulted in the best vegetative and reproductive development of Phalaenopsis plants, this saving could be even greater, representing the uses of only 24% of the total water and fertilizer consumed, compared to the overhead fertigation system.
These results confirm the assertion made by Semananda et al. (2018) that the capillary irrigation systems significantly reduce water usage compared to other conventional irrigation systems. In floriculture, fertilization is predominantly applied with irrigation; therefore, systems that reuse or maximize the use of available water and fertilizers offer advantages such as reduced costs and fertilizer quantity (Rouphael et al., 2016). The entire solution is contained in a larger container that is in constant exchange with the substrate and plant roots. This allows the plant to access water and fertilizers according to its requirements at different stages of development. It avoids periods of deficit or stress related to water shortages or high temperatures which are currently reported as the main conditions related to climate change and have effects on longevity, quality and ornamental value of ornamental plants (Sukpitak et al., 2024).
The Nutripool system used in our study primarily relies on capillary forces between the nutrient solution in the larger external container at the bottom of the substrate and the substrate, which supports and exchanges water with the roots of the cultivated plant, similar to that proposed by Semananda et al. (2018). Ferrarezi et al. (2015) state that capillary-based irrigation systems are widely used for cultivating ornamental plants in controlled environments. Similarly, Semananda et al. (2018), in their review of capillary-based irrigation systems, reported that more than 90% of studies in this system were conducted in controlled environments, with over 60% involving ornamental plants. This demonstrates that irrigation by capillary methods has expanded worldwide in these species and cultivation systems.
Importantly, this study used progeny from a controlled cross, which resulted in higher genetic variability compared with a cloned individual genotype. Despite this and the existing variability, however, significant statistical differences were detected between the different treatments, with low coefficients of variation. This demonstrates that the Nutripool system positively impacts cultivation, even in the presence of greater genetic variability, favoring the use of this technology for wider number of commercial genotypes in Phalaenopsis genus.
CONCLUSIONS
The Nutripool system, a simplified system based on the natural capillary forces of the substrate to carry water and nutrients to the roots has emerges as new potential technology for the cultivation of high-quality Phalaenopsis orchids assemble high quality of flowering plants with significant savings of water and fertilizer use, compared with conventional overhead fertigation. The sphagnum moss, independently of the stone layer, proved to be the best adapted substrate for Nutripool capillary fertigation system. Another advantage of the Nutripool system is that it reduces the risk of stress associated with water deficiency because the nutrient solution is always available according to the plants' requirements. However, considering the multiple factors associated with cultivation, further studies on saline formulations, electrical conductivity, nutrient solution volume and nutrient solution change intervals are necessary to improve the efficiency, economy and sustainability of this fertigation system, while aiming to improve the quality of plants produced using Nutripool. In addition, larger-scale tests using other commercial cultivars and multiple genotypes need to be carried out to assess the viability of their commercial application in orchid production. Finally, the Nutripool cultivation system has proven better performance in the cultivation and development of pot Phalaenopsis orchids, with higher quality of plants and saving water and fertilizers.
Acknowledgements
ACCA thanks to Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp) for it scholarship, Process number 23/00462-6 and AMCB thanks to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) for it scholarship, Process 1661. JCC thanks to CNPQ, processes number 317162/2021-7 and 308207/2025-4.
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All authors allow Horticultura Brasileira to publish the manuscript
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Data availability statement:
Part of the data are in the repository of Federal University of Sao Carlos, disposable at https://repositorio.ufscar.br/items/7e883ad4-b477-44dd-a1af-0941e9936793. Complementary data also can be requested directly by e-mail to authors.
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Declaration of generative
AI and AI-assisted technologies in the writing process: We declare that we not use any AI or AI-assisted technologies for the writing process. All the content is original and produced by authors.
Part of the data are in the repository of Federal University of Sao Carlos, disposable at https://repositorio.ufscar.br/items/7e883ad4-b477-44dd-a1af-0941e9936793. Complementary data also can be requested directly by e-mail to authors.
