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Article

Effect of Coffee Grounds as a Bio-Input in Lettuce Cultivation

by
Amanda Ayda Garcia Basílio
,
Mariana Souza Gratão
,
Geovana Cristina Macedo
,
Sarah Jamilly Leones Xavier
,
Maria Eduarda Borges Rodrigues Silva
,
Luiz Antônio Freitas Soares
,
Pedro Henrique Lopes Macedo
,
Talles Eduardo Borges dos Santos
and
Fábio Santos Matos
*
Plant Production Physiology Research Group, State University of Goiás, Ipameri Unit, GO 330 Highway, Km 241, Ring Road, University Sector, Ipameri 75780-000, Goiás, Brazil
*
Author to whom correspondence should be addressed.
Sustainability 2026, 18(2), 649; https://doi.org/10.3390/su18020649
Submission received: 5 November 2025 / Revised: 3 January 2026 / Accepted: 4 January 2026 / Published: 8 January 2026
Browse Figures
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Abstract

Coffee grounds can be used in agriculture as a bio-input to enhance soil fertility and biodiversity in the long term. Furthermore, the use of coffee grounds in agriculture is a sustainable practice because it reuses an organic waste product as natural fertilizer and minimizes the environmental impact resulting from the improper disposal of waste. This study aimed to identify the effects of coffee grounds on the growth and yield of iceberg lettuce plants. The experiment was conducted in a greenhouse using 4 kg of substrate in containers with a 5.356 dm3 capacity, following a completely randomized design in a 2 × 2 factorial arrangement. The primary treatment consisted of plants grown in two types of substrate: soil and sand (01) and soil, sand, and 10% coffee grounds (02). The secondary treatment corresponded to irrigation with water (01) and a 10% coffee ground extract solution (02). Coffee grounds incorporated into the soil increase soil fertility; however, they reduce lettuce growth due to the toxicity of the compounds present and should not be used without prior treatment. Processing coffee grounds into irrigation solutions shows promise due to its high potential for use as an agricultural bio-input in lettuce production. This solution enhances the growth and development of the species, resulting in vigorous plants with market value.

1. Introduction

Brazil is the world largest producer and exporter of coffee and is renowned for its high-quality coffee produced in different regions [1]. The national production reached 54.79 million processed coffee bags in the 2023 harvest, and the per capita annual consumption of roasted and ground coffee is 4.9 kg. This is the preferred consumption form for 91% of the population [2,3].
The demand for coffee has grown in recent years, leading to an increase in associated industries, such as processing plants. Consequently, the residues generated during the coffee processing stage, including husks, parchment, mucilage, and wastewater, have significantly increased alongside rising consumption [4]. These residues account for approximately 50% of processed coffee [5]. According to [6], for every ton of instant coffee produced in Brazil, 480 kg of waste is generated. The production and preparation of instant coffee generate between 8 and 15 million tons of coffee grounds worldwide annually [7].
Coffee grounds are a potentially polluting by-product. This by-product reduces seed germination and radicle growth in lettuce and cabbage plants while altering soil fauna, leading to a decline in earthworm populations [1,8]. As a result, this by-product becomes a strong environmental pollutant candidate due to the large amount of waste generated and its high toxicity potential. It increases substrate salinity, raising electrical conductivity and negatively affecting susceptible species.
Arabica coffee contains between 12% and 18% oils, predominately palmitic and linoleic fatty acids. Additionally, coffee grounds are low in nitrogen but rich in potassium, proteins, fibers, and phenolic compounds [9]. Coffee grounds have significant nutritional value, with substantial concentrations of calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), phosphorus (P), and nitrogen, as well as an electrical conductivity ranging from 2.67 mS cm−1 to 4.5 mS cm−1 [10,11,12,13].The use of coffee grounds in agriculture can constitute an important sustainable alternative for increasing agricultural productivity by using an organic byproduct that would previously be improperly disposed of in household waste or sewers, consequently contaminating waterways [14,15].
Raw coffee grounds improve the biological, chemical, and physical properties of the soil by enhancing microbial activity, increasing organic matter content, improving aggregate stability, and promoting greater water retention. However, for optimal plant growth, vermicompost is recommended, as raw coffee grounds contain toxic polyphenols [16]. Brazil is one of the largest importers of fertilizers, and using coffee grounds as a bio-input through composting presents a valuable alternative for reducing mineral fertilizer costs [17]. Additionally, the presence of lipids enhances the potential of coffee grounds for producing high-value-added energy sources, such as biodiesel [18].
The Brazilian vegetable market is highly diverse and segmented, with production volume concentrated on six main crops: potato, tomato, watermelon, lettuce, onion, and carrot. Family farming accounts for over half of this production [19]. Lettuce (Lactuca sativa L.) is the leading leafy vegetable produced in the country, both in terms of volume and market value [20]. It is an excellent source of vitamins and minerals, offering high nutritional value [21].
Since small-scale farmers widely cultivate lettuce, it is essential to develop techniques that optimize its production [22]. Organic residues, such as coffee grounds, could serve as an alternative, as they possess characteristics that may help reduce production costs while increasing crop yield [23]. Lettuce is an important bioindicator plant due to its high sensitivity to various environmental contaminants such as heavy metals, aluminum, copper, and toxic compounds like phenols. The short life cycle of lettuce allows for the rapid and precise study of phytotoxicity, facilitating decision-making, and in this sense, the use of this species for studying the effects of coffee grounds becomes viable and relevant.
Coffee grounds aged between seven and eight months increase the growth of tomato and radish plants and have a repellent effect, reducing herbivory [7]. In this context, research efforts aimed at incorporating coffee grounds into a fast-cycle production chain become important. Therefore, this study aimed to identify the effects of coffee grounds on the growth and production of lettuce plants.

2. Material and Methods

2.1. Experimental Design

The study was conducted in a greenhouse covered with transparent plastic and sidewalls made of shade cloth, which intercepted 50% of solar radiation. The greenhouse was located at the Goiás State University (Universidade Estadual de Goiás), South Campus, UnU-Ipameri (17°43′19″ S, 48°09′35″ W, and an altitude of 773 m) in Ipameri, Goiás. This region has a tropical climate with dry winters and wet summers (Aw), according to the Köppen classification, with an average temperature of 20 °C [24].
The experiment was conducted in August and September 2024 using 4 kg of substrate in polyethylene containers with a volume of 5.356 dm3 following a completely randomized design in a 2 × 2 factorial arrangement. The primary treatment consisted of plants grown in two types of substrate: the first containing three parts soil and one part sand (01) and the second containing three parts soil, one part sand and 10% coffee grounds (02). The secondary treatment corresponded to irrigation with water (01) and irrigation with 10% coffee ground extract solution (02). The soil used was a medium-textured red-yellow latosol. Five replications were used, and the experimental unit consisted of a single pot containing one iceberg lettuce plant.
The coffee grounds used in the study were exclusively from Coffea arabica L. and were subjected to drying under full sun for one day after being spread in 2 cm thick layers. Regarding the primary treatments, a substrate was initially prepared by mixing three parts of soil with one part of washed sand. Coffee grounds were incorporated into the substrate at 10% of the final weight, meaning that for every 900 g of substrate (soil + sand), 100 g of coffee grounds were added. This mixture underwent an incubation process in the greenhouse for six months, during which it was aerated and irrigated monthly.
The methodology proposed by NBR 10.006 [25] was adopted for the secondary treatments with modifications. Then, 100 g of coffee grounds was added to 1000 mL of tap water, followed by agitation. The process was modified by incorporating heating to extract the solubilized compounds. The mixture was heated and boiled for 10 min, then left to rest for 24 h. After this period, it was filtered using a membrane filter, and the resulting liquid was used in the experiment. The obtained extract was diluted according to the fertigation treatments, ensuring that each 100 mL of irrigation solution contained 90 mL of tap water mixed with 10 mL of the extracted solution. The control treatment was irrigated with tap water sourced from the local water supply.
The plants were irrigated with water or fertigated with a coffee grounds solution for 60 days. The irrigation volume applied was 250 mL from day 1 to day 20, 300 mL from day 21 to day 40, and 350 mL from day 41 to day 60 after planting, and was calculated based on the daily evapotranspiration of the lettuce crop. Since the crop coefficient (Kc) for lettuce has not yet been determined for the Ipameri-GO region, a Kc value of 1.00 was used, as estimated by FAO 56 [26]. The volume was calculated by determining the reference evapotranspiration and the crop coefficient according to the following equation:
ETc = ETo × Kc
where
  • ETc = crop evapotranspiration.
  • Kc = crop coefficient.
  • ETo = reference evapotranspiration.
The daily ETo calculation was performed using the Qirriga application [27] based on the Penman–Monteith method recommended by FAO [28]. This calculation was based on daily data for maximum and minimum air temperature, relative humidity, solar radiation, and wind speed collected from the INMET meteorological station in the municipality of Ipameri, GO. Irrigation was carried out in two stages during the day, with half of the water volume applied in the early morning (between 8:00 and 9:00 a.m.) and the other half in the late afternoon (between 4:00 and 5:00 p.m.). The water used was tap water obtained from the local water supply system. After 60 days of cultivation, the plants were evaluated.

2.2. Agronomic Variables and Nutrition

The head diameter was measured using a graduated ruler, assessing the lettuce head from one end to the other. The number of leaves was determined by counting all the leaves on the plant. Leaf area analysis was performed using the CI-202 Portable Laser Leaf Area Meter, measuring fully expanded leaves. Fresh mass was obtained by weighing the plant after harvest, while dry mass was determined by weighing the plant after drying for 72 h in an oven at 70 °C.
The chlorophyll index was determined using a portable chlorophyll meter, ClorofiLOG model CFL 1030, which provided values for chlorophyll a, chlorophyll b, and total chlorophyll, obtained by summing both, expressed in SPAD Chlorophyll Index units.
To evaluate leaf nitrogen content, 100 g of dry mass from each plant were separated, ground, and sent for laboratory analysis to quantify nitrogen content in the plants. The leaf potassium content was measured using a portable potassium meter, HORIBA model LAQUAtwin K-11, which provided the nutrient content for each plant.
After collecting 250 g of substrate from each plot, soil chemical analysis and organic matter content were determined. The samples were then sent to a soil analysis laboratory for evaluation using atomic absorption equipment.

2.3. Mycorrhizal Colonization (MC)

To assess mycorrhizal colonization, the finest roots of each lettuce plant were separated, washed in running water, and preserved in 50% alcohol. The method proposed by [29] was used to clarify and stain the roots. Quantification was performed using the grid plate method under a stereomicroscope according to [30], and the percentage of colonization was determined by the following equation:
CM = sc/(sn + sc) × 100
where:
  • CM: mycorrhizal colonization (%).
  • sn: number of non-colonized segments.
  • sc: number of colonized segments.

Mycorrhizal Spore Density (MSD)

For analysis of mycorrhizal spore density (MSD), the rhizosphere soil of lettuce plants was collected and sieved. From 50 g of soil, the mycorrhizal spores were separated and collected using a combination of the decantation and wet sieving methods [31] with centrifugation and flotation in sucrose [32]. Mycorrhizal spore counting was performed using an acrylic plate with concentric rings, under a stereoscopic microscope with 40× magnification.

2.4. Statistical Procedures

The variables were subjected to analysis of variance (ANOVA) and the Newman–Keuls mean test, following a completely randomized design in a 2 × 2 factorial scheme with five replications. Multivariate data analysis was conducted using a correlation network approach with the qgraph package, and canonical variable analysis was performed using the candisc package, both executed in the RBio statistical software version 01 [33].

3. Results and Discussion

The results obtained for the number of leaves, fresh mass, leaf area, potassium content in leaves, dry mass, total chlorophyll content, mycorrhizal colonization and mycorrhizal spore density in iceberg lettuce plants irrigated with a coffee ground solution and grown in soil containing coffee ground residue are shown in Table 1. The coefficients of variation for the main plot (CV1) and subplot (CV2) were well below 30 and, together, point to the reliability of the results obtained, indicating adequate precision and scientific rigor of the work.
The results showed that irrigation with a coffee ground solution and adding incubated coffee grounds to the soil significantly affected the parameters evaluated (Table 1). However, significant interactions between treatments were observed only for total chlorophyll content, fresh mass, shoot dry mass and mycorrhizal spore density indicating that the effect of one treatment influenced the levels of the other treatment. These findings align with studies reporting that coffee grounds impact plant growth and development depending on the combinations and application rates used [10,11].
The results presented in Table 2 refer to the pH, levels of phosphorus, potassium, calcium, and magnesium, the sum of bases, and organic matter in the soil used in the containers containing coffee grounds and irrigated with the coffee grounds solution. Significant interactions between treatments were observed for phosphorus, potassium, calcium, and magnesium levels.
It is possible to identify that all variables showed some level of significance, indicating that coffee grounds significantly influence the chemical properties of the soil. Some studies suggest that coffee grounds affect soil chemical characteristics and may impact physical and biological properties, such as aggregate structural stability, water retention, soil hydrophobicity, and microbial diversity [34]. Additionally, according to [35], studies conducted with lettuce showed that composted coffee grounds, when applied in low doses, improved the Mg, Mn, K, and Na levels. This effect was attributed to the increased availability of these elements for plant uptake during composting and caffeine degradation.
The results of the mean test for the variables that did not show significant interaction between treatments are presented in Table 3, including the following variables: number of leaves, leaf area, leaf potassium content, soil pH, base sum, soil organic matter content and mycorrhizal colonization. The mean test for fresh mass, dry mass, total chlorophyll content and mycorrhizal spore density in lettuce plants is presented in Figure 1, demonstrating the presence of significant interaction between treatments.
In general, coffee grounds added to the soil and incubated over several months reduced the growth of lettuce plants by decreasing leaf area, shoot fresh mass, shoot dry mass, chlorophyll content and mycorrhizal colonization. These results are likely related to the toxic effects of substances present in coffee grounds, as in all treatments where coffee grounds were incorporated into the soil (even before planting), regardless of whether they were irrigated with water or the coffee grounds solution, the plants exhibited reduced development. According to [11], the direct application of coffee grounds to the soil drastically reduces plant growth due to the presence of compounds that are toxic to plants. Some studies suggest the use of vermicompost or some type of decomposition of coffee grounds before incorporation into the soil [16,34]. The present study proposed the use of the raw byproduct and, despite improvements in the chemical properties of the soil, the presence of caffeine and phenolic compounds such as tannins and chlorogenic acid may have caused toxicity to lettuce plants. Therefore, in the short term, applying raw coffee grounds to the soil can harm plant development; however, in the long term, the increase in soil fertility can be useful and viable for agriculture.
Despite the negative effects on lettuce growth, coffee grounds incorporated into the soil improved the soil and plant nutritional properties by increasing foliar potassium content by 22%, sum of bases by 27%, and organic matter content by 27%, as well as enhancing phosphorus, potassium, calcium, and magnesium levels (Figure 2). These results are consistent with those reported by [36], who found that incorporating coffee grounds into different soil types increased all organic matter fractions and raised total extractable carbon by approximately 200%. Therefore, it is suggested that coffee grounds contain some type of toxic agent when they reach the soil solution, due to the wide range of organic compounds such as tannic acid, cellulose, hemicellulose, lipids, organic acids, and polyphenols [37].
The significant increase in P content when coffee grounds were applied to the soil (Table 3) may explain the significant 22.79% decrease in mycorrhizal colonization of lettuce plants, as the increase in P content may inhibit the mutualistic symbiosis between fungus and plant, as demonstrated by [38] when studying the reduction in mycorrhizal colonization of the root, induced by phosphorus fertilization, and cadmium accumulation in wheat crops.
The use of coffee grounds in the irrigation solution proved to be the most promising treatment, as it enhanced plant vigor by promoting greater vegetative growth, evidenced by a 21% increase in the number of leaves, a 13% increase in leaf area, and a 34% increase in dry mass compared to the control treatment. Additionally, it raised leaf potassium content by 37%, although it had little impact on the chemical properties of the soil and the rate of mycorrhizal colonization of lettuce plants (Table 3). These results indicate that incorporating coffee grounds into the soil and irrigating plants with a coffee grounds solution affect lettuce plant development differently. While diluting coffee grounds in water seems to mitigate the toxic effects, at least through dilution, direct application to the substrate, despite increasing soil fertility, reduces lettuce growth due to some type of toxicity. While diluting coffee grounds in water seems to mitigate the toxic effects, at least through dilution, direct application to the substrate, despite increasing soil fertility, reduces lettuce growth due to some type of toxicity. These results point to coffee grounds as an important and promising organic residue for sustainable use as a biofertilizer; however, its use should follow dilution criteria for positive short-term effects. According to [10], coffee grounds can be a biostimulant in plant development. However, the findings contradict those of [39], who reported reduced lettuce growth when using a coffee grounds solution.
The higher fresh and dry mass values in lettuce plants shown in Figure 1 indicate that treating coffee grounds by preparing a solution for irrigation is an important alternative for using this organic residue in agriculture. Conversely, the lower biomass accumulation in plants that received raw coffee grounds directly in the soil points to a toxic effect from direct use. The higher chlorophyll content in treatments containing coffee grounds, especially in the treatment with coffee grounds incorporated into the soil, may be related to the greater availability of nutrients in this treatment, mainly magnesium, which is a central element of the chlorophyll molecule. The availability of nutrients that are components of the chlorophyll molecule is an essential condition for the greater synthesis of this photosynthetic pigment, as highlighted by [40]. The significant decrease in the density of mycorrhizal spores under the use of coffee grounds in the soil and irrigation solution can be explained by the fact that coffee residues contain toxic compounds such as tannins [41] and chlorogenic acid [42] which have deleterious effects on soil microorganisms [43].
The phosphorus, potassium, calcium, and magnesium levels in the soil used in the treatments are shown in Figure 2. The results indicate that when coffee grounds are incorporated into the soil, there are increases of 25% in phosphorus, 23% in potassium, 24% in calcium, and 23% in magnesium levels compared to the control treatment. These findings align with studies showing that coffee grounds improve soil chemical fertility by increasing organic carbon, nitrogen, and potassium levels in the soil, as well as enhancing the absorption of certain macronutrients (Ca, Mg, K) and micronutrients (Co, Cu, Zn) [44].
According to [45], in a study comparing coffee grounds with NPK fertilizer, coffee grounds outperformed NPK in all evaluated parameters when applied to Japanese fennel. These results indicate that raw coffee grounds applied directly substantially increase soil fertility and can constitute an important source of nutrients for plants in the long term; however, in the short term, the impact on lettuce was adverse, due to reduced growth, highlighting that its use should be regulated to avoid toxicity.
The canonical variable analysis for ordering the variables along two axes is shown in Figure 3 and represents 99.2% of the data variation. Component 1 separates the variables around the treatments into two groups, with treatments with greater growth grouped to the left of axis 1 where plants were irrigated with coffee grounds solution, and plants irrigated with water grouped to the right. Component 2 ordered the treatments according to the substrate, with soil containing coffee grounds and therefore higher fertility grouped in the lower portion, and the common substrate without coffee grounds and lower fertility grouped in the upper part of component 2. These findings align with those reported by [34], who highlight the improvement in soil fertility and increased crop yield associated with using coffee grounds. The results demonstrate a clear distinction between the more developed plants when irrigated with a coffee grounds solution and the less developed lettuce grown in soil containing incorporated coffee grounds. Therefore, the use of raw coffee grounds incorporated into the soil is not recommended, because despite increasing soil fertility, the toxic compounds likely remain active.
The use of coffee grounds represents an innovative and sustainable approach, as when properly managed, it functions as a high-quality organic biofertilizer suitable for use in agriculture, clearly reducing environmental impacts from improper waste disposal. This research is innovative in that it utilizes a byproduct with no commercial value. The results indicate that coffee grounds are a promising byproduct for agricultural use; however, their application requires careful management to avoid adverse effects on plant development. Horticultural crops can achieve greater profitability by benefiting from the enhanced growth and development provided by coffee grounds, a low-cost byproduct [7]. Our results demonstrate that the use of raw coffee grounds increases soil fertility, but the toxic components of the grounds likely remain active and inhibit plant development in the short term. However, handling the grounds through a diluted coffee grounds solution for irrigation represents an important alternative to increase plant production using this organic byproduct.

4. Conclusions

The direct incorporation of coffee grounds into the soil reduces lettuce growth in the short term and should not be used without prior treatment. However, soil fertility is improved under this application condition due to the increase in macronutrients and organic matter; therefore, subsequent studies are recommended to verify the existence of long-term soil fertility benefits.
Irrigation with a coffee grounds solution is a promising approach, as it demonstrates high potential as an agricultural bio-input for lettuce production. This solution improves the growth and development of the species, producing vigorous plants with market value.
The use of coffee grounds in agriculture alters the coffee production chain, adding value to a byproduct without commercial significance and redirecting it towards a biorational agricultural practice, as it uses a potentially polluting byproduct for a sustainable agricultural purpose.

Author Contributions

Conceptualization, F.S.M.; Methodology, M.S.G., S.J.L.X., M.E.B.R.S., L.A.F.S., P.H.L.M. and T.E.B.d.S.; Validation, T.E.B.d.S.; Formal analysis, G.C.M. and F.S.M.; Investigation, A.A.G.B., M.S.G., G.C.M., S.J.L.X., L.A.F.S. and P.H.L.M.; Resources, M.E.B.R.S.; Writing–original draft, A.A.G.B. and G.C.M.; Writing–review & editing, F.S.M.; Visualization, T.E.B.d.S.; Supervision, F.S.M. All authors have read and agreed to the published version of the manuscript.

Funding

To the State University of Goiás for providing resources under the Pro-Projects Notice—Bioinputs—Strategic Institutional Project No. 23/2023, PrP protocol: 202303041, Sei Process No. 202200020023146. The authors thank the State University of Goiás for the financial resources provided by the PrP/UEG 01/2023 grant, pro-programs, funding agreement: 75593594, SEI: 202300020011690.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

No new data were created or analyzed in this study.

Conflicts of Interest

The authors declare no conflict of interest.

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Sustainability 18 00649 g001
Figure 1. Newman–Keuls mean test for fresh mass (FM), dry mass (DM), total chlorophyll content (Chl a+b), and mycorrhizal spore density (MSD) in lettuce plants grown in a soil containing coffee grounds and irrigation with water (CG_C2) or soil containing coffee grounds and irrigation with coffee grounds solution (CG_CGS) or common substrate and irrigation with coffee grounds solution (C1_CGS) or common substrate and irrigation with water (C1_C2). Uppercase letters compare bars with the same internal color (white or gray), indicating the effect of the irrigation type, with coffee grounds solution (CGS) or with water (C2), while lowercase letters compare bars with the same internal outline and indicate the effect of the substrate with coffee grounds in the soil (CG) and without coffee grounds in the soil (C1). Bars with similar letters do not differ at a 5% probability level, according to the Newman–Keuls test.
Figure 1. Newman–Keuls mean test for fresh mass (FM), dry mass (DM), total chlorophyll content (Chl a+b), and mycorrhizal spore density (MSD) in lettuce plants grown in a soil containing coffee grounds and irrigation with water (CG_C2) or soil containing coffee grounds and irrigation with coffee grounds solution (CG_CGS) or common substrate and irrigation with coffee grounds solution (C1_CGS) or common substrate and irrigation with water (C1_C2). Uppercase letters compare bars with the same internal color (white or gray), indicating the effect of the irrigation type, with coffee grounds solution (CGS) or with water (C2), while lowercase letters compare bars with the same internal outline and indicate the effect of the substrate with coffee grounds in the soil (CG) and without coffee grounds in the soil (C1). Bars with similar letters do not differ at a 5% probability level, according to the Newman–Keuls test.
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Sustainability 18 00649 g002
Figure 2. Newman–Keuls mean test for the levels of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in a soil containing coffee grounds and irrigation with water (CG_C2) or soil containing coffee grounds and irrigation with coffee grounds solution (CG_CGS) or common substrate and irrigation with coffee grounds solution (C1_CGS) or common substrate and irrigation with water (C1_C2). Uppercase letters compare bars with the same internal color (white or gray), indicating the effect of the irrigation type, with coffee grounds solution (CGS) or with water (C2), while lowercase letters compare bars with the same internal outline and indicate the effect of the substrate with coffee grounds in the soil (CG) and without coffee grounds in the soil (C1). Bars with similar letters do not differ at a 5% probability level, according to the Newman–Keuls test.
Figure 2. Newman–Keuls mean test for the levels of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in a soil containing coffee grounds and irrigation with water (CG_C2) or soil containing coffee grounds and irrigation with coffee grounds solution (CG_CGS) or common substrate and irrigation with coffee grounds solution (C1_CGS) or common substrate and irrigation with water (C1_C2). Uppercase letters compare bars with the same internal color (white or gray), indicating the effect of the irrigation type, with coffee grounds solution (CGS) or with water (C2), while lowercase letters compare bars with the same internal outline and indicate the effect of the substrate with coffee grounds in the soil (CG) and without coffee grounds in the soil (C1). Bars with similar letters do not differ at a 5% probability level, according to the Newman–Keuls test.
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Sustainability 18 00649 g003
Figure 3. Canonical variable analysis of nitrogen (N), leaf area (LA), fresh mass (FM), number of leaves (NL), leaf potassium (KL), soil potassium (KS), total chlorophylls (Chl), phosphorus (P), base saturation (BS), magnesium (Mg), calcium (Ca), carotenoids (Car), mycorrhizal colonization (MC), mycorrhizal spore density (MSD), and organic matter (OM) in soil and lettuce plants grown in a soil containing coffee grounds and irrigation with water (CG_C2) or soil containing coffee grounds and irrigation with coffee grounds solution (CG_CGS) or common substrate and irrigation with coffee grounds solution (C1_CGS) or common substrate and irrigation with water (C1_C2).
Figure 3. Canonical variable analysis of nitrogen (N), leaf area (LA), fresh mass (FM), number of leaves (NL), leaf potassium (KL), soil potassium (KS), total chlorophylls (Chl), phosphorus (P), base saturation (BS), magnesium (Mg), calcium (Ca), carotenoids (Car), mycorrhizal colonization (MC), mycorrhizal spore density (MSD), and organic matter (OM) in soil and lettuce plants grown in a soil containing coffee grounds and irrigation with water (CG_C2) or soil containing coffee grounds and irrigation with coffee grounds solution (CG_CGS) or common substrate and irrigation with coffee grounds solution (C1_CGS) or common substrate and irrigation with water (C1_C2).
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Table 1. Summary of the analysis of variance for the number of leaves (NL), fresh mass (FM), leaf area (LA), leaf potassium content (K), dry mass (DM), total chlorophyll content (Chl a+b), mycorrhizal colonization (MC) and mycorrhizal spore density (MSD) in lettuce plants grown in soil containing coffee grounds and subjected to irrigation with a coffee ground solution.
Table 1. Summary of the analysis of variance for the number of leaves (NL), fresh mass (FM), leaf area (LA), leaf potassium content (K), dry mass (DM), total chlorophyll content (Chl a+b), mycorrhizal colonization (MC) and mycorrhizal spore density (MSD) in lettuce plants grown in soil containing coffee grounds and subjected to irrigation with a coffee ground solution.
Sources of VariationMean Square
DFNLFMLAKDMCl (a+b)MCMSD
Soil (S)15.0 ns413.0 *35.0 *41,314 *3.0 *11.0268.3 *262,663 **
Error 181.025.00.442050.10.310.72241
Irrigation (I)164.0 *255.0 *8.0 *142,974 *12.0 *1.053.3 ns254,025 **
SxI11.0 ns265.0 *0.0 ns4234 ns2.0 *2.069.1 ns180,500 **
Error 282.0265.00.627411.10.133.13957.27
Total19
CV16.812.57.317.58.113.511.5117.94
CV28.510.99.2 14.2 8.88.520.2111.72
* Significant at 5%, ** significant at 1% significance and “ns” is not significant at 5% probability.
Table 2. Summary of variance analysis for soil pH (pH), levels of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), the sum of bases (BS), and organic matter in soil containing coffee grounds and cultivated with lettuce irrigated with a coffee grounds solution.
Table 2. Summary of variance analysis for soil pH (pH), levels of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), the sum of bases (BS), and organic matter in soil containing coffee grounds and cultivated with lettuce irrigated with a coffee grounds solution.
Sources of VariationMean Square
DFpHPKCaMgBSOM
Soil (S)10.0 ns897 *10,951 *1.0 *1.0 *6.0 *2.0 *
Error 180.06.03890.30.00.20.1
Irrigation (I)10.1 *0.5 ns6552 *0.3 *0.1 ns0.3 ns0.2 ns
SxI10.1 ns331 *7296 *0.2 *0.1 *0.3 ns0.2 ns
Error 280.0605320.00.00.20.1
Total19
CV1%3.113.65.714.116.413.914.3
CV2%2.411.56.710.79.08.816.4
* Significant at 5% and “ns” is not significant at 5% probability.
Table 3. Newman–Keuls mean test for number of leaves (NL), leaf area (LA), leaf potassium content (K), soil pH (pH), soil base sum (BS), soil organic matter content (O.M) and mycorrhizal colonization (MC) with coffee grounds (CG) or common substrate-control (C1) and irrigated with water-control (C2) or coffee grounds solution (CGS).
Table 3. Newman–Keuls mean test for number of leaves (NL), leaf area (LA), leaf potassium content (K), soil pH (pH), soil base sum (BS), soil organic matter content (O.M) and mycorrhizal colonization (MC) with coffee grounds (CG) or common substrate-control (C1) and irrigated with water-control (C2) or coffee grounds solution (CGS).
TreatmentNLLA
(cm2)		K
(ppm)		pHBS
(cmolc dm−3)		O.M
(%)		MC
(%)
Substrate with and without coffee grounds
CG15.2a7.7b415.0a6.3a3.9a2.2a24.82b
C116.2a10.4a324.1b6.3a2.8b1.6b32.15a
Type of irrigation
CGS17.5a9.6a454.1a6.4a3.2a1.7a30.11a
C213.9b8.4b285.0b6.2b3.5a2.0a26.85a
Means followed by the same letter in the columns do not differ at a 5% probability level according to the Newman–Keuls test.
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MDPI and ACS Style

Basílio, A.A.G.; Gratão, M.S.; Macedo, G.C.; Xavier, S.J.L.; Silva, M.E.B.R.; Soares, L.A.F.; Macedo, P.H.L.; dos Santos, T.E.B.; Matos, F.S. Effect of Coffee Grounds as a Bio-Input in Lettuce Cultivation. Sustainability 2026, 18, 649. https://doi.org/10.3390/su18020649

AMA Style

Basílio AAG, Gratão MS, Macedo GC, Xavier SJL, Silva MEBR, Soares LAF, Macedo PHL, dos Santos TEB, Matos FS. Effect of Coffee Grounds as a Bio-Input in Lettuce Cultivation. Sustainability. 2026; 18(2):649. https://doi.org/10.3390/su18020649

Chicago/Turabian Style

Basílio, Amanda Ayda Garcia, Mariana Souza Gratão, Geovana Cristina Macedo, Sarah Jamilly Leones Xavier, Maria Eduarda Borges Rodrigues Silva, Luiz Antônio Freitas Soares, Pedro Henrique Lopes Macedo, Talles Eduardo Borges dos Santos, and Fábio Santos Matos. 2026. "Effect of Coffee Grounds as a Bio-Input in Lettuce Cultivation" Sustainability 18, no. 2: 649. https://doi.org/10.3390/su18020649

APA Style

Basílio, A. A. G., Gratão, M. S., Macedo, G. C., Xavier, S. J. L., Silva, M. E. B. R., Soares, L. A. F., Macedo, P. H. L., dos Santos, T. E. B., & Matos, F. S. (2026). Effect of Coffee Grounds as a Bio-Input in Lettuce Cultivation. Sustainability, 18(2), 649. https://doi.org/10.3390/su18020649

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