Next Article in Journal
The Assessment of Residents’ Perception of Possible Benefits and Challenges of Home Vertical Gardens in Kigali, Rwanda
Previous Article in Journal
Developing a Conceptual Framework for Characterizing and Measuring Social Resilience in Blue-Green Infrastructure (BGI)
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Sustainability
Volume 16
Issue 9
10.3390/su16093848
sustainability-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

The Effect of Varying Olive Mill Wastewater Concentrations on Soil Free-Living Nematode Communities and Lettuce Growth

by
Panagiotis Kekelis
1,2,
Cleopatra Pantazi
1,
Snezhana Mourouzidou
1,
Aphrodite Theofilidou
1,2,
Maria D. Dimou
3,
Vassilis Aschonitis
2 and
Nikolaos Monokrousos
1,*
1
University Center of International Programmes of Studies, International Hellenic University, 57001 Thessaloniki, Greece
2
Soil and Water Resources Institute, Hellenic Agricultural Organization—Dimitra, 57001 Thessaloniki, Greece
3
Department of Ecology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(9), 3848; https://doi.org/10.3390/su16093848
Submission received: 29 February 2024 / Revised: 25 April 2024 / Accepted: 30 April 2024 / Published: 3 May 2024
Browse Figures
Versions Notes

Abstract

:
We assessed the impact of increasing olive mill waste (OMW) concentrations (10%, 35%, 70%, and 100% v/v) on soil free-living nematode communities and Lactuca sativa (lettuce) growth, 10 and 45 days after application (DAA). L. sativa plants showed a survival threshold at OMW10%, with higher concentrations proving fatal. Contrary to expectations, nematode abundance increased with OMW concentration. OMW10% induced a rapid surge in nematode abundance, stabilizing at 45 DAA, resembling control values. OMW35%, OMW70%, and OMW100% plots exhibited persistent, gradual increases, surpassing control values at 45 DAA. All treatments favored fungal feeders, resulting in the overdominance of the genus Aphelenchus both at 10 and 45 DAA. Even though OMW did not exert a toxic effect on nematode populations, this shift in the community structure towards the dominance of a single genus could suggest an imbalance in the soil community, which could have negative implications for soil health and ecosystem functioning. Overall, our study provides insights into the complex interactions between OMW, soil nematode communities, and plant growth, emphasizing the importance of understanding soil ecology for sustainable agricultural management.

1. Introduction

Agricultural practices continually evolve as the demand for sustainable solutions intensifies in the face of environmental challenges. In this context, the utilization of by-products from various industries as soil amendments has gained attention for its potential benefits and drawbacks. One such by-product, olive mill wastewater (OMW), presents a complex mixture of organic compounds, posing both opportunities and challenges in agricultural ecosystems. The olive oil manufacturing process generates significant quantities of olive mill waste which presents a notable problem due to its high acidity and concentrations of chemical oxygen demand (COD) and biological oxygen demand (BOD) [1,2]. Given the impracticality of various tested physical, chemical, and biological technologies for olive mill wastewater treatment, it is often discharged untreated into sewer systems, water streams, or inefficiently stored in evaporation ponds; nevertheless, this practice leads to the degradation of the soil system and greenhouse gas emissions [3,4]. However, repurposing OMW within the waste-to-resource paradigm and recycling it could contribute to a successful strategy for implementing the circular economy model. This approach has the potential to yield significant socioeconomic benefits, particularly for low-income Mediterranean countries [5].
OMW’s polyphenols exhibit strong antimicrobial and phytotoxic effects, hindering its biodegradation [1,6]. Preliminary studies suggest that the application of olive mill wastewater can alter soil nutrient availability, affect root development, and influence the overall physiological processes of crops. Even a brief exposure of raw OMW to Mentha spicata L. cuttings led to irreversible damage to rhizogenesis and shoot development [7]. The diluted OMW demonstrated a negative impact on the seed germination of maize and tomato. Researchers achieved a significant decrease in monomeric phenols through anaerobic digestion. However, this reduction did not decrease toxicity towards germination, implying that other components may also contribute to phytotoxicity [8].
Despite its toxic aspects, OMW contains organic compounds, sugars, minerals, and growth-promoting substances; the nature of these constituents is influenced by the olive cultivar, maturation degree, climate conditions, and agricultural practices [9]. The richness of compounds present in OMW enables an increase in organic matter content and enhances soil fertility, making it a potential candidate for use as a fertilizer and soil conditioner [10,11]. This conversion into agricultural input stands out as a highly promising valorization approach. When treated with OMW, the soil’s water retention capacity increased due to a reduction in bulk density, resulting in increased soil porosity and the formation of stable aggregates [12]. The land application of olive mill wastewater has been reported to increase organic matter content and enrich essential inorganic nutrients (P, K, Mg, Fe), vital for promoting plant growth [13]. Numerous studies reported that OMW contributed to positive metabolic and physiological responses in plants, enhancing their growth [4,10,14]. However, interest has arisen regarding its impact not only on subsequent effects on crop productivity but also on soil organisms.
Several studies demonstrated that OMW addition caused significant shifts in the structure and function of microbial communities, which in turn had an impact on soil fertility [15,16]. Additionally, other studies highlighted that raw OMW and its polar fraction were highly toxic not only to microorganisms but also to invertebrates (Daphnia magna, Thamnocephalus platyurus, Chironomus riparius) and vertebrates (Danio rerio, Cyprinus carpio), exhibiting toxicity even at low concentrations [17,18]. Furthermore, the use of OMW has also attracted attention as having the potential to control plant pathogens and post-harvest diseases [2,19]. Biopesticide properties were assigned to OMW phenolic extract compounds, which were reported by many as having ecotoxicological effects on soil habitat function [20,21]. Although many studies were conducted on OMW’s suppressiveness of plant-parasitic nematodes [2,10], the literature regarding its effect on the soil nematode community is limited [22]. Further investigation is required to comprehensively understand their response to the addition of OMW.
Soil nematodes are considered an essential category of soil organisms and serve as useful indicators of soil health and soil recovery due to their rapid response to changes in soil conditions [23,24,25]. Their sensitivity to environmental changes, including variations in soil structure, nutrient content, and organic matter [26], positions them as a reliable reflection of soil ecosystem dynamics [27]. Although herbivorous soil nematodes can be harmful for agricultural production, by closely monitoring the abundance and diversity of free-living nematode communities, researchers gain an understanding of the subtle shifts in soil status, offering a real-time assessment of soil health, especially after chemical or biological applications [28].
The aim of our study was to assess the impact of OMW on soil nematode communities. We hypothesized that the application of olive mill waste to soil with low organic matter content would significantly affect the abundance and composition of soil nematode communities. Specifically, we anticipated that increasing concentrations of OMW would reduce their abundance and diversity. Additionally, we sought to evaluate the impact of OMW on plant productivity. Recognizing the intricate relationship between soil ecology and crop performance, our objective was to provide valuable insights for the development of environmentally responsible agricultural practices. Furthermore, we aimed to contribute to the broader discourse on utilizing industrial by-products in agriculture while ensuring soil biodiversity and resilience preservation.

2. Materials and Methods

2.1. Experiment Design

The present study utilized olive mill wastewater (OMW) sourced from a three-phase olive oil mill located in Souroti, proximate to the city of Thessaloniki, Greece. The collected OMW was extracted from settled reservoirs and subsequently preserved at −20 °C, until its application in the experimental procedures. Soil samples for the study were obtained from agricultural fields in Thermi, Thessaloniki. Post-collection, the soil underwent homogenization, the breaking of large aggregates, and sieving through a 6 mm sieve. The soil type was identified as loam using the Bouyoucos method [23]. Furthermore, pH was measured in a soil-distilled water paste (1:1), organic carbon (%) was measured using the titration method [24], and total nitrogen was measured using the Khendjal apparatus [25]. The results are elucidated in Table 1 to provide comprehensive insight into its composition for this investigation.

2.2. Pot Experiment

Lettuce (Lactuca sativa) seeds, obtained from a commercial supplier specializing in plant seeds, were planted in a seed container filled with soil that had been sieved through a 2 mm mesh. The growth period spanned 45 days under open-air conditions. Upon attaining the four-leaf stage, individual lettuce plants were transplanted into 0.5 L pots filled with non-sterilized, sieved soil. Four specific dilutions of olive mill wastewater (OMW) were formulated to establish distinct levels of application: 10% v/v (OMW10%), 35% v/v (OMW35%), 70% v/v (OMW70%), and 100% v/v (OMW100%). A control group that received no OMW application was also included. Each dilution, totaling 80 mL, was carefully administered to its corresponding pot to prevent spillage and ensure containment. OMW application was conducted as a one-time event. Control soils, without OMW, were created by substituting OMW with distilled water. Diverse dilutions were created using water as the diluent substance.
The pots were organized in a completely randomized design, with five replicates per treatment. The pots were consistently watered throughout the experimental duration to maintain a moisture content of 10% w/w, a level that does not hinder plant growth. The daily weighing of pots was conducted to ascertain water loss, following the method outlined by Troelstra et al. [26]. No fertilizers were applied to the pots. To assess the short- and long-term effects of the treatments on both plant development and soil nematodes, two destructive samplings were conducted at 10 and 45 days after the application of olive mill wastewater (referred to as 10 and 45 DAA), with 25 samples collected for each sampling event. The soil was maintained at a cool temperature (4 °C), until processing. After oven-drying plant shoots and roots for 48 h at 70 °C, the total biomass of the plants was determined.

2.3. Nematode Extraction, Identification, and Indices

Nematodes were extracted from 150 mL of each soil sample using the modified Cobb’s sieving and decanting method, as detailed by S’Jacob and van Bezooijen [27], culminating in the use of a cotton wool filter in the final step. After quantifying the overall nematode abundance under a stereoscope, nematodes were heat-killed and then preserved in 4% formaldehyde. Approximately 100 randomly selected nematodes were identified at the genus level under a microscope using Bongers’ [28] identification key and considering morphological characteristics, including the stomodeum, reproductive organs, and tail. Nematode taxa were then classified into trophic groups following the colonization–persistence gradient (c-p values) by Bongers [29] and Bongers and Bongers [30] and grouped into functional guilds according to Ferris et al. [31] and Bongers and Bongers [30], signifying portions of specific trophic groups exhibiting the same c-p value.
The nematode functional indices employed in our study capture various attributes of the nematode community. The maturity index (MI) for free-living nematodes and the plant parasitic index (PPI) for taxa feeding on plants were computed based on Bongers [29]. Lower MI values indicate greater soil disturbance, as measured by Yeates et al. [32] and Bongers and Ferris [33]. The PPI serves as a maturity index for taxa feeding on plants. The weighted faunal analysis proposed by Ferris et al. [34] was employed to calculate the enrichment index (EI), channel index (CI), and structure index (SI), reflecting the functional structure of the soil food web. The SI provides insights into whether the soil ecosystem is more trophically linked and organized or less trophically linked and degraded, following Ferris et al. [34]. The metabolic footprint (MF), representing carbon utilization by nematodes and encompassing the sum of the lifetime amount of carbon allocated to growth, egg production, and respiration, was computed in accordance with Ferris [34], using the nematode indicator joint analysis online platform (NINJA) [35].

2.4. Statistical Analysis

To assess the influence of time, various treatments, and the interplay between these variables on the soil nematode community and plant characteristics, a two-way analysis of variance (ANOVA) incorporating treatment and time as independent variables was conducted. Initial scrutiny involved testing the data for adherence to ANOVA assumptions, including considerations such as the normality and homogeneity of variance. Subsequently, to discern significant effects, a least square differences (LSD) test was applied, facilitated by STATISTICA 9 Software. Renyi and nonmetric multidimensional scaling (NMDS) graphs, along with a SIMPER test table, were generated using PAST SOFTWARE to visually represent and interpret the observed patterns in the data.

3. Results

Our results on plant characteristics are presented in Figure 1. The OMW10%-treated specimens exhibited greater upper length values (10.48 ± 0.25 cm) at 45 days after application (45 DAA) (Figure 1a). In contrast, the dry mass was lower (0.33 ± 0.01 g) compared to the control (0.44 ± 0.02 g) when OMW10% was applied (Figure 1). Notably, the plants treated with OMW35%, OMW70%, and OMW100% exhibited burn-like symptoms and eventually died.
Our samples contained nematode genera comprising 16 bacterivores, 5 fungivores, 8 herbivores, and 7 omnivores (Table S1). The abundance of distinct nematode trophic groups across different treatments, assessed at 10 days after application (DAA) and 45 DAA, is depicted in Figure 2. Overall, a higher number of nematodes (550 ± 107.85 individuals/100 mL soil) were recorded in the first sampling (10 DAA). Moreover, at 10 DAA, the total nematode population exhibited a significant increase across all treated samples compared to the control, except in the OMW100% treatment, where the increase was not significant. A similar pattern was also evident in bacterivores and fungivores; nevertheless, the OMW35%-treated samples did not show a significant increase in fungivores compared to the control. The populations of the herbivores were solely affected by the Time factor and were significantly lower (19 ± 7.51 individuals/100 mL soil) in the second sampling (45 DAA). At 45 DAA, OMW70% and OMW100% showed significantly elevated values in the total nematode population (735 ± 133.97 and 607 ± 122.47 individuals/100 mL soil, respectively), bacterial feeders (192.1 ± 21.19 and 98.02 ± 18.74 individuals/100 mL soil, respectively), and fungal feeders (496 ± 118.67 and 492.73 ± 101.39 individuals/100 mL soil, respectively). Herbivores exhibited levels similar to the control in treated samples at 45 DAA. Predators and omnivores showed low abundances (10 ± 5.16 and 11 ± 4.72 individuals/100 mL soil) in both sampling instances, consistent with expectations for cultivated soils.
Although an increase in abundance was recorded in some applications, this was not reflected in the relative abundance (Figure 3), suggesting that the composition remained unaffected, with changes observed only in abundance. The percentage contribution noticeably changed only in the OMW70% and OMW100% treatments at 45 DAA, where fungal feeders were more enhanced (Figure 3b). Evidently, at 45 DAA (Figure 3b), the OMW35%, OMW70%, and OMW100% treatments presented a higher relative abundance of fungal feeders (66.2, 67.6, and 76.3%, respectively).
In Figure 4, the disturbance at 10 DAA is not as evident, as both treated and control samples are clustered in the middle of the graph, except for OMW-10%, which exhibited a significant distance from the control. At 45 DAA, on the other hand, the distance between treated and untreated samples becomes clearer, with treated samples observed to be as distant from the control as the concentration of OMW application increases.
At 10 DAA, there is a notable enhancement in Aphelenchus abundance across all applications (Figure 5). Additionally, the abundance of two bacterivores (Acrobeloides and Chiloplacus) shows a substantial increase in each application, resulting in minimal observable changes in the overall percentage contribution. At 45 DAA, a distinct trend emerges where the OMW70% and OMW100% treatments were characterized by a greater dominance of Aphelenchus (419 ± 118.87 and 386 ± 88.76 individuals/100 mL soil, respectively). This observed dominance suggests a disturbance within the system, indicating that a significant and pronounced impact has occurred. This enhancement in Aphelenchus abundance was also evident through the SIMPER test (Table S2). This enhancement closely correlated with the corresponding OMW concentration applied. Although the overall structure remained consistent, the difference between treatments was primarily attributed to the increase in Aphelenchus population.
The EI, CI, MI, bacterivore, and fungivore footprint values were estimated at 10 and 45 DAA and are presented in Table 2. OMW application affected only bacterivore and fungivore footprints. The interaction between OMW and Time affected only the fungivore footprint; interestingly, the OMW70% and OMW100% treatments had low values (31.16 ± 13.93 and 23.64 ± 10.57, respectively) at 10 DAA but appeared to be the highest (52.72 ± 10.97 and 46.94 ± 9.57, respectively) at 45 DAA. Conversely, the Time factor significantly affected the CI and EI with values higher (94.22 ± 3.71 and 43.30 ± 1.49, respectively) at 45 DAA. On the contrary, the bacterivore footprint was significantly higher (10.98 ± 1.73) in the first sampling (10 DAA).
The food web analysis based on the EI/SI ratio of the OMW treatments and the control for both samplings is presented in Figure 6. All samples from both samplings were aligned in the lower left quadrant, indicating that all soil samples were experiencing stress due to low nitrogen concentration.

4. Discussion

4.1. Impact of OMW on Lactuca sativa

We studied the impact of OMW on Lactuca sativa plants and determined a survival threshold at OMW10%, with higher dosages proving fatal. Dilution with water, a proposed mitigation strategy, has been shown to decrease OMW phytotoxicity [36,37], which clarifies the observed phytotoxic effects (e.g., acidity, salinity) on plants with increasing concentrations of OMW (above 10%). Presumably, the boundary between beneficial and harmful concentrations is narrow and likely crop-specific, consistent with findings by Rusan and Malkawi [4] and Elayadi et al. [38].

4.2. Effect on Nematode Abundance, Community Composition, and Genera Diversity

Due to the observed plant demise in all treatments exceeding OMW10%, exploring the relationship between plant growth and nematode abundance, diversity, and plant interaction was not feasible. Our initial hypothesis was that nematode abundance and diversity would decrease with increasing waste concentration; however, our results proved the opposite. At 10 DAA, OMW10% induced a rapid surge in nematode abundance, stabilizing at 45 DAA resembling control values, indicating that the organic material was decomposed by the time of the second sampling. In contrast, OMW35%, OMW70%, and OMW100% plots showed persistent, gradual increases, significantly surpassing the control group at 45 DAA. The presence of phenolics in OMW did not exhibit toxicity effects on soil nematode populations, suggesting a collaborative degradation of lignin-derived aromatic compounds by fungi and bacteria [39,40]. At 10 DAA, in all treated plots, even though fungal feeders increased their abundances, this was also accompanied by an increase in bacterivorous numbers; however, by 45 DAA, fungal feeders dominated in OMW70% and OMW100% plots, highlighting their interconnection with OMW-rich environments. The delayed increase in the fungivore population numbers in the plots treated with higher OMW concentrations (over 35%) was likely due to the higher OMW concentrations containing larger amounts of less labile organic compounds. This resulted in slower decomposition by microorganisms and an increased dominance of fungivores in the long term. These findings differ from those recorded after the incorporation of other types of organic amendments with high C/N ratios in the soil system, which typically increase bacterial populations, causing a spike in bacterivorous nematodes [41,42]. Several studies reported increased fungal populations and fungal/bacterial ratios in OMW-amended soils, suggesting that OMW serves as a suitable substrate for fungi [36,43,44,45,46] and thus explaining the dominance of fungivores post-OMW addition. Presumably, OMW phenolic compounds stimulate yeasts, fungi, and consequently enhance the population of their predators, i.e., fungivorous nematodes [47].
A contrasting pattern was observed for herbivores compared to the increase in non-herbivorous nematodes. By 45 DAA, there was a visible decline in their abundance across all plots. Several studies have indicated that plant-derived phenolics have a detrimental effect on plant-parasitic nematodes but exert minimal or no negative impact on free-living nematodes [48,49]. Dutta et al. [50] explain this differential response due to variations in chemosensory gene sequences, which make PPNs more responsive to plant-derived metabolites. Lastly, the decline in PPNs by 45 DAA can be explained by the subsequent demise of plants in treatment groups with increased concentrations, leaving herbivorous nematodes without a viable food source. This scarcity accounts for the absence of a notable increase in their abundance.
While we observed differences in nematode abundances among all treatments at 10 DAA, the percentage contribution of trophic groups did not differ compared to the control, indicating an unaltered community composition. The incorporation of OMW resulted in increased numbers of fungal and bacterial feeders, proportionally. The genus Aphelenchus, a cp2 fungal feeder belonging to the family Aphelenchidae, was the most affected and increased in numbers. Bacterivorous genera such as Chiloplacus (cp-2) and Acrobeloides (cp-2), members of the Cephalobidae family, were also positively affected by OMW additions. However, at 45 DAA, the OMW70% and OMW100% treatments exhibited a completely different community composition, with the overdominance of Aphelenchus. This overdominance of the Aphelenchus genus in response to increasing organic waste concentrations can be attributed to the adaptive capabilities of Aphelenchus nematodes to tolerate a wide range of pH levels (including highly acidic) and maintain osmotic balance in response to changing environmental conditions, contributing to their resilience in the presence of high concentrations of OMW [51].
The increased abundance of these cp-2 nematodes indicates stress in the soil system [31,52]. The MI values remained near 2 across all treatments and the control, indicating a stressful environment due to a disturbance unrelated to nutrient enrichment. The low MI values in the control suggest that the soil from the field site may have been disturbed even before the application of the treatments. Notably, although an increase in cp-1 nematodes, indicative of an enriched nutrient status, was expected with the addition of OMW, their rapid population expansion was not observed. The incorporation of OMW did not significantly alter the food web condition. The EI and CI values, observed across all treatments including the control, remained low (<50), indicating limited nutrient availability and a predominant fungal decomposition pathway [33,53]. Additionally, the low SI values suggest that OMW application resulted in the increase in the abundance of soil nematodes belonging to lower c-p guilds rather than omnivores/predators [54]. The impact of stress factors (i.e., low nitrogen concentrations resulting in high C/N values) on community functionality and stability could be significant, potentially leading to a decline in diversity due to the disappearance of the most sensitive species (cp-4 and cp-5) [30,55]. Thus, no significant increase in cp-4 nematodes was recorded, indicating a further decline in the soil food web condition along with the depleted stage (Figure 6).

4.3. Assessing Levels of Disturbance

At 10 DAA, OMW10% caused the highest level of disturbance relative to the control group, as evident in the NMDS plot. However, this change was reflected in a proportional increase in both fungivores and bacterivores, suggesting a balanced response within the community. By 45 DAA, the community structure had reverted to its pre-disturbance state in the OMW10% plot, exhibiting no significant deviations from the control. This may indicate the resilience of the nematode community and its capacity to restore equilibrium following transient perturbations. A contrasting scenario was observed at 45 DAA for plots OMW75% and OMW100%, with a pronounced overdominance of a single genus—Aphelenchus—marking a substantial deviation from the control. This, in turn, indicates a persistent disturbance and suggests a long-term alteration of the nematode community dynamics, as is also evident from the SIMPER test (Table S2). Given the correlation between diversity and ecological stability, defined by the resistance and resilience of the soil’s ability and speed to recover after disturbances [56], the overdominance of one specific genus may weaken the diversity of ecosystems, which are better equipped to withstand environmental perturbations when there is the presence of species with varying traits [57]. Hence, despite the absence of reductions in abundance or genera numbers, the community is evidently under increasing pressure due to the disturbance from OMW, and subsequently, the stability of the community is compromised and could potentially lead to problematic outcomes if another disturbance were to occur within this system.

5. Conclusions

We conducted a pot experiment using varying concentrations of olive mill waste diluted with water (10%, 35%, 70%, and 100%). All amendments increased nematode abundance, particularly favoring fungal feeders, whereas higher concentrations (35%, 70%, 100%) resulted in a permanent shift in the community towards the dominance of the genus Aphelenchus, decreasing species diversity. OMW did not promote plant growth and had detrimental effects, leading to plant mortality at concentrations exceeding 10%. Our findings suggest that the application of OMW10% has the potential to be utilized as an organic amendment without eliciting negative impacts on the soil nematode community, structure, or soil stability. Hence, we attempted to investigate the complex interactions between OMW, plants, and soil nematodes. Despite the challenges posed by OMW’s phytotoxicity, implementing careful management practices, such as dilution and monitoring application concentrations, may offer sustainable solutions. Redirecting research efforts toward exploring alternative wastewater treatment techniques, particularly those that would be, most importantly, techno-economical viable options, is crucial. Additionally, it is required to assess the long-term consequences of these practices on soil ecosystems. Ultimately, this 45-day experiment provided valuable insights into the immediate effects of these practices at a small scale, and it is further required to assess the long-term consequences of such practices on soil ecosystems. Moreover, studying the effects of OMW on other types of soils is necessary, which potentially could lead to different outcomes. Further research should prioritize the implementation of proper nematode sampling schemes in large-scale experiments to define the exact distribution patterns and co-occurrence of soil nematode communities under real field conditions [58].

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/su16093848/s1, Table S1: The genera observed in both samplings (10 DAA and 45 DAA) with their cp values and respective trophic group (10 DAA: ten days after application; 45 DAA: forty-five days after application); Table S2: Dissimilarity percentages between treatments and results of Similarity Percentage analysis (SIMPER) based on Bray-Curtis. Genera accounting for ∼70% of overall dissimilarity are ranked in order of importance of their contribution. The upper right half of the table refers to the first sampling (10 DAA) and the lower left half of the table refers to the second sampling (45 DAA) (DAA: days after application). For every treatment n = 5.

Author Contributions

Conceptualization, N.M. and M.D.D.; investigation, P.K., C.P., A.T. and M.D.D.; data curation, P.K. and C.P.; writing—original draft preparation, P.K., C.P. and A.T.; writing—review and editing, S.M., V.A. and N.M.; supervision, N.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Dermeche, S.; Nadour, M.; Larroche, C.; Moulti-Mati, F.; Michaud, P. Olive mill wastes: Biochemical characterizations and valorization strategies. Process Biochem. 2013, 48, 1532–1552. [Google Scholar] [CrossRef]
  2. El-Abbassi, A.; Saadaoui, N.; Kiai, H.; Raiti, J.; Hafidi, A. Potential applications of olive mill wastewater as biopesticide for crops protection. Sci. Total Environ. 2017, 576, 10–21. [Google Scholar] [CrossRef] [PubMed]
  3. Belaqziz, M.; Lakhal, E.K.; Mbouobda, H.D.; El Hadrami, I. Land spreading of olive mill wastewater: Effect on maize (Zea maize) crop. J. Agron. 2008, 7, 297–305. [Google Scholar] [CrossRef]
  4. Rusan, M.J.; Malkawi, H.I. Dilution of olive mill wastewater (OMW) eliminates its phytotoxicity and enhances plant growth and soil fertility. Desalin. Water Treat. 2016, 57, 27945–27953. [Google Scholar] [CrossRef]
  5. Enaime, G.; Dababat, S.; Wichern, M.; Lübken, M. Olive Mill Wastes: From Wastes to Resources. Environ. Sci. Pollut. Res. 2024, 31, 20853–20880. [Google Scholar] [CrossRef] [PubMed]
  6. De Marco, E.; Savarese, M.; Paduano, A.; Sacchi, R. Characterization and fractionation of phenolic compounds extracted from olive oil mill wastewaters. Food Chem. 2007, 104, 858–867. [Google Scholar] [CrossRef]
  7. El Hassani, F.Z.; Zinedine, A.; Bendriss Amraoui, M.; Errachidi, F.; Mdaghri Alaoui, S.; Aissam, H.; Merzouki, M.; Benlemlih, M. Characterization of the harmful effect of olive mill wastewater on spearmint. J. Hazard. Mater. 2009, 170, 779–785. [Google Scholar] [CrossRef]
  8. Enaime, G.; Baçaoui, A.; Yaacoubi, A.; Belaqziz, M.; Wichern, M.; Lübken, M. Phytotoxicity assessment of olive mill wastewater treated by different technologies: Effect on seed germination of maize and tomato. Environ. Sci. Pollut. Res. 2020, 27, 8034–8045. [Google Scholar] [CrossRef] [PubMed]
  9. Pinho, I.A.; Lopes, D.V.; Martins, R.C.; Quina, M.J. Phytotoxicity assessment of olive mill solid wastes and the influence of phenolic compounds. Chemosphere 2017, 185, 258–267. [Google Scholar] [CrossRef]
  10. Sciubba, F.; Chronopoulou, L.; Pizzichini, D.; Lionetti, V.; Fontana, C.; Aromolo, R.; Socciarelli, S.; Gambelli, L.; Bartolacci, B.; Finotti, E. Olive mill wastes: A source of bioactive molecules for plant growth and protection against pathogens. Biology 2020, 9, 450. [Google Scholar] [CrossRef]
  11. Chartzoulakis, K.; Psarras, G.; Moutsopoulou, M.; Stefanoudaki, E. Application of olive mill wastewater to a Cretan olive orchard: Effects on soil properties, plant performance and the environment. Agric. Ecosyst. Environ. 2010, 138, 293–298. [Google Scholar] [CrossRef]
  12. Khalil, J.; Jaafar, A.A.K.; Habib, H.; Bouguerra, S.; Nogueira, V.; Rodríguez-Seijo, A. The Impact of Olive Mill Wastewater on Soil Properties, Nutrient and Heavy Metal Availability—A Study Case from Syrian Vertisols. Environ. Manag. 2024, 351, 119861. [Google Scholar] [CrossRef] [PubMed]
  13. Rousidou, C.; Papadopoulou, K.; Zervakis, G.; Singh, B.K.; Ehaliotis, C.; Karpouzas, D.G. Repeated application of diluted olive mill wastewater induces changes in the structure of the soil microbial community. Eur. J. Soil Biol. 2010, 46, 34–40. [Google Scholar] [CrossRef]
  14. Khalil, J.; Habib, H.; Alabboud, M.; Mohammed, S. Olive mill wastewater effects on durum wheat crop attributes and soil microbial activities: A pilot study in Syria. Energy Ecol. Environ. 2021, 6, 469–477. [Google Scholar] [CrossRef]
  15. Sierra, J.; Marti, E.; Montserrat, G.; Cruanas, R.; Garau, M.A. Characterisation and evolution of a soil affected by olive oil mill wastewater disposal. Sci. Total Environ. 2001, 279, 207–214. [Google Scholar] [CrossRef]
  16. Mekki, A.; Dhouib, A.; Aloui, F.; Sayadi, S. Olive wastewater as an ecological fertiliser. Agron. Sustain. Dev. 2006, 26, 61–67. [Google Scholar] [CrossRef]
  17. Isidori, M.; Lavorgna, M.; Nardelli, A.; Parrilla, A. Chemical and toxic evaluation of a biological treatment for olive-oil mill wastewater using comercial microbial formulations. Appl. Microbiol. Biotechnol. 2004, 64, 735–739. [Google Scholar] [CrossRef] [PubMed]
  18. Babic, S.; Malev, O.; Pflieger, M.; Lebedev, A.T.; Mazur, D.M.; Kuzic, A.; Coz-Rakovac, R.; Trebse, P. Toxicity evaluation of olive oil mill wastewater and its polar fraction using multiple whole-organism bioassays. Sci. Total Environ. 2019, 686, 903–914. [Google Scholar] [CrossRef] [PubMed]
  19. Vagelas, I.; Sugar, I.R. Potential use of olive oil mill wastewater to control plant pathogens and post harvest diseases. Carpathian J. Food Sci. Technol. 2020, 12, 140–144. [Google Scholar] [CrossRef]
  20. Hentati, O.; Oliveira, V.; Sena, C.; Bouji, M.S.M.; Wali, A.; Ksibi, M. Soil contamination with olive mill wastes negatively affects microbial communities, invertebrates and plants. Ecotoxicology 2016, 25, 1500–1513. [Google Scholar] [CrossRef]
  21. Jarboui, R.; Saber Azab, M.; Bilel, H.; Moustafa, S.M.N. Antifungal Effect of Fresh and Stored Olive Mill Wastewater and Its Ethyl Acetate Extract against Plant Pathogenic Fungi. Plant Prot. Sci. 2024, 60, 65–79. [Google Scholar] [CrossRef]
  22. Dimou, M.D.; Monokrousos, N.; Katapodis, P.; Diamantopoulou, P.A.; Argyropoulou, M.D.; Papatheodorou, E.M. Use of Microbially Treated Olive Mill Wastewaters as Soil Organic Amendments; Their Short-Term Effects on the Soil Nematode Community. Diversity 2023, 15, 497. [Google Scholar] [CrossRef]
  23. Girgan, C.; du Preez, G.; Marais, M.; Swart, A.; Fourie, H. Nematodes and the effect of seasonality in grassland habitats of South Africa. J. Nematol. 2020, 52, 1–22. [Google Scholar] [CrossRef] [PubMed]
  24. Theofilidou, A.; Argyropoulou, M.D.; Ntalli, N.; Kekelis, P.; Mourouzidou, S.; Zafeiriou, I.; Tsiropoulos, N.G.; Monokrousos, N. Assessing the Role of Melia azedarach Botanical Nematicide in Enhancing the Structure of the Free-Living Nematode Community. Soil Syst. 2023, 7, 80. [Google Scholar] [CrossRef]
  25. Gee, G.W.; Bauder, J.W. Particle-size analysis. In Methods of Soil Analysis; Klute, A., Ed.; SSSA: Madison, WI, USA, 1986; pp. 383–411. [Google Scholar]
  26. Troelstra, S.R.; Wagenaar, R.; Smant, W.; Peters, B.A.M. Interpretation of bioassays in the study of interactions between soil organisms and plants: Involvement of nutrient factors. New Phytol. 2001, 150, 697–706. [Google Scholar] [CrossRef]
  27. S’Jacob, J.J.; Van Bezooijen, J. Manual for Practical Work in Nematology; Landbouwhogeschool: Wageningen, The Netherlands, 1984; pp. 40–70. [Google Scholar]
  28. Bongers, T. Systematisch gedeelte. In De Nematoden van Nederland: Vormgeving en Technische Realisatie, 2nd ed.; Uitgeverij Pirola: Schoorl, The Netherlands, 1994; pp. 67–383. [Google Scholar]
  29. Bongers, T. The maturity index: An ecological measure of environmental disturbance based on nematode species composition. Oecologia 1990, 83, 14–19. [Google Scholar] [CrossRef] [PubMed]
  30. Bongers, T.; Bongers, M. Functional diversity of nematodes. Appl. Soil Ecol. 1998, 10, 239–251. [Google Scholar] [CrossRef]
  31. Ferris, H.; Bongers, T.; de Goede, R.G.M. A Framework for Soil Food Web Diagnostics: Extension of the Nematode Faunal Analysis Concept. Appl. Soil. Ecol. 2001, 18, 13–29. [Google Scholar] [CrossRef]
  32. Yeates, G.W.; Bongers, T.D.; De Goede, R.G.M.; Freckman, D.W.; Georgieva, S.S. Feeding habits in soil nematode families and genera-an outline for soil ecologists. J. Nematol. 1993, 25, 315–331. [Google Scholar]
  33. Bongers, T.; Ferris, H. Nematode Community Structure as a Bioindicator in Environmental Monitoring. Trends Ecol. Evol. 1999, 14, 224–228. [Google Scholar] [CrossRef]
  34. Ferris, H. Form and Function: Metabolic Footprints of Nematodes in the Soil Food Web. Eur. J. Soil. Biol. 2010, 46, 97–104. [Google Scholar] [CrossRef]
  35. Sieriebriennikov, B.; Ferris, H.; Goede, R. NINJA: An automated calculation system for nematode-based biological monitoring. Eur. J. Soil Biol. 2014, 61, 90–93. [Google Scholar] [CrossRef]
  36. Mekki, A.; Dhouib, A.; Sayadi, S. Changes in microbial and soil properties following amendment with treated and untreated olive mill wastewater. Microbiol. Res. 2006, 161, 93–101. [Google Scholar] [CrossRef] [PubMed]
  37. Ouzounidou, G.; Asfi, M.; Sortirakis, N.; Papadopoulou, P.; Gaitis, F. Olive mill wastewater triggered changes in physiology and nutritional quality of tomato (Lycopersicon esculentum Mill.) depending on growth substrate. J. Hazard. Mater. 2008, 158, 523–530. [Google Scholar] [CrossRef] [PubMed]
  38. Elayadi, F.; El Adlouni, C.; El Herradi, M.A.E.; El Krati, M.; Tahiri, S.; Naman, M.N.F. Effects of raw and treated olive mill wastewater (OMW) by coagulation-flocculation, on the germination and the growth of three plant species (wheat, white beans, lettuce). Moroc. J. Chem. 2019, 7, 111–122. [Google Scholar] [CrossRef]
  39. Wu, W.; Dutta, T.; Varman, A.M.; Eudes, A.; Manalansan, B.; Loqué, D.; Singh, S. Lignin Valorization: Two Hybrid Biochemical Routes for the Conversion of Polymeric Lignin into Value-added Chemicals. Sci. Rep. 2017, 7, 8420. [Google Scholar] [CrossRef] [PubMed]
  40. Magdich, S.; Ben Ahmed, C.; Jarboui, R.; Ben Rouina, B.; Boukhris, M.; Ammar, E. Dose and frequency dependent effects of olive mill wastewater treatment on the chemical and microbial properties of soil. Chemosphere 2013, 93, 1896–1903. [Google Scholar] [CrossRef] [PubMed]
  41. Shu, X.Y.; He, J.; Zhou, Z.H. Organic amendments enhance soil microbial diversity, microbial functionality and crop yields: A meta-analysis. Sci. Total Environ. 2022, 829, 154627. [Google Scholar] [CrossRef] [PubMed]
  42. Kekelis, P.; Argyropoulou, M.D.; Theofilidou, A.; Papatheodorou, E.M.; Aschonitis, V.; Monokrousos, N. The Differentiations in the Soil Nematode Community in an Agricultural Field after Soil Amendment Using Composted Coffee Waste in Various Concentrations. Agronomy 2023, 13, 2831. [Google Scholar] [CrossRef]
  43. Karpouzas, D.G.; Rousidou, C.; Papadopoulou, K.K.; Bekris, F.; Zervakis, G.I.; Singh, B.K.; Ehaliotis, C. Effect of continuous olive mill wastewater applications, in the presence and absence of nitrogen fertilization, on the structure of rhizosphere-soil fungal communities. FEMS Microbiol. Ecol. 2009, 70, 388–401. [Google Scholar] [CrossRef]
  44. Justino, C.I.L.; Pereira, R.; Freitas, A.C.; Rocha-Santos, T.A.P.; Panteleitchouk, T.S.L.; Duarte, A.C. Olive oil mill wastewaters before and after treatment: A critical review from the ecotoxicological point of view. Ecotoxicology 2012, 21, 615–629. [Google Scholar] [CrossRef]
  45. Laor, Y.; Saadi, I.; Raviv, M.; Medina, S.; Erez-Reifen, D.; Eizenberg, H. Land spreading of olive mill wastewater in Israel: Current knowledge, practical experience, and future research needs. Isr. J. Plant Sci. 2011, 59, 39–51. [Google Scholar] [CrossRef]
  46. Jarboui, R.; Sellami, F.; Kharroubi, A.; Gharsallah, N.; Ammar, E. Olive mill wastewater stabilization in open-air ponds: Impact on clay-sandy soil. Bioresour. Technol. 2008, 99, 7699–7708. [Google Scholar] [CrossRef] [PubMed]
  47. Tardioli, S.; Bánnè, E.T.G.; Santori, F. Species-Specific Selection on Soil Fungal Population after Olive Mill Waste-Water Treatment. Chemosphere 1997, 34, 2329–2336. [Google Scholar] [CrossRef] [PubMed]
  48. Valdes, Y.; Viaene, N.; Moens, M. Effects of yellow mustard amendments on the soil nematode community in a potato field with focus on Globodera rostochiensis. Appl. Soil Ecol. 2012, 59, 39–47. [Google Scholar] [CrossRef]
  49. Sikder, M.M.; Vestergård, M. Impacts of root metabolites on soil nematodes. Front. Plant Sci. 2020, 10, 1792. [Google Scholar] [CrossRef]
  50. Dutta, T.K.; Akhil, V.S.; Dash, M.; Kundu, A.; Phani, V.; Sirohi, A. Molecular and Functional Characterization of Chemosensory Genes from the Root-Knot Nematode Meloidogyne Graminicola. BMC Genom. 2023, 24, 745. [Google Scholar] [CrossRef] [PubMed]
  51. Neher, D.A.; Powers, T.O. Nematodes. In Encyclopedia of Soils in the Environment; Hillel, D., Ed.; Columbia Universiy: New York, NY, USA, 2005. [Google Scholar]
  52. Ürkmez, D.; Sezgin, M.; Bat, L. Use of nematode maturity index for the determination of ecological quality status: A case study from the Black Sea. J. Black Sea/Mediterr. Environ. 2014, 20, 96–107. [Google Scholar]
  53. Du Preez, G.; Daneel, M.; De Goede, R.; Du Toit, M.J.; Ferris, H.; Fourie, H.; Geisen, S.; Kakouli-Duarte, T.; Korthals, G.; Sánchez-Moreno, S.; et al. Nematode-based indices in soil ecology: Application, utility, and future directions. Soil Biol. Biochem. 2022, 169, 108640. [Google Scholar] [CrossRef]
  54. Pan, F.; Han, X.; Li, N.; Yan, J.; Xu, Y. Effect of Organic Amendment Amount on Soil Nematode Community Structure and Metabolic Footprints in Soybean Phase of a Soybean-Maize Rotation on Mollisols. Pedosphere 2020, 30, 544–554. [Google Scholar] [CrossRef]
  55. Korthals, G.; Goede, R.G.M.G.; Kammenga, J.E.; Bongers, T. The Maturity Index As An Instrument For Risk Assessment of Soil Pollution. In Bioindicator Systems For Soil Pollution; van Straalen, N.M., Krivolutsky, D.A., Eds.; Kluwer Acad. Publ.: Dordrecht, The Netherlands, 1996; pp. 85–93. [Google Scholar] [CrossRef]
  56. Griffiths, B.S.; Bonkowski, M.; Roy, J.; Ritz, K. Functional stability, substrate utilisation and biological indicators of soils following environmental impacts. Appl. Soil Ecol. 2001, 16, 49–61. [Google Scholar] [CrossRef]
  57. Tilman, D.; Downing, J.A. Biodiversity and stability in grasslands. Nature 1994, 367, 363–365. [Google Scholar] [CrossRef]
  58. Abd-Elgawad, M.M.M. Optimizing Sampling and Extraction Methods for Plant-Parasitic and Entomopathogenic Nematodes. Plants 2021, 10, 629. [Google Scholar] [CrossRef] [PubMed]
Sustainability 16 03848 g001
Figure 1. The mean abundance values (±st. error) of plant (a) length and (b) dry weight under different concentrations of olive mill wastewater (OMW), and the results of the two-way ANOVA 10 DAA and 45 DAA (DAA: days after application). In the case of a significant effect, different letters (a, b, c) indicate significant differences among treatments based on Fisher’s LSD post hoc test (*: p < 0.05; ***: p < 0.001, for all cases n = 5). In concentrations exceeding 10%, the plants died, exhibiting burn-like symptoms, and were consequently excluded from the two-way ANOVA. The letter “a” always points out the highest value.
Figure 1. The mean abundance values (±st. error) of plant (a) length and (b) dry weight under different concentrations of olive mill wastewater (OMW), and the results of the two-way ANOVA 10 DAA and 45 DAA (DAA: days after application). In the case of a significant effect, different letters (a, b, c) indicate significant differences among treatments based on Fisher’s LSD post hoc test (*: p < 0.05; ***: p < 0.001, for all cases n = 5). In concentrations exceeding 10%, the plants died, exhibiting burn-like symptoms, and were consequently excluded from the two-way ANOVA. The letter “a” always points out the highest value.
Sustainability 16 03848 g001
Sustainability 16 03848 g002
Figure 2. The mean abundance values (±st. error) of nematode trophic groups under different treatments and the results of the two-way ANOVA regarding “olive mill wastewater” (OMW) 10 DAA and 45 DAA (DAA: days after application). In the case of a significant effect, different letters (a, b, c, d, e, f) indicate significant differences among treatments based on Fisher’s LSD post hoc test (*: p < 0.05; **: p < 0.01; ***: p < 0.001; ns: p > 0.05, for all cases n = 5). The letter “a” always points out the highest value.
Figure 2. The mean abundance values (±st. error) of nematode trophic groups under different treatments and the results of the two-way ANOVA regarding “olive mill wastewater” (OMW) 10 DAA and 45 DAA (DAA: days after application). In the case of a significant effect, different letters (a, b, c, d, e, f) indicate significant differences among treatments based on Fisher’s LSD post hoc test (*: p < 0.05; **: p < 0.01; ***: p < 0.001; ns: p > 0.05, for all cases n = 5). The letter “a” always points out the highest value.
Sustainability 16 03848 g002
Sustainability 16 03848 g003
Figure 3. The percentage contribution of the trophic groups at different treatments 10 DAA and 45 DAA (DAA: days after application). For all cases, n = 5.
Figure 3. The percentage contribution of the trophic groups at different treatments 10 DAA and 45 DAA (DAA: days after application). For all cases, n = 5.
Sustainability 16 03848 g003
Sustainability 16 03848 g004aSustainability 16 03848 g004b
Figure 4. A nonmetric multidimensional scaling (NMDS) plot showing the diversity of soil ecosystems. A Bray–Curtis distance similarity matrix was calculated based on the pairwise taxonomic profiles of 40 soil samples and used to generate NMDS coordinates of each sample. The distance linking two samples is shorter, indicating higher similarity between these samples. Samples from the five different treatments (control, 10%, 35%, 70%, and 100%) are illustrated by different colors in two different time intervals ((a): 10 DAA and (b): 45 DAA) (DAA: days after application). For every treatment, n = 5. The central symbol of each polygon is the mean value.
Figure 4. A nonmetric multidimensional scaling (NMDS) plot showing the diversity of soil ecosystems. A Bray–Curtis distance similarity matrix was calculated based on the pairwise taxonomic profiles of 40 soil samples and used to generate NMDS coordinates of each sample. The distance linking two samples is shorter, indicating higher similarity between these samples. Samples from the five different treatments (control, 10%, 35%, 70%, and 100%) are illustrated by different colors in two different time intervals ((a): 10 DAA and (b): 45 DAA) (DAA: days after application). For every treatment, n = 5. The central symbol of each polygon is the mean value.
Sustainability 16 03848 g004aSustainability 16 03848 g004b
Sustainability 16 03848 g005
Figure 5. Rank abundance graphs for nematode genera at different treatments (a) 10 and (b) 45 DAA (DAA: days after application). Genera are ranked from the most to the least abundant. The numbers above bars indicate the c–p value of each genus. Light gray columns indicate the fungal feeders, white columns indicate the bacterial feeders, black columns indicate the omnivores/predators, and dark gray indicate the herbivores. For all cases, n = 5.
Figure 5. Rank abundance graphs for nematode genera at different treatments (a) 10 and (b) 45 DAA (DAA: days after application). Genera are ranked from the most to the least abundant. The numbers above bars indicate the c–p value of each genus. Light gray columns indicate the fungal feeders, white columns indicate the bacterial feeders, black columns indicate the omnivores/predators, and dark gray indicate the herbivores. For all cases, n = 5.
Sustainability 16 03848 g005
Sustainability 16 03848 g006
Figure 6. Food web analysis according to the ordination of the samples based on the EI and SI mean values of different treatments at 10 DAA and at 45 DAA (DAA: days after application). Different colors show a different treatment. For all cases, n = 5.
Figure 6. Food web analysis according to the ordination of the samples based on the EI and SI mean values of different treatments at 10 DAA and at 45 DAA (DAA: days after application). Different colors show a different treatment. For all cases, n = 5.
Sustainability 16 03848 g006
Table 1. The mean values (±st. error) of the physicochemical parameters of the soil used in our study (n = 5).
Table 1. The mean values (±st. error) of the physicochemical parameters of the soil used in our study (n = 5).
Soil ParameterValue
Sand (%)47%
Clay (%)24%
Silt (%)32%
pH7.51± 0.01
Soil Organic C (%)1.82 ± 0.01
Total N (%)0.15 ± 0.02
Table 2. The mean values of the channel index (CI), enrichment index (EI), bacterivore footprint (BF), and fungivore footprint (FF), under the different treatments 10 DAA and 45 DAA (DAA: days after application). For each sampling occasion, within columns, means followed by the same letter are not significantly different (two-way ANOVA and Fisher’s LSD post hoc comparisons; p > 0.05; *: p < 0.05; **: p < 0.01; ***: p < 0.001; ns: non significant; for all cases, n = 5).
Table 2. The mean values of the channel index (CI), enrichment index (EI), bacterivore footprint (BF), and fungivore footprint (FF), under the different treatments 10 DAA and 45 DAA (DAA: days after application). For each sampling occasion, within columns, means followed by the same letter are not significantly different (two-way ANOVA and Fisher’s LSD post hoc comparisons; p > 0.05; *: p < 0.05; **: p < 0.01; ***: p < 0.001; ns: non significant; for all cases, n = 5).
TimeOMWCIEIMIFFBF
10 DAAControl89.00 ± 3.4136.40 ± 1.892.08 ± 0.0312.7 ± 5.68 d8.60 ± 0.60
OMW1093.00 ± 3.1233.50 ± 3.072.05 ± 0.0345.76 ± 20.46 ab12.20 ± 2.05
OMW3583.60 ± 6.9837.00 ± 2.792.01 ± 0.0124.69 ± 11.04 cd11.70 ± 2.92
OMW7094.30 ± 2.5037.60 ± 0.352.04 ± 0.0131.16 ± 13.93 bc10.90 ± 0.56
OMW10085.00 ± 6.1640.20 ± 2.922.01 ± 0.0323.64 ± 10.57 cd11.50 ± 1.56
45 DAAControl92.30 ± 3.8843.10 ± 1.292.08 ± 0.0411.74 ± 2.37 d7.90 ± 0.38
OMW1089.80 ± 5.4242.60 ± 1.322.04 ± 0.0316.59 ± 3.39 cd8.70 ± 0.31
OMW3594.60 ± 4.0843.50 ± 1.502.06 ± 0.0221.68 ± 3.00 cd7.30 ± 1.20
OMW70100.00 ± 0.0040.90 ± 1.712.04 ± 0.0252.72 ± 10.97 a8.20 ± 0.86
OMW10094.40 ± 2.7046.40 ± 1.132.03 ± 0.0146.94 ± 9.57 ab4.70 ± 1.45
Time****nsns***
OMWnsnsns*****
Time*OMWnsnsns***ns
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Kekelis, P.; Pantazi, C.; Mourouzidou, S.; Theofilidou, A.; Dimou, M.D.; Aschonitis, V.; Monokrousos, N. The Effect of Varying Olive Mill Wastewater Concentrations on Soil Free-Living Nematode Communities and Lettuce Growth. Sustainability 2024, 16, 3848. https://doi.org/10.3390/su16093848

AMA Style

Kekelis P, Pantazi C, Mourouzidou S, Theofilidou A, Dimou MD, Aschonitis V, Monokrousos N. The Effect of Varying Olive Mill Wastewater Concentrations on Soil Free-Living Nematode Communities and Lettuce Growth. Sustainability. 2024; 16(9):3848. https://doi.org/10.3390/su16093848

Chicago/Turabian Style

Kekelis, Panagiotis, Cleopatra Pantazi, Snezhana Mourouzidou, Aphrodite Theofilidou, Maria D. Dimou, Vassilis Aschonitis, and Nikolaos Monokrousos. 2024. "The Effect of Varying Olive Mill Wastewater Concentrations on Soil Free-Living Nematode Communities and Lettuce Growth" Sustainability 16, no. 9: 3848. https://doi.org/10.3390/su16093848

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop