Field Of Olive Trees Research Articles

Enhancing olive tree (Olea europaea) rhizosphere dynamics: Co-inoculation effects of arbuscular mycorrhizal fungi and plant growth- promoting rhizobacteria in field experiments

We investigated the outcome of the interaction between the arbuscular mycorrhizal fungus (AMF) Rhizophagus (R) irregularis DAOM 197198 and the Plant-Growth-Promoting Rhizobacteria (PGPR) (mix of Bacillus megaterium, Burkholdria cedrus and Streptomyces beta-vulgaris) by conducting an olive field experiment. Our data provide evidence that the co-inoculation of R. irregularis and PGPR has important effects on the rhizosphere microbial community. The largest proportional increase was found for the PLFA biomarkers indicative of Gram-negative bacteria (16:1ω9, 18:1ω7 and 18:1ω9), fungi (18:2ω6) and actinobacteria (10Me16:0 and 10Me18:0). Microbial inoculants application of all tested treatments caused a significant decrease in the level of trehalose in the olive rhizosphere. The most pronounced decrease was observed in the plant inoculated with R. intraradices only, suggesting that the presence of AMF may have relaxed the bacterial stress. Co-inoculation of PGPR and AMF significantly improved the nutritional status of olive roots. Specifically, the interaction of PGPR and R. intraradices led to an increase in N (26 %), P (60 %), Fe (25 %), Mn (18 %), Zn (26 %), B (22 %) and Cu (14 %) compared with the control. We also found that the co-inoculation of AMF with PGPR causes a shift in the accumulation of secondary metabolites in olive roots. In particular, the most important effect induced by AMF was an improvement of oleuropein concentration, while co-inoculation of R. irregularis and PGPR positively modulated verbascoside concentration. The novelty of the present work lies in the use of microbial inoculants in the field of olive trees. This approach provided direct information regarding the advantages of using AMF and PGPR inoculants, allowing the reduction of chemical inputs and positively influencing the olive tree performance.

Rock phosphate improves nutrient uptake and oil accumulation in olive fruit

Phosphorus deficiency is one of the main constraints to olive production in alkaline soils. The high cost of phosphorus fertilizers may represent an insurmountable obstacle in many countries, leaving the exploitation of their own rock phosphate (RP) as the only low-cost and long-term alternative. The aim of this work was to study the long-term effect of agronomic application of RP (amounts applied: 150 kg ha−1) in a field of olive trees on specific microbial groups in the rhizosphere, nutrient uptake and oil accumulation in the fruit. The results revealed that agronomic application of RP increased the rhizosphere fatty acid methyl ester (FAME) biomarkers indicative of Gram-negative bacteria, fungi and actinobacteria. The level of FAME 16:1ω5 in rhizosphere decreased significantly after agronomic application of RP, indicating that the functioning of arbuscular mycorrhizas was altered. Decreased FAME 16:1ω5 due to RP amendment was not associated with a significant reduction of nutrient concentrations in the olive root; while a significant increase in root P and K contents was observed. However, the level of N did not appear to be significantly influenced. The experimental results also showed that RP-fertilized plants had significantly greater fruit weight and pulp/stone ratio. Fruits of RP-fertilized plants also had significantly higher oil content (+8.67% on average). Our results support the hypothesis that, following agronomic application of RP, the complex interactions of root and microbial community in the olive rhizosphere is a potential factor influencing oil accumulation in the olive fruit.

The Impact of Different Techniques of Soil Management on Soil Fertility and the Associated Bacterial Communities in Semi-arid Olive Tree Fields

A remarkable decrease in olive production has been observed in Tunisia since 2000, particularly in the semi-arid region. This downfall was mainly due to a notable change in climatic conditions as a result of wind erosion and over cultivation. The aim of this work was to study the biological, physical, and chemical properties of several semi-arid soils from olive tree fields subjected to different farming practices, such as crop time and type of crop, olive mill wastewater (OMW) application rates, and tillage timing and depth (deep or conventional plowing). We noted that hydraulic conductivity (HC) was proportional to the age of the soil tillage, and the highest values were recorded in the soil cultivated for 100 years, with an average value of 33.05 ± 0.02 mm h−1. An important increment of the iron soil content was observed, especially after the fig tree introduction among the olive trees (12,094 ng μL−1) in 2007. Also, a significant increase of the organic matter (OM) content (up to2.6 mg-OM/g-soil) was identified in soil treated with OMW compared to the lowest OM content (0.83 mg-OM/g-soil) recorded in the soil cultivated since 1901. The bacterial communities of the different soils were characterized by 454 pyrosequencing technology, and showed an important diversity, mainly corresponding to Proteobacteria, Actinobacteria, and Acidobacteria. Many operational taxonomic units (OTUs) are raretons, indicating a high resilience of the soil bacterial communities. Statistical analyses showed significant correlations with the different soil parameters. However, an unexpected correlation was determined between soil respiration and OM (r = − 0.583*), suggesting that OM increases the retention of CO2, a greenhouse gas. The farming techniques analyzed in this study resulted in a reduction of the bacterial diversity, even though the total bacterial biomass augmented.

Copper tolerance and antibiotic resistance in soil bacteria from olive tree agricultural fields routinely treated with copper compounds.

Heavy metal pollution may act as persistent selective pressure that favors the spread of antimicrobial resistance in natural environments. The aim of this study was to isolate and identify metal-tolerant bacteria from soils in olive tree fields routinely treated with copper-derived compounds and to evaluate the tolerance of bacterial strains to other metals and their resistance to clinically relevant antibiotics. Five hundred and ninety-five bacterial isolates from 45 olive tree agricultural fields were studied. Minimum inhibitory concentrations (MICs) ≥ 16 mmol L-1 were detected for copper (57% of isolates), zinc (37%) and lead (62%), while only 3% had MICs ≥ 12 mmol L-1 for nickel. Ninety-six metal-tolerant strains were selected for identification and antibiotic resistance determination. Most isolates belonged to the genera Pseudomonas (37%), Bacillus (23%) and Chryseobacterium (20%), while 6% were identified as Variovorax, 4% as Stenotrophomonas and 2% as Serratia or Burkholderia. Highest copper tolerance was detected among Pseudomonas. Over 75% of the strains with high copper tolerance were also resistant to vancomycin, 50% to ampicillin and 40% to erythromycin or trimethoprim/sulfamethoxazole. Bacteria from olive soils are tolerant to metals, mainly copper, but also zinc and lead, as well as resistant to clinically important antibiotics, which could be a troublesome issue in clinical settings. © 2019 Society of Chemical Industry.

Long-term field evaluation of the changes in fruit and olive oil chemical compositions after agronomic application of olive mill wastewater with rock phosphate

The objectives of this study were to determine the long-term effects of agronomic application of olive mill wastewater (OMW) with rock phosphate (RP) in a field of olive trees, on olive fruits and oil quality. The results revealed that olive fruits of OMW-RP amended plants had higher contents of polyphenols and mannitol indicating that agronomic application of OMW with RP generated an oxidative stress. Land spreading of OMW with RP altered the relative proportions of individual sugars in leaves and fruits. Consequently, the oil content decreased significantly, and a marked decrease in the contents of carotenoids and chlorophylls was also observed. Changes also took place in the composition of fatty acids, particularly by the increase of linoleic acid and the decrease of oleic acid. Our results suggested that the use of OMW in combination with RP is expected to have a major negative impact on olive fruit and oil quality.

Impact of water quality, cultivation, and cropping systems on infiltration and physical properties of an arid clay soil

Irrigation with treated wastewater is essential for increasing crop production in arid and semi arid regions. Field experiments were conducted on rainfed clayey soil to investigate the impact of water quality, cultivation, and different cropping systems on cumulative infiltration (F<sub>(t)</sub>), field saturated hydraulic conductivity (HC<sub>fs</sub>), penetration resistance (PR), and water stable aggregates (WSA). Treatments were: (1) barley fields tilled for the past 20 years (C<sub>B</sub>-T), (2) olive tree fields tilled for the past 20 years (C<sub>O</sub>-T), (3) non-cultivated field for 20 years, tilled for the last 2 years (NC-T<sub>2yr</sub>), and (4) non-cultivated non-tilled field (NC-NT) for the past 20 years (control). Results indicated that F<sub>(t)</sub>, HC<sub>fs</sub>, PR, and WSA in NC-NT were significantly higher than in all other treatments. Compared to fresh water (FW), treated wastewater (TWW) significantly reduced F<sub>(t)</sub> and HC<sub>fs</sub> in all treatments. This study showed that irrigation with TWW and protection of soil from any physical manipulation improved soil hydraulic and physical properties to acceptable levels. Therefore, application of such practices could be recommended in arid clayey soils.

Agronomic application of olive mill wastewaters with rock phosphate increase the 10Me18:0 fatty acid marker of actinomycetes and change rhizosphere microbial functional groups under long-term field conditions

The objectives of this study were to determine the long-term effects of agronomic application of olive mill wastewaters (OMW) with rock phosphate (RP) in a field of olive trees on the soil microbial community structures. Ester-linked fatty acid methyl ester (EL-FAME) profiles were used for characterizing the numerically dominant portion of soil microbial communities. EL-FAME analysis showed significant shifts of specific groups of fatty acids after application of OMW with RP. In particular, the FAME 10Me18:0 indicative of actinomycetes increased and the FAME 18:1ω9 and 18:2ω6 commonly found in fungi decreased. The soil microbial cells reacted to the addition of OWM and RP with an increase in the percentage of cy17:0 and cy19:0 cyclopropane fatty acids. Other changes in FAME composition included the increase of saturated/unsaturated ratio. It seems that alterations of fatty acid composition, after agronomic application of OMW and RP, are responsible for the substantial maintenance of cell membrane integrity, physiological functions and growth.

A yearly spraying of olive mill wastewater on agricultural soil over six successive years: Impact of different application rates on olive production, phenolic compounds, phytotoxicity and microbial counts

Olive mill wastewater (OMW) spraying effects onto olive-tree fields were investigated. Three OMW levels (50, 100 and 200m3ha−1year−1) were applied over six successive years. Olive-crop yields, phenolic compounds progress, phytotoxicity and microbial counts were studied at different soil depths. Olive yield showed improvements with OMW level applied. Soil polyphenolic content increased progressively in relation to OMW levels in all the investigated layers. However, no significant difference was noted in lowest treatment rate compared to the control field. In the soil upper-layers (0–40cm), five phenolic compounds were identified over six consecutive years of OMW-spraying. In all the soil-layers, the radish germination index exceeded 85%. However, tomato germination test values decreased with the applied OMW amount. For all treatments, microbial counts increased with OMW quantities and spraying frequency. Matrix correlation showed a strong relationship between soil polyphenol content and microorganisms, and a negative one to tomato germination index.

Object-based classification of remotely sensed olive tree fields, using mathematical morphology

Object-based classification of remotely sensed olive tree fields, using mathematical morphology

Effects of agronomic application of olive mill wastewater in a field of olive trees on carbohydrate profiles, chlorophyll a fluorescence and mineral nutrient content

Olive mill wastewater (OMW) management is a serious environmental issue for the Mediterranean area where there is the most production of olive oil. OMW contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. We studied the influence of irrigation with OMW (amounts applied: 30, 60, 100 and 150m3h−1) in a field of olive trees on root colonization, photosynthesis, chlorophyll fluorescence, leaf nutrient concentration and soluble carbohydrate. The soil fatty acid methyl ester (FAME) 16:1ω5 was used to quantify biomass of arbuscular mycorrhizal (AM) fungi and the root FAME 16:1ω5 analysis was used as index for the development of colonization in the roots. Agronomic application of OMW decreased significantly the abundance of the soil FAME 16:1ω5 and the root FAME 16:1ω5 in the soil amended with 60, 100 and 150m3ha−1 OMW. Decreased root FAME 16:1ω5 due to OMW amendment was associated with a significant reduction of tissue nutrient concentrations in the olive trees. The highest application of OMW to the soil reduced significantly the olive trees uptake of N, P, K, Ca, Mg, Fe, Cu, Mn and Zn. Land spreading of OMW increased concentration of soluble carbohydrate in the olive leaves, mostly due to decreased sink demand for carbon by the root. In the olive trees amended with 150m3ha−1 OMW, net CO2 uptake rate (A), quantum yield of photosystem II electron transport (ΦPSII), maximal photochemical efficiency of photosystem II (Fv/Fm), photochemical quenching (qp) and the electron transport rate (ETR) were significantly depressed, whereas non-photochemical quenching (NPQ) was found to increase. Taken with data from experiments in field conditions, our results suggest that agronomic application of OMW alters the functioning of arbuscular mycorrhizas and can even disrupt the relationship between AM fungi and olive trees.

Olive mill wastewater effects on the microbial communities as studied in the field of olive trees by analysis of fatty acid signatures

The aim of this work was to study the effects of spreading olive mill wastewater (OMW) on the soil surface of an olive grove on the soil microbial communities. Analyses of ester-linked fatty acid methyl esters (EL-FAME) were used to assess variations in the soil microbial community structure following land spreading of OMW. Our data provide evidence that agronomic application of OMW has important effects on soil microbial community. Bacteria were relatively more reduced by these treatments than fungi and actinomycetes as revealed by an increased index of fungal/bacterial FAME and actinomycetes/bacterial FAME. Specific FAME markers indicated a significant reduction in the Gram-positive bacteria. However, the relative proportion of the Gram-negative bacteria was not significantly different after agronomic application of OMW. The ratios of cyclopropyl/monoenoic precursors decreased and the total monounsaturated/total saturated fatty acids increased in the OMW amended soils, suggesting that the microbes inhabiting the control soil are more carbon limited than the OMW amended soils. The changes in the FAME pattern of the soil organisms possibly were related (i) to an altered substrate quantity, that is the availability of substrates after the treatments, (ii) the complex nature of OMW which also contains high molecular-mass recalcitrant polyphenols.

Olive orchard amended with olive mill wastewater: Effects on olive fruit and olive oil quality

The aim of this work was to study the effects of agronomic application of olive mill wastewater (OMW) in a field of olive trees on olive fruit and olive oil quality. Agronomic application of OMW increased significantly the fungal:bacteria ratio, whereas the root colonisation and the photosynthetic rates decreased significantly. Consequently, the oil content expressed as a percentage of dry weight, decreased significantly after agronomic application of OMW. Land spreading of OMW altered the relative proportion of individual olive fruit sugar and decreased significantly the nitrogen (N) and phosphorus (P) of the fruit. A significant increase was observed in total phenol content of oil after agronomic application of OMW. α-Tocopherol content, on the contrary, decreased with OMW application. The fatty acid composition of the oil was not affected by the treatments. To our knowledge, this is the first report of change in the olive fruit and olive oil quality following agronomic application of OMW.

Change in soil properties and the soil microbial community following land spreading of olive mill wastewater affects olive trees key physiological parameters and the abundance of arbuscular mycorrhizal fungi

Olive mill wastewater (OMW) constitutes a major environmental problem for Mediterranean countries, where most of the world olive oil production takes place. The recycling of the OMW and its use as water for irrigation in agriculture, provided that its impact on soil and plant is established, is an attractive possibility for the Mediterranean countries. Investigations were performed on the influence of agronomic application of OMW (amount applied: 30, 60, 100 and 150 m 3 ha −1) in a field of olive trees on trees characters (photosynthesis, root-soluble carbohydrate and root colonisation), soil properties, and soil microbial community structure. Specific attention was paid to arbuscular mycorrhizal (AM) fungi. The soil fatty acid methyl ester (FAME) 16:1 ω5 was used to quantify biomass of AM fungi and the root FAME 16:1 ω5 analysis was used as index for the development of colonisation in the olive trees roots. A significant increase in organic C, C/N ratio, extractable phosphorus and exchangeable potassium was found after one year of agronomic application of OMW. The development of saprophytic fungi was significantly higher in the OMW amended soils, whereas the abundance of the soil FAME 16:1 ω5, root FAME 16:1 ω5, photosynthetic rates and the amount of the total root-soluble carbohydrate were decreased significantly after agronomic application of OMW. A principal component analysis (PCA) of the trees characteristics profiles showed discrimination between the nonirrigated and the OMW irrigated olive trees. These findings suggest that the altering functioning of arbuscular mycorrhizas should be considered as potential factors mediating olive trees responses to agronomic application of OMW when the OMW dose applied is higher than 30 m 3 ha −1. To our knowledge, this is the first report of alterations in the soil FAME 16:1 ω5 and root FAME 16:1 ω5 due to land spreading of OMW.

Short-term effects in soil microbial community following agronomic application of olive mill wastewaters in a field of olive trees

Olive mill wastewater (OMW) creates a disposal problem. The large amounts generated, combined with the high phenol and chemical oxygen demand concentrations, are the main difficulties in finding a solution for the management of these wastewaters. We investigated the short-term effect of spreading OMW on the soil surface of an olive grove on the soil microbial communities. Analyse of ester-linked fatty acid methyl ester (EL-FAME) were used to assess variation in soil microbial community structure after agronomic application of OMW. EL-FAME analysis showed significant shifts of specific groups of fatty acids 30 days after application of OMW to a field of olive trees at rates of 0 (control soil), 30, 60, 100, and 150 m 3 ha −1 of OMW. In particular, the branched saturated fatty acids indicative of Gram-positive bacteria decreased and the unsaturated fatty acids commonly found in Gram-negative bacteria and fungi increased. The fungal/bacterial ratio measured increased significantly with increasing OMW. Lower cy19/18:1ω7c and cy17/16:1ω7c ratios were found in the amended soil than the control soil, and we interpret that as an indication that nutrient availability may be more limiting in the control soil. Similarly, the relative abundances of monounsaturated fatty acids increased with added OMW, and this is consistent with the presence of high substrate availability in OMW-treated soil. Principal Components Analysis of the FAME profiles showed discrimination between the control soil and OMW amended soil. Differences in fatty acid profiles between OMW-treated soil and control soil suggests that amendment of soil with OMW favors specific groups of organisms. To our knowledge, this is the first report of alterations in the FAME profile in soils due to agronomic application of OMW.

Agronomic application of olive mill wastewaters with phosphate rock in a semi-arid Mediterranean soil modifies the soil properties and decreases the extractable soil phosphorus

Olive mill wastewater (OMW), a by-product of the olive-mill industry, is produced in large amounts in Mediterranean countries. The presence of indigenous phosphate deposits in some countries like Tunisia provides an incentive for direct application or local chemical treatment at low cost to improve the solubility of low reactive phosphate rocks (PRs). The use of naturally occurring low-molecular weight organic acids (LMWOAs) that are present in OMW represents a new perspective in PR research and a possible solution for the recycling of the OMW. The present work was aimed at evaluating, under natural situations (field of olive trees), the effects of agronomic application of OMW (amounts applied: 30, 60 m 3 ha −1) with PR (amounts applied: 150 kg ha −1) on olive trees soil properties. We measured organic C, nitrogen (N), extractable phosphorus (P), exchangeable calcium (Ca), and exchangeable potassium (K), as well as other properties (pH and electrical conductivity). Our data provide evidence that agronomic application of OMW with PR has important effects on soil properties. Increases in organic C, total N, extractable P and exchangeable potassium (K) were found after the first agronomic application of OMW and PR. These increases were only temporary, following the second agronomic application of OMW and PR, significant reductions were detected in the extractable soil P (19.67 mg kg −1 in the control soil vs. 8.99 mg kg −1 in the amended soil). Changes in the extractable soil P could alter plant productivity and plant community structure because shifts in nutriment availability can affect the balance between limiting and non-limiting nutrients.

Effects of trawler discard availability on egg laying and breeding success in the lesser black-backed gull Larus fuscus in the western Mediterranean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 132:43-46 (1996) - doi:10.3354/meps132043 Effects of trawler discard availability on egg laying and breeding success in the lesser black-backed gull Larus fuscus in the western Mediterranean Oro D The availability of trawler discards is likely to have a pronounced effect on the reproduction of seabirds, but this importance is normally difficult to quantify. A comparison between 2 breeding seasons of the lesser black-backed gull, one of them affected by a trawling moratorium, has allowed an assessment of the effects of discard availability on its egg laying. When trawlers operated, diet was dominated by fish from discards, while during the trawling moratorium gulls fed from refuse tips, olive tree fields and especially rice fields. Although neither breeding phenology was different nor was clutch size significantly lower in the year of the trawling moratorium, the volume of the eggs decreased significantly, showing the importance of trawler discard availability as a proximate determinant of egg production of scavenging seabirds. Since the moratorium overlapped with the chick rearing stages in both years, breeding success was probably lower than before the establishment of the trawling moratorium in 1991. However, the breeding success was higher in 1994 than in 1995, when the moratorium overlapped with the entire period of chick growth. Population dynamics of the species is probably affected by changes in trawler discard availability, especially if a trawling moratorium continues for many years. Trawler discards . Food availability . Moratorium . Lesser black-backed gull . Egg-laying . Population dynamics . Reproduction Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 132. Publication date: February 29, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.