Search

Soil management in orchards can have several economic and environmental implications. In this study, three different soil management systems were compared in a dry-farmed olive grove: conventional tillage (tillage), glyphosate-based herbicide (herbicide) and sheep grazing. The experiment lasted eleven years (2011–2022) and was carried out after a previous trial conducted on the same plot with the same treatments and duration (2001–2011). However, in the earlier trial, the herbicide and sheep grazing treatments switched positions in the plot, while the tillage treatment remained in its original place. The average total accumulated olive yields between 2011 and 2022 were 225.1, 230.9, and 245.0 kg tree−1 for the sheep grazing, tillage, and herbicide treatments, respectively. However, no significant differences were observed between the treatments. The levels of total organic carbon in the soil, measured in samples collected in the last year of the study, were 41.3, 33.7, and 37.3 g kg−1, respectively, for the same treatments. These findings indicated that the tillage treatment exhibited lower soil organic matter content and reduced bioavailability of some nutrients, which raises concerns about its sustainability. On the contrary, employing sheep grazing with an appropriate stocking rate, effectively controlling vegetation in the spring, ensured favourable soil properties and olive yields comparable to the other treatments. Moreover, the sheep grazing approach provides supplementary advantages to the farmer, including revenue from the sale of animal products and the opportunity to transition to organic farming systems, which better align with the preferences of contemporary societies. [ABSTRACT FROM AUTHOR]

Olive orchards represent a key agricultural system in the Mediterranean Basin. Soil degradation processes associated with unsustainable agronomic practices and climate change could severely impact the sustainability of Mediterranean rainfed olive orchards. In this context, soil amendments are important tools that can be used to enhance soil fertility for sustained environmental quality and plant performance. In this study, a field trial was conducted for 4 years in olive tree (Olea europaea L.) to assess the effects of a mineral fertilizer compound and the combination with a single application of zeolites or biochar on the physiological and biochemical performance, tree nutritional status, crop yield and soil chemical and biological properties to gain knowledge towards more sustainable management. Our results showed that the addition of zeolites and biochar to mineral fertilizer ameliorated the physiological and biochemical performance, as evidenced by consistent increments of relative water content, stomatal conductance and net photosynthesis and by lower signs of oxidative stress during the periods of greater climate adversity. However, crop yield was not significantly different among soil treatments. On the other hand, soil chemical and biological traits at the surface layer (0–10 cm) have shown different and relevant responses after 4 years of soil amendment application. In fact, zeolite supply stood out as increased pH, extractable K, cation exchange capacity, microbial biomass carbon and microbial biomass quotient and reduced extractable Cu. Furthermore, zeolites induced positive changes in soil enzymatic activity, leading to increases in 10 enzymes involved in C, N and P cycles. In contrast, the effects of biochar on soil properties were much more reduced, given that it decreased the microbial biomass nitrogen and enhanced the activities of three P‐cycle enzymes. In summary, our data demonstrated that both soil amendments can be an interesting complement to mineral fertilization, in order to increase trees' resilience under rainfed conditions and to promote soil health, although the use of zeolites appears to be a more promising strategy because of the induction of higher soil sustainability. [ABSTRACT FROM AUTHOR]

In the northeast of Portugal, like in many parts of the world, most soils are acidic, which may hamper crop productivity. This study presents the findings of a factorial experiment on olive (Olea europaea L.) involving three factors: (i) soil type [schist (Sch) and granite (Gra)]; (ii) cultivars [Cobrançosa (Cob) and Arbequina (Arb)]; and (iii) fertilizer treatments [liming (CaCO3) plus magnesium (Mg) (LMg), phosphorus (P) application (+P), boron (B) application (+B), all fertilizing materials combined (Con+), and an untreated control (Con-)]. Dry matter yield (DMY) did not show significant differences between cultivars, but plants grown in schist soil exhibited significantly higher biomass compared to those in granite soil. Among the treatments, +B and Con+ resulted in the highest DMY (50.8 and 47.2 g pot−1, respectively), followed by +P (34.3 g pot−1) and Con- (28.6 g pot−1). Treatment LMg yielded significantly lower values (15.6 g pot−1) than Con-. LMg raised the pH above 7 (7.36), leading to a severe B deficiency. Although Con+ also raised the pH above 7 (7.48), it ranked among the most productive treatments for providing B. Therefore, when applying lime to B-poor sandy soils, moderate rates are advised to avoid inducing a B deficiency. Additionally, it seems prudent to apply B after lime application. [ABSTRACT FROM AUTHOR]

Soil degradation and climate change are threatening the sustainability of Mediterranean olive orchards, typically grown under rainfed conditions and conventional soil tillage. Thus, implementing sustainable soil management practices is crucial to preserve soil health and mitigate the negative effects on plant performance. In this study, we assessed the effects of conventional tillage (T), an early maturing and self-reseeding annual legume cover crop (LC) and its combination with natural zeolites (ZL) on plant physiological performance, tree nutritional status, crop yield, and soil physicochemical and microbiological properties. Although both LC and ZL enhanced the photosynthetic activity, tree nutritional status, soil moisture and olive yield relative to T, ZL was clearly more efficient at improving some soil health indicators, namely at the 0–10 cm soil layer, once soil acidity decreased and Kjeldahl N, extractable P and B, cation exchange capacity and microbiological activity increased, as evidenced by the higher concentrations of easily extractable and total glomalin-related soil protein, microbial biomass carbon, microbial biomass quotient, and actinomycetes. Therefore, using natural zeolite with leguminous cover crops appears to be a promising strategy of sustainable soil management in rainfed olive orchards, as it is able to provide numerous ecosystem services. [ABSTRACT FROM AUTHOR]

In acid soils, when no‐tillage farmers intend to apply lime, the question arises as to whether it should be incorporated into the soil or whether it can be left on the soil surface. In this study, two types of limestone, calcitic (Lcal) and dolomitic (Lmag), were tested in two olive groves of cv. Cobrançosa, with an initial pH of 4.9 (S. Pedro) and 5.5 (Raparigas). In S. Pedro, limestone was incorporated into the soil (Lburied) and in Raparigas, it was left on the floor (Lfloor). The use of limestone significantly increased soil pH in the 0–0.10 m layer in both experiments. In the 0.10–0.20 m soil layer, only Lmag increased significantly the soil pH in comparison with the control. Lmag was more effective than Lcal in increasing cation exchange capacity (CEC) and reducing exchangeable acidity (EA) and aluminium (Al3+) in the Lfloor experiment. Both limes increased leaf calcium (Ca) concentration, and Lmag increased the leaf levels of magnesium (Mg). In Lfloor experiment (higher soil pH), soil microbial carbon (C) decreased, and microbial nitrogen (N) increased with liming, which may indicate an increase in bacteria in the soil and a decrease in fungi. In Lburied experiment (initial pH of 4.9), liming significantly increased accumulated (2018–2021) olive yield (56 and more than 67 kg tree−1, respectively, in the control and liming treatments). In Lfloor experiment (initial pH of 5.5), the accumulated olive yields did not differ significantly between treatments (average values between 105 and 115 kg tree−1). The results of this study provide evidence that liming may increase olive yield in very acid soils and that dolomitic limestone should preferably be used by no‐tillage farmers, due its higher solubility and faster effect on soil and trees. [ABSTRACT FROM AUTHOR]

Under climate change threats, there is a growing need to adapt the conventional agronomic practices used in rainfed olive orchards by sustainable practices, in order to ensure adequate crop yield and olive oil quality and to preserve soil health. Therefore, for two years, the effects of conventional tillage practice (T) and two sustainable soil management strategies, a leguminous cover crop (LC) and its combination with natural zeolites (ZL), on the yield, fatty acid composition, polyphenolic profile and quality indices of olive fruits and oil were evaluated. Crop yield was significantly increased by LC and ZL in the first year. Although in the second year no significant differences were verified, the cumulative yield increased significantly by 31.6% and 35.5% in LC and ZL trees, respectively. LC enhanced the moisture and size of olives, while ZL increased, in general, the concentrations of oleuropein, verbascoside, caffeic acid and epicatechin, as well the oleic/linoleic ratio in fruits and the levels of 3,4-dihydroxyphenylglycol, tyrosol, verbascoside and caffeic acid in olive oil. Despite the higher concentration of total phenols in the fruits and oil from T trees in the warmer and dryer year, the quality of the oil decreased, mainly when compared with ZL, as evidenced by the peroxide value and K232 and K270 coefficients. In short, both sustainable soil management strategies appear to be promising practices to implement in olive orchards under rainfed conditions, but the innovative strategy of combining zeolites with legume cover crops, first reported in the present study, confers advantages from a nutritional and technological point of view. Nevertheless, studies subjected to the long-term use of these practices should be conducted to ensure the sustainability of the crop yield and olive oil quality. [ABSTRACT FROM AUTHOR]

The use of humic substances in agriculture has increased in recent years, and leonardite has been an important raw material in the manufacture of commercial products rich in humic and fulvic acids. Leonardite-based products have been used to improve soil properties and to help plants cope with abiotic and biotic stresses. In this study, the effects of two commercial leonardites and an organic compost, in addition to a control treatment, were assessed for pot-grown olive plants over a period of fourteen months on soil properties, tissue elemental composition and dry matter yield (DMY). Three organic amendments were applied at single and double rates of that set by the manufacturer. The study was arranged in two experiments: one containing the seven treatments mentioned above and the other containing the same treatments supplemented with mineral nitrogen (N), phosphorus (P) and potassium (K) fertilization. Overall, organic compost increased soil organic carbon by ~8% over the control. In the experiment without NPK supplementation, N concentrations in shoots and P in roots were the highest for the compost application (leaf N 12% and root P 32% higher than in the control), while in the experiment with NPK supplementation, no significant differences were observed between treatments. Total DMY was ~10% higher in the set of treatments with NPK in comparison to treatments without NPK. Leonardites did not affect significantly any measured variables in comparison to the control. In this study, a good management of the majority of environmental variables affecting plant growth may have reduced the possibility of obtaining a positive effect on plant nutritional status and growth from the use of commercial leonardites. The leonardites seemed to have caused a slight effect on biological N immobilization. This is not necessarily an advantage or a drawback; it is rather a feature that must be understood to help farmers make better use of these products. [ABSTRACT FROM AUTHOR]

Two field trials (FieldExp1 and FieldExp2) and a pot experiment (PotExp) were c0onducted over a period of 3 years to assess olive tree response to nitrogen (N) applications and to estimate apparent N recovery. FieldExp1 was installed in a 3-year-old olive grove. FieldExp2 consisted of a plantation of young rooted plants. Two treatments were applied in both experiments: N application and a nonfertilized control. In PotExp, 4 N rates were used. In FieldExp1, olive yield significantly increased with applied N in only 1 of the 3 growing seasons. In FieldExp2, aboveground dry matter yield significantly increased with N application. In PotExp, total dry matter yield displayed a typical saturation curve in response to N rates. The poor response of olive yield to N application might be due to the reduced amount of N removed in the crop, and also to the negative interaction found between N application and water deficit. Apparent N recovery reached values varying from 13.1% in FieldExp2 to ~100% in PotExp. The results indicate that the olive response to N and N use efficiency seem to be influenced more by the agroecological conditions defining target yield and N loss, rather than by plant species. [ABSTRACT FROM AUTHOR]

Pruning has been seen as a means of improving olive tree productivity. The presumed importance of pruning was described by Columella (born 4 AD) and has persisted in general terms to the present. In this work, the effect of different pruning regimes was assessed from two field trials conducted in Mirandela, NE Portugal, in an olive grove of cv. 'Cobrancosa', rainfed managed. The first trial began after a light crop ("off" year) and received four pruning regimes (hard, moderate, light and nonpruned control). The second trial started the following year, after a heavy crop ("on" year) and received two pruning regimes (hard and nonpruning). The study was carried out from 2012 to 2016. The accumulated crops of the four harvests performed after pruning in the first experiment did not significantly vary among nonpruning (8754 kg ha-1), slight pruning (8850 kg ha-1) and moderate pruning (8334 kg ha-1) but was significantly lower in hard pruning (6449 kg ha-1). The olive trees showed a high plasticity or tolerance to pruning, since olive yield did not decrease in response to light or moderate pruning regimes. It seems that it is possible to carry out light to moderate pruning to achieve several objectives of orchard management without significant loss of production. The results also showed that if pruning is done under a hard regime it should only be performed after a heavy crop. In addition, if done under a light regime, pruning can also reduce the alternate-year bearing behavior of the olive tree. [ABSTRACT FROM AUTHOR]

Studies on the effect of groundcover treatments on perennial tree crops have been common in recent decades. However, few have included leaf analysis as an aid to understand the effects of groundcover treatments on tree crop growth and yield, in particular in rainfed olive orchards. Field experiments took place in northeast Portugal, over the course of eight consecutive years, in two commercial orchards selected on the basis of their contrasting situation regarding the floor-management system before the trial started. An orchard located in Braganca, currently managed as a sheep-walk, received the following treatments: sheep-walk (SW), where the natural vegetation was managed with a flock of sheep; mechanical cultivation (MC), which consisted of two tillage trips per year in the spring; and glyphosate (Gly), where the herbicide was applied once during the first fortnight of April. Another orchard near Mirandela, currently managed by tillage, received the following treatments: mechanical cultivation (MC); glyphosate (Gly); and residual herbicide (RH), where an herbicide with a residual component was applied late in the winter. The trees that underwent Gly treatments produced the greatest tree crop growth and olive yield. The worst results were achieved with the SW and MC treatments in the Braganca and Mirandela experiments, respectively. Leaf nitrogen (N) and boron (B) concentrations were significantly higher and lower, respectively, in the treatments that caused the higher and lower olive yields in both experiments. In the Mirandela orchard, where the leaf potassium (K) concentrations were close to the lower limit of the adequate range, the leaf K levels followed the pattern registered for N and B. The results showed a strong link between tree crop nutritional status and tree crop growth and olive yield. The groundcover treatments that facilitate nutrient absorption by olive trees yielded more crops. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and boron (B) are mobile elements in soil. Therefore, the application of these nutrients is typically performed annually, as a single dose, or even split into several fractions in the case of N. In olive (Olea europaea L.), however, controversial literature has suggested that yearly application of N may not be required. In the case of B, some authors indicated that one single application is sufficient for 3 or 4 years. Thus, the effects of these elements on olive yield, leaf N and B concentrations, as well as soil available N and B were investigated during a field trial performed in an olive orchard located in northeast Portugal, in which N and B were not applied for four consecutive growing seasons. Fertilizer treatments consisted of the following: the control, which was a complete fertilization plan where N and B were included (N + B treatment); -N treatment, with N excluded from the fertilization plan; and -B treatment, with B excluded. Available soil N and B were estimated from a pot experiment with Italian ryegrass (Lolium multiflorum L.) and from chemical laboratory extractions. Olive yield decreased significantly in the -N treatment in comparison to the control. A slight yield reduction in the -B treatment in comparison to the control was also observed. Leaf N and B concentrations decreased significantly in the -N and -B treatments, respectively, in comparison to the N + B treatment. Soil available N and B at the end of the experiment were significantly lower in the -N and -B treatments, respectively, in comparison to the N + B control. The results showed a continuous decrease in olive yield and leaf N and B concentrations, which reflected the reduction in soil-available N and B in the treatments lacking the respective nutrient. Therefore, it seems prudent to recommend adjustments to the rates of N and B every year to prevent reduction in tree crop performance and improve nutrient-use efficiency. [ABSTRACT FROM AUTHOR]

In this work, diagnosis of boron (B) nutritional status based on leaf B concentrations was compared for the most common leaf-sampling times for olive trees, January and July. For this purpose, field experiments were conducted over 4 years (2003-2006) in two rainfed olive groves located in Mirandela and Braganca, northeastern Portugal. Leaf samples were collected in January and July and analyzed for B by standard procedures. Fruit harvest occurred in December of each year. The crops followed typical alternate fruiting cycles. During the 4 years of the study, mean olive yields in the Braganca orchard fluctuated, yielding 3.6, 28.1, 5.5, and 22.7 kg tree-1. Yield variation per individual tree was also great. In the Braganca orchard and in the 2004 harvest, yields ranged from 1.2 to 52.7 kg tree-1. Leaf B concentrations also varied greatly between individual trees. In the Braganca orchard in the July sampling of 2004, values for individual trees varied from 12.2 and 23.7 mg B kg-1. From a total of 16 scatterplots generated from the relationship between leaf B concentrations and olive yields, 10 significant linear relationships were established; six of them were related to July sampling dates and four were related to January dates. The number of significant linear relationships established between leaf B concentration and olive yield was used as a criterion of the accuracy of the B nutritional diagnosis, because this represented the lowest experimental variability. By using this criterion, the July sampling date proved as better for B nutritional diagnosis, although the difference from January sampling date was not sufficient to disregard this. Leaf B concentrations were consistently greater in July than in January. Averaged across the 4 years of the study in both orchards, the difference was 4.3 mg B kg-1. This difference should be taken into account in the interpretation of leaf analysis results when B levels are close to the deficient critical concentration. [ABSTRACT FROM AUTHOR]

Soil conditioners and beneficial microorganisms are important tools that can be used to increase the sustainability of agro-systems. However, the high diversity of conditions where they can be applied may influence the results, which requires extensive field research. In this study, a field trial of four years was conducted in olive (Olea europaea L.) to assess the effect of biochar, zeolites and a commercial mycorrhizal inoculum in the photosynthetic performance, nutritional status of trees, olive yield and soil properties. The experimental design also included a fertilizer treatment with nitrogen (N), phosphorus (P), potassium (K) and boron (B), which nutrients were applied at 50 kg ha−1 of N, P2O5 and K2O and 2 kg ha−1 of B, and an untreated control. The mineral fertilizer treatment increased significantly the dry mass of pruning wood and the average olive yield by 21% over the control treatment. The mineral treatment increased plant N nutritional status, the most likely reason why the trees of this treatment performed better. Overall, the soil treatments had net photosynthetic rates similar to each other and higher than the control treatment, from the second year onwards. Biochar increased soil organic matter, as a result of the carbon (C) contained in the amendment itself, and probably by stimulating soil biological activity. Biochar and zeolites did not improve the productive performances of the tress, but increased the soil cation exchange capacity (CEC), which can benefit the system in the long-term. Mycorrhizal fungi did not show any benefit for soil or plants, which could mean that mycorrhization was not established, or their effect was not better than that of native microorganisms. In the conditions of this study, the interest of using commercial mycorrhizal fungi in a mature olive orchard seems to be low. [ABSTRACT FROM AUTHOR]

Strategies for waste valorisation from domestic and agro-industrial activities must be pursued, and its use as a soil amendment is an interesting possibility. In this four-year study, the effect of applying municipal solid waste (MSW), farmyard manure (FYM), bottom wood ash supplemented with nitrogen (Ash + N), the inorganic fertilization common in the region (50 kg ha−1 N, P2O5 and K2O) (Control) and this inorganic fertilization supplemented with 70 kg N ha−1 (High N) was assessed in a rainfed olive grove planted in a shallow soil with low organic matter and managed with conventional tillage. The High N treatment significantly increased olive yield in comparison to the other treatments (165% more than MSW), and soil available N proved to be the main driver for tree productivity. MSW and FYM increased soil organic matter, as well as the levels of phosphorus and cation exchange capacity, leaving good indications for future production cycles, although during the four years of the study these treatments provided little N to the trees. The High N treatment significantly reduced soil organic matter (63% less than MSW). The result was attributed in part to the soil management system that did not allow the development of herbaceous vegetation, but also to an effect known as "added N interaction", in which the excess of inorganic N in the soil might have contributed to accelerate the mineralization of native soil organic matter, an aspect that compromises the sustainability of this fertilization strategy. Although MSW and wood ash are sometimes associated with risks of environmental contamination with heavy metals, in this study the levels of heavy metals in soils and in plant tissues were not of concern. [ABSTRACT FROM AUTHOR]

Phosphorus (P) application in olive orchards is very common in the Mediterranean basin although experimental evidence of crop response to applied P is practically non-existent. In this work soil P and tree P nutritional status of the olive groves of NE Portugal were assessed from a population of 1808 soil and 2252 leaf samples. Plant response to applied P was evaluated from two field and two pot experiments carried out with the cultivar ‘Cobrançosa’. The analyses of soil and leaf samples of the olive orchards of the region indicate that P fertilizer recommendations should be based on leaf rather than on soil analyzes, since the latter seems to overestimate the need for P. The field and pot experiments hardly showed any positive response to P applications, which is a sign that the use of P fertilizer in olive can be substantially reduced. Nonetheless, in one pot experiment, P application significantly increased total dry matter yield during three consecutive years, in a strict association with higher tissue P concentrations and enhanced photosynthetic activity, as revealed by gas exchange and chlorophyll fluorescence traits. The experimental results also showed that the roots can uptake and store P when available in the soil, which may buffer the levels of P in the shoots. The acid phosphate activity can provide useful information but deserves caution in the interpretation of results since it depends not only on the availability of inorganic P in the soil, but also on the available organic substrate and pH. [ABSTRACT FROM AUTHOR]

• Kaolin (KL) improved olive trees performance under sustained deficit irrigation (SDI). • KL improved photosynthetic efficiency at high light intensity. • KL improved cellular metabolic functions and reduced oxidative damages. • KL increased crop yield, oil yield and oxidative stability of olive oil. Regarding the foreseeing climate change is reasonable to expect harmful consequences to olive tree (Olea europaea L.), an iconic species of Mediterranean basin. In large areas of the Region, the sustained deficit irrigation (SDI) accounts with a reduced amount of water that might not be enough to keep the plant functioning at desirable levels. In this study the use of a reflective clay, kaolin, was evaluated in order to alleviate the negative summer stress effects on olive trees (cv. Cobrançosa) under an SDI system. Kaolin reduced the stomatal and the non-stomatal limitations to photosynthesis at high light intensity, improved plant water status, and decreased the oxidative damages. The amelioration of physiological and metabolic functions and the lower allocation of resources to summer stress tolerance mechanisms, allowed the KL-sprayed trees to increase crop yield, the oil yield and its oxidative stability, with the reduction of peroxide index and K 232. Thus, the application of kaolin had a positive synergistic effect with SDI, especially important for semi-arid areas where water available for irrigation do not cover all the necessities. [ABSTRACT FROM AUTHOR]

• Commercial mycorrhizal fungi increased soil labile P fraction and P concentration in olive tissues. • Mycorrhizal fungi increased soil organic carbon. • Mycorrhizal fungi did not reduce excessive levels of Fe and Mn in shoots. • In this study, commercial mycorrhizal fungi did not increase dry matter yield of potted olive cuttings. • Commercial mycorrhizal fungi should be targeted towards specific purposes rather than for general uses. Biofertilizers of mycorrhizal fungi have been mainly tested in nutrient-limited soils or harsh environmental conditions, which have helped to highlight their beneficial role in plant growth. However, their benefits in stress-free growing conditions have not yet been properly proven. In this work, a commercial mycorrhizal fungi, composed of 18 ecto and endomycorrhizal fungi, was tested in a pot experiment with young olive cuttings, under an experimental apparatus allowing the evaluation of dry matter yield and plant nutritional status after one and two years of growth. The results highlighted the role of the mycorrhiza in increasing P bioavailability, either evaluated by soil P labile fraction or through tissue P concentration. The role of mycorrhiza in increasing soil organic C was also relevant (7% higher than the control). Mycorrhiza had little effect on the uptake of other nutrients and on the alleviation of excessive levels of metals, in particular Fe, in the shoots. Instead, olive showed its own exclusion mechanisms, registering root Fe levels 50 times higher than in shoots. Mycorrhiza did not improve plant growth compared to the other fertilized treatments. The increase in plant dry matter observed in the mycorrhiza treatment in comparison to the control was probably due to the initial content of the commercial product of N, P and K (3% N, 3% P 2 O 5 and 3% K 2 O). Under the conditions of this experiment, the farmer would not benefit from the use of this mycorrhizal fungi, but it nevertheless proved its value for agriculture, suggesting that commercial products should be targeted more towards specific purposes, than for generalized uses. [ABSTRACT FROM AUTHOR]