INTRODUCTION
From the fertilization of the “rapa” (olive flower) until the olive reaches maturity, the fruit goes through a series of stages according to a precise and determined pattern (Figure 1).
During fertilization, pollination occurs, that is, the transfer of pollen from the anther of the flower to the stigma of the same or another flower. Normally, only one of the four seed primordia of the ovary is fertilized and begins its growth. In numerous olive varieties, it has been observed that cross-pollination anticipates the growth of the fertilized seed primordium compared to self-pollination, increasing the demand for assimilates in these fruits. This fact causes intense competition between them and the unfertilized flowers, which translates into massive abscission of less competitive flowers and young fruits. This is the reason why the percentage of set flowers that give rise to fruit development is so low (1-2%). If you are interested in knowing how floral differentiation and induction occur and what factors affect pollination and fruit setting in olive trees, and how, we invite you to consult our Cultinews May 2020.
GROWTH AND DEVELOPMENT OF THE FRUIT
From a quantitative perspective, the growth of the olive, like that of any other drupe, goes through several phases (Figure 2). In the first phase of growth, both cell division and expansion contribute to the increase in fruit size. This phase concludes approximately with the end of sclerification, or hardening of the pit (endocarp), which occurs approximately 7 to 9 weeks after flowering. After a period during which growth slows or stops, a second phase begins, during which the olive undergoes a further increase in size, concluding with veraison, or the change in color of the skin (epidermis or epicarp) to yellowish-green tones that indicate the beginning of ripening.
Fruit size is a critical factor for olive quality, especially for table or green olives. During normal fruit growth, the tree's bearing capacity, i.e., the number of olives, is possibly the main determining factor for fruit size under specific environmental and growing conditions. In other words, The greater the number of fruits, the smaller their size.. Therefore, fruit size is the main quality criterion for table olives, just as fat yield is for olives for oil. The pulp/bone ratio, which is in turn related to the size of the fruit, is a determining factor of fat performance, since the oil from the pulp represents more than 95% of the total olive (Rayo and Cuevas, 2017).
After fertilization, a rapid process of cell division occurs, although this rapid cell growth is only observable after 10-15 days. During this phase I, cell division completes in most of the olive's tissues. The tissue that shows the greatest degree of development is the endocarp, which can reach up to 80% of the fruit's volume, while the mesocarp or pulp and the exocarp (the outermost part) increase in size to a lesser extent. The process continues until July with the sclerification and hardening of the pit. Water stress during this period produces smaller pits (Lavee, 1986), which can result in fruits with abnormally high pulp-to-pit ratios and, under high water stress conditions, can even compromise fruit viability.
During phase II, fruit growth slows, the embryo and endocarp reach their final size, and the hardening of the pit is complete. Phase III is characterized by rapid fruit growth due to the enlargement of the mesocarp cells, which determines its final size. During this phase, oil biosynthesis and its accumulation in the parenchymal cells of the pulp (lipogenesis) begin. Water availability in this phase determines the final fruit size and oil content, resulting in smaller fruits with lower oil contents under stress conditions. This phase ends in early autumn when the fruits undergo the first changes in pigmentation. Coinciding with the change in fruit color, the seed reaches maturity and exhibits a high germination rate, which subsequently decreases when the fruits turn black (Rayo and Cuevas, 2017).
After phase III, fruit growth and oil accumulation slow significantly as ripening takes place. Once the pulp reaches its final size, its weight may fluctuate as a result of moisture fluctuations due to environmental conditions (rainfall and frost).
Lipids, lipogenesis and changes in oil composition during fruit ripening
The synthesis of fatty acids (lipogenesis) The accumulation of lipids in the cells of the olive pulp (mesocarp) determines fat yield. Lipid accumulation begins during the growth arrest phase of the drupe and concludes at the beginning of ripening; that is, lipogenesis occurs from the end of stone hardening until veraison (Figure 3). These data appear to confirm previous studies on olive fat yield, which indicate that the amount of oil per olive peaks at the beginning of ripening, and that fluctuations from this period onward are mainly due to variations in the moisture content of the pulp.
During lipogenesis, three distinct phases can be established (Frías et al., 1991):
1.Phase slow biosynthesisIt occurs in newly formed fruits until the pit hardens, reaching a fat content, expressed in fresh weight, of 4%. During this phase, structural lipids (phospholipids and galactolipids) are formed, causing the fruit to behave as a photosynthetic tissue.
2.Phase of accelerated biosynthesis. It occurs after the hardening of the bone, around the second half of July. An active synthesis of diglycerides and triglycerides begins, which will undergo a notable acceleration during the months of August (about 18 weeks after full flowering) and September, to reach its peak. maximum towards the end of September or beginning of October (García Martos and Mancha, 1992), coinciding with the change in fruit pigmentation from green to yellowish-green. At the end of this stage, the fruit's fat content can reach 27% of its fresh weight.
3.Phase stationary or slowing down. At this stage, the rate of oil formation in the fruit begins to progressively decline from mid-October until it disappears at the beginning of December, which corresponds to week 28-29 after flowering.
The ripening of the olive involves a series of changes related to its compactness, color, sugar content, organic acids and taste factors that make it edible, regardless of abscission or collection (Figure 4). This is the result of a complex combination of physiological and biochemical pathways, with a high genetic component, which can also be influenced by climatic and cultivation conditions (Beltrán et al., 2017).
Throughout the fruit ripening process, significant changes occur in the oil's fatty acid composition. Thus, the palmitic acid content decreases, as does the content of all saturated fatty acids. Oleic acid, the majority fatty acid in olive oil (55-83%), varies, either remaining constant or slightly increasing in content. Linoleic acid increases its percentage throughout the fruit ripening process. In general, a tendency in fatty acid biosynthesis toward more unsaturated forms is observed. An important parameter from both a nutritional and commercial perspective, primarily responsible for the oxidative stability of oils, is the ratio of monounsaturated fatty acids to polyunsaturated fatty acids (MUFAs/PUFAs); this ratio decreases during fruit ripening due to the increase in linoleic acid and the constant or slight increase in oleic acid content.
An important fraction in virgin olive oil is the minority compounds, which, despite their low concentration, are of great importance due to their nutritional properties and their effect on the oil's organoleptic characteristics. Phenolic compounds stand out due to their high antioxidant potential. These compounds perform their antioxidant function at the cellular level, protecting the oil against autoxidation processes and are also responsible for some of the oil's organoleptic characteristics (bitterness and spiciness). During fruit ripening, there is a decrease in the total content, as well as in general, of the different individual phenolic compounds, although slight increases in their concentration are occasionally observed as a result of the loss of moisture in the fruit caused by autumn frosts and its effect on the partition coefficients of these compounds.
Other natural antioxidants are tocopherols, which exhibit vitamin E activity and also protect the body against oxidative processes. During fruit ripening, there is a decrease in the total content, as well as in the content of each of the tocopherols present in the oil.
The sterols present in the oil constitute a regulated quality parameter for virgin olive oil and also exert a healthy effect by reducing blood cholesterol levels. During the fruit ripening process, the total sterol content of the oil decreases. Triterpenic acids and triterpenic alcohols have bioactive properties, protecting against oxidative stress and cellular damage. In the case of acids, a decrease has been described during fruit ripening (Pérez Camino and Cert, 1999), while in the case of alcohols, no differences have been observed, although there is a tendency for their content to increase (Sánchez et al., 2004).
Oxidative stability is a measure of an oil's resistance to rancidity. It depends on its acidic composition (MUFAs/PUFAs or oleic/linoleic) and polyphenol content. Throughout the fruit's ripening process, oil stability decreases as a result of the increase in linoleic acid, its effect on the fatty acid ratios described above, and the decrease in total polyphenol content.
Oil color is considered a quality parameter and is related to its pigment content and composition (Mínguez et al., 1991). Oil color varies from deep green to yellowish, gradually losing intensity. As the fruit ripens, the pigment content of both chlorophyll and carotenoids decreases, although chlorophyll pigments decrease more rapidly, hence the increase in the carotenoid-to-chlorophyll ratio.
Another parameter that decreases throughout fruit ripening is total sterol content (Gutiérrez et al., 1999). Finally, the organoleptic characteristics of the oils are strongly influenced by the ripening stage of the fruit, with less bitter oils and less pronounced sensory characteristics being obtained as ripening progresses.
FACTORS AFFECTING LIPID BIOSYNTHESIS
The biosynthesis and accumulation of oil in the mesocarp (pulp) of the olive is a process that is influenced by a series of factors. internal and external factors, from the influence of the variety, since there are varieties with greater potential for oil accumulation, to technical factors or plantation design, climatic factors and nutritional factors.
La influence of the genotype or variety (Figure 5) on the capacity for biosynthesis and accumulation of oil in the fruits is a very important factor, although it cannot be separated from the environment. That is, the genotype-environment interaction This is what truly determines a variety's ability to achieve a higher or lower oil yield. However, it is true that the "Picual" variety is potentially capable of accumulating a greater amount of oil (% dry matter) than the "Arbequina" variety in the same environment. However, the biosynthesis and accumulation of oil in the fruit of the same variety does not necessarily have to be the same in one environment as in another. Therefore, the genotype is an important source of variation, not only of the main fatty acids, but also of the minor components of oil, although its interaction with the environment is also significant, so part of the variability will depend on where a variety is planted. This must be taken into account when choosing a variety, as it could even have important commercial connotations (Navas López, 2019).
Within the influence of the climatic factors, The lighting (or radiation) and the temperature, vary jointly, such that greater illumination means a greater incidence of radiation and, therefore, a higher temperature. The combined effect of both parameters results in an increase in the enzymatic activity of different metabolic pathways (lipogenesis and phenolic synthesis). Thus, more illuminated fruits reach a higher temperature and lower humidity, achieving greater ripeness, greater oil accumulation, and higher polyphenol content. However, excessive temperatures can slow the tree's photosynthetic activity, decreasing the oil biosynthesis process and also causing a loss of fruit size. Therefore, the optimum temperature is between 20 and 30°C. Temperatures below 20°C or above 30°C imply a decrease in photosynthesis, while above 35°C, COXNUMX uptake processes are inhibited.2 and photosynthetic, would suffer a drastic decline. To improve lighting and temperature conditions, we can influence this through pruning, always opting for lobed forms that allow greater radiation interception, compared to globose forms (Figure 6).
The technical or plantation design factors They do not pose a limitation in traditional or intensive olive grove plantations, as the planting frames are wide enough to allow illumination of all four sides of the olive tree and its upper part. However, in super-intensive or hedgerow olive grove systems, a series of design considerations must be taken into account in order to improve lighting and maximize the productive potential of the hedge. When the first hedgerow olive groves were established, it was observed that some were poorly designed and managed, and that the large size of the hedges and the short distance between them prevented light from reaching the lower areas, resulting in defoliation of these areas and production being localized to increasingly higher areas. These observations made it possible to establish a series of tests to determine the optimal characteristics that a hedge (Figure 7) should have, with a porosity of 20%, to achieve maximum production: the height of the hedge vegetation (Alt) must be less than or equal to the free distance between the hedges (d), therefore Alt/d<1 (Connor and Gómez del Campo, 2013). If the porosity is reduced, the free distance between hedges (d) should be increased or their height (Alt) and width (a) should be reduced.
Continuing with the influence of plantation design in hedgerow olive groves, oil production per hectare increases as the street width, since we are increasing the number of trees per hectare. However, oil production per tree is greater as the street width increases, something that is more accentuated with an EW orientation relative to NS, where the influence of the street orientation has hardly any effect on oil production per tree (Trentacoste et al., 2015a). Other trials carried out with different orientations where hedges have been designed with a street width of 4 meters, a porosity of 20% and a Alt/d ratio = 0,69 indicate that hedges with an EW orientation had a similar amount of oil production as the NS hedges, even slightly higher in rainy autumns and, therefore, scarce radiation (Gómez del Campo et al., 2009). In summary, when the hedge is well designed, the effect of orientation on oil production is small (Trentacoste et al., 2015b).
La climatology has a great influence on the olive harvest and also on the formation of oil. lack of water in the cultivation to cover their needs, called water stress, directly affects photosynthesis. The plant's response generally results in a longer stomatal closure than under normal conditions in order to reduce transpiration (thereby saving water). This directly affects gas exchange, reducing the rate of photosynthesis and therefore the formation of assimilates. The duration and the moment in the cycle at which water stress occurs determine the plant's vegetative and productive response (Figure 8).
Spring is the time of year when highly important processes occur in the crop. This includes the formation of inflorescences, followed by flowering and fruit set until the pit hardens. Most of the shoot growth that leads to the following year's fruit-bearing positions also occurs. Under normal conditions, and with relatively deep soils and high water storage capacity, winter rainfall is sufficient to avoid spring water stress. However, in some olive groves, serious problems can arise in years with very dry winters (poor flower quality, poor fruit set, and poor shoot growth).
Summer is the time of year when the first stages of fruit growth occur. Water stress during lipid biosynthesis causes a reduction in oil-forming capacity (Lavee, 1991), as well as a slowdown in fruit growth. If the olive is ultimately intended for oil production, some water stress can be assumed, causing a reduction in fruit size. Depending on the degree of stress and its duration, production losses can be significant.
Autumn is a period of intense lipogenic activity (oil formation) and fruit development (size) and is generally the most sensitive period to water stress in our conditions (Figure 9). During this time, it is essential to meet the crop's water needs through irrigation, in the event of insufficient rainfall, in order to obtain the greatest possible amount of oil (Leyva et al., 2017).
Importance of controlling water deficit during lipogenesis:
- If high levels of water deficit are reached, fruit growth would slow down and even stop if it is severe and prolonged.
- Increases in irrigation doses translate into increases in production.
- Autumn rains are essential for good oil production (Leyva et al., 2017).
- Irrigation application decreases the concentration of components related to oil quality (chlorophylls, polyphenols, carotenes and pigments (Amilo et al., 2019).
Some conditions of water stress during lipid biosynthesis cause, together with an abnormally low pulp/stone ratio, a reduction in oil-forming capacity and therefore, its fat content. There is a negative correlation between production and fruit size and fat content of the pulp. Thus, years of large harvests tend to produce smaller fruits with lower fat content than those obtained in years of low production (Lavee and Wodner, 1991).
El water It is the other major component of the fruit along with the oil and decreases during the ripening process, showing notable variations as a result of climatic conditions from mid-November onwards (rain and frost). In order to eliminate water interference when expressing the fruit's fat content and, therefore, to more accurately indicate the end of the oil formation phase, it is advisable to express the fat content on a dry matter basis, since this parameter remains constant once lipid synthesis stops, unlike when expressed on a fresh weight basis, which increases until very late periods (late January), mainly due to the decrease in fruit moisture (Figure 10).The fat content on a dry matter basis remains constant from the moment lipid synthesis is completed., that is, oil formation stops between mid-November and early December, depending on the variety considered (Beltrán et al., 2017).
Finally, within the external factors, the nutrition It significantly affects the biosynthesis of fatty acids. The olive tree is a hardy plant, capable of growing and producing fruit even under adverse environmental conditions for many other species. Like all perennial plants, it has nutrient storage organs that it easily reuses. For all these reasons, the nutritional requirements of olive groves are lower than those of other crops. Nitrogen (N) is the nutrient required in the greatest quantities by plants, including olive trees, which is why it has traditionally been the primary fertilization of olive groves. In dryland conditions, the greatest nutritional problem is potassium (K) deficiency, which worsens in the event of a heavy harvest. In calcareous soils, in addition to potassium, iron (Fe) and, possibly, boron (B) deficiencies can be found, and in acidic soils, calcium (Ca) deficiencies can be expected. These are the nutritional imbalances that can affect most olive groves and which, ultimately, should be monitored by performing the corresponding analyses. However, these imbalances will hardly appear concentrated in a single plantation (Fernández Escobar, 2017).
To promote the synthesis of fatty acids it is necessary to maintain a good nutritional level of the olive tree, based mainly on the elements to be provided during this stage, in order to be able to express the greatest potential of the cultivated variety in terms of fat yield.
Nitrogen is the major nutrient component of plants., which is why it is usually the most commonly used mineral element in fertilization programs. In cases of diagnosed deficiency, the symptoms of which are characterized by a generalized loss of chlorophyll resulting in nonspecific chlorosis in the leaf blade (Figure 11), a nitrogen dose should be used for correction based on the tree's size, its production level, and the growing medium. This dose should be adjusted by periodic foliar analysis, which, when correctly interpreted, will indicate the need to increase or decrease the applied dose. Due to the positive nitrogen balance—that is, the input of nitrogen into the olive grove is greater than output—it is difficult to find nitrogen deficiency situations in most olive groves.
Historically, few studies have been conducted to highlight the potential adverse effects of excessive nitrogen fertilization on the plant, although an increased susceptibility of trees to pests and diseases and a lower tolerance to cold have been cited, although with some controversy among authors. More recently, studies have been carried out in this regard, showing that excessive nitrogen fertilization in olive trees increases nitrogen accumulation in the fruit and causes a significant decrease in oil quality (Fernández Escobar et al., 2006). A Delay in fruit ripening, which often causes a decrease in fat yield (Fernández Escobar et al., 2014). Nitrogen concentrations in leaves above 1,7% have caused these effects, which is why this value has been established as a toxicity level.
What has historically been observed in olive groves is the lack of response of the olive tree to excessive or unnecessary applications of nitrogen. Annual maintenance nitrogen fertilization is pointless in olive groves, and nitrogen application is only appropriate when the concentration in the leaves indicates a deficiency. Therefore, foliar analysis is a useful tool for planning annual fertilization for an olive grove.
El Phosphorus It is an important element in crop fertilization, related to the formation of root tissue and flowering, although it is vitally important for the plant for other reasons. It is a essential element with a difficult dosage form and is required in significantly smaller quantities than nitrogen. It is absorbed in anionic forms, usually as the orthophosphate ion (H2PO4-), depending on the soil pH. In the plant it is present in constituent compounds (phosphate sugars, nucleic acids, phospholipids and coenzymes) and in the energy-carrying compounds (ATP, NADP, FAD) (Westerman, 1990). Its main physiological role is the phosphorylation of organic substances. Phosphoric acid temporarily combines with a carbonyl, enol or nitric group to form an energy-rich compound: adenosine triphosphate (ATP), which, when broken down into ADP, releases this energy, which is used in metabolic processes (Baeyens, 1970). These metabolic processes constitute chemical reactions that directly intervene in the survival, growth and reproduction of plants, such as photosynthesis, respiration, solute transport, translocation, protein synthesis, nutrient assimilation, tissue differentiation, and in general the formation of carbohydrates, lipids and proteins that intervene in these processes or are a structural part of plants.
It is likely that only in trees grown in soils very poor in this element, concentrations in leaves reach deficient levels (Figure 12). Symptoms of deficiency They begin on the lower leaves, that is, the oldest ones, turning from a dull dark green to a reddish or purple color characteristic and that reach dry the leaves completely. The number of outbreaks decreases, with the presence of thin, short stems with small leaves. As well Root development and regeneration, flowering and fruit setting are reduced.
Potassium is the element that the crop extracts in the greatest quantity during harvest. This means that it is an important element in the nutrition of the olive tree and is magnified due to the influence that the growing medium has on the availability of potassium to the tree. In fact, it constitutes the main nutritional problem of dryland olive groves, with great repercussions on the crop since potassium intervenes in the mechanism of closing and opening of stomata. Inside the plant it is found in the cytoplasm and helps keep it turgid. Under conditions of deficiency, the stomatal closure is not complete and the tree continues to lose water through transpiration, and may even show dehydration symptomsWell-nourished trees, on the other hand, tolerate drought conditions better by completely closing their stomata during times of high radiation.
Potassium deficiencies, or low levels, are widespread in much of the olive grove. Deficient trees show apical or lateral necrosis of leaves and defoliation of twigs; in harvest years,, the fruits appear wrinkled and smaller than normal. These deficiencies are most evident in the dryland olive grove and in the dry years, since the low humidity of the soil limits the diffusion of the potassium ion (K+) in soil dissolution and prevents its absorption by the roots. Deficiencies are also common in soils with low clay content, since the buffering power of the soil is lower and, consequently, the K+ available for the tree.
The causes of potassium deficiency are diverse. In addition to the lack of soil moisture in dryland plantations, the alternate-bearing nature of the cultivated varieties and interactions with calcium (Ca2+) and magnesium (Mg2+) ions are also significant. In calcareous soils, these factors, combined, can explain widespread potassium deficiencies.
Olive groves with potassium deficiency are difficult to correct, since potassium supplied in the form of fertilizer is absorbed in smaller quantities by deficient trees and trees with water stress, even when applied foliarly (Restrepo et al., 2008a). Therefore, it is advisable to monitor the concentration of potassium in leaves annually. and apply this element when low values are reached, before reaching deficiency. When applying to the soil, it should be noted that potassium, unlike nitrogen, has low mobility, particularly if the clay content is high. This means that potassium remains on the soil surface, unless it is located near the root system (Fernández-Escobar, 2017). Therefore, in dry land, it is advisable to make 2 to 4 foliar applications at 1-2% of the soil. K+ depending on the nutritional status of the tree, although it is usually necessary to repeat it in successive campaigns until the concentration of K+ on leaves at their proper level. That is, foliar applications should be made both in years of crop load and in years with marked alternate bearing.
Young leaves absorb potassium in greater proportion than adult leaves, which is why applications of this nutrient in spring are very effective (Restrepo-Díaz et al., 2009). Furthermore, from the period of bone hardening, when lipogenesis begins, K+ treatments are of great interest for two reasons. First, proper nutrition of this element improves the stomatal behavior of the plant, which will close the stomata during the periods of greatest radiation during the summer, thus reducing the water stress of the plant (lower transpiration rate). On the other hand, during the fatty acid synthesis phase, the fruit is the greatest potassium sink, whose levels must be adequate for improve fat performance of the fruit and the Increase in size of the same. Post-veraison applications will not improve either the size or the fat content of the olive.
In addition to this, potassium is essential for the following physiological functions:
- For the synthesis of carbohydrates or the formation and transformation of starch, as well as in the production of albumins.
- Participates in nitrogen metabolism and protein synthesis.
- It controls and regulates the activities of several essential mineral elements.
- It participates in the neutralization of physiologically important organic acids. These acids tend to lower the pH of the cell juice, which are then neutralized by the K+ (Baeyens, 1970).
- It is an activator of several enzymes, which catalyze phosphorylation and, on the contrary, inhibit those of respiration.
- Promotes growth in meristematic tissues.
A good part of the Spanish olive groves are located on calcareous soils with alkaline reaction, which has made it difficult to find calcium deficiencies in this olive grove. It would be more likely to find calcium deficiencies in soils acids, manifesting at the plant level through reduced growth and, in severe cases, affecting the consistency of the olive pulp, which can cause quality problems in table olives. In these cases, the soil should be limed with calcium carbonate or calcium oxide. Conversely, excess calcium can cause potassium and magnesium deficiencies, as these three ions interact with each other in the soil exchange complex. In some cases, a non-pH-related calcium deficiency from the ground. In these cases the foliar applications with complexed calcium with organic acids would be a good short-term solution.
El Magnesium It is an element that is usually found in significant quantities in soil solutions, and its behavior is similar to that of calcium. Therefore, deficiency of this element in olive groves is very rare. In the case of acidic soils, deficiencies may be found that would need to be corrected by trying to neutralize the acidity, as in the case of calcium. It should be noted that magnesium deficiencies can sometimes be induced by high concentrations of potassium, calcium, and ammonium, since these ions compete in the soil solution. If the K exchange/Mg exchange ratio is greater than 1, these deficiencies can be expected. Symptoms of magnesium deficiency manifest as a chlorosis in the older or basal leaves, causing a significant loss of photosynthetic activity. As in the case of calcium, foliar applications of chelated magnesium would prove to be very effective in the short term.
La deficiency of ironKnown as iron chlorosis, is a nutritional imbalance that can affect olive groves established in very calcareous soils with a high pH. In this environment, the ionic forms of iron are poorly soluble and are not available to plants even when present in sufficient quantities in the soil. Trees affected by iron chlorosis show characteristic symptoms of leaf chlorosis (in this case, younger leaves), characterized by a Yellowing of variable intensity on the leaf blade but with the veins remaining green, accompanied by a decrease in the size of the apical leaves, little growth of the shoots and a decrease in production (Figure 14). These symptoms are the means of diagnosing the deficiency, since foliar analysis is of no use in this case, as iron accumulates in leaves even in deficiency situations. Iron deficiency is also related to poor soil aeration conditions., as it increases the concentration of bicarbonate anion in the soil solution, aggravating iron chlorosis. Therefore, must be avoided terms of puddles in calcareous soilsCorrecting iron chlorosis is difficult and expensive. The best solution for new plantations is to choose a variety tolerant to this anomaly. In established olive groves, the remedy is to annual application of iron chelates to the soil, which allow the availability of iron to the plant for a moderately long period of time compared to other products.
The required quantities of manganese and zinc The mineral deficiencies of manganese in olive trees are even lower than those of other elements, and they are usually readily absorbed from the soil solution. Relatively little is known about the relationship between these elements and the olive tree, as they are usually found in the leaves at relatively adequate levels, so any deficiencies must be local in scope. Manganese is involved in biological processes such as photosynthesis, respiration, nitrogen assimilation, etc., and is related to protein metabolism and enzyme activation. It also acts on carbohydrate and fatty acid metabolism, phosphorylation reactions, and the formation of nucleic acids. Zinc, for its part, is a very important micronutrient as it acts as an enzyme activator in the synthesis of certain proteins, although its main function is related to the regulation of stem growth and elongation, as it is directly related to the synthesis of auxins. Organic amendments applied to the soil can improve the availability, mobility, and absorption of these micronutrients, while foliar applications of chelates can also be an effective solution for improving the levels of these nutrients in olive trees.
The olive tree is a plant that is considered to be high boron requirements and, in fact, it is more tolerant to excess boron in the soil solution than other fruit species. Boron availability to plants decreases under drought conditions and as soil pH increases, particularly in calcareous soils. These environmental conditions are common in olive groves. Boron deficiency manifests as apical and marginal chlorosis in leaves that eventually dry out and show a chlorotic zone between the dry and still-green parts of the leaf. Shoot defoliation, giving rise to so-called "witches' brooms," and fruit deformations are also common. It is very important not to confuse boron deficiency with potassium deficiency (Figure 15), hence the importance of performing a foliar analysis to diagnose these types of nutritional problems. In fact, an additional problem is that excessive boron application is a toxic ion, which can even lead to the death of olive plants, particularly young ones (Benlloch et al., 1991).
RECOMMENDATION
For all this, from the Cultifort Technical Department, we recommend making interventions during the fruiting period with specific nutritional products, adapted to each phenological stage, in order to improve the quality of the fruit. In the case we are dealing with in this article, the olive grove, whether dry or irrigated, we offer different formulations specially developed for the stages of ripening and fattening of the fruits.
MACROFOL RED PLUS It is a soluble NPK, with a 15-5-30 balance formulated with magnesium and micronutrients. Its composition is designed to promote the development, fattening, ripening and consistency of the fruits, increasing the storage of carbohydrates and proteins in them. It also provides an ideal nitrogen supply, with a concentration that does not negatively affect fruit ripening during the phenological stages in which its application is most recommended. MACROFOL RED PLUS is a product highly soluble, very stable and behaves well in front of the mixtures with other products on the market, does not form lumps During its dissolution, it has a slightly acidic pH and, best of all, it is a fertilizer chlorine-free.
CULTIFORT K y CULTINEUTRAL K, are two liquid potassium formulations de high richness and chlorine-free. They are designed to Promote the process of fattening and ripening of fruits, increasing their size and uniformity, increasing the synthesis and accumulation of sugars and improving color and firmness of the same. Thanks to their formulation technology, they are rapidly assimilated products, with high absorption, mobility, and translocation within the plant. They are similar in terms of richness and their differences lie mainly in the pH, 9 in CULTIFORT K There 6 in CULTINEUTRAL K, and in density, 1,5 and 1,24 kg/l, respectively.
At the Cultifort catalog We also have a complete range of amendments and deficiency correctorsSolutions for all needs and/or deficiencies: Calcium, Magnesium, iron, manganese, zinc, boron, micronutrient mix, etc., all formulated with high-quality raw materials, chelated with various agents or complexed with organic acids to improve their assimilation. Furthermore, our formulas are "zero residue," and many of them are certified for use as inputs in Organic Agriculture.
REFERENCES
Baeyens, J., 1970. Nutrition of crop plants. Madrid (Spain). Lemos Editions.
Beltrán, G., Uceda., M., Hermoso, M. and Frías, L., 2017. Olive Cultivation. Ripening. Madrid (Spain). Mundi-Press Editions. 198-203.
Benlloch, M., Arboleda, F., Barranco, D., Fernández Escobar, R., 1991. Response of young olive trees to sodium and boron excess in irrigation water. HortScience, 26: 867-870.
Connor, DJ, & Gomez del Campo, M., 2013. Simulation of oil productivity and quality of NS oriented olive hedgerow orchards in response to structure and interception of radiation. Scientia Hortícolae, 150: 92–99.
Emilov H., Pérez H., Cuevas A. and Sastre B., 2019. Comparative study of six olive tree varieties grown in dry and irrigated land in the Community of Madrid. Horticulture Proceedings 84. XNUMXth National Conference of the Olive Growing Group. Spanish Society of Horticultural Sciences.
Fernández Escobar R., 2017. Olive Cultivation. Fertilization. Ed. Mundi-Press. Madrid. 419-460.
Fernández Escobar R., Beltrán G., Sánchez Zamora MA, García Novelo JM, Aguilera MP, Uceda M., 2006. Olive oil quality decreases with nitrogen over-fertilization. Hort Science, 41: 215-219.
Fernández Escobar R., Braz Frade R., Beltrán G., López Campayo M., 2014. Effect of nitrogen fertilization on fruit maturation of olive trees. Acta Horticulturee, 1057: 101-105.
Frias, L., Garcia-Ortiz, A., Hermoso, M., Jimenez, A., Llavera, M.P., Morales, J., Ruano, T. and Uceda, M., 1991. Olive mill laboratory analysts. Series Notes 6/91. Ministry of Agriculture, Livestock, Fisheries and Sustainable Development. Regional Government of Andalusia.
García-Martos, JM and Mancha, M., 1992. Evolution of lipid biosynthesis during ripening of the “Picual” and “Gordal” olive varieties. Fats and Oils, 43(5): 277-280.
Gomez del Campo M., Centeno A., Connor DJ, 2009. Yield determination in olive hedgerow orchards I. Yield and profiles of yield components in north-south and east-west oriented hedgerows. Crop and Pasture Science 60: 434-442.
Gutiérrez, F., Jiménez, B., Ruiz, A. and Albi, MA, 1999. Effect of olive ripeness on the oxidative stability of virgin olive oil extracted from varieties “Picual” and “Hojiblanca” on the different components involved. . Journal of Agricultural and Food Chemistry, 47: 121-127.
Lavee, S., 1986. CRC Olive. Handbook of Fruit Set and Development. pp. 261-274. Monselise, SP Ed., CRC Press, Florida.
Lavee, S. and Wodner, M., 1991. Factors affecting the nature of soil accumulation in fruit of olive (Olea europea L.) cultivars. Journal of Horticultural Science 66(5): 583-591.
Leyva A., Hidalgo JC, Vega V., Pérez D., Hidalgo J., 2017. Water stress and olive oil formation. IFAPA. Ministry of Agriculture, Fisheries and Rural Development. Junta of Andalusia.
Minguez, MI, Rejano, JL, Gandul, B., Higinio, A. and Garrido, J., 1991. Color pigment correlation in virgin olive oil. Journal of the American Oil Chemists' Society, 68: 669-671.
Molina de la Rosa, JL, Jiménez, B., Ruiz, F., García, F., López, F., Salmerón, E., 2010. Agronomy and Olive Pruning. Ministry of Agriculture and Fisheries. Regional Government of Andalusia.
Navas López JF, 2019. Olive tree breeding for adaptation to different environmental conditions and cultivation systemsDoctoral Thesis. University of Córdoba, Spain.
Pérez Camino, MC and Cert, A., 1999. Quantitative determination of hydroxypentacyclic terpene oils in vegetable olive oils. Journal of Agricultural and Food Chemistry, 47: 1558-1562.
Rallo, L. and Cuevas, J., 2017. Olive Cultivation: Fruiting and Production. Madrid (Spain). Mundi-Press Editions. 162-167.
Restrepo, H., Benlloch, M. and Fernández-Escobar, R., 2008a. Plant water stress and K+ starvation reduces absorption of foliar applied K+ by olive leaves. Scientia Horticulture, 116: 409-413.
Restrepo, H., Benlloch, M. and Fernández-Escobar, R., 2009. Leaf K accumulation in olive plants related to nutritional K status, leaf age and foliar application of K salts. Journal of Plant Nutrition, 32(7): 1108-1121.
Trentacoste, E.R., Connor, DJ, & Gomez-del-Campo, M., 2015a. Effect of row spacing on vegetative structure, fruit characteristics and oil productivity of NS and EW oriented olive hedgerows. Scientia Hortícolae, 193, 240–248.
Trentacoste ER, Connor DJ, Gómez del Campo M., 2015b. Effect of olive hedgerow orientation on vegetative growth, fruit characteristics and productivity. Scientia Hortícolae, 192: 60-69.
Vega, V., Hidalgo, JC, Pariente, N., Martín, L., Hidalgo, J., Leyva, A., 2018. Correction of Iron Chlorosis in Olive Groves Using Chelates. IFAPA. Ministry of Agriculture, Fisheries and Rural Development. Junta of Andalusia.
Westerman, RL, 1990. Soil Testing and Plant Analysis. Soil Science Society of America Book Series No. 3. Madison, Wisconsin (USA). Editorial Committee.