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OLIVE HARVESTING
Harvest time in the olive industry is a defining moment for olive oil and table olive producers. Efficient harvesting not only determines yield and profitability but also impacts fruit quality and timing for processing. Traditionally, picking olives by hand with poles, rakes, and nets was an arduous, labour-intensive process - in fact, manual harvesting with rakes and nets can account for 50% of an orchard’s production costs. Today the rising labour shortages and tighter margins, modern growers are increasingly turning to mechanisation to save time and money. The Olive Centre, a specialist supplier for the Australian olive industry, offers a full spectrum of harvesting equipment to address these needs - from state-of-the-art mechanical shakers like the Sicma harvesters to portable electric comb rakes, pneumatic rakes, nets, wheelable frames, and other accessories. This range of tools, paired with research-driven best practices, allows commercial groves to optimise harvest efficiency while maintaining fruit quality. Below, we explore each category of harvesting equipment available through The Olive Centre, focussing on key features, suitable applications, and insights from recent studies and field experience.
Mechanical harvesters are the heavyweights of olive harvesting - high frequency vibration systems built into the machines that shake fruit off trees with speed and efficiency. The Olive Centre provides a leading range of mechanical harvesters, including tractor-mounted shaker heads, skid-steer loader attachments, and dedicated self-propelled “buggy” harvesters. These systems use a vibrating head equipped with a clamp system that attaches to the tree’s trunk or main branches, transmitting high-frequency oscillations that travel with force to the higher branches holding olives to their stems. The result is a rapid cascade of olives into catching systems, often an inverted umbrella or frame beneath the tree. In well-designed groves, a single mechanical shaker can typically harvest 40–60 trees per hour (with a clamp-and-shake cycle of only 5-7 seconds per tree) - a dramatic improvement over manual picking rates. One Australian field review notes the jump from roughly 100 kg of olives per hour using the latest pneumatic or electric hand tools to approximately 500 kg per hour with efficient mechanical harvesting machines. This efficiency in throughput allows growers to bring in the crop at optimal ripeness and throughput, provided the subsequent milling capacity keeps pace.
A Sicma B411 Plus self-propelled olive harvester with its 6 m catching umbrella deployed. The Olive Centre’s partnership with Sicma gives Australian growers access to Italian-engineered mechanical harvesters known for efficiency and robust design.
Modern trunk shakers come in various configurations to suit different operations and grove terrain. The Olive Centre’s lineup includes tractor PTO-driven models (e.g., vibrating heads mounted on a tractor’s three-point linkage or front-end loader), retrofittable kits for skid-steer loaders and telehandlers, and stand-alone self-propelled units often nicknamed “buggies.” For example, the Sicma B411 Plus is a compact 4-wheel-drive buggy harvester with a telescopic vibrating head and a 6-meter diameter catching umbrella. This machine can clamp onto trunks up to ~40 cm in diameter and shake the fruit free, which falls into the umbrella. The built-in catch frame on such harvesters typically holds 200–300 kg of olives, and can be emptied through a hydraulic trap door into bins or trailers for easy collection. Thanks to features like high-frequency self-centering shaker heads and rubberised clamps, these systems minimise bark damage while maximising fruit removal.
In fact, a recent Italian field study on two olive cultivars achieved a 97% fruit removal rate using an advanced vibrating head and catch-frame system - virtually clearing trees in one shake. Mechanical harvesters are the workhorses of modern olive groves, enabling the timely harvest of large tonnages with a fraction of the manpower once required.
Practical considerations: Adopting trunk shakers does require that groves be compatible with the machinery.
Not every olive grove can accommodate a large shaker in their operation, and not every producer needs one. Electric and pneumatic olive harvesters - essentially motorised or air-powered “comb” or “rake” units – fill an important role for small to mid-sized producers and for groves on difficult terrain. These are handheld or pole-mounted tools with vibrating tines that comb through the olive branches, knocking olives off much faster than purely manual picking. The Olive Centre offers several options in this category:
Despite being smaller-scale than trunk shakers, electric and pneumatic harvesters substantially improve productivity over manual hand picking. Field data and grower reports suggest a single worker with a modern pneumatic or electric rake can harvest on the order of 80–120 kg of olives per hour (depending on tree yield and skill) - several times what hand picking would yield. One recent analysis noted about 100 kg/hour as a benchmark using the latest pneumatic or electric rakes. These tools are therefore very useful for reducing labour hours and addressing seasonal labour shortages, which have become a recurrent obstacle in olive production. They also excel in groves where tree spacing or steep hilly terrain make it impractical to bring in heavy machinery. Operators can simply lay out nets under a tree and work through the canopy with the powered rake, a method that is far less fatiguing than beating branches with poles.
Handheld harvesters do require proximity to each tree and are typically used by multiple workers. The efficiency per person is lower than a single large shaker with a catch frame (which can outpace a whole team of people), so producers must balance equipment investment with their useage capability and available labor. In many cases, electric or pneumatic combs are the preferred solution for small olive groves, where gentle handling and selective harvesting might be needed. They cause minimal damage when used properly, though some fruit bruising can occur – so harvested olives, especially table varieties, usually are collected onto nets or padding and not dropped from excessive heights to avoid bruising. Research into gentler harvesting continues: for instance, trials in California have combined canopy shaking with trunk shaking to improve efficiency for table olives. This method increased fruit removal by 75% and delivered higher-quality, less-damaged fruit compared to using either method alone. While such dual-method harvesters are still in development for table olives, it underscores that even in the realm of smaller-scale equipment, innovation is boosting performance. The Olive Centre stays abreast of these developments, supplying trusted brands (like Electric tools by Infaco, & Pneumatic equipment by Lisam) that have a track record in international olive cultivation. For growers, electric and pneumatic harvesters represent a relatively affordable and versatile investment to significantly cut harvest time and labour costs without the need for heavy machinery and a much bigger budget.
Harvesting equipment is not just about the machines that detach olives - it also encompasses all the tools that catch, collect, and transport the fruit once it’s off the tree. The Olive Centre offers a wide array of “catch and carry” accessories to support efficient harvesting operations. Among these are harvest nets and catching frames. Traditionally, tarps or nets are spread under olive trees to collect olives as they are hand-picked or knocked down with poles. Today’s purpose-made olive nets are durable, UV-resistant, and come in various sizes that can be fitted around trunk bases. They drastically reduce the time needed to gather fallen olives and prevent fruit loss on the ground. Some modern harvesters use an umbrella-style catching frame – essentially a large circular net on a frame that can be deployed under the tree (either by a person or as an attachment on a machine) to catch olives as they rain down. The Olive Centre offers products like a 5–6 m diameter catching frame that can be positioned around the trunk to funnel olives into an Industry-standard Orange Crate and will fit about 20kgs of fruit per crate. Such frames can be a game-changer for groves still harvested by hand or with electric or pneumatic combs, as they keep fruit off the soil (maintaining cleanliness and quality) and make collection faster.
Image: Major Catching Harvest Frame
The introduction of nets and basic mechanical aids in the mid-20th century was one of the first steps to mechanising olive harvests, replacing ladders and ground picking to reduce work time and safety risks for workers.
Another staple harvest accessory is hand rakes and picking tools. These simple, hand-driven rake devices (often plastic combs capable of making them a reachable unit by installing a broom handle) allow pickers to strip olives from branches more efficiently than by handpicking each fruit. A broom handle sourced at a local hardware store can be inserted into the back of the handle to make these reach greater heights. The Olive Centre’s catalogue includes these manual rakes that are useful for growers starting out, for very small operations or used with a large team. .
Picking bags and baskets are also important: workers can wear a picking bag to drop olives into as they hand-pick or move along the rows, then empty the bags into crates or bins periodically. Good picking bags distribute weight, are not too large and often have a quick-release bottom to safely transfer olives without spillage and impact which minimises bruising.
Crates and bins round out the harvest accessories – The Olive Centre provides vented plastic orange olive crates (around 15–20 kg capacity each) and heavy-duty pallet bins (~400 kg capacity) to safely store and transport harvested olives. These containers are food-grade and ventilated to prevent heat buildup or fermentation of olives before milling. They can be moved with tractors or forklifts, streamlining the post-harvest logistics.
Image: Orange Olive Crate
When it comes to moving bulk olives in the field, trailers and bins become essential. Many mechanical harvesting setups integrate with trailers; for example, a tractor shaking unit might drop fruit onto a towed trailer with a catching cloth, or a self-propelled buggy like the Sicma has its own bin reservoir that can be emptied into a trailer via a trap door. Even independent of mechanical shakers, growers often use tractor-pulled trailers to ferry filled pallet bins from the grove to the processing area. The Olive Centre can supply specialised bin trailer equipment and tipping mechanisms that make this process more efficient. The overall goal of all these accessories is to preserve fruit quality and save labour between the tree and the mill. Every hour saved collecting olives from the ground or transferring them to storage is efficiency gained in getting the olives to processing, which can be critical for oil quality. Research consistently emphasises rapid processing of olives after harvest (generally within 24 hours is best practice) to maintain low free fatty acidity and high polyphenol content. By using proper harvest aids - nets to keep olives clean, bins to avoid fruit piles overheating, and trailers to quickly haul fruit - producers can better achieve those quality goals.
Equipping an olive operation with the right tools is half the battle; the other half is using them in an optimised harvest strategy. Fortunately, extensive academic and industry research offers guidance on how to mechanise effectively without compromising the olives. One key concept is fruit detachment force (FDF) - essentially, how strongly an olive is attached to its branch. FDF decreases as olives ripen, which is why oil olives (allowed to ripen longer) are generally easier to remove, whereas table olives (picked green) are much more stubborn. A University of California study noted that table olives have a fruit removal force of about 0.5 kg - meaning they require significantly more shaking or even chemical loosening to enhance fruit removal. Oil olives, usuall progressed in manturation (compared to green table fruit), have a lower detachment force, and modern high-density oil cultivars are usually harvested by over-the-row machinery like an Moresil, Oxbo, New Holland or Colossus. This explains why trunk shakers and canopy shakers are an innovation mainly needed for table olive orchards (to address their high FDF), whereas oil olive groves in super-high-density (SHD) systems can be harvested by modified grape harvesters that strip fruit with minimal effort. For producers, understanding their varieties’ detachment characteristics can inform which equipment to use and whether strategies like applying an abscission agent (fruit loosening spray) might be worthwhile. In ongoing trials, compounds like ethephon are being tested to reduce olive attachment strength and thus increase mechanical harvester efficiency. Use fruit loosening agents with caution as improper use can defolate the entire tree.
Another insight from research is the importance of grove design and pruning in mechanical harvesting success. A tree with an open, accessible structure (single trunk, properly managed canopy) should yield better results with shakers. Studies from Europe have documented that tree architecture and pruning style significantly affect vibration transmission and fruit removal. Many growers now implement mechanical pruning and keep trees shorter to accommodate harvest machinery - a necessary adaptation as “there is no mechanical harvesting without orchard and canopy adaptation,” as one agricultural engineer famously put it. This might mean switching to hedgestyle planting (250–300 trees/ha) if one plans to use over-the-row harvesters, or simply maintaining a 6– 8 m spacing and a vase or single leader form for traditional orchards using trunk shakers. The Olive Centre, beyond just providing equipment, also provides grove consulting services to help producers plan such transitions, ensuring that investments in machinery are matched by an orchard setup that maximises efficiency and minimises fruit loss.
Finally, research confirms that speed and timing of harvest are crucial for quality. Mechanical harvesters enable a very fast picking .... entire blocks can be harvested at the optimal ripeness window rather than stretched over weeks. By concentrating harvest in the optimal period, growers can obtain olives at peak oil quality and get them milled promptly.
Evidence from studies in Spain and Italy shows that when olives are harvested at the right maturity and processed quickly, mechanisation does not impair oil quality metrics; on the contrary, timely harvesting can result in higher-quality extra virgin olive oil compared to a protracted hand harvest, where some fruit inevitably becomes overripe or delays in processing occur due to extended time duration needed.
For table olives, minimising bruising is a bigger concern, and the research offers pointers - for instance, experiments have shown harvesting in the cool pre-dawn hours can reduce fruit bruising and respiration, improving the condition of mechanically harvested table olives. Such findings are encouraging producers to adjust harvest schedules and techniques (e.g., adding padding to catch frames or using conveyors instead of dropping olives into bins) to protect fruit quality.
Tthe modern olive grower has an unprecedented range of harvesting equipment at their disposal, and when these tools are coupled with informed practices, the results are compelling: lower costs, higher efficiency, and preserved quality. Offering industry leading equipment - from Sicma’s cutting-edge shakers to nimble electric rakes, and all the supporting gear - reflects the evolving landscape of olive harvesting. By leveraging both technology and research-based know-how, commercial olive producers can confidently tackle the critical harvest season, bringing in the crop efficiently and at peak quality to ultimately produce better oil and table olives for the market.
Harvesting will always be a pivotal and challenging aspect of olive production, but it no longer needs to be a bottleneck. The range of equipment available through TheOliveCentre.com empowers growers to choose solutions tailored to their grove size, layout, and production goals. Whether it’s a robust mechanical harvester shaking 500 kg of olives per hour into an umbrella, or a team of workers with electric combs and nets swiftly stripping trees on a hillside, each approach offers advantages that can improve the bottom line. Importantly, ongoing innovation - much of it supported by academic and government research from Australia and abroad - continues to refine these tools and techniques for greater efficiency, ensuring that higher productivity does not come at the expense of fruit quality. With The Olive Centre’s expertise and equipment range (including their partnership with world-class harvesting machine manufacturers), Australian olive growers have access to the best of both worlds: advanced technology proven in international groves, and local knowledge and support to implement it successfully. The result is a harvest that’s faster, easier, and more profitable – helping producers focus on what comes next, turning those olives into exceptional oil and table olives for consumers to enjoy.
Waterlogging is a significant challenge in many Australian olive groves due to the combination of heavy clay soils and episodic intense rainfall. Even brief periods of saturated soil (“wet feet”) can harm olive tree health and predispose trees to root diseases. This article explores why waterlogging is harmful to olive trees, how soil factors like clay pans and sodicity contribute to poor drainage, and the link between waterlogged conditions and root pathogens such as Phytophthora and Rhizoctonia. It also outlines how growers and agronomists can diagnose waterlogging risk both before planting and in established groves, and recommends practical prevention and mitigation strategies (from soil mounding and gypsum application to engineered drainage systems) tailored to Australian conditions.
Olive trees require not just water but also oxygen in the root zone for normal function. When soil becomes waterlogged, the air spaces in soil pores fill with water, depriving roots of oxygen. Without sufficient oxygen, root cells cannot respire properly, leading to energy starvation, root damage, and eventually root death. In prolonged waterlogging, this cascade can kill fine roots and impair the tree’s ability to take up water and nutrients, causing symptoms similar to drought or nutrient deficiency despite the excess water. Above-ground, waterlogged olive trees often show leaf wilting, yellowing (e.g., iron chlorosis or nitrogen deficiency from leached soils), and premature leaf drop as roots asphyxiate. In severe cases, entire branches may die back, and the tree can collapse if critical roots rot.
One physiological disorder in olives related to excess soil moisture is oedema, where high soil moisture causes cells near the stem lenticels to engorge and burst. This results in small corky growths on stems, and indicates that roots have been in saturated, low-oxygen conditions. Roots in such conditions may suffocate (“asphyxiate”) due to oxygen depletion, leaving portions of the root system dead or weakened. These weakened roots no longer function effectively and are prone to invasion by opportunistic soil microbes. In fact, waterlogged olive roots are often observed to become infected by normally minor pathogens or decay organisms like Fusarium, Pythium, and various bacteria that exploit the stressed, oxygen-starved tissue. Thus, beyond the direct damage from lack of oxygen, waterlogging indirectly predisposes olive trees to root rot diseases and decline.
It is important to note that olive trees, while drought-hardy, do not tolerate poor drainage. They evolved in well-drained Mediterranean-type soils and will suffer in waterlogged ground. A common adage is that olive trees can “drown” in waterlogged soil. In fact, extension specialists warn that olive trees are often killed by poor drainage when saturated soil conditions persist in the root zone. Even a few days of soil saturation can begin to injure roots; pot experiments in related tree crops show growth reduction after 3–7 days of waterlogging, and shallow stagnant water in hot weather can kill trees within hours. The faster excess water can drain or recede, the better the chances of the olive tree’s survival and recovery. This underscores why good site drainage is critical for sustainable olive production.
Soil properties largely determine whether an olive grove will drain well or waterlog after rain. Sandy or loam soils tend to have ample macroporosity and usually drain freely, whereas clay-rich soils have tiny pores that hold water and allow it to percolate slowly. In dry climates, a clay soil’s water-holding capacity can be beneficial; however, under high rainfall or poor drainage, the same clay can lead to prolonged saturation. Many Australian olive groves are on heavy duplex or clay soils, and naturally well-structured, free-draining soils with deep profiles are hard to come by. (Indeed, as noted for other orchards, ideal soils are “difficult to find in Australia,” and many orchards succeed on marginal soils only through good soil and water management .) Two common soil constraints in Australia that contribute to waterlogging are clay pans and sodicity.
Clay-panning refers to the presence of a dense, hard layer of clay or compacted soil below the surface that roots and water cannot easily penetrate. In olive groves, clay pans can form due to poor soil preparation or natural soil horizons. For example, working the soil when it is too wet or repeated machinery traffic can smear or compact a subsurface layer, effectively creating a “pan”. Additionally, some duplex soils have a naturally abrupt clay subsoil. This hard subsurface layer prevents olive roots from growing downward and also impedes internal drainage, often causing a perched water table to form above the pan during wet periods. The result is that the tree has a shallow, pancake-like root system trapped above the hardpan. Such trees may initially grow okay in dry times, but they become unthrifty and prone to stress-related dieback because their roots are confined to the shallow layer. During heavy rain, water quickly saturates the shallow root zone (since it cannot drain through the pan), leading to temporary waterlogging around the roots. This induces the oxygen deprivation and root stress discussed earlier, compounding the tree’s problems. Conversely, during dry spells, the shallow-rooted tree cannot access deeper moisture below the pan, so it experiences drought stress more readily. Thus, clay-panning creates a double vulnerability: it causes waterlogging stress in wet conditions and drought stress in dry conditions. Affected trees often show chronic ill health and may even blow over in strong winds due to poor anchorage from the shallow roots. In short, a clay pan under an olive grove is a serious impediment to both drainage and root development.
Sodic soils are another common culprit behind poor drainage. A soil is sodic when it has a high proportion of sodium ions attached to clay particles (often measured as Exchangeable Sodium Percentage > 6%). Sodium causes clay particles to disperse (deflocculate) when wet, which plugs soil pores and collapses soil structure. Many Australian agricultural soils are sodic and dispersive – estimates suggest roughly one-third of Australia’s soils have sodicity issues. In Western Australia, for instance, dispersive sodic clays are widespread in duplex profiles, and when these soils get wet, the dispersed clay clogs the pore spaces, drastically restricting water infiltration and drainage. The result is that water sits on or near the surface, creating waterlogged conditions even with moderate rainfall. In medium to high rainfall regions, sodic duplex soils are especially prone to waterlogging because their subsoils percolate so poorly. Once saturated, they also take a long time to dry out. Sodicity often coexists with other constraints like alkalinity or salinity, further complicating management, but from a drainage perspective, the key issue is dispersed clay = sealed pores = no aeration. You can often identify dispersive sodic clays by a milky cloud when a soil clod is dropped in water (dispersion) or by a hard-setting, crusted surface after rains. In field pits, sodic subsoils may appear mottled and dense, indicating periodic perched water tables. Without intervention, olive trees on such soils will struggle each time rainfall leads to a perched water table around their roots.
Gypsum (calcium sulfate) is a well-known amendment for sodic clay soils. The calcium in gypsum can replace sodium on clay particles, helping the clay to flocculate (clump) rather than disperse. This improves soil structure and opens up pore space for better drainage. For olive groves on sodic clay, incorporating gypsum into the soil can significantly improve permeability and reduce waterlogging. The exact amount should be guided by soil tests (gypsum requirement) – often several tons per hectare or a generous application in each planting hole. One practical guideline given by olive advisors is to mix roughly a quarter of a standard bucket of gypsum into each planting hole or tree site when preparing clay soil. This helps “break up” the clay structure and promote drainage. However, gypsum is not a magic fix for all clay issues; it works best if the poor drainage is due to sodicity or dispersive clays. If a hardpan or heavy texture is the issue (rather than sodium dispersion), mechanical soil loosening and surface drainage may be needed in addition to or instead of gypsum. It’s also worth noting that adding gravel or sand to the planting hole will NOT improve drainage in heavy clay – a common misconception. Small gravel in a clay hole can actually create a pseudo-“pot” with water perched on the interface; it’s ineffective at best and harmful at worst. Improving the overall soil structure and profile drainage (through gypsum, organic matter, and deep ripping) or planting above the natural surface (mounding) are more effective approaches for heavy clay.
In summary, understanding your grove’s soil profile is critical. A bit of investigative work – digging soil pits or augering – can reveal if you have an impermeable clay layer or a sodic dispersive subsoil that could cause waterlogging. Identifying these issues before planting allows you to take corrective action (ripping, gypsum, mounding, etc.) rather than watching trees suffer later. As the old adage goes, “plant your olive trees in $10 holes, not 10¢ holes” – investing in soil preparation pays off enormously in preventing water problems down the track.
Excessively wet soils create an inviting environment for certain root pathogens that plague olive trees. Foremost among these is Phytophthora, a water-mold (oomycete) often responsible for root rot and collar rot in olives. Phytophthora thrives in waterlogged soil – it produces motile spores that swim through free water in soil, infecting roots under wet conditions. Not surprisingly, Phytophthora root and crown rot in olive is consistently associated with poorly drained, wet soils, clay pans, or any situation of prolonged waterlogging. Surveys in Australia have isolated multiple Phytophthora species (such as P. palmivora, P. cinnamomi, P. cryptogea, P. citricola, and others) from olive root or trunk rot cases, almost always in groves with drainage problems. Young trees are especially vulnerable – infections often strike within the first few years if a susceptible young tree is planted into waterlogged ground. Infected trees show telltale symptoms: reduced vigor and stunted growth, sparse canopies, dieback of shoot tips, yellowing leaves that drop prematurely, and darkly discolored or rotting roots. Sometimes, a reddish or cinnamon-brown staining under the bark near the crown is seen, and gummosis or cankers may appear at the base. If the disease progresses, parts of the canopy wilt as the decayed roots can no longer supply water, and trees can collapse suddenly during periods of stress (e.g., a hot, dry spell following the wet conditions). Phytophthora root rot can kill trees outright or set them into a decline over several years. An olive grower from NSW DPI noted that Phytophthora root rot is often observed when “excessively wet soils, clay-panning or poor drainage” occur in the grove. This pathogen was particularly problematic in Eastern Australian groves during unusually wet summers; for instance, a spike in olive root rot was reported on the east coast (NSW) following very high summer rainfall in 2008. Australian olive growers must therefore regard Phytophthora as a primary hazard wherever water may accumulate around roots.
Another pathogen of concern is Rhizoctonia, a fungus that causes root rots and “damping off” in many crops. Rhizoctonia in olives has been found in several Australian states, typically affecting young trees or nursery stock. Infected olive roots develop brown lesions, the outer bark may slough off, and under a microscope, you might see the characteristic brown resting structures (sclerotia) on the roots. Above-ground, Rhizoctonia infection can mimic drought stress – leaves get dry tips, yellow, defoliate, and the plant can even die back as if it were water-starved. Interestingly, Rhizoctonia root rot in olive is not as strictly tied to waterlogging as Phytophthora is. Reports indicate Rhizoctonia outbreaks can occur under both dry and moist soil conditions. This fungus often lives in soil and plant debris and can persist through adverse conditions by forming resilient sclerotia. Rather than requiring flooded soil, Rhizoctonia tends to attack when plants are weakened or roots are growing poorly. For example, if waterlogging has damaged roots, Rhizoctonia can invade the dying tissue; conversely, if the soil is very dry and the roots are stressed, Rhizoctonia might also take advantage. In practice, severe Rhizoctonia root rot has mainly been noted in young or potted olive plants. Healthy mature trees are usually less susceptible, presumably because they have more extensive roots and stored resources. Nonetheless, the presence of Rhizoctonia in many Australian olive groves (NSW, SA, QLD, VIC have all reported it ) means that any condition that stresses roots – including waterlogging – could open the door to this pathogen. A waterlogged olive may later show Rhizoctonia root rot symptoms once the soil dries, as the fungus colonizes the damaged root cortex. Thus, water management helps indirectly to prevent Rhizoctonia by keeping roots robust.
In addition to Phytophthora and Rhizoctonia, waterlogged conditions can favor other root diseases: - Pythium species (another water mold) can cause feeder root rot in saturated soils, especially in young trees or nurseries, though it is generally a weaker pathogen than Phytophthora. It often acts as an opportunist on stressed roots. - Fusarium fungi have been isolated from olive roots with rot, showing reddish-brown discoloration and poor growth in young plants. Like Rhizoctonia, Fusarium can persist as hardy spores in soil and tends to strike when plants are predisposed by stress (e.g., excess moisture followed by dryness). - Verticillium dahliae, which causes Verticillium wilt, is a serious olive pathogen, particularly in soils with a history of susceptible crops (e.g., cotton, tomatoes). Verticillium is not directly caused by waterlogging (it doesn’t require saturated soil), but wet, cool conditions can favor its infection cycle. There is some evidence that water stress (either too much or too little) can exacerbate Verticillium symptoms.
Finally, secondary wood decay fungi and bacteria can exploit olive trees after waterlogging injury. Waterlogged roots and lower trunks may develop cracks or cankers (from swelling and shrinkage or bacterial infections), and fungi such as Botryosphaeria or Armillaria (if present in soil) can invade. Australian olive experts have noted that many trunk and branch canker diseases become problematic when trees are stressed or wounded, and waterlogging is one stress that can precipitate those infections. A clear management recommendation from plant pathologists is to “ensure soil drains freely to avoid waterlogging and subsequent root pathogen infections.”. Good drainage is thus a frontline defense against not only Phytophthora and Rhizoctonia, but a whole suite of diseases that take advantage of trees in waterlogged, weakened conditions.
Identifying areas at risk of waterlogging – and detecting early signs of poor drainage – can save growers much trouble. Assessment should be done both before planting a new grove and as an ongoing practice in established orchards (especially after extreme weather). Here are some diagnostic approaches:
Before Planting – Site and Soil Evaluation: Start with a thorough look at the land and soil where you intend to plant olives. Low-lying paddocks, valley bottoms, or sites near river flats are obvious risk zones for flooding and waterlogging. If a site has a history of ponding water after rain or you notice water-loving weeds/reeds in parts of it, take caution. Beyond surface clues, a soil profile examination is extremely useful. Dig soil pits or use a backhoe to create a trench about 1 m deep in representative spots. Inspect the soil layers: is there a distinct, dense clay subsoil? Is there a bleached or mottled layer indicating past waterlogging (gray or orange mottles often mean seasonal saturation)? Look for any “wet layer” or seepage line in the pit – sometimes you’ll find a saturated zone or even seeping water at a certain depth, which indicates a perched water table and poor drainage. Also note any hardpan or compaction layer (for example, from prior farming) – you might see old root growth flattened out horizontally along a hard layer, signaling roots couldn’t penetrate. If you find a compacted or smeared layer in your pit, record how deep it is; that guides how deep you’ll need to break it up (e.g., via ripping).
A simple in-field drainage test can be very illuminating as well. One recommended method is the overnight hole drainage test: dig a hole about 30–40 cm deep and fill it with water. Let it sit overnight. If the water has not fully drained away by the next morning, that soil has poor infiltration and is likely to cause waterlogging issues. Ideally, a well-draining soil will absorb that water within a few hours. If it’s still there after 8–12 hours, you have a problem. Performing this test in a few locations (especially in any suspected heavy soil patches) before planting will tell you where drainage amendments or mounding are necessary.
It’s also wise to test the soil for sodicity and texture through a lab. A soil analysis can reveal a high exchangeable sodium percentage (sodic soil), which would warn you that dispersion and drainage issues are likely unless ameliorated. If laboratory tests or field dispersion tests (like an Emerson crumb test) show the soil is dispersive, plan on applying gypsum or other soil conditioners before planting. Additionally, understanding the soil’s clay content and type (e.g., reactive clays vs. sandy loams) helps predict how prone it is to waterlogging.
After Planting – Monitoring and Early Warning: Once the olive grove is established, growers should remain vigilant, especially in seasons of abnormal rainfall. One straightforward practice is to observe the orchard after heavy rains. Take note of any sections where water pools or drains slowly. Puddles that remain for more than a day, or wheel tracks that stay boggy, are red flags. You might see a greasy shine or algae on soil that stays wet too long. If only small patches are waterlogged, it could be due to a local pan or a low spot – mark those for remedial action (drainage or replanting on a mound, discussed later). Also, inspect the trees themselves for early stress signals. In winter or early spring, when rains are frequent, watch for any trees that develop an overall light yellow hue or begin dropping leaves out of season – this can indicate their roots are struggling from a lack of oxygen or root rot infection in saturated soil. Compare growth and yield: sections of the grove that lag could be suffering from suboptimal root conditions underground (often wet feet or poor soil structure).
A useful technique is to use an auger or spade to check the soil moisture around roots after rain. Dig down near the root zone of a few trees: is the soil waterlogged (gleysolic grey color or foul smell indicating anaerobic conditions)? Does the hole fill with water from below, suggesting a high water table? Healthy, drained soil will feel moist but friable, whereas waterlogged soil may be soupy or have a sewage-like odor (from anaerobic bacteria). Another diagnostic sign in heavy clay soils is a surface crust or hard pan that forms after waterlogging and drying – this can indicate dispersive clay. If you observe a surface crust, you may need to break it up (light cultivation) to allow oxygen back in; its presence also suggests you should address the underlying soil structure for the longer term.
For diagnosing root disease issues related to waterlogging, consider testing suspect trees. If a tree declines after wet conditions, you might have Phytophthora or other root rot at work. Commercial lab services (such as Grow Help Australia or state department diagnostic labs) are available to test soil or root samples for pathogens. For example, SARDI (South Australian Research and Development Institute) offers a DNA-based soil testing service (like Predicta B for broadacre, and similar for horticulture) to detect Phytophthora and other soil-borne diseases before or after planting. These tests can confirm if Phytophthora spores are present in your soil or if a dying tree’s roots have Phytophthora or Rhizoctonia. While such testing incurs a cost, it can be invaluable in pinpointing the cause of decline and informing management (e.g., whether to treat with fungicides or improve drainage, or both).
In summary, before planting, dig and percolation-test your soils to identify drainage issues and rectify them early. After planting, keep an eye (and shovel) on how water moves and dissipates in your grove. Early intervention – whether it’s digging a quick trench to drain water or treating a root rot outbreak – can prevent minor waterlogging from snowballing into major tree losses.
An olive tree in a low-lying part of the grove showing signs of waterlogging: the soil is saturated and puddled around the trunk, and the tree exhibits leaf drop and dieback. Such areas should be identified and addressed proactively (through drainage or mounding) to avoid root disease development.
Preventing waterlogging in olive groves starts with good site selection and preparation, and continues with strategic management and engineering solutions in the field. Below are key methods – both traditional cultural practices and engineered interventions – to keep olive roots high and dry (or at least prevent them from drowning). Emphasis is placed on techniques proven under Australian conditions, where heavy clay subsoils and intense rain events are common.
1. Site Selection and Layout: If you have the luxury of choosing or modifying the planting site, favor locations and layouts that facilitate drainage. Avoid planting olives in natural drainage sumps or flood-prone flats. A gentle slope (even just a 1-2% gradient) is beneficial to shed surface water. If the grove site is flat, you may need to create a slope by laser-leveling or at least plan surface water runoff routes. As a rule, ensure there is somewhere for excess water to go – a lower corner, a dam, a runoff channel – before planting trees. Also consider row orientation and planting density: rows oriented downhill can sometimes act as channels for water flow, whereas contour planting (following the land’s contours) can slow runoff – the best approach depends on your topography and should aim to avoid water accumulating around trunks.
2. Deep Tillage (Subsoil Ripping): For soils with a suspected hardpan or dense clay layer, performing deep ripping or subsoil plowing before planting is highly recommended. Running a stout ripper (with tines that penetrate 50–80 cm deep) through the planting lines will break up compacted layers and fracture the subsoil, improving vertical drainage and root access. Olive experts note that if you have at least ~1.2 m of uninterrupted, well-structured soil profile, you might not need deep ripping. But if a restrictive layer is present at, say, 30–60 cm, ripping is vital. Ripping is often done in two passes (in a cross-hatch pattern) and ideally when the soil is moist (but not wet plastic) to achieve shattering of the pan. In severe cases of textural contrast (e.g., a sharp clay layer), some growers use a slip plow or mouldboard to invert or mix soil layers, but this is a more intensive operation. Deep tillage encourages olive roots to explore deeper and allows rainwater to penetrate the soil profile rather than pooling on top. It must be done well before planting (the season prior) so the soil can settle and rainfall can re-form some structure in the profile. Note that if the subsoil is sodic, ripping alone is not enough – it should be combined with gypsum incorporation so that the shattered clay does not simply disperse and re-seal.
3. Raised Beds and Mounding: One of the most effective strategies for waterlogging-prone sites is to raise the olive tree root zone above the natural ground level. This can be done either by establishing raised beds across entire orchard rows or by mounding individual tree planting sites. In Australia, raised beds have been widely used in other horticulture and even broadacre cropping to manage waterlogging, and the same concept applies to olive groves. A raised bed can be created by heaping and berming soil along the row, typically using a grader blade or bed-forming implement. For individual mounds, soil can be scraped from the inter-row area and piled where the tree will go, or additional soil (preferably a loamy soil) can be imported and added. The mound should be at least 45–80 cm high and about 0.9–1 m in diameter to be effective. In practice, many olive growers aim for roughly knee-height mounds. This elevation ensures that even if water pools in the paddock, the tree’s crown and upper root system are above the saturation zone. It also encourages lateral roots to grow outward into better-aerated topsoil. In South Australia and Western Australia, some growers have reported success planting on long raised berms, especially on duplex clay soils – these berms function like narrow ridges that shed water to the furrows between rows. Raised beds significantly reduce the incidence of waterlogging by allowing excess rain to run off the bed and by improving soil aeration in the root zone. Keep in mind that raised beds can dry out faster in summer, so irrigation might need adjustment (drip lines on top of the mound, etc.). The cost of mounding (earthworks) is an investment, but it is far cheaper than losing trees or yielding to waterlogging. If one cannot mound the entire block, at least mound the low or heavy-soil sections, or mound individual high-value trees.
4. Soil Amendments – Gypsum and Organic Matter: As mentioned, gypsum is the go-to amendment for dispersive (sodic) clays. Applying gypsum in the planting row or even broadcasting and incorporating it into the topsoil can improve soil structure over time. For new plantings, incorporate gypsum into the soil during ground preparation (rates might be in the order of 2.5–5 t/ha or more, depending on soil tests). In an existing grove, surface-applied gypsum (e.g., a band along the tree row) will eventually leach into the soil and help flocculate clay, though incorporation is better if feasible. Gypsum takes effect over months to years, so be patient and reapply as needed based on soil test ESP levels. Alongside gypsum, building soil organic matter can also enhance drainage. Adding compost or manure in moderate quantities can improve soil aggregation and porosity, especially in lighter soils. However, in very heavy clays, too much organic matter at once can actually hold more moisture; the key is a balanced approach. Cover crops or mulches can also improve soil structure over the long term and help create macropores (via root channels and earthworm activity) that assist drainage. Just be cautious that any added organics are well rotted – raw manures can sometimes temporarily worsen structure or tie up nitrogen.
5. Surface Drainage Systems: Engineering the surface water flow can prevent water from ever accumulating around olive roots. A common method is installing spoon drains or diversion banks to channel runoff away. Spoon drains are shallow, broad depressions dug across a slope that act like artificial creeks; they intercept overland flow (or excess rain from a flat) and convey it to a safe outlet (such as a dam or a natural waterway). They can be constructed with a grader and should have a gentle grade to encourage flow. It’s important to place such drains above the orchard or in inter-row areas to catch water before it settles around trees. In flatter groves, even a small ditch (30–40 cm deep) along one side of the block can help drain water out. Ensure any surface drain is kept clear of silt and trash, especially after storms. Also, avoid discharging the water onto a neighbor’s land without permission – route it to a designated drainage line. In orchards that are already planted, growers have dug emergency drains when facing waterlogging; for example, running a single furrow with a tractor through a waterlogged aisle to give water an escape route. While this isn’t ideal for root disturbance, it can save trees in a pinch by getting water off the orchard quickly. Remember, the faster water drains after heavy rainfall, the better the chance your trees won’t suffer.
6. Subsurface Drainage Systems: For chronic waterlogging in high-value groves, a subsurface drainage system may be warranted. This typically involves burying perforated or slotted PVC “agricultural pipes” (aka tile drains or ag lines) below the root zone to lower the water table. A common design is to trench in slotted pipes at a depth of 60–100 cm, in parallel lines across the orchard, with a slight gradient to lead water out to a sump or outlet. These trenches are backfilled with gravel or coarse sand around the pipe to act as a filter and encourage water entry. The spacing of drains depends on soil permeability – heavy clays might need drains every 10–20 m, whereas loams can have wider spacing. Subsurface drainage is best designed by an engineer or experienced drainage contractor because the specifics (depth, spacing, outlet, gradient) are critical for it to function properly. When done correctly, subsurface drains can effectively draw excess water out of the root zone before it causes harm. This solution is more common in larger orchards or where waterlogging is severe and persistent (e.g., an olive grove on a flat clay plain). It is an expensive up-front solution, but it can make an otherwise unviable site productive. Some Australian growers have combined subsurface drains with raised beds – the raised bed keeps the surface roots dry, while the buried pipes lower the overall water table. If you install subsurface drains, also install observation points (e.g., riser pipes or inspection pits) to monitor flow and allow maintenance (flushing out silt, etc.) in the future.
7. Water Management and Irrigation Practices: Growers should also adjust their irrigation strategy to the soil’s capacity. Over-irrigation can mimic waterlogging even on well-drained sites. In heavy soils or areas prone to saturation, use shorter, more frequent irrigation rather than deep, infrequent soaking. Ensure drip emitters are not leaking excessively in one spot. It’s also prudent to pause irrigation if rain is forecast or after heavy rain – monitor soil moisture and only resume when the profile has drained sufficiently. Smart irrigation controllers or soil moisture sensors (tensiometers, capacitance probes) can aid in preventing inadvertent waterlogging from irrigation by giving real-time feedback on soil saturation. Essentially, match your irrigation volume to the soil infiltration rate; any water applied beyond what the soil can absorb will stagnate and harm roots. During cooler months or rainy periods, many Australian olive groves need little to no irrigation – trees can often sustain on stored subsoil moisture until conditions dry out.
8. Remedial Actions for At-Risk Trees: Despite best efforts, you may still find pockets of waterlogging in an established grove – for example, an unexpected seep area or a spot you thought would drain that did not. In such cases, it’s important to take corrective action quickly. For individual trees suffering in a boggy spot, one option (labor-intensive but effective) is to dig out and replant the tree on a mound. Carefully remove the tree during winter dormancy or a cool period, lifting as much of the root ball as possible (or take cuttings if the tree is small and root rot is advanced). Then improve that site – scoop out a wide planting hole, mix in gypsum if clay, and backfill to create a mound 0.5 m or more high – and replant the olive on this raised position. This essentially “rescues” the tree from the swampy ground. It’s best done before the tree is too weakened. Afterwards, monitor it closely for recovery and consider protective fungicide (e.g., phosphite) treatments for root rot.
For larger sections of the grove that prove wet, you might implement a new drain or trench as discussed, even if it means sacrificing a row middle for drainage. Cutting a shallow drain along a contour above the wet area can intercept water, or a deeper trench through the wet area can drain it. These fixes can be done after harvest when equipment access is easier and minor root damage from trenching will be less impactful. Always restore ground cover or mulch over disturbed soil to prevent erosion after digging drains.
9. Disease Management in Waterlogged Situations: If trees have experienced waterlogging, there is a risk of root disease taking hold. As a preventive measure in waterlogged-prone orchards, some Australian agronomists recommend applying phosphorus acid (phosphonate) routinely. Phosphorous acid is a low-toxicity fungicide that is very effective at suppressing Phytophthora in many crops. It can be applied as a foliar spray (commonly at 2.5–10 mL/L depending on product strength) every 6–8 weeks during the wet season. The chemical boosts the tree’s own defenses and can halt incipient Phytophthora infections. In olives, phosphonate is often applied to the leaves (or even as a trunk spray or injection if the canopy is sparse) and allowed to translocate to the roots. This is a preventative approach – it’s most effective when applied before or at the onset of waterlogging conditions, not after a root rot is advanced. If your grove is in a region with warm, wet summers (e.g., Northern NSW or Queensland) where Phytophthora is known to be present, a proactive phosphonate program on young trees can be a lifesaver. Additionally, ensure good sanitation: avoid moving soil from wet infected areas to clean areas (Phytophthora spreads via water and soil), and quarantine any new nursery stock (check their roots for health).
Should Rhizoctonia or other fungi be suspected after waterlogging, there are no specific curative sprays, but improving conditions for the tree to recover is key. This may involve fertilizing the foliage (since compromised roots can’t uptake nutrients well). Foliar feeds of calcium and boron, for instance, have been observed to help olives push new healthy root and shoot growth after water stress. A complete foliar nutrient spray (including NPK and trace elements) can support the tree while its roots regenerate. Prune out any dead or dying branches caused by dieback, but avoid heavy pruning of live tissue – the tree needs as much healthy leaf area as possible to recover. Instead, only remove the clearly necrotic wood and allow any new suckers from the base to grow (they help rebuild the canopy and root system balance). Once the tree shows recovery and the soil has been fixed (drained or mounded), it should regain strength over subsequent seasons.
10. Regional Considerations: Across Australia, the strategies above should be tailored to the local climate. In Mediterranean-climate regions (e.g. South Australia, WA), the highest waterlogging risk is in winter and early spring when rains are frequent – here, focus on winter drainage and perhaps covercropping in summer to maintain structure. In summer-rainfall areas (e.g., eastern Australia), intense downpours can cause flash waterlogging even in midsummer; ensure drainage is ready year-round and be cautious with summer irrigation. In some parts of NSW and QLD, heavy clay soils underlay the valleys – these are classic cases for raised bed planting plus prophylactic phosphonate sprays in the storm season. Contrastingly, in parts of Victoria or southern NSW, waterlogging might coincide with cooler weather, which slows tree metabolism; there, one must be wary of diseases like Verticillium, too, which can co-occur in cool wet soils. No matter the region, always aim to “get the water off the paddock, or get the tree above the water.” A combination of the discussed methods often yields the best result – for instance, ripping + mounding + surface drains + gypsum application might all be employed on a particularly challenging block of sodic clay.
In conclusion, managing waterlogging in olive groves requires diligence in planning, observation, and intervention. The effort is justified by the potentially severe consequences of inaction: tree losses, disease outbreaks, and reduced yields. By understanding your soil’s quirks (clay pans, sodicity) and using the preventive tools available (from mounds and drains to chemical treatments for root rot), you can successfully grow olives on difficult soils and in wet climates. As Australian experience has shown, even marginal clay lands can produce healthy olive crops if waterlogging is kept at bay through smart agronomy. The key takeaways for growers are: prioritize drainage in every decision, regularly inspect and maintain soil structure, and act quickly at the first sign of water stress or root disease. With these practices, olive trees can thrive in regions of heavy rain and clay, yielding bountifully without getting their feet too wet.