Understanding water movement in soil for irrigation success
Water is a precious resource and critical in crop production. Its efficient use is more important than ever. Whether driven by drought, research or experience in the field, crop industries continue to learn the need to continually adapt – to not only overcome the challenges thrown at it, but to stay ahead of the game.
Bringing improved water-use efficiency to the field, drip irrigation has made a massive impact in many crop industries. As technology improves and our knowledge expands it will continue to do so. With increased pressure on agriculture to use fewer resources, the fundamental challenge remains: how can we maximise crop yield and quality while using less water? The answer lies beneath our feet—understanding how water moves through soil is key to scheduling irrigation effectively and ensuring optimal plant performance.
Soil Insights
Each soil type has unique characteristics that affect water movement. Factors such as infiltrability, hydraulic conductivity, water retention, and porosity determine how water is absorbed, distributed, and stored in the soil profile. These factors impact the answer to the important question: What affects water distribution in soil?
- Infiltrability is the rate at which water can penetrate the soil, or in other words, the ability of the soil to absorb water at the surface and allow it to move in the soil. If irrigation exceeds infiltration capacity, water spreads horizontally on the soil surface resulting in puddles or run-off and increasing evaporation losses and the risk of shallow root zones.
- Hydraulic conductivity is the water’s potential to move in soil or how quickly water moves through soil. It is a measure of the soil’s ability to move water through its pores under a hydraulic gradient. This is influenced by the soil’s texture, structure and pore size. Furthermore, the wetter the soil, the more easily water flows; in dry conditions, water infiltration slows down significantly.
- Water retention depends on soil texture—clay retains more moisture than sandy soils, which drain quickly.
- Porosity affects oxygen availability in the root zone. While soil should retain moisture, excessive saturation displaces oxygen, limiting root respiration and nutrient uptake.
Saturated Circles
When crops are drip irrigated, the water is delivered in one spot, and we rely on the soil’s physical ability to distribute the water. A wetted bulb or saturated circle form under the dripper. Your soil’s physical characteristics and the delivery rate of the dripper will determine the dimensions of this circle.
Remember, roots require oxygen to grow and take up water and nutrients. It is therefore important that there is balance between the water and air that fills soil pores. As water infiltrates soil, it replaces air in the pores. In drip irrigation this creates a gradient between low and high oxygen levels in the soil.
Balancing Water Distribution
Optimal irrigation demands understanding the soil, the irrigation system, the crop and local climatic conditions. “Efficient irrigation provides the tools for precise crop management. It’s about timely, need-based water delivery and integrating all influencing factors to manage the crop based on phenological stages for optimal production. A holistic approach is necessary where all data and impacting factors are integrated.
However, the reigning idea that drip irrigation must be ‘understood’ in order to manage it successfully places, draws skewed emphasis. It is about understanding how water moves in soil. This may be difficult to explain or learn theoretically, but often easy to illustrate. We must dig profile pits after active irrigation or do water distribution test before system planning, all the forces that affect water movement changes from theoretical concepts to something you have seen in action. A lot happens in an orchard or field, the more you understand the effect water can have as tool for optimal production, the better you can use it.
Flow and infiltrability
Drippers with higher deliver rates displace more air faster, creating variation in the soil’s oxygen levels and leading to lower uptake of water. Drippers with lower delivery rates allow for better hydraulic conductivity without rapidly reducing the levels of oxygen in the root zone. An ideal point of balance between water and oxygen, at which plants will thrive, exists for each soil. When we irrigate, our aim is to manage the root-zone with precision in order to maintain the perfect soil-water-oxygen balance.
A low infiltrability rate combined with a high flow rate will lead to very wide horizontal distribution, but very shallow vertical distribution. This is often when you see ponding, high run-off and shallow root-zones. By lowering the delivery rate, distribution is more uniform with balanced horizontal and vertical water distribution and a more balanced oxygen level.
Lower flow rates make the necessary balance possible by achieving good infiltration on moist soils. The forces of gravity and capillary action become more equal and soil/ water/air ratios can be kept more constant throughout the wetted area.
To conclude our thoughts around flow rates, infiltrability rates and soil characteristics, here are three of the many lessons Team Netafim has learned through experience in orchards, vineyards and beyond:
- Higher delivery rates in sandy soils tend to create deep but narrow wetted zones, often leading to water loss beyond the root zone.
- Lower delivery rates promote better capillary action, allowing water to spread more evenly and ensuring balanced root-zone hydration.
- Compacted soils alter water movement by restricting infiltration, causing water to pool horizontally above compaction layers, potentially suffocating roots.
Holistic Success
With any crop, success will depend on everything from soil preparation to harvesting practices, it will depend on important decisions the farmer and the experts he consults will make, and it will depend on many factors beyond the farmer’s control. Two of the many impacting factors of success in a drip-irrigated crop production is dripline selection and irrigation scheduling. Dripline selection is about selecting a quality dripline with suitable features and specifications to do the job at hand.
Scheduling, as is about understanding all impacting factors and integrating these in a holistic approach. By monitoring soil moisture trends and using tools such as profile pits or probes, producers can adjust irrigation duration and frequency to optimize soil moisture without over-saturating the soil.
To achieve the best results, farmers should embrace a data-driven approach:
- Use soil moisture sensors to track trends rather than relying on guesswork.
- Regularly inspect dripper performance to ensure consistent water delivery.
- Adjust irrigation scheduling based on weather conditions, soil moisture levels, and phenological stage of the plant.
- Leverage modern irrigation technology to automate precise water and nutrient delivery.Impactful Insight
Effective irrigation is not just about applying water—it’s about understanding how it moves through soil. By adopting a tailored, soil-conscious irrigation strategy and applying this strategy with quality precision irrigation equipment, farmers can produce high-quality yields while conserving water. The more we align irrigation with soil movement dynamics, the greater our ability to enhance both sustainability and profitability on the farm.
Article by Netafim – Click here to visit their website
Join us for the 4th edition of Ambermacs’ Macadamia Expo, the largest of its kind, taking place on 13th and 14th February 2025. With over 150 exhibitors and top-tier guest speakers, this two-day event is a must-attend for anyone in the macadamia industry!
Highlights of the Expo:
- Dawie Roodt, renowned economist, will provide a macro-economic outlook on the South African economy in 2025 (Thursday, 13th February).
- Seminars and presentations on macadamia farming and industry insights.
- Parking available for 1,000 vehicles, with convenient shuttle services by Safari Jeeps.
- Entertainment:
- Live broadcast by Radio Laeveld 100.5FM across both days.
- Voodoo Kudu and Pieter Smit performing live on Friday, 14th February, from 2 PM to 8 PM
Event Details:
- Date: 13th & 14th February 2025
- Tickets: R60 per person – online registration required (limited to 3,000 entries).
- Entry: Only valid with a ticket presented at the gate. The first 1,000 visitors will receive a goodie bag filled with gifts from sponsors and exhibitors.
- Food & Drinks:A variety of food vendors will be on-site, along with drinks by Gin & Co, The Thirsty Bartender, and more.
For more information on exhibitors, seminars, and guest speakers, visit our Expo page at https://ambermacs.com.
To book your tickets, click here: https://www.quicket.co.za/events/289747-ambermacs-macadamia-expo-feb-13th-and-14th-2025/
Centuries of selective breeding with apples has led to an increase from 100 trees per ha to up to 10 000 trees per ha in the last 70 years. Macadamia’s natural vigour may restrict options for high-density plantings in certain contexts, and comparing the evergreen macadamia with an inclination to grow vigorously by nature with deciduous apples, is not that simple. Nevertheless, differences aside, basic plant physiology still applies to both of these horticultural crops, and much can be learned by “borrowing” information and principles on which cultivation and tree manipulation in other tree crops are based. Dense, vigorous macadamia trees may limit tree productivity due to source-sink competition and a deficient photosynthetic capacity. So if one wants to increase tree productivity, does that mean strong vigour needs to be curbed? The answer is somewhat contradictory.
Strong vegetative growth at the juvenile stage is crucial for orchard establishment and uniformity. Initial vigour with good upper ground growth (a large effective leaf surface) provides sufficient photosynthates to be transported to the roots, to promote the development of a well-buffered root system, able to withstand environmental stressors such as drought spells. New flushes are very important for future bearing branches and the production of leaves. The leaves can be seen as the “factory” of the plant, photosynthesising to produce carbohydrates. There is also a positive correlation between early vigour and precocity.
But on the contrary, strong vigour in mature trees is not necessarily desirable. The goal should be to obtain initial high vigour, with low (or rather controlled) vigour at maturity. The aim of all pre-planting and post-planting practices should always be on achieving a balance between vegetative and reproductive growth. If done correctly and timeously, these practices will create good tree architecture with an adequate supply of carbohydrate reserves stored in the permanent parts of the tree in autumn and summer. Such parts include the trunk, branching structure and root system. The better these organs are developed, the higher the storage capacity for carbohydrate reserves. These carbohydrates are utilised during the stages of nut growth and oil development since carbohydrate production through photosynthesis alone is not sufficient to provide in the very high demand of such sinks during these stages.
A prerequisite for opting for a high density planting scenario in macadamia, is moderate, controlled growth. In high-density plantings with dwarfing rootstocks, tree volume will be restricted and precocity promoted. Research in apples has proven that dwarfing rootstocks allocate a higher amount of dry weight to reproductive growth, accompanied by a decrease in vigorous vegetative growth. Unfortunately, there are currently no vigour controlling rootstocks, commercially available in the macadamia industry.
In early years training can be done so that vegetative growth and thus nut distribution is improved. With almonds, apples and pears, branches are trained horizontally which eliminates apical dominance, produces a shorter branch with shorter internodes, fewer nodes and more and longer racemes. Flowering and fruitfulness are increased with this practice. Such relationships in macadamia are unclear at this stage. It is interesting that the natural branching angle on dwarfing rootstocks also tends to be wider, which then naturally have the same result as achieved with the manipulation of limb bending.
Deciduous horticultural species have been researched much more comprehensively when compared to the relatively few research results available on evergreen, naturally vigorous forest trees such as macadamia. Macadamia has only been domesticated for about 150 years, and most commercially cultivated varieties are only two to five generations removed from their wild ancestors. Compare that to the apple industry (between 4 000 and 10 000 years old) and the viticultural industry (11 000 years old), and it becomes clear that best practices in macadamia still need to be refined to the same extent.
To take the young macadamia industry to the next level, much research is needed on advanced tree training, pruning systems and dwarfing rootstocks, all of which are widely applied and well-researched principles in the cultivation of apples and grapes. These practices allow for a reduction in tree spacing and increased flowering points per hectare, resulting in high yield efficiency, and reduced and controlled growth. The current focus of research in macadamia is on increased yield and quality of nuts of scion cultivars, with very little research on dwarfing varieties in macadamia and understanding of canopy architecture specific to macadamia. The fact that the gene pool of macadamia is largely untouched is a big positive, and opens up tremendous scope for future breeding. Principles already thoroughly researched in other industries may be explored which may lay a solid foundation for future research in macadamia.
By Anneli Bosman from TopNut
References:
Dhakal Poudel, P., Cowan, M., De Faveri, J., Topp, B., & Alam, M. (2023) Macadamia breeding for reduced plant vigor: Progress and prospects for profitable and sustainable orchard systems. Sustainability. 2023; 15(19): 14506
Huett, D. O. (2004) Macadamia physiology review: a canopy light response study and literature review. Crop & Pasture Science 55: 609-624.
Poudel, P.D., Cowan, M., Topp, B., & Alam, M. (2022) Evaluating Seven Macadamia Seedling and Cutting Rootstocks for Their Effect on Scion Growth. Biol. Life Sci. Forum 2022, 11, 90
Robinson, T. (2003) Apple-orchard planting systems, p. 335-407. In: D.C. Ferree and I.J. Warrington (eds.) Apples: Botany, production and uses. CABI publishing, Oxfordshire, UK.
Smart, R. & Robinson, M. (1991) Sunlight into wine: A handbook for winegrape canopy management. Winetitles, Broadview, South Australia, Australia.
Toft, B.D., Alam, M.M., Wilkie, J.D., & Topp, B.L. (2019) Phenotypic association of multi-scale architectural traits with canopy volume and yield: moving toward high-density systems for Macadamia. HortScience horts, 54(4), 596-602.
Zeng, H., Yang, W., Lu, C., Lin, W., Zou, M., Zhang, H., Wan, J., & Huang, X. (2016) Effect of CPPU on Carbohydrate and Endogenous Hormone Levels in Young Macadamia Fruit. PLoS ONE, 11.
Smith Power Equipment, the exclusive distributor of Kubota tractors and implements in South Africa, is working tirelessly to predict annual as well as seasonal parts and service requirements for its tractors through the use of artificial intelligence.
To spearhead the drive the company has appointed Gerhard Taljaard as the new Parts Manager to ensure the extensive dealer network is properly stocked at all times. He has a long track record and is well-known in the industry for his efficiency in establishing efficient supply networks for the distribution of parts and spares for various agricultural equipment suppliers.
In his new role he plans to further optimise the already efficient logistics and inventory management by ensuring the availability of the correct parts at the right time and place. He aims to reduce excess stock while improving stock levels for essential parts. This includes having the correct parts readily available at dealer locations to further minimize downtime for customers.
Achieving this goal involves a delicate balance of maintaining sufficient stock levels without overstocking. This will incorporate the use of artificial intelligence (AI) tools for enhanced forecasting to predict demand more accurately and manage inventory efficiently. This approach involves analysing previous sales data, market trends and dealer inputs to forecast parts requirements.
He will also oversee a transition from air freight to sea freight for parts orders, which can reduce costs by 20-25%. This cost-saving can then be passed on to dealers and customers, making Kubota parts more affordable. To do this he plans to leverage the extensive experience and market knowledge of Kubota dealers, some of whom have been with the brand for over a decade and more, to ensure that the right parts are stocked based on regional demands and common issues.
“I am keen to implement advanced technological solutions to support inventory management to even predict seasonal variations in demand, especially for things like haymaking, picking, harvesting and sowing equipment, which requires precise forecasting to ensure parts availability during peak periods. The different regions in South Africa have distinct agricultural cycles and we are working on having tailored inventory strategies for each area.”
Ten years after adopting quiet battery-operated landscaping and lawncare equipment the pioneering Hill Top Trading in Johannesburg has grown into a large and thriving enterprise employing more than 250 people and maintaining the gardens of more than 60 residential and corporate office parks.
Amidst rising fuel prices and tougher competition in an over-traded market segment the company has grown beyond owner Richard Potter’s wildest expectations and demand for its services shows no sign of slowing down any time soon. Thanks to his magical foresight and adopting vastly different strategies to the norm the company has changed the game and left it to others to play catchup.
Among the many innovations, the company has introduced two milestone strategies that have rocketed the company to success and allowed it to take full advantage of two of the biggest trends shaping the world at present. The first and foremost strategy to switch to an all-battery fleet has played an outsized role in its success of the business and allowed it to capitalise on the trend of people moving to home offices.
Richard explains, “Before the Covid-19 pandemic we made good inroads in office parks where our quiet electric tools allow us to use battery-operated mowers, blowers and edge-trimmers without causing a disturbance to office workers. When the pandemic struck people moved their offices home and noise levels in residential complexes also became an issue and gave us a huge advantage when quoting for new business. With the inherently low-maintenance requirement of battery-powered equipment and no fuel bills our pricing also reflects these savings making our offering still more attractive.”
The second strategy that sets it apart is equally ingenious and involves storing the equipment on site rather than transporting machines to and from sites using trucks and trailers as is the norm among its peers. While the initial outlay for equipment is higher, Richard’s model is a logistical masterpiece. It eliminates the need for far more costly vehicles, trailers and fuel, while allowing him to redeploy driver positions to dedicated landscaping and garden work allowing for reduced wage bills. Storage of battery-operated equipment also eliminates the need to store fuel which is both hazardous and requires ample space for tanks and fuel transfer equipment. The model simply works best with battery-operated equipment.
Lionell Adams of Smith Power Equipment, supplier of Ego Power+ cordless equipment in South Africa, says the battery-operated equipment is becoming increasingly popular for use in estates, office parks and education facilities among users who prefer quieter operation of the equipment. Advanced battery technology means the equipment can be matched to the right battery for the required runtime which enables it to easily compete with fuelled models without the fuel bill which quickly adds up.
The Ego Power+ range consist of mowers from 46cm cutting width push mowers to large zero-turn ride-ons for larger areas and fields. Hedge trimmers, brush cutters, chainsaws and blowers among others are available and use the manufacturers own patented 56V ARC Lithium batteries. All equipment is commercial grade and is designed with tough commercial use in mind making use of the best available motors, batteries, chargers and materials available to give them the longest useful life possible.
General manager for Smith Power Equipment, Mark Chittenden, says the combination of the right equipment in the right applications to suit individual customers’ needs is critical in the success of a business. In the case of Hill Top Trading we have the right equipment to meet Richard’s ambitious needs and are extremely fortunate to be working with such an innovative company that is expanding its operations ever further.
Pictured above: Igus has developed maintenance-free polymer-hybrid spherical bearings that need no lubrication
The constant need for relubrication of metallic bearing points on rod ends industrial applications is a time consuming and expensive exercise and poses a real contamination risk.
As a result, global polymer manufacturer, igus, has developed maintenance-free polymer-hybrid spherical bearings which are a more cost-effective and safer alternative able to withstand higher loads and constant repetitive movements without the need for lubrication.
The new model features a robust combination of a stainless-steel or zinc die cast housing, a self-lubricating polymer inner ring and a stainless-steel spherical ball. This design allows for applications with higher loads to transition seamlessly to this advanced tribo-technology. Rod ends are critical in everything from manufacturing, to processing, food and many other industries where they are pivotal in the operation of industry machinery, from filling plants to meat-processing and packaging systems, where they transmit dynamic forces through various movements.
Bearing specialist, Juan-Eric Davidtz, of igus South Africa says the benefits of the new product is developed with the inner ring made of either iglidur J- series of polymers for industrial applications or the food grade iglidur A160, a high-performance plastic compliant with both FDA and EU 10/2011 standards, ensuring top-tier hygiene and safety. The iglidur A160 contains a solid lubricant released in microscopic amounts over time, ensuring low-friction dry operation between the inner ring and the stainless-steel spherical ball.
“Our lubrication-free approach significantly reduces cleaning time, as the absence of grease prevents dirt and dust accumulation. Furthermore, in the food and hygienic industries our high-performance plastic’s blue colour enhances food safety by making residues and mould spores easily detectable during cleaning inspections.
“The new igubal rod ends are designed for durability, even in challenging outdoor conditions. They exhibit higher breaking strength and rigidity compared to traditional plastic rod ends and are resistant to moisture, acids, alkalines and UV rays. With a temperature range of -40°C to +90°C, these bearings are versatile across various applications. Laboratory tests indicate that the abrasion resistance of iglidur A160 is ten times better than that of polyamide, even under fast rotational movements.
“Users can significantly increase the reliability of their systems with a modest investment.” The new rod ends are available in sizes M6, M8, M10, M12, M16, and M20, catering to diverse industrial needs. We think it is set to revolutionise the way we built machines by providing a blend of hygiene, robustness and efficiency in rod end bearings with virtually no need for further maintenance,” concludes Juan-Eric.
