Undercover
farming
ucf
MaY/JUNE 2021
I Volume 18 No 3 I I R45.00 per issue
SHADE NET
HYDROPONICS
ENERGY
AQUAPONICS
Apple Production under Shade Net Page 4
Vertical Hydroponics Farming the Solution? Page 12
Sustainable Energy for Greenhouses a Possibility? Page 17
Maintaining Oxygen Levels Page 18
greenhouses I shade net I hydroponics I aquaponics PROPRIETOR I ADVERTISING SUZANNE OOSTHUIZEN 082 832 1604 suzanne@axxess.co.za EDITORIAL CONTENT & COMPILATION Johan Swiegers 082 882 7023 editors@axxess.co.za ADDRESS PO Box 759, Montana Park 0159 E-MAIL magazine@axxess.co.za FAX 086 518 3430 DESIGN Fréda Prinsloo DISCLAIMER Undercover Farming accepts no responsibility for claims made in advertisements or for opinions and recommendations expressed by individuals or any other body or organisation in articles published in Undercover Farming.
Contents 4 8
Western Cape’s Apple Production under Shade Net New Initiatives in Southern Hemisphere Fruit Exports 10 Growing peppers in a hydroponics system 12 Population explosion – nutritious food sustainability – water and energy shortages – mineral resources under pressure – eco systems failing: Vertical hydroponics farming the solution? 14 Drapenet – its success on pome fruit farms 17 Sustainable Energy for Greenhouses a Possibility? 18 Aquaculture: Maintaining Oxygen Levels 19 Subscription form
FRONT PAGE: Knittex Shade net over apples. Image supplied by Knittex
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The Scriptures
The Lord is good to those whose hope is in him, to the one who seeks him; it is good to wait quietly for the salvation of the Lord. Lamentations 3:25-26
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Farming 15
C
limate change still remains a global discussion topic. Unfortunately, like in the case of the current pandemic, people are swept up in frenzy by ‘ghost’ writers that write on hearsay, rather than from scientifically founded and unbiased sources. Fortunately there are people that are putting heads together finding technologies and simple ways to still keep up production in the face of mineral energy shortages, excessive carbon spillage and imminent water shortages. In the undercover farming world, interesting things are happening; Montreal, Canada boasts with the recently finished largest in the world (15 000 square meters) top of a warehouse greenhouse. News has it that UK, France and other countries are gearing up to follow. Several large stores overseas are putting up greenhouses on top of their buildings to create a local, fresh supply with the least carbon footprint. There are new ideas on coating greenhouses at the start of extra warm summers to keep out the strong rays of the sun, while still getting the best out of their flower and vegetable plants. And then electricity; one of the biggest headaches in our country – government seems to realize their folly of underservicing their main energy production plants and now opens up the door (a little more) for bio-energy through solar or wind energy sites. Solar energy installation and maintenance is costly at the beginning, but as with many technologies that are now available at every corner shop at much cheaper prices, will in due course follow the same trend. The fresh produce farmer will just have to do a proper return on investment analysis before investing. We looked at the fantastic outcomes of shade net over pome fruit and report on two farms in different locations for readers who may want to increase their pack-out of their fruit. Keep warm, keep safe and keep smelling the roses!
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The K20 white shade net above the apple trees is visible in this picture. Image supplied by Knittex.
The Western Cape’s most well-known apple producing district is Grabouw. Some refer to the district around Grabouw as Elgin, but in fact, Elgin is the name of a former train station adjacent to the town. However, this remarkable district is almost worldwide known for its quality apples it exports from the farms spread around Grabouw.
Western Cape’s Apple Production under Shade Net
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or many years apples were produced here for export purposes and also later, for the Appletiser factory close to town. Global warming and its evident change in weather patterns brought about variable conditions and even harshness of the sun’s UV rays. Therefore, during the past decade or so and after thorough research and trials with different density, colours and hues of shade net, apple producers started to turn to shade net structures over their orchards, or at least, over certain varieties. During an interview with Brandon Myburgh, general manager at Drumearn
(Pty) Ltd farms, the positive effects of shade net structures over apple varieties became evident. Needless to say, proper farm management and good planning have much to do with success and progress. In this aspect, Brandon climbed the ranks in the apple industry from a young age. He began in 1992 at Two a Day (Pty) Ltd in their apple receiving bay but soon was recognised for his technical strengths, and received experience in fruit size measurements, storage trials and preharvest maturity sampling. He was then spotted by a Grabouw apple producer and picked up experience on the wider management of an apple production unit. Going from strength to strength, Brandon later worked for a number of years at Lourensford Estates at Somerset West, but having family and friends in his hometown, eventually landed him a position at Drumearn company farms,
Knittex Shade net over apple trees. Image supplied by Knittex.
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Grabouw. He was soon advanced to be general manager, the position he still holds. According to Brandon, the company has three farming Brandon Myburgh, units; two which general manager at Drumearn (Pty) Ltd are in Grabouw apple farms. area and one in Villiersdorp. The apple varieties grown are; Golden Delicious, Granny Smith, Braeburn, Royal Gala, Fuji, Pink Lady, Kanzi and Sundowner. “To remain competitive, the producer constantly needs to adapt according to consumer demand. As new varieties and rootstocks become available and show good prospects, we gear our production sites up early in order to keep our markets satisfied,” he said.
Where apples grow best The ideal soil in which apple trees would flourish, should consist of the following; well-drained soil to a depth of more than 80cm and a clay content of less than 25 – 30%. In shallow soils of less than 40cm you need to make ridges in order to achieve at least 60cm. Generally, the apple producing areas in the world are located between 40° north and 50° south from the Equator. This results in favourable conditions with sufficient chilling units in the winter without constant below-freezing temperatures. The summers in these regions are also mild; therefore never above 30°C. Since apple production farms in South Africa are situated around 34° south of the Equator, they are in a marginal area. Therefore, at
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PROTECTING YOUR
CROPS FROM THE
wind, sunburn, hail damage, birds & larger insects Undercover farming I May/June 2021 I Volume 18 No 3
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least two low chilling units are required during winter for optimal quality in apples and in summer, shade net protects the crop from sun burn and other defects. Apples are produced in tropical regions where the height above sea level exceeds 1800m. In this situation the height above sea level assists in achieving the required chilling units in winter and dampens the effect of a possible heat wave during summer. In Grabouw district there are approximately 8 000 ha that is suitable for the production of apples. The average trees planted per hectare are between 1 445 – 1 778, but new plantings are seeing 2 800 trees planted per hectare in order to be financially viable. Income per hectare depends totally on the amount of first class fruit produced per hectare to be financially viable. At this stage a minimum of 60 tons per hectare needs to be achieved in order to recover input costs. “South African apple producers alone will never be able to satisfy the world’s demand as they annually supply less than 2% of the world’s apples. Therefore an excessive crop or lesser crop amount from SA would have no real effect on the world’s demand,” Brandon explained. “In terms of water supply to the orchards, we have always used micro irrigation in all our orchards, which allows us the added advantage of being able to “Pulse Irrigate” when temperatures become excessive in the summer months. This help us to lower the micro climate temperature in the orchards during a heat wave, resulting in less sunburn and stress on the apples,” he further said.
Shade nets over apples When enquiring on the advantages of shade net over apple trees, Brandon said they have made use of a K20 White net in all their netted orchards which effectively
provides 8% shade. Nets are hung at 4.5m above the ground and the tree height is between 3m and 3.5m depending on plant spacing. Producers have noticed that the full benefit of shade nets is only noticeable once the trees have a bit more body. Younger, less vigorous trees are still susceptible to sunburn damage under nets and from experience only from the 4th leaf stage they experience the advantage of shade nets.
Harvesting of apples goes quick under shade net structures and vehicles transporting the bins can move freely.
History with shade nets “Our first apple trees planted under net was in 2013.
We made the decision that we would plant all Granny Smith orchards under net as we reduced our cull percentage from 40% to 15% in orchard. This obviously resulted in more first grade fruit going to the pack house which in turn had a positive effect on the bottom line. “We are fortunate not be affected by Image supplied by Knittex. hail or wind normally, but the results of global warming/ Apples under Knittex climate change are definitely being West Black shade noticed and recently we have had an net structure. Image increase in hail and wind damage,” supplied by Knittex. Brandon said. General maintenance is required annually after the season to ensure that the nets are in good shape for the winter winds and rain. From experience they learnt that a small tear which has not been repaired in time, results in substantial damages and costly repairs later. Tree heights are kept to 500mm below the nets and they have
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greenhouses I shade net I hydroponics I aquaponics Western Cape’s Apple Production
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invested in a self-propelled platform to perform maintenance on trees.
Knittex shade net structure with slanting side wall. Image supplied by Knittex.
Higher pack outs with shade net covered orchards “Besides the extra income as a result of higher pack outs, we also have an additional saving, in that we do not need to insure the orchards under net for hail or wind damage. Surprisingly we have noticed that orchards under net are less vulnerable to wind damage compared to those without nets. Lockdown influence “Covid 19 has been challenging for the fruit industry to say the least. The wellbeing of our employees as well as the scarcity of containers for export obviously was a huge concern. Fortunately we are adaptable to change and have adjusted
“The results of global warming/ climate change are definitely being noticed and recently we have had an increase in hail and wind damage.”
to the new normal and kept our heads up,” Brandon explained. “All our fruit is delivered to Two A Day (Pty) Ltd who manages our packing and marketing. We are fortunate to have a brilliant technical department which supports us in all aspects. Future plans “All our orchards under nets are fixed nets which mean that we do not open or close
them as we wish. In future this will be a consideration as well as testing bi-colour varieties under shade net structures. “As a farmer you need the support of your family - especially as irregular hours and last minute cancellations of family commitments are part of the package. Without an understanding and supportive family you will not achieve your goals,” Brandon Myburgh wisely concluded.
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The Southern Hemisphere Association of Fresh Fruit Exporters (SHAFFE) was founded in the early 1990’s from the leading trade organisations from Australia, Argentina, Brazil, Chile, New Zealand, Peru, South Africa and Uruguay.
New Initiatives in Southern
Hemisphere Fruit Exports
T
he idea was to form a common presidency led by Mr. Charif Christian Carvajal M. from the Chilean Fruit platform for exchange on Exporters Association (ASOEX) and the most crucial market Ms. Marta Bentancur from Upefruy access matters in Northern Uruguay, the organisation is focusing Hemisphere markets, including on strengthening resource availability, phytosanitary protocols, food safety, creating a supportive consumption, and environment for trade trends. With the digital era formation of fruit In its more than 30 kicking in its members trade professionals, years of existence, developed a strategic plan developing closer SHAFFE has of action with the objective collaborations with undertaken important of connecting the Southern other similar industry initiatives, such as bodies, modernizing Hemisphere’s fresh setting up data-sharing information sharing, on key crops, organize fruit industry through and communicating the global membership knowledge-sharing, role and contribution forums, develop joint of SHAFFE to the facilitating market access research initiatives, global produce trade. and promoting global analyse and monitor With the objective fruit trade. policy changes in global of bringing Southern markets as well as Hemisphere and provided important exchange and learning Northern Hemisphere industries closer opportunities amongst its members. together in a period of limited travel With the digital era kicking in its members and to allow better planning for the upcoming year, SHAFFE kicked off 2021 developed a strategic plan of action with with its very first “Southern Hemisphere the objective of connecting the Southern Fresh Fruit Trade Congress” under the Hemisphere’s fresh fruit industry through defining theme “Keeping the world knowledge-sharing, facilitating market supplied” in the last week of March access and promoting global fruit trade. 2021. With a renewed Secretariat and a new
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John Giles of Promar International Ltd, who has years-long experience in cooperating with trade associations, attended the conference and chronicles the strategic evolution of the organisation. “SHAFFE is in many ways a remarkable organisation. Together, the countries involved account for around 11 million tonnes of fruit exports, worth some US$14 billion and which account for about 25% of world trade. SHAFFE’s first online congress bought together over 326 delegates from around the world. What struck me, in particular, was how much these countries have in common, despite to some extent all being in competition with each other,”said Giles. Among the challenges they all have to overcome the next few years — as well as the opportunities they have to take advantage of — include the following: • Fruit consumption in many parts of the world is still below the recommended levels as set by the WHO. • Considerable disruption to international trade caused by the COVID pandemic 9
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requires a need a need for the redevelopment of dynamic and resilient trade infrastructure. • There is a need to meet the challenges of climate change, water scarcity and the development of a more holistic view of sustainability and what it means. • The adoption of so-called “green tech” presents the opportunities for better crop yields, reduced wastage, reduced costs of production and better levels of efficiency. • There needs to be more collaboration between governmental/NGO organisations and the private sector in more agile, innovative and proactive partnerships to bring about “transformative change.” • There is a common issue with the availability and movement of seasonal labour. • The better use of e-commerce and trends toward healthy eating are great opportunities and key market-drivers for the future. • There will be new plantings and the development of new varieties across the SHAFFE countries. • There is concern over the rising cost of agricultural inputs and the increase in domestic protectionism and “eat local” campaigns. The feedback received suggests that despite the obvious challenges ahead, optimism in SHAFFE is high: 70% of respondents in a SHAFFE survey felt that 2021 would be a good export season, and 80% thought that the future prospects over the next 5 years were similarly positive. It seems to me that many agri food sectors around the world could learn from the collaborative approach of SHAFFE taken to tackling common problems, such as knowledge-sharing and tech-transfer work, market access covering both tariff and non-tariff barriers, the development of sustainable agricultural and horticultural production and global trade development. But as the newly elected President of SHAFFE, Charif Christian Carvajal also said: “SHAFFE, will only be as strong as its most proactive members”. Never a truer By: N Hajdu and J Giles. word was spoken.
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Greenhouse peppers can be a challenging crop to grow. Once the plants establish a pattern of growth it can be different to manage them in another direction. For example, if the plants are strongly vegetative, it can take some time to direct the plants to be more generative and vice versa.
Growing peppers in a hydroponics system
G
reenhouse pepper production is based on a full year cycle. The transplants go into the production greenhouse in approximately mid December. Pepper seeds germinate slowly, take 10-16 days and plants are ready to transplant at 6-7 weeks. The first pick of fruit begins in about late March, early April and continues to the following December. Plants also grow slowly from transplanting to harvest almost 80-90 days.
Spacing Use double rows spacing when planting in tunnels. In summer put 2.5 or 2 plants per square meter and in winter put 2.1 plants per square meter. Producers also claim that the higher the population of the plants the smaller the fruits; but then denser leaves protect the fruit better against sunburn. Cultivars Selection of greenhouse pepper cultivars depends on colour, disease resistance, performance and yield. It is important to
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choose the right cultivars; some cultivars as the root system is fairly small and have long internodes and can be grown does not need a lot of growing space. for a period of six months because of The growing media should be wetted the high growing for 24 hour before the Selection of greenhouse habit. Fruit sizes plants are set onto the differ between the pepper cultivars depends on media. cultivars. It is also important to colour, disease resistance, There are six performance and yield. It is ensure that the media different fruit important to choose the right is at 20°C for the entire colours available growing season. For cultivars; some cultivars and can be used the first week in the have long internodes and in different greenhouse the day/ combinations night temperature can be grown for a period for packaging of six months because of the should be maintained purposes. at a constant 20-21°C high growing habit. Fruit Remember that and target a relative sizes differ between the all the fruits of humidity of 70-80 %. cultivars. different cultivars Trellising and are green during Pruning the young stage and will colour usually at 2-3 weeks later than the fully developed Pepper plants are indeterminate; that is, they continually grow new stems and green fruits. Because of that, coloured leaves. For this reason the plants have to peppers are more expensive than the be pruned and trained on a regular basis green ones. in order to ensure a balanced growth Seedling transplant for maximum fruit production. Pepper Transplant the seedling into 10 liter bags plants are managed with 11
greenhouses I shade net I hydroponics I aquaponics Growing peppers in a hydroponics system
10
two main stems per plant, resulting in a density of 6 stems /m2 from an initial planting density of 2.5 to 3 plants/ m2. Most of the producers select the two strongest stems and tie them separately to the horizontal cable (in V-shape). Remove all additional side shoots as soon as they developed. When using three stems the fruit sizes may decline. As the plants develops and grow taller, twist the main stems around the vertical string. The vertical strings are to support the plants and to keep them upright.
removed as soon as they appear.
Three to four flowers are removed at the bottom of the plant stems therefore giving the roots a chance to develop as the first fruits take up a lot of energy. Under developed and malformed fruits that are squeezed between the stems should be
Irrigation Pepper plants can take up to 3.5 to 4.0 liters of water a day during the summer. Night watering may be considered during summer. Harvesting and grading It takes between 7 and 9 weeks from fruit set to harvest, taking longer during the low light periods of the year. The
plant is harvested at 85-90 % colour and a disinfected, sharp knife is used to make clean cuts on the peduncle (fruit stem). Care must be taken not to cut into an adjacent fruit or stem. Fruit are graded according to size and the larger sized peppers usually obtain a higher price. The size potential of pepper fruit is determined by the cultivar, but the management of the crop determines whether or not the maximum size potential is met for the maximum number of fruit picked. Source: GDAC
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greenhouses I shade net I hydroponics I aquaponics Inside a vertical hydroponics system.
Population explosion – nutritious food sustainability – water and energy shortages – mineral resources under pressure – eco systems failing:
vertical hydroponics farming the solution? In the major food producing countries globally, around 80% of water resources are applied for irrigation on farmland. An even higher percentage can be expected in drier areas where farmers are trying to produce a reasonable crop.
T
his is a cause for concern to the inhabitants of the world as, although they depend on producers to put food on the table, open land, or irrigated production systems calls for more water as it expands to supply in the fast increasing demand. Even if wastewater is used, harmful pathogens are introduced into the food supply and therefore put humans at risk. Further negative influences by irrigation practices is that it may cause waterlogging and salinization. When over-watering, the soil becomes oversaturated and plant roots get damaged, causing loss of plants. With salinization soil becomes saltier than it should be, as its water has been drawn away for irrigation elsewhere. The high salinity causes barren land because plants are unable to access what water remains in the soil. Pollution due to irrigation runoff can be a serious problem in the areas near commercial farming operations. Chemical pesticides and fertilizers are carried away from crops and into the local water supply, leading to health risks and posing a
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threat to natural waterways and the local environment.
Comes Vertical Farming There are several pros and cons to consider in the vertical farming idea. However; should one weigh up the negative aspects – which are largely due
to under-qualified management and poor business planning – this relatively new system should become the answer to multiplying nutritious food supplies quicker than conservative methods; even with its increased technologies.
System assistants should always wear protective clothing for hygienic purposes
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In a vertical hydroponics system plants are grown in water with no soil present. They are stacked vertically in towers or trays, arranged within a structure such as a greenhouse or other building. Since the growing happens indoors, matters such as climate and weather have no influence on crops. Therefore healthy crops such as leafy greens can be grown year-round in any part of the world, city or town regardless of the climate conditions outside.
Stable yields, quality Stable crop yields are possible in the vertical farming system. Production takes place all year round as the system is constructed inside a greenhouse, former warehouse or old pack house. This means there is protection against pests as the assistants are highly hygiene aware and plant quality conscious. For obvious reasons there is no movement of animals or even invasive plant species. This is in answer to food security, bringing food to people with a low carbon footprint producing up to one five to six hundred kilograms of food per square meter. Mostly leafy plants (greens) with smaller root systems are produced like salads, cherry tomatoes, strawberries, broccoli, cabbage and spinach. According to specialists in this system, it is estimated to be two thousand per cent more effective against traditional rain fed systems and up to four to five hundred per cent against other hydroponics systems at a fraction of the cost. There are no fossil fuel utilised in the process or pathogen control; CO² is taken from the air, bound with water (H²CO³) to obtain carbonic acid to regulate pH levels. When sunlight falls on the plants the photosynthesis breaks down the carbon leaving water and oxygen. Natrium chloride is used with electrolysis to control pathogens. Luminaforce is used to let only red and blue light through for better grow light in the tunnels and temperatures of between 16°C-22°C are retained for optimal growth. With the ability of growing a variety of plant species, comes the advantage of water saving as the system is designed to recirculate and purify, before adding nutrients for the next cycle. These days, it is fine-tuned to the extent that the system saves on nutrients as it manages the run-off and only adds up to the needs of the plants at a particular growing stage. This is not possible with open land farming.
LED lighting runs above every shelf of produce to produce even lighting.
There are of course, some who foresee negative aspects of vertical farming; such as plants that are not open to pollination, no direct sunlight, less employment opportunities, etc. But on the contrary are the much over-arching aspects of higher food volumes, consistency in quality and supply, high water saving and more. Energy use by LED red or blue lighting (which are the colours plants flourish under) can be obtained by solar panels on the roof or even wind energy. Site, Carbon Footprint The site at which vertical hydroponics systems are constructed can be selected close to the main fresh produce outlets to save carbon footprint and transport distance. Empty standing warehouses and even open company buildings exist all over the world and often in close proximity to food outlets. As far as the economics of constructing a vertical hydroponics system is concerned, a proper business plan should be in place with costing of every aspect of the
business and most important; a market that offers sustainable and even increased business from the producer. Furthermore, all lawful, environmental, employment, transport and management aspects must be in place in order to roll out such a new venture. Vertical farming has taken off tremendously in other countries and there is no reason why we in South Africa should not generate the will and funding to ensure our nations’ sustainable supply of JS fresh food by using this system.
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South Africa’s apple and pear production areas experienced excellent growing conditions during the current season and is set for a record export crop. Apple exports are expected to rise by five per cent year-on-year to 38,4 million 12.5kg equivalent cartons.
Drapenet
– its success on pome fruit farms
P
ears are due to grow by six per cent to 17.9 million 12.5kg equivalent cartons, which are about a six per cent increase from last year. This is according a recent report by Hortgro’s Trade and Markets Manager, Jacques du Preez. Pome fruit is the fourth biggest contributor to South Africa’s agriculture exports after citrus, wine and grapes and an important contributor to employment. The main producing areas are Ceres, Elgin, Grabouw, Vyeboom, Villiersdorp (all in the Western Cape) and the Langkloof region in the Eastern Cape. The total production area for apples in 2020 was 25,320 hectares, and for pears 12,925 hectares. Production in the northern part of the country is small compared to these regions.
Giraffe Boerdery farm An initial trial with DrapeNet was executed on the Giraffe Boerdery farm
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of Denné Strydom in the Langkloof. Only a small area of the 312ha pome fruit farm was used to test the outcome of DrapeNet over apple trees. Currently, a total of 110ha is covered under DrapeNet, the rest is either under shade net structure, or open.
The main purpose of the DrapeNet is to prevent apple trees from damage by hail, sunspot, wind chafing or loss of branches. In comparison with insurance premium Denné Strydom, expenses, it is more owner of Giraffe cost effective to install Boerdery. DrapeNet or even shade net structures. Most pome varieties like Granny Smith, Golden Delicious, Packhams and Early Bon Chretien do best under black net. The Bi-Colour variety is covered with a white net and a further trial was completed recently with silver shade net. The cultivars which proved to be successful under the silver net were African Carmine and Royal Beaut. According to Denné, they covered 36ha of Forelle pears with white shade net and on trial; three hectares under black net. They found Forelle lose its colour under the black net causing loss in marketable quality. Grey or white net over Forelle
At Giraffe Boerdery, they did trials with black, grey and white shade net structures and drapenet.
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Pome fruit is the fourth biggest contributor to South Africa’s agriculture exports after citrus, wine and grapes and an important contributor to employment. The main producing areas are Ceres, Elgin, Grabouw, Vyeboom, Villiersdorp (all in the Western Cape) and the Langkloof region in the Eastern Cape. obtain best results. Around 40% Vermont Beaut pears were packed (grown under white net) and on top of this, the fruit’s colour was not lost at the time of sugar increase. The difference between DrapeNet and shade net structures is that the first covers each individual tree from top to bottom which prevents it from damage; sometimes the end-of-row trees may be slightly damaged; whereas with shade net structures, the trees are well below the nets and more protected(although outside perimeter trees are sometimes less protected). Denné is satisfied
Of the 320ha at Giraffe Boerdery, only 90ha still needs to be covered, and will be covered in the next three years.
that both systems prove to be almost 99% effective. They have a few Granny Smith orchards which are left in the open to compare results with the covered trees, and the pack-out on these was around 57%. These apples have a ‘blush’ while the same variety under shade net maintains its green, realistic Granny Smith appearance. The pack-out from trees under shade net realizes a magnificent 88-92% (including the damaged ones). Thus; only 8% of the production under shade net is apples that were thrown out or being under-sized. In particular, the Golden Delicious apples pack out just under 100%. Four orchards
of the Packham pear variety were covered under white net as a trial to establish its effectiveness, but Donné wants to test the grey net over these and also black net which will cover Early Bon Chretien (it is rated the same as Goldens and Granny’s) orchards as well. It was found that the Packham pears have sunburn spots under white net, but under black net no sunburn was detected at all. As far as wind damage on his orchards, Denné says when walking in among structure net or DrapeNet covered orchards during average wind, there is almost no sense of wind; he therefore strongly advise the use of shade net over
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pome fruit orchards. Some farmers have it that one needs not spray fruit under DrapeNet , but Denné prefers to have a longer spraying cycle as he wants to ensure that if a moth should creep up a tree under DrapeNet , his crop is well-protected. He also advises producers to be ‘spot on’ with their spraying programs and fervent in managing these. The DrapeNets are tied up above the trees when bio-chemical thinning out takes place and afterwards the nets are let down again to protect the trees. Denné’s opinion of those producers who said they obtain smaller fruit from their orchards, possibly lacked in thinning out the trees properly. Careful but proper thinning out of sucker branches will have the tree produce even-sized fruit. On the question of bitter pit disorders, Denné says that some people think shade nets to be the culprit, but bitter pit may not be evident at harvest and is said to develop in stored fruit and could result in extensive losses. He sprays an additional Calcium crop spray in case the nets might be the cause, but by and large to ensure his crop is safe against most known pests.
Return on investment and installation “It takes one digger machine and eight assistants to install the DrapeNets. It is a relatively quick process and we found that, with two teams and machines we install around five hectares per day. The DrapeNets are not taken off during harvesting or thinning out; a cable above the trees allow the assistants to roll up the DrapeNet and tie it neatly above the trees until they have finished working in the orchard, when they untie and let the nets down again. This largely accounts for less tears and replacement during handling,” Denné explained. On the Giraffe Boerdery farm a 63ha orchard paid off the installation of its DrapeNets within one year. Even when they experienced extraordinary hail storms, Denné found the ultimate period for recoup of investment on DrapeNet installation less than three years. Irrigation programs The older trees under DrapeNet on the farm are being irrigated every two weeks according to tensiometer readings. The other and younger orchards are being sprayed weekly according to soil moist readings.
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Apples produced under drapenet produce more than 90 % at pack out, according to Denné Strydom.
According to Denné Strydom, production under shade net is an absolute must to obtain maximum pack out.
When picking or servicing trees, the drapenet is simply lifted and tied at the top to move faster through the orchards.
The difference between DrapeNet and shade net structures is that the first covers each individual tree from top to bottom which prevents it from damage; sometimes the end-of-row trees may be slightly damaged; whereas with shade net structures, the trees are well below the nets and more protected(although outside perimeter trees are sometimes less protected).
SUKSES MET DRAPEERNET OOR POMOLOGIESE VRUGTEBOORDE Denné Strydom van Giraffe Boerdery, Krakeel in die Langkloof, is oortuig van die sukses van skadunet en veral drapeernet oor sy appel en peerboorde. Op sy sowat 320ha plaas is daar slegs 90ha wat hy gaan dek met drapeernet binne die volgende drie jaar. Volgens Denné, met goeie oes aan sy kant, verhaal hy sy investering op net strukture binne een jaar, maar konserwatief gesproke, behoort die produsent sy koste binne ‘n maksimum van drie oeste te verhaal. “Ons kan eenvoudig nie die uitpak resultate verkry sonder nette oor ons boorde nie,” sê Strydom.
greenhouses I shade net I hydroponics I aquaponics
Could this become a reality in South Africa soon?
Sustainable Energy for Greenhouses a Possibility? South Africa has been plagued by power supply issues for many years. Mostly because of the significant reliance on Eskom, which is struggling to meet electricity demands. Every year the electricity tariffs increase by 15% and continue to squeeze profits of businesses, including farmers.
A
ccording to the World Economic Forum (WEF) Energy Transition Index 2021, the rising electricity price is one of the major contributing factors placing South Africa near the bottom of the list, at 110 out of 115 countries. Energy efficiency is increasingly becoming a way of life for many people around the world. Even in South Africa, the government has started with the decommissioning of coal-fired power stations, while creating a favourable environment for ‘green energy’. The government is also supporting municipalities that aim to generate their own power through renewable energy, and this has resulted in a number of Western Cape municipalities adopting renewable energy in a bid to move off Eskom’s grid.
Managing the energy The idea of relying entirely on natural resources for electricity supply across sectors can have high-cost implications if is not done right, no matter how visionary it may be for farms, businesses and homeowners. Managing the energy demand and being more energy efficient is just as crucial as doing thorough research before installing systems that generate alternative energy, according
instance, are considered cheaper than to Duncan Abel, Energy Finance Eskom’s tariffs. And it is important Principal at Nedbank. to note that energy demand does ‘It is not just about generating your not always follow the sunshine cycle. own power. There are certain steps This means that solar panels should that you need to take first to ensure be supplemented by batteries, which that you generate enough power. If you require dedicated solar panels and extra go off the grid completely, then you energy to charge them. don’t need Eskom’s You will also need a Energy efficiency is permission. You have generator for backup. increasingly becoming free will to do what you So, typically batteries want when it comes a way of life for many double the cost of to energy supply. It is people around the a system, while the only when you are still world. Even in South generators that back up partially connected to the batteries come with Africa, the government Eskom’s grid that there fuel costs. has started with the are certain licencing The best time to decommissioning and registration consider moving your requirements to think of coal-fired power business off the grid about.’ stations, while creating a is when you see there favourable environment is a significant energy Off the grid for ‘green energy’. security issue. That costs is if lost production Abel adds that not all and operations far outweigh the cost agriculture businesses or farmers can of going off grid or installing a hybrid afford to go off the grid. Installation solution. costs for renewable-energy systems Ultimately, farming businesses need are expensive, although they can to manage their electricity demand, become cost effective in the long term. be more energy efficient and generate Depending on the property size and only as much electricity as they can use energy need, going off the grid can cost every day. north of R500 000 for a farm. By John Hudson Solar photovoltaic (PV) panels, for
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greenhouses I shade net I hydroponics I aquaponics
Aquaculture: Maintaining Oxygen Levels The oxygen level in fish tanks and ponds needs to be maintained at levels above 5mg/ℓ for the heath and efficient performance of the fish and filter bacteria. Aeration is usually the preferred method of replenishing the oxygen and removing the carbon dioxide from the culture environment, and two devices are commonly used to supply this aeration in tanks: air pumps and blowers. Each device represents a range of options - but which is the most appropriate equipment choice to use in a particular situation?
T
he oxygen level in fish tanks and ponds needs to be maintained at levels above 5mg/ℓ for the heath and efficient performance of the fish and filter bacteria. Aeration is usually the preferred method of replenishing the oxygen and removing the carbon dioxide from the culture environment, and two devices are commonly used to supply this aeration in tanks: air pumps and blowers. Each device represents a range of options - but which is the most appropriate equipment choice to use in a particular situation? Air pumps provide low amounts of air (up to about 10/m3/hr) but can deliver it to a depth exceeding what is normally utilized in fish farming (3.5m). By contrast, blowers typically produce massive quantities of air, but are inefficient in deep water (>1.5m). Being small, air pumps are also typically less expensive than blowers. When fish farming, we very seldom use water deeper than 1.5m, and when we
Comparison of the efficiency of a range of air pumps and blowers
do it is generally combined with the use of liquid oxygen, so this evaluation falls away. Thus, the power of the air pump is seldom of relevance, so let’s focus on the other factors relevant to the comparison. Going forward all comparisons are done at a water depth of 1.0m. The graph above provides a comparison of a range of air pumps (ACQ models) and blowers (S and K models) ranging in size from 75W to 11kW. To make matters more interesting the larger blowers are 3-phase units The unit on the left below is a typical air pump, and on the right is a blower. whereas
18 Undercover farming I May/June 2021 I Volume 18 No 3
the smaller models are all single phase, but, although highly relevant in reality, we can ignore this for now for illustrative purposes. Consider the graph which displays the efficiency of each machine in 2 ways for comparison, the amount of aeration delivered at 1.0m water depth vs. the amount of power consumed, and the aeration delivered vs. the retail price of the unit. It can be seen that the blowers are significantly more efficient per unit of aeration in terms of cost, but even the larger blowers are more cost efficient than the smaller blowers. In terms of power efficiency, a more complex picture emerges where there is more variation between models than between the different equipment types. The ACQ9 air pump is as efficient as some of the blowers, whereas the two smallest blowers, S2M and S3M are the least efficient of all.
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greenhouses I shade net I hydroponics I aquaponics Aquaculture: Maintaining Oxygen Levels
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In designing the aeration system for a fish farm we need to calculate the total aeration volume required and the delivery depth. With this information we then assess the most appropriate tool for the job. Let’s look at the chart above differently to compare 3 unique design requirements of 10, 50 and 1 000m3/hr. In the case of the 10m3/hr requirement it is clear that the least expensive option is the ACQ7 (2 units) or ACQ12 air pumps, both in terms of capital cost
and kW consumption. When the need climbs to 50m3/hr the S4M blower is the most cost effective, but, although the capital cost is far higher, the air pumps are more energy efficient in this case. By the time we get to commercial scale applications as demonstrated by the 1 000m3/hr graph the blowers are far more cost effective and generally more power efficient too. Thus we conclude that in a small installation an air pump is probably going to be the most appropriate, but by the time the usage exceeds about 20m3/hr, it becomes more efficient to purchase and operate blowers. By: Leslie Ter Morshuizen, Aquaculture Africa
Drapenet – its success on pome fruit farms
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Picking under DrapeNet There are two methods of picking apples and pears under DrapeNet ; one is to throw a lane’s net across the next lane and picking under the ‘roof’ and the other, by creeping in under each tree’s DrapeNet to pick. The first option offers the advantage of a faster harvesting process, but nonetheless, with experienced farm assistants, trees and fruit are not hurt. Future prospects Denné Strydom is confident that his
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farm of 312 hectares will be completely covered with DrapeNet within three years. There is only about 90ha of orchard still to be covered. He is outspoken about the fact that his farm’s success rely on his shade net structures but all new orchards are and in future will be covered with DrapeNet . “We just cannot obtain the results we already experienced without covering our orchards,” Denné By JS concluded. Granny Smith apples freshly picked.
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I VolUME 18 No 3 I I R45.00 per issue
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SHaDE NET
HYDRoPoNICS
ENERGY
aQUaPoNICS
apple Production under Shade Net Page 4
Vertical Hydroponics Farming the Solution? Page 12
Sustainable Energy for Greenhouses a Possibility? Page 17
Maintaining oxygen levels Page 18
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