Undercover
farming
ucf
SEPTEMBER/OCTOBER 2021
I VOLUME 18 NO 5 I I R45.00 per issue
MICRO GREENS
OPTIMIZE IRRIGATION
WHITEFLY MANAGEMENT
AQUACULTURE FILTRATION
Micro greens at Full Circle Page 4
Optimal Irrigation methods Page 10
Whitefly damage on crops Page 14
Aquaculture Biofilters Page 16
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 PRINTING Business Print Centre 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 6
The Microbial world of FULL CIRCLE
A look at fresh produce markets
Agricultural produce agents’ council (APAC) -
8 Getting the most from your irrigation system 10 SA LOGISTICS Versus Citrus Industry Growth 12 How Whitefly Pest Damages Greenhouse Tomato
FRONT PAGE: Full Circle is a specialized greens production farm in the Elgin Valley, Western Cape. Read pp3-4
INSIDE ...
Crops
14 Looking at your Feeding Water Quality 16 Growing Greenhouse Cannabis – THE BASICS 19 Aquaculture: Biological Filters prevent Poisoning of Fish
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COPYRIGHT Copyright is reserved and the content may only be reproduced with the consent of the Editor.
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THE SCRIPTURES
SCRIPTURE FOR A NEW SEASON! Isaiah 43:19 “Behold, I will do a new thing; now it shall spring forth; shall ye not know it? I will even make a way in the wilderness, and rivers in the desert.”
Subscription details on p19
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P
roduction methods in the undercover farming industry have changed dramatically over the years. When Undercover Farming magazine rolled off the press first in 2003, we mostly had hoop greenhouses and a few large multi-spans. Multi-spans were generally used for large scale production of seedlings. During the past two decades we have observed some fantastic advances in the industry, especially in architecture, cladding, electronic management systems, irrigation systems, climate control and production increase per plant. New entrants to the industry brought with them technological and scientific experience which they applied to increase the level of undercover farming technology and production at an enormous rate. Our main editorial features an individual that brought his research and development background into his new venture and you only need to look at the pictures to realize the high quality of crop this farmer produces. We are glad to also notice elsewhere how young people are showing interest in hydroponics and fresh food production as a whole! One of the leading causes of greenhouse gas emissions is something we can all help to reduce, but state officials globally are not debating it in public. In the next few days, world leaders meet at COP26 in Glasgow to discuss their climate change mitigation strategies, and we already know that the biggest talking points are likely to be moving away from fossil fuels, reducing emissions from the global transportation industry (especially maritime and aviation transport), and protection of natural resources like rainforests that act as huge carbon sinks. Again, whatever is decided, little at base level will be rolled out. Unless, we as population of earth change our minds about the food we eat. Globally, people are forced to get in the habit to consume less meat and dairy, and eat more greens (I can hear grumbles by the Braai & Beer readers!) to increase intake of the full range of vitamins and decrease the superfluous intake of fatty acids. Well, let’s ponder over this, but in the meantime; undercover farmers, get ready for an increase in production! Stay well.
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The Microbial world of FULL CIRCLE
Full Circle is a specialized greens production farm in the Elgin Valley, Western Cape. Produce are grown in four hydroponics units in 3ha multi-span greenhouses. The farm produces several crops with special focus on soft herbs. Full Circle delivers to three retail chain groups with individual production programs for each of these.
C
obus Pienaar, CEO of Full Circle has an interesting background. Both his parents were in education, but in the broader family, a number were engaged in grains and sheep farming. Cobus became engaged in the technical arena and did product development for different companies. A culmination of circumstances offered him the opportunity to investigate intensive farming. Cobus was fascinated by this farming sector and it led him to new prospects. This resulted that even now, eleven years later he is looking forward to new horizons in this
exciting field. “The microbial world is phenomenal and plays a cardinal role in plant development. My background in research and development continually produces new applications under the microscope. Through close cooperation with local and international experts, we developed a unique growing process called the Integrated Growing Method (IGM),” Cobus explains. “IGM put us in the position to grow purely organic, semi-organic and even purely conventional by using hydroponic techniques. Depending on the market and product requirements, we are able to interchange between the different methods relatively quickly,” he said. “Haygrove is an important role player in Full Circle’s business. Their knowledge and experience made it possible to make quick decisions at strategic times. Their continuous interaction with Full Circle is
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most important especially when it comes to new product development and best practice innovation. A unique function of Haygrove is its capacity to integrate historic product lines with developments without drama,” Cobus said, much impressed. Full Circle uses two different grow methods. Firstly, DWC (Deep Water Culture) and secondly organic media beds are used. This allows them to acquire high plant density (up to 1100/m2). They use both active and passive control over the most important parameters during the growth process. The process is dynamic and important to manage with precision. If control is lost, it is very challenging to get back to the flow of the process. “Wastage in any business is a bad principle, especially in intensive farming. We invest continually in research and development activities with a view on improved utilization of all our inputs. This results in continuous improvement in profitability and sustainability. “Water is one of our most important input resources. Through IGM we are able to recirculate our water and only add when required. We never have to discard water
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like in conventional hydroponics systems. Water remaining in our DWC system has been there for almost ten years,” Cobus said. Each crop has its own unique preferences, which makes management quite challenging. Over and above temperature and humidity, there are plant feed requirements and dynamic water parameters which require proper management. Dissolved oxygen, pH fluctuations and water temperature were initial challenges for which Full Circle needed solutions. Also, a solution is only a solution when it is cost-effective.
Training staff takes place regularly at Full Circle.
Innovation and dedication to problem solving – for sure characteristics every farmer should have. Greenhouse farming offers a buffer against environmental changes in any climate zone. Though, all implicates costs to the producer. Cost effective interventions and control systems remains a challenge but it is for the individual farmer to decide how solutions will be applied. “At Full Circle we intend to function along with nature and the environment as far as possible; rather than fight against it. This influences the crops and seasonal cultivar choices we make. In our specific market it is all important to deliver sustainable supplies during 52 weeks of the year. “Labour is one of our main cost drivers. We have specialist teams that rotate between production units to maximise labour efficiency. To us it is important to keep the teams stimulated otherwise their daily tasks can quickly become boring, which in turn may lead to other problems. “We primarily deliver to pack houses which packs for retail chain groups. The relationship between producer, packer and consumer is most important and demands years of dedication. Trust and mutual agreement are not built without sustained dedicated effort. Full Circle is
Cobus Pienaar of Full Circle Farm
Global Gap and Farming for The Future Certified and committed to continually strive for improvements in all we do. “The future looks pretty attractive for our business. There are numerous opportunities in which to expand our horizon. However, Rome was not built in a day and therefore we take each step with careful planning. The consumer determines what we do and when we are able to do so. It is a dynamic relationship that we respect and value very much,” Cobus Pienaar of Full Circle concluded. JS
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Agricultural produce agents’ council (APAC) -
A look at fresh produce markets
F
rancois Knowles, Registrar and CEO at the Agricultural Produce Agents Council (APAC) has a long history in the Fresh Produce industry. Undercover Farming interviewed him prior to the Undercover Farming Western Cape Conference 2021, where he will also be presenting an overview on APAC and the current state of the fresh produce industry that he regulates. Francois shared figures for the 12 months (1 July 2020 to 30 June 2021) relating to the turnover and mass sales which are handled by 23 Fresh Produce Markets around the country and 16 Off-market Agents (Agencies performing under the same rules as Fresh Produce markets). In total 39 market platforms handles fresh produce in South Africa (SA).
of inflation, price increases, etc.). “We are perturbed over volume figures reported by markets. In the same year a growth was reported, there was a decrease of 11.7% in volumes sold at markets. This could largely be due to the influence of the Covid-19 epidemiology, adverse weather conditions which influenced optimal production, logistical problems at chain groups and unfortunately, the lootings in Kwa-Zulu Natal.
INCREASED TURNOVER According to Francois, the turnover figures up to 30 June 2021 indicated R20.04MM against the previous book year’s R18.2MM (Growth 9.8%; taking into account growth
APAC advises that security at fresh produce markets should be upgraded. If conditions are not safe for buyers at markets, they will resist visiting such markets. There is a shortage in proper
A recent visit to a city market revealed the shocking conditions that can only be due to poor management. The market areas and general infrastructure that is totally neglected, poor service delivery and overall, dirty conditions in which no buyer or even public would want to do business, gave Francois the idea that management lost interest in their market.
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maintenance, and a gaping hole at the entrance gate is enough to have regular buyers turn away and seek other resources. Hygiene plays a major role at fresh produce markets; nobody will be in a buying spirit if there is dirt, smelly produce or other objects where foodstuff is displayed which actually should attract buyers. “Proper management is a precursor to a flourishing market – if it is not in place, disorder and eventually less buyers on the floor is imminent,” Francois said. COVID-19 2020 EWA Early warning action was taken when APAC met the management team at Johannesburg Market with representatives of market agents as they have foreseen problems which could arise during the pandemic period. Covid -19 protocols were designed as a team and a minimum requirements list was drawn up together. Hygiene measures included spraying of hands, wearing masks, keeping social
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distance, cleaning of premises, and more. APAC played a very pertinent part in establishing protocols at Johannesburg Market after which it was rolled out to the rest of South African markets. During the whole pandemic all markets were open for business as usual as it is an essential service. “At first, we experienced pressure on potato stocks, since informal markets closed as well as restaurants. Though, many new clients visited the fresh produce markets and consumers returned to purchasing basic foodstuffs. A small impact was experienced in the fruit sector as people purchased necessities. Generally speaking, markets did not do bad at all and held their own through the Pandemic,” Francois said. “The first signs of Covid-19 appeared at the Pietermaritzburg market in April 2020, but with APAC’s protocols in place, processes were fast-paced to keep the market on an even keel. As such, I am confident and proud of our markets to come through the Covid period smoothly,” Francois mentioned. COMPETITION COMMISSION During the pandemic, the Competition Commission responded with concern to the President’s request that food prices be stabilized. On behalf of APAC, Francois approached the Commission when fresh produce prices soared. He explained advantages of price discovery to markets. Once one stirs at demand and supply, it is possible to sow devastation in the industry. There were out-of-the-middle lane lines such as garlic and ginger, of which either home-made medicines, or beer from pineapples was made. Therefore ginger jumped up to R2 000.00 per ten kilogram box at a stage. The Competition Commission immediately asked APAC to answer why ginger skyrocketed and suitable answers were given to have them understand the tendencies and influences which factored price. KZN LOOTING The disastrous lootings at business premises in KZN, immediately had market managers and agents at Durban and Pietermaritzburg defend their individual markets in solidarity. Thus the market at Pietermaritzburg was closed for only four days and Durban five days. APAC arranged with Potatoes SA and the main tomato producers to carry on with supplies to the markets. Generally, markets were functioning at full capacity by the fifth day.
EXPORTS markets as this increase adds to the numbers who have to be fed. Looking “During the Covid-19 period Transnet at the decreasing figures of produce Port Terminals declared themselves reaching the current market floors, it a ‘force majeure.’ On 22 July their can only reach consumers through other computer system was hacked and held channels. Therefore, if the fresh produce ‘hostage’, with the result the system markets do not increase their customer’s could not handle in- and exports and the (producers, agencies) awareness and logistics around fresh produce cargo. satisfaction, the number of farmers The only conclusion drawn is that it was marketing their produce directly or blatantly mismanaged. Durban Harbour through other means to retailers or handles around 60% of containers consumers, will increase,” Francois arriving in, and being transported from Knowles warned. South Africa. “Markets are where prime prices are Therefore, over and above the looting obtained and are the only firm platforms acts, Covid pandemic and a poor where consumers are able to gauge economy, this incident added to their whether the price they see at different demise. Throughout this incident APAC stores are on par with market-related was involved to assist with whatever was prices. Another major reason why fresh required and to use this as a learning produce markets are important is to curve for future similar situations offer the semi-commercial producer a elsewhere. place where prices are negotiated at a Fresh produce export agencies were level that is acceptable by the average under pressure while APAC was involved consumer – much different from where in keeping harbours open for in and he have to subject to a single consumer exports from the country. Harbours are or dealer’s offer for his produce. still far from operating optimally and only “Private markets are on the rise in because of poor Transnet infrastructure. recent times. These are not subjected The harbours are unquestionably an to municipal regulations and lengthy important factor to the economy of any administrative issues, therefore much country and government must be held easier to deal with by the producer. accountable for concurrent investment 8 and maintenance of such infrastructure. There were blockages in harbours as far Worldwide Expertise for Food & Flowers as export flow is concerned, but through APAC involvement, these were sorted out to a large extent. WAY FORWARD “According to available statistics, The SA population count reached 60 million people. The increase of the population (with deaths calculated) is about 750 k annually. This is an unbelievable opportunity for fresh produce producers and
Specialists in Horticulture More information? Herbert Stolker Consultant KZN, Gauteng, Mpumalanga and Limpopo T +27 (0) 72 545 5757 E h.stolker@delphy.nl
Yulandi Holtzhausen Consultant Cape Town region T +27 (0) 82 896 2156 E y.holtzhausen@delphy.nl
www.delphy.nl
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Cherry irrigation
Although often not the most expensive part of an undercover growing system, the irrigation infrastructure can be likened to the cardiovascular system of the human body – the essential system responsible for conveying water and nutrients to our highvalue, sensitive crops being grown in the climatic environment created in tunnels or greenhouses.
Getting the most
from your irrigation system
T
he role of the irrigation designer entails not only planning the system in terms of water and energy requirements based on sound principles as one would for any new irrigation system, but due to the nature of undercover irrigation systems also giving particular attention to the quality of the water supply, carefully selecting the most appropriate micro-irrigation system for the growing system, and making provision for the water required for climate control and other peripheral systems. Undercover crops are often sensitive to pH, and nutrient dosing require EC monitoring and control. The water supply may therefore require pH correction through acid injection, and the correct nutrient dosing system must be specified to be able to maintain the required injection rates. The effectiveness of the
automatic dosing machines must also be checked in the field with an appropriate monitoring system using handheld EC meters.
plants need to be irrigated, overhead irrigation by means of micro-sprinklers is used. In all applications, the use of high-quality products from reputable As far as the irrigation system is concerned, water is manufacturers is of most often point-applied to great importance to ensure uniform water the growing medium or soil applications.
Physical water quality also has to be addressed by means of effective automatic filters to remove any with drip irrigation. physical impurities Where crops are from the water before grown in soil bags or it enters the system, to prevent clogging of pots, or in the case of hydroponic systems, emitters. consideration must also be given to the drainage and/or recirculation system. This As far as the irrigation system is will entail careful planning of the whole concerned, water is most often pointsystem to ensure that it is laid out at applied to the growing medium or soil suitable angles for water to drain correctly, with drip irrigation. Inline drip irrigation and designing the necessary systems to is mostly used in soil, while button drip remove or recirculate the drainage water. with tubes and stakes are used in growing bags and pots. In the case of nurseries where high concentrations of small
The irrigation designer may also be required to make provision for additional
APAC presented to the Committee in person.
license. There is also the need to create Trust accounts at livestock and export agencies. They will have to fund towards the Fidelity Fund (the same as fresh produce agencies currently do) which enables to assist a producer which lost money through an agency default (in case of theft and fraud).
8 FRESH PRODUCE However, these outlets need to have a market agent or more to ensure a steady flow of the main consumer lines such as potatoes, cabbages, beans, onions and more. This effects an on-going flow to the market by retailers and spaza shop keepers,” according to Francois. CHANGING THE ACT APAC is currently busy changing their Act (Act 12, 1992) and they have now prepared a new Act with Department changes. This was discussed with Minister for Agriculture, Mrs Thoko Didiza and presented to the Agricultural Committee to be passed by Parliament. Francois Knowles in his capacity as Registrar at
The Department of Agriculture’s main reason for changing the Act is to enable us to increase our service level to the producer and also to protect him in his dealing with fresh produce agents. At the same time, this will benefit the markets too. Currently the market agencies perform well and within regulations, but export and livestock agencies also need to be regulated far better. In essence, if an export agent or livestock agent steps over the line in terms of ethics or undesirable business related acts, APAC should be able to execute disciplinary hearings which may lead to the offender losing his business
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“Communications between APAC and agencies, markets, producers and local and National Government is sharpened up to fulfil in the needs of feeding millions of hungry mouths and rebuilding trust in a South African food chain; exports and all that runs efficient,” Francois concluded. JS
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water distribution infrastructure such as overhead cooling systems using misting sprinklers or wet walls for evaporative cooling. Furthermore, a system for supplying clean water to different parts of the farm may be required for filling of fertiliser tanks or hand water in the grow houses. The relationship between the grower and the irrigation designer is of great importance to ensure the most appropriate system is planned from the start and management problems are addressed timeously for the grower to get the optimum benefit from the
irrigation system. As intensive growing systems are often developed in phases due to the capital costs involved, a long term partnership between grower and designer is needed to ensure smooth and
sustainable implementation of irrigation infrastructure across phases. By: Isobel van der Stoep, Cherry Irrigation
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Fresh Plaza
SA LOGISTICS
Versus Citrus Industry Growth
S
outh Africa is the second-biggest exporter of citrus in the world after Spain, the largest in the southern hemisphere and the global leader in long-distance exporting. Exports account for 95% of earnings from citrus, which overtook wine as South Africa’s largest agricultural export in 2010. The citrus sector is SA’s prime value earner in terms of exports and responsible for the employment of some 120 000 citizens, making it the biggest employer in the agricultural space. An exceptional performance by the citrus industry saw production grow 25% between 2019 and 2020, making the sector one of the success stories in a dismal year for economic growth. With a few weeks of the 2021 export season left, output is expected to grow another 6% from 150 million cartons produced in 2020 to 159 million cartons this year. This is slightly down on the projected 163 million cartons, largely due to smaller fruit than anticipated, and the stronger rand will mean lower returns to the farms.
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Logistics concern But, in the long term there is increasing concern about the substantial impact that South Africa’s failing logistics infrastructure could have on the sector and its significant contribution to our economy. This will become more pronounced if not addressed without delay, as citrus output is expected to grow to 200 million cartons in the next five years and to 260 million cartons by 2030. The large-scale geographic spread of the citrus industry means that some growers truck fruit more than a thousand kilometres to their nearest port, so the road infrastructure presents the first challenge. In particular, roads in and around Durban’s port become heavily congested, particularly over the past two years when bumper grain harvests have coincided with record citrus harvests. Ports at 30% In the World Bank and IHS Markit’s
I Volume 18 No 5
Comparative Assessment of Container Port Performance, South Africa’s ports of Cape Town, Gqeberha, Durban and Coega were at the bottom of 351 ports in various countries. Our ports operate at around 30% of international norms, which means that all of them are processing a third of what they could in a day in terms of loading and offloading containers. Add to this the pandemic-induced disruption in global shipping lines, growing container ship shortages and costs, theft of Transnet infrastructure, and most recently, the port cyberattacks, and we have a challenging situation at our ports that threatens the outstanding efforts of the South African citrus industry. Is there a plan? The good news is that there have been coordinated efforts between significant
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logistics role-players such as Transnet and agricultural organisations, to address the challenges our exports face on their way to global markets. For example, about 80% of South Africa’s agricultural produce is transported by road, but a move from road to rail will require increased investment and security at rail lines to eliminate the constant theft of Transnet infrastructure. However, the Citrus Growers’ Association of Southern Africa (CGA) is working closely with Transnet Freight Rail to increase rail transportation of agricultural crops. In addition, the CGA has developed a medium- and long-term plan to alleviate the pressures around logistics, which includes finding alternatives to Transnetoperated ports, sourcing additional specialised reefer ships during citrus season, and a dedicated specialised reefer ship service between Cape Town and the European Union and Britain. Reefer ships are refrigerated cargo ships typically used to transport goods where the cold chain must not be interrupted. They are also quicker to load, making their turnaround times in South African ports shorter. Private Sector Participation The CGA has also identified an urgent
Citrus under drape nets – Smart net systems.
need for increased private sector participation. In fact, the Department of Public Enterprises recently announced a master plan for the Port of Durban to invest R100 billion worth of potential private investments into the port infrastructure, terminals and freight infrastructure over the next 10 years. The plan also sees the South African National Defence Force’s naval base and the bulk terminal, which houses the petroleum, chemicals, vegetable oils and lubricants operations, relocating to Richards Bay, which would become an
industrial port. The plan also includes upgrades to the road and railway network around the port and city to limit the high volumes of trucks causing bottlenecks. For the citrus industry, as with the rest of the agricultural sector, it is imperative to continue to identify areas that need improvement and engage with key logistics role-players and government to find solutions. By: John Hudson, Agricultural Head at Nedbank
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How Whitefly Pest Damages Greenhouse Tomato Crops Approximately 300 pests are known to attack vegetables in South Africa. Most of these pests may damage crops wherever they are grown, but a few are especially damaging under protected environments. A few common greenhouse pests include aphids, thrips, leafminers, whiteflies and red spider mites. Of these, whiteflies, when the adults are present, are the most easily recognizable because of their habit to fly up in strikingly white swarms when disturbed.
Figure 4. Sooty mould growing on tomato fruit.
W
hiteflies are not flies, but tiny white insects belonging to the same insect order as aphids, i.e. Hemiptera. They occur world-wide, and are common pests of crops that are planted in protected environments. They have piercing-sucking mouthparts and, like aphids, suck the sap from plants. Whiteflies attack a variety of agricultural crops, including potato, tomato, sweet potato, legumes, cucurbits, crucifers, lettuce, tobacco, cotton, cassava and various other crops and weeds. Approximately 16 whitefly species occur in South Africa, of which two, the tobacco whitefly, Bemisia tabaci, and the greenhouse whitefly, Trialeurodes vaporariorum, are commonly found on vegetables in greenhouses.
when leaves are turned upside down. They have a milky-white appearance, and are approximately 1–2 mm in length (Fig. 1). Whitefly nymphs (larvae) are very different in appearance from the adults. They are wingless and
translucent (Fig. 2 arrow) and become im-mobile after the first moult. Only the first instars (also called crawlers) are capable of moving around while searching for a feeding site on the
Figure 1. Whitefly adults on the underside of a potato leaf.
Whiteflies hide on the underside of leaves, and are usually only noticed
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undersides of leaves. Because of their translucency, they take on the colour of the leaf and are not often noticed. The nymphs resemble flat scale insects, and on some crops, e.g. cucurbit leaves, they are nearly invisible to the naked eye.
Figure 2. Whitefly adults with sedentary nymphs (white arrow).
Whiteflies may damage crops in three different ways. Firstly by direct feeding (sucking plant sap), secondly, by acting as vectors of virus diseases, and thirdly by producing copious amounts of honeydew. The sucking action of whiteflies does not always damage plants. However, when plants are very small or when plants are under stress, direct feeding may cause wilting and eventually yellowing of leaves and dieoff. Up to 50% yield losses have been reported on some crops, directly linked to whitefly feeding. However, serious yield losses may occur when certain viruses, e.g. the tomato curly stunt virus (ToCSV) or Gemini-viruses, are present in the ecosystem. Whiteflies may transmit these viruses when moving between healthy and infected plants. Viruses cause mal-formed and chlorotic leaves, stunted growth and poor yield. Heavy yield losses are usually encountered when young plants are infected. Similarly to a few other sucking pests, e.g. aphids and mealy-bugs, whiteflies are notorious for their honeydew secretions. Honeydew is the sweet, sticky, excretions of plant-feeding hemipterans, usually secreted in such a way that it always lands on the upper leaf surfaces lower down from their feeding sites. Sooty mould (Fig. 3) may grow on the honeydew on the leaves, eventually killing individual leaves. Sometimes entire plants may be killed, e.g. the potato plant in Fig. 3. Sooty moulds are saprophytic black or brown fungi that grow superficially on leaf and fruit surfaces (Fig. 4), on which honeydew has accumulated. Sooty mould colonies may consist of mixed populations of eight or more different fungal species belonging to different families of the order Dothideales. It does not cause disease, but may downgrade the value of produce because the sticky brown/black powdery growth does not easily rub off. The black layer of fungal growth also prevents photosynthesis and therefore interferes with physiological processes of the affected plant.
Figure 3. Sooty mould growing on potato leaves.
that are more harmful and difficult to control. It is important to be aware of the nymph stage of this pest. Control measures should be implemented before the nymphs change into adult flies which move between plants and transmit viruses.
on the undersides of leaves, is therefore necessary. Always read the insecticide label and use strictly according to label instructions. By: Dr Diedrich Visser; Crop Protection Division, ARC.
Good insecticide coverage, especially
Whiteflies can be controlled with various insecticides. However, certain strains (or biotypes) of the tobacco whitefly exist
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Looking at your Feeding Water Quality
T
he term ‘feeding water’ is used to describe an untreated water source that is available to prepare nutrient solutions for soil-less crop production. Different factors can be used to define feeding water quality, but the chemical composition as well as the presence of potentially dangerous micro-organisms needs special attention. Chemical composition Feeding water EC: The concentration of ions, measured as EC, can be used as an indication of the potential quality of feeding water. Water with a low EC can be used to grow any crop. High EC feeding water, usually high in sodium (Na+), magnesium (Mg2+), sulphate (SO42-) and chloride (Cl-) can only be used to grow saline-tolerant crops. These include amaranths, Swiss chard and cherry tomatoes. Examples of crops that are extremely sensitive to saline conditions are blueberries, disas, anthurium, cymbidium and roses. Most of the remaining greenhouse crops vary between moderately sensitive to moderately tolerant, as can be deducted from the EC levels, associated with the nutrient solutions as recommended for different crops. It should be kept in mind that the absorption of water is restricted at increased root zone EC levels. The water in the lake of Galilee is widely used in
Israel, even though it has an EC of ±1.0 mS cm-1. The EC of water in the Vaal Dam varies between 0.3 and 0.9 mS cm-1 but the EC in the lower Vaal River may be higher in relatively dry seasons. Compared to this, the quality of Stellenbosch’s water is excellent, with an EC of about 0.1 mS cm-1, as is also found in other water streams from unpolluted, high rainfall mountainous areas. However, there is no guarantee that water with a low EC can safely be used for soil-less crop production, since micronutrients may be present at phytotoxic levels without affecting the EC. Two examples are high zinc (Zn) levels in rainwater gathered from galvanised roof surfaces and high copper (Cu) levels where copper water pipes are used. Macronutrients in feeding water Water should be chemically analysed in order to determine the levels of the different nutrients in solution. In low rainfall areas, high levels of salts are usually present. Apart from Na+ and Cl-, high levels of essential nutrients such as calcium (Ca2+) magnesium (Mg2+) and sulphate (SO42-) may also be present in high-EC water. The other essential ions are usually found at lower concentrations, depending on the area and the water source. The higher the ratio of useful ions compared to Na+ and Cl-, the better the potential of the water. These
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essential nutrients should be topped up to optimum levels. Since Mg2+ may be present at high concentrations in high-EC water, it may reach toxic levels when Mg fertilizers are simply added to the water at normal recipe levels. A high Mg2+ concentration in nutrient solution may restrict the uptake of Ca2+ and K+. Micronutrients in feeding water Apart from high sodium, chloride or macronutrient levels in high-EC water, it may also contain high or toxic micronutrient levels. Micronutrients are usually present at such low concentrations that even at relatively high micronutrient concentrations they do not affect EC readings. Should feeding water contain micronutrients at high levels, exceeding the concentrations prescribed for different crops (consult your crop specialist) the water should be avoided or handled with care. As with macronutrients, the micronutrient levels in feeding water should be considered when planning nutrient solutions and should be topped up to optimum levels. Micronutrient phyto-toxicity Strawberries need relatively low boron (B) levels due to physiological problems with B at >0.32 mg L-1. Tomatoes can tolerate B at levels of up to 1.1 mg L-1, almost four times higher than the recommended level. It is recommend
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Growing Greenhouse Cannabis – THE BASICS Cannabis grown in a greenhouse can be set up in either one of two ways. The grower may grow the plants in separate containers or pots, or plant them straight in soil. There are advantages and disadvantages for both options, but basically it depends on what fits best for the producer’s production site and his business strategy.
B
y choosing the container route, it makes it easier to move the growing plants whenever necessary. This is particularly handy as one can simply move the plants elsewhere. Another reason to move the container-grown plants might be if the greenhouse or shade net structure needs replacement. Should the grower wish to plant cannabis directly into the ground on the other hand, the plants will produce much better when they are left alone for a longer period of time (such as a week). Naturally, this is only to be expected if the soil they are planted in was properly prepared with the necessary nutrients and remain at the right pH level. Another option exists for more innovative greenhouse growers: hydroponics. Producers who used this method in a greenhouse have had big success, making it a potentially good idea if it suits your lifestyle and experience. Of all the growing methods, hydroponics is known to provide the highest potential yield. If done right, growing marijuana in water indoors can maximize your plant’s growth. Cannabis genetics The most important advice is to buy high-quality cannabis seeds. It is worth the extra financial outlay to be assured
of setting up for a successful growing season. Should the grower obtain poor quality seeds instead, then he may not achieve the same level of success, no matter how much effort and time is spent on caring for the plants. Buy high quality seeds to get best result One of the best things about really intensive greenhouse growing is that it can be highly automated. In other words, it can be much easier for the grower because they don’t need to do as much day-to-day care for their plants. One such automated system is a watering system that delivers water to the plants automatically, or with little effort on the grower’s part.
Automatic irrigation in the greenhouse (Pic GPN news) A grower may want to consider installing some automated systems of your own if he is technically innovative and enjoys planning such things ahead of time; if he has a high enough budget for it, and if he don’t enjoy the daily tasks of cannabis plant care as much as the setting up process. Important: Security A good way to keep the cannabis plants safe from detection if the greenhouse is not located in an inconspicuous or private location, is to paint the exterior with
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white shading paint. You can find this at a garden centre, and it serves the dual purpose of preventing the greenhouse from getting far too hot on the warmest days during the summer. When you have a painted greenhouse, people will not be able to peer inside and identify what you are growing. Start early To truly take advantage of growing cannabis plants inside a greenhouse, try starting the growing season early this year. This is possible as greenhouses get much warmer than the outside temperature once the sun is out fully. More sun makes it possible to start growing earlier Since the growing season is started earlier, the producer has more time for the vegetation phase of the cannabis plants. When you have more time for the vegetation phase, your cannabis plants will be bigger and stronger for the flowering phase. As a result, your harvest at the end will be much better. The key to doing this successfully is not to allow the greenhouse to get too cold at night during the early part of the season. You can do this by installing greenhouse heaters, found at your local garden centre, to be run during cold nights. This ability to lengthen the growing season for cannabis plants is one big reason why, and an increasing number of cannabis growers are opting to grow
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their plants in a greenhouse instead of an indoor or outdoor setup. These plants have the opportunity to grow far greater in size than their outdoor counterparts, assuming the seed genetics, soil, and other care aspects are sound. Believe it or not, some growers have even opted to grow just one big plant in their greenhouse setup — and that plant gave them hundreds of grams of high-quality buds at the end of it. If the plant starts getting too out of control, it could actually start growing out through any open windows that might be in your greenhouse, and therefore steps need to be taken to “tame” the plant. This is best done via tying techniques. One big plant in a greenhouse It is a good problem to have, but growing gigantic cannabis plants is not necessarily an easy thing to deal with. Properly
grown, fully maximized cannabis plants cultivated in a greenhouse will be tall and extremely bushy. This is particularly true if you have been giving your plants huge amount of space in the soil for their roots, good quality soil to begin with, land lots of sun. Make sure you are prepared for the “worst.” Using a darkening system Many greenhouse growers will opt to use what is known as a “darkening” system which, when set up correctly, should be dark enough that there is a complete blackout within the greenhouse — even during the middle of a sunny afternoon. The point of installing a darkening system is to simulate shorter days and longer uninterrupted nights, thus spurring your cannabis plants into an early flowering phase.
Maximizing your cannabis greenhouse setup This is an expensive addition, but it will certainly ensure that you acquire your cannabis much faster than if you waited for the natural sunlight conditions to change over the course of the season. The way to “trick” your plants into entering the flowering season early is to have 12 hours of uninterrupted darkness and 12 hours of sunlight every day without fail. The darkness is the most important part of this process — you must not allow any light in at any point, even for an instant. After a couple weeks of this, you should start seeing signs of flowering. Extending the growing season A greenhouse can also be the perfect environment for manipulating the length of the end of your marijuana plants’ growing season. Many growers choose to use this to their advantage and lengthen the end of the growing season. High yield while growing in a greenhouse The main reason why a greenhouse is beneficial in this way is that it keeps the air around the plants (in other words, the air inside the greenhouse) toasty warm when it is sunny while the colder temperatures of autumn are creeping in. Source: Growing Marijuana by Robert Bergman Read more about greenhouse cannabis growing in the next edition of Undercover Farming.
14 WATER QUALITY that Zn be used at 0.33 mg L-1 for substrate-grown tomatoes, but toxicity can be expected at only twice this concentration. High Zn-levels are usually found in water gathered from galvanised roof surfaces. Copper-sulphate is a well-known chemical, used to kill algae in swimming pools. Thus, the potential phytotoxic effect of high Cu-levels is well-known. Most crops need Cu at 0.05 mg L-1. According to Steiner (1984), Cu may be phytotoxic when its concentration is doubled to 0.1 mg L-1. Copper pipes should thus be avoided in hydroponic units.
Manganese toxicity problems may develop on lettuce (open or loose tulip shaped heads) where seedlings are raised on sphagnum peat, due to high levels of Mn in this European substrate. High iron (Fe) and manganese (Mn) levels in some feeding water sources may block irrigation drippers. These water sources should be treated to lower Fe and Mn levels. Total alkalinity (pH) The pH of water and nutrient solutions can be manipulated by adjusting the total alkalinity. Total alkalinity is the aggregate concentration of carbonate, bicarbonate
and hydroxide. The total of these ions (CO32- & HCO3 - & OH-) in water is determined with a titration, by adding acid to the sample until the pH reaches a level of 4.5. Some water-soluble fertilizers may be slightly acidic. Thus, the total alkalinity of the water should not be too small to prevent the pH from dropping when these fertilizers are dissolved. It is important to adhere to these factors when serving greenhouse plants with a balanced diet of water through the irrigation system! By Dr NJJ Combrink from his book: Nutrient Solutions Management.
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Aquaculture: Biological Filters prevent Poisoning of Fish In recirculating aquaculture systems (RAS) water is cycled continuously from the fish through filtration and temperature control systems, and back to the fish. The temperature control enables one to farm fish species under ideal conditions year round, getting them to market sizes on time, disease free, with improved health, reducing mortalities and enabling producers to farm the fish outside of the natural climatic zones.
“H
owever, to best justify the capital cost of a RAS, we hold the fish at the same sort of high densities that are used in cage farming, resulting in lots of metabolic wastes being released into the water. This in turn would poison the fish if it was allowed to accumulate, and the biological filter (biofilter) is there to prevent this from happening,” Leslie Ter Morshuizen of Aquaculture Africa said.
Many types of biological filters have been used over the years but in the past 2 decades an almost complete shift came by using fluidised filters. Inert, neutrally buoyant media is placed
An example of a homemade biofilter for an Aquaponics unit. For a commercial unit there are professionally manufactured filters available.
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inside the filter tank and vigorously stirred by means of aeration from below. Water enters the filter at a convenient point and exits elsewhere, the position of these two points typically being opposite each other to allow for maximum residence time. Two groups of bacteria arrive and colonise the media; they will arrive on their own in association with the fish but can be added to the system in various ways, but this is not necessary. The first group convert the ammonia, excreted by the fish, to nitrite, and the second group convert the nitrite to nitrate. Nitrate is only mildly toxic to fish and as such can accumulate to much higher
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concentrations in the recirculating water before a water change or the addition of plants through aquaponics, is required to prevent it from increasing further. In this way the biofilter enables fish farmers using RAS technology to stock their fish at far higher densities and heat the water cost effectively, as water changes are only infrequently required. The biofilter bacteria are aerobic and oxygen levels above 4 mg/ℓ are essential for this conversion to occur fully. In addition, the breakdown of ammonia via nitrite to nitrate utilises alkalinity, and as such the pH of the water needs to be managed to prevent it from falling. A final consideration is that the biofilter
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SEPTEMBER/OCTOBER 2021
I VOLUME 18 NO 5 I I R45.00 per issue
For more information contact Suzannne Oosthuizen (+27) (0) 82 832 1604 or e-mail suzanne@axxess.co.za
MICRO GREENS
OPTIMIZE IRRIGATION
WHITEFLY MANAGEMENT
AQUACULTURE FILTRATION
Micro greens at Full Circle Page 4
Optimal Irrigation methods Page 10
Whitefly damage on crops Page 14
Aquaculture Biofilters Page 16
Biofilters make RAS farming possible. These incredible little critters require minimal attention or care whilst performing an incredibly valuable function that enables us to harness the many benefits associated with farming fish in a RAS. By: Leslie Ter Morshuizen, AquacultureAfrica
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bacteria thrive at a temperature around 27°C, which is superb if you farm warm water fish but those farming cold water species require a relatively larger biofilter due to the slower rate of the ammonia conversion.
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