Vol 14 No 6
R30.00 (RSA) VAT & Postage incl.
BI-MONTHLY MAGAZINE FOR GREENHOUSE, TUNNEL, SHADE NET AND HYDROPONICS FARMERS
• Wolwekrans Farm: About personal attention • Growing peppers • Thrips in the greenhouse • Nanotechnology in agriculture?
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NOVEMBER | DECEMBER 2016
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BLESSED CHRISTMAS AND PROSPEROUS 2017 GESEËNDE KERSFEES EN VOORSPOEDIGE 2017
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Sakata tomatoes caters for local producers The agricultural industry has faced many challenges in recent years. It is thus reassuring that Sakata’s local tomato breeding programme is focused on releasing new varieties that are adapted for local environmental conditions. This is of course a major advantage to the tomato producer who needs to overcome major challenges when it comes to managing their crops and adapting to local conditions.
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akata’s tomato breeding station that is located at Sakata’s head office in Lanseria has recently added some new exciting varieties to the already well known indeterminate Salad tomatoes in the market. One of the main aspects of the Sakata varieties is that they are vigorous and fairly easy to manage. Irrigation and fertilizing is two very important factors that need to be managed when it comes to these varieties – especially not to over fertilize and irrigate at the early stage. Tomato producers should know that it is important to get good fruit set early on as this is beneficial for the entire crop cycle of the plant. Furthermore, having consistence in fruit set, both in number of fruit and fruit size is also very important. Inga* is one of the newest indeterminate Salad varieties that comes out of the local programme and this variety is sure to make a difference in the market. Inga* is well adapted for local condition and good results were obtained under protection. The variety is characterized by outstanding fruit quality and uniform fruit size. The distribution of size for large to medium size fruit is very good which enables the producer to use Inga* over various
packing sizes, from boxes to the 1kg bags. Inga* has a compact growth habit, but with good vigour, especially later in the season. The fruit size is also maintained later in the season. Inga* performed well in winter conditions in the moderate climatic areas and colour up was excellent. Yield is comparable to opposition varieties with quality also being outstanding. The variety has a strong root system and performs well without grafting. Inga* has resistance to Tomato spotted wilt virus, which is one of the viruses that is occurring in most of the production areas, although it is sporadic. There are other new releases from the Sakata programme that is also sure to make a difference in the market. Jasmine* is but one of these varieties, which is adaptable for both open field production and under protection, with Tomato spotted wilt and Tomato curly stunt virus. For more information on Sakata’s tomato varieties or to view the whole product range, visit the website at www.sakata.co.za. *Experimental: This variety does not appear on the current South African Variety list, but has been submitted for registration.
DISCLAIMER: This information is based on our observations and/or information from other sources. As crop performance depends on the interaction between the genetic potential of the seed, its physiological characteristics, and the environment, including management, we give no warranty express or implied, for the performance of crops relative to the information given nor do we accept any liability for any loss, direct or consequential, that may arise from whatsoever cause. Please read the Sakata Seed Southern Africa (Pty) Ltd Conditions of Sale before ordering seed.
Tel: 011 548 2800 www.sakata.co.za e-mail: info.saf@sakata.eu
PROPRIETOR / ADVERTISING SUZANNE OOSTHUIZEN 012-543 0880 / 082 832 1604 Email: suzanne@pop.co.za EDITORIAL CONTENT & COMPILATION Johan Swiegers 082 882 7023 editor@pop.co.za SUBSCRIPTIONS Annual Subscription R 180.00 (RSA only) (VAT. Incl.) ONLINE SUBSCRIPTIONS Email to ucoverfmg@pop.co.za ADDRESS PO Box 759, Montana Park 0159 E-MAIL ucoverfmg@pop.co.za
GREENHOUSE CHAT...
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ith only a few weeks before the Festive Season, it is all systems go for vegetables, fruit and flower growers under covered protection of plastic tunnels or multi-spans or shade-net. It is the time of the year for company parties, organisations and family festivities. These all call for greens, vegetables, fruit and floral décor. We will be most satisfied if all our readers who are in to production of these do exceedingly well this season. I spoke to a person who wants to start with greenhouse farming ‘because it looks so wonderfully technical and you do not need hundreds of hectares’. I have learnt about these in the past fourteen years in the industry to immediately wake a newcomer up to the facts of greenhouse farming without putting him or her off the challenge. Because to progress and become successful poses a challenge. Our main story in this edition is about a female who took up the challenge and does very well with her multispan and open land production. No sooner I visited the farm when a hailstorm followed with disastrous effect to a few farms along with hers. My first thoughts are about crop insurance or some form of financial protection in cases like these. This does not happen every season. But maize and other open land crops can be covered with crop insurance and infrastructure on the farm can be covered too. Why can’t the greenhouse industry not lobby with an insurance company to obtain cover for their operations too? Good luck to those who will make it through the patched heavy electric storms we currently experience! Thank you for our faithful supporters during 2016 and we are looking forward to a prosperous 2017 for all undercover farmers. Ed.
FAX 086 518 3430 ADDRESS PO Box 759, Montana Park 0159 DESIGN Fréda van Wyk PRINTING All Trade 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. Copyright is reserved and the content may only be reproduced with the consent of the Editor.
Another Day, Another Month, Another Year, Another Smile, Another Tear Another Winter, Another Summer too! COMPLIMENTS OF THE SEASON. Wishing you & your family a Merry Christmas and a FABULOUS New Year. Keep Safe & Enjoy. Best Wishes From all at Undercover Farming
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FRONT PAGE: Greet Tijssen in her multispan with cucumber plants. See pages 4 & 5.
Sakata tomatoes caters for local producers 2 Wolwekrans farm: personal attention perfects production 4 Managing wastewater from intensive horticulture: a wetland system 6 So you want to produce peppers? 8 Thrips in greenhouse crops – biology, damage and management 11 Maarten D Koppenol – RIP 11 Speedline offers top quality of synthetic monofilaments to greenhouse farmers 13 New ways to extend shelf-life of produce 15 Nanotechnology: Engineering better building blocks for agriculture 16 The purpose and advantages of a screening system 17 Seed Company is celebrating their 15th year of business… 18 A letter from a visitor to a prospering young greenhouse farmer 19 Subscription form 19
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Contents • Inhoud
Wolwekrans farm: personal attention perfects production
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The Wolwekrans Farm's multispan in neat surroundings.
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Greet Tijssen might be taken for the teacher she used to be, or patient female with compassion for disabled or the aged. Actually, behind the friendly and welcoming face, a strong willed female farmer stands firm in her passion for her business, those that work for her and her family.
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and therefore difficult to plan ahead especially if the producer has no steady olwekrans used to be a chrysanthemum farm years ago. supply contract with a major chain outlet. To Greet quality is top priority and With the slump in the cut flower business the farm came must be adhered to at all times. Therefore, already some of the chain stores into the market and Greet’s father in law decided to have indicated that her quality meets their standards and intermittently they purchase the land with intent to make use of it at a later do business with Greet. She currently supplies the Johannesburg market stage. The farm of about 40 hectares is in the Wolwekrans and around twelve steady clients that are worthwhile. Some producers that area, in the vicinity of Broederstroom. experience a shortfall on their capacity at times would also purchase from Greet started with fresh produce farming in 2013, not having any Wolwekrans Farm. knowledge of the industry whatsoever. She used to be a teacher and worked Already there are plans on the table for production of her salad with disabled people. Greet and her husband Herman and four children crops under shadenet, but currently she is constructing another multispan have been to the Netherlands for three and a half years. On their return for peppers. This bright female farmer does not believe in jumping into to South Africa she needed to get involved as it suits her personality – a venture before having all the therefore the farm owned by her father ducks in a row and prefer to rather in law, Dirk Tijssen provided her with increase production with what is an opportunity to start farming. She available to her right now rather was offered the farm to produce and than expanding simply to keep the decided to try her hand at cucumbers financial botttomline on an even under a 1,6ha plastic covered multi keel. span and broccoli, salads and sweet The temperature in the Wolwe corn on open land adjacent to the krans area drops to far below zero multispan. The cucumbers are planted directly into the soil after proper soil analysis and preparation has been implemented. Overhead sprinklers Another multispan is being are used to moisten the plants and constructed for pepper to apply fertilizer. Dirk Tijssen still production. is Greets’ mentor and she admits that her father in law plays a major A bunded tank stores the hot water after it role in her business life on the farm. was circulated in order to save on coal. The Tijssen family is well known in agricultural circles and Greet enjoys the benefit of their accumulative experience over many years in the business. Fortunately for her, she has the advantage of three boreholes on the farm, providing potable water in a steady supply for her farming operation. The water is of such good quality filtration is not necessary. The market for salads is unstable To page 5
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more farmers planted cucumbers and flooded the market, but Greet’s aim is to produce throughout the year and she also does intercropping in order to utilise her production space optimally throughout the year. During the past winter it was never necessary to heat up the greenhouse – a saving grace, as the cucumber prices was so low it would have been difficult to play even. Currently the insect pest that is more prevalent is Thrips which is controlled by spraying, although Greet applies biological control as far as possible on the farm. During the first two years on the farm all seedlings were purchased, but Greet Tijssen now grows her own seedlings. Only the cucumber seedlings are purchased from Multiplant outside Brits. The personal attention to detail, Dennis van den Burg of Greenzone visits Greet's farm regularly to assist with advice. sharp eye for anything that may go wrong and a will to make a success of her farming enterprise places Greet Tijssen in winter – she even experienced minus fifteen degrees Celcius in 2015, among the remarkable women in agriculture. Being mother of four, wife to therefore the production facility makes use of a coal-fired boiler to heat up a husband with own business and running a fresh produce farm takes wit, the greenhouse but, in order to minimise the coal account, a bunded tank passion and perseverance. is installed in which the water is stored at reasonable warm temperature. Dennis van den Burg of Greenzone supplies the accessories required Before it is run through the greenhouse, less coal is used to get the water during production and is a friend of the Tijssens over many years. His temperature up to the degrees required. Greet expressed her future wish regular visits to Greet’s enterprise are valuable as his background is also to be able to install solar energy panels to save on mineral and municipal Dutch farming and his experience of undercover farming adds value to energy expenses. Wolwekrans Farm. Cucumber prices were excellent during 2015 but fell in 2016 as
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From page 4 WOLWEKRANS FARM
Managing wastewater from intensive horticulture: a wetland system
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Wastewater or ‘run-off’ from intensive horticulture usually contains a high level of nutrients – and possibly some sediments and plant pathogens. Described as nutrient-loaded, this wastewater is defined as effluent. Responsible land use is about preventing wastewater from entering the environment. High nutrient and sediment loads can cause environmental problems, such as algal blooms and fish kills.
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olid matter and sediment in wastewater originate from soil-based production systems and may include organic matter as well as sand and clay particles. Hydroponic media can also be a source of solid materials carried in wastewater – for example, commonly used growing media, such as sawdust and perlite. Turbidity can be used as a measure of how much sediment is in the water. As the level of sediment increases, so does the turbidity of water. Water appears cloudy or muddy when turbidity exceeds 5 NTU (Nephelometric Turbidity Unit is a unit for measuring suspended matter in water). Sediments can result in blockages in irrigation equipment and, in the environment, can be harmful to some aquatic animals. Furthermore, if the water is being reused and requires disinfection, turbidity needs to be less than 1 NTU. This is because sediment and organic matter in the water impair some methods of disinfection.
build up of salts around the plant roots by washing them out of the growing medium. RESIDUAL NUTRIENT SOLUTION The second type of wastewater is the residual nutrient solution that is periodically replaced – dumped – in re-circulating systems or when a nutritional or disease problem arises. In the latter situation, discarding the nutrient solution and starting again is often the most economic option.
WHAT TO DO WITH WASTEWATER
Nitrogen and phosphorus
The first step in managing wastewater is to contain it on-farm so that nutrients and sediments can be removed from the water. An advantage of hydroponics is that the nutrient solution is a known quantity and concentration and is readily collected from the hydroponics system. As a result, it is easier to manage wastewater responsibly in a hydroponics system. Cleaning the wastewater means removing or reducing the sediment and the nutrient load. A number of methods can be used to stop nutrients and sediments being carried into watercourses, including bio-filtration (wetlands), filtration, evaporation and reverse osmosis. Soil production systems will have a lot more sediment than hydroponics systems, while both systems may have relatively high amounts of nutrients.
SOIL PRODUCTION
THE TWO KEY NUTRIENT POLLUTANTS FOUND IN WASTEWATER ARE PHOSPHATES AND NITRATES Phosphates tend to be attached to sediments, particularly clay particles, and can be removed through sedimentation. Nitrates are highly soluble compounds, which can be removed by plant uptake and biological conversion to nitrogen gas. In wetlands, conversion to nitrogen gas is the main process of removal. The nitrogen gas is released into the atmosphere. Nitrogen is also taken up by growing plants. The organic matter produced by the growing plants can be used as a mop to pull some of the nutrients out of the water. Weeding, mowing and otherwise removing plant material then remove nutrients from the system. Green waste is much easier to manage than nutrients dissolved in water. Plant material can be composted, used in the garden or orchard, or disposed of through a local green-waste collection service. Once you have a system in place to manage the wastewater, you need to check that it works. Water samples should be taken from time to time and tested for the level of nutrients. Monitoring the system also includes carrying out routine maintenance.
Nitrate and nitrite are naturally occurring forms of nitrogen. In the natural water systems, total nitrogen levels of 0.1-0.75 mg/l contribute to algal blooms, though the level of phosphorus in water is often the key factor causing algal blooms. Total phosphorus levels of 0.01- 0.1mg/l contribute to algal blooms. Growth of algae in irrigation systems can also lead to clogging of drippers and filters. Total Dissolved Solids (TDS) TDS is a measure of the inorganic salts and small amounts of organic matter that are dissolved in water. Electrical conductivity (EC) can be used as an approximate measure of the TDS, where: EC (mS/cm) x 670 ≈ TDS (mg/L = ppm) High salt levels in water can impact on other agricultural activities. For example, while crops have varying degrees of tolerance to salt, yields of all crops ultimately decline as salt levels increase. Also, relatively low levels TDS in overhead irrigation can result in crop damage. In the environment, high levels of TDS can impact on aquatic organisms. In field production and soil-based greenhouse production, wastewater is often not even noticed as it drains away through the soil profile, moves off-farm as run-off and evaporates. As a result, the contaminants can be carried in the wastewater. Market gardens and intensive soilbased horticultural operations can address the problem of wastewater by containing run-off. Erosion of soil is a bigger concern in this industry than nutrient run-off. Nutrients and sediments should be removed. Drainage water from greenhouses and runoff from orchards and market gardens can be directed to a holding dam or tank. It can then be contained until the nutrients and sediments are removed.
WASTEWATER FROM HYDROPONICS There are two types of wastewater:
RUN-TO-WASTE The first type of wastewater comes from flowthrough hydroponic systems – often called ‘runto-waste’ – that use a soilless growing medium. It is possible to have no excess water from these systems. However, most growers will have wastewater because it makes the management of plants and nutrients easier. For example, applying more water than the plant uses can prevent the
The soil-based “constructed wetlands gives the waste water a final polish to remove the fine sediments and nitrogen.
PASSIVE WASTE WATER TREATMENT
An effective passive system can continually clean waste water with only minor maintenance and minimal running costs. A wetland-based system is such a system. It is passive, low cost and fairly low maintenance – needing only periodic removal of sediment and vegetation. A wetland-based waste water treatment system uses lessons learned from nature. In normal natural processes, run-off water carries sediments, nutrients and plant material into water courses. These natural ‘contaminants’ are used (and removed) by the micro-organisms, plants and animals downstream. Intensive farming – along with other activities such as residential develop ments – can lead to a higher level of nutrients To page 5
From page 6 MANAGING WASTEWATER
Using some of the principles of wetlands, and testing the efficiency of the components of a wetland, it is possible to identify key elements to use in designing feasible systems for individual farms. A feasible system must be compact, easy to build and flexible enough to incorporate existing components that might be found on a farm. The key tasks of a passive water treatment system are the removal of sediments and litter, the removal of nutrients – particularly nitrates and phosphates – and a sustainable maintenance program. Four basic components of a system are sediment traps, filter beds, wetlands and retention ponds.
BASIC PRINCIPLES SEDIMENT TRAP The sediment trap removes heavy sediment and litter from the water. A sediment trap is built so that materials settle out of the water or are left behind when the water moves on. The design needs to ensure that the trapped material can be easily removed for disposal. As phosphates tend to be attached to sediments, some of the phosphorus will be removed simply by capturing the sediment. Intensive farming systems however, often have a very high phosphate level in the run-off. To accommodate this, the sediment trap stage could possibly be modified to act as a strong phosphate filter using lime enriched sand. FILTER BED A soil based, vegetated area is used as a natural filter bed. This section removes fine sediments and the primary nitrate load. To ensure no nutrients are leached to the water table, this area is contained with a water tight barrier such as a plastic sheet or dam liner. Grass is an effective user of nitrogen and is also easy to maintain, making it useful for the filter bed area. By removing grass clippings, nutrients are taken out of the system. WETLAND The wetland stage of the system removes the remaining nutrients and gives the water a final ‘polish.’ This stage can either use a vegetated gravel bed through which the water flows (separated from the water table with a plastic barrier), defined here as an artificial wetland, or use a soil based, vegetated area (ideally, separated from the water table with a plastic barrier), defined here as a constructed wetland. RETENTION POND The retention pond is a deep holding area for cleaned water, before disposal or re-use. This component may be either a deep water section of a constructed wetland or a separate pond. A tank can also be used. The size of the system is based on the desired retention time for the water in the system. That is, the time taken from when the water enters the system to when it exits. The
MAINTENANCE
The concentration of nutrients in the effluent should be checked when planning the maintenance program. Maintenance is an important task and it must not be overlooked. In a wetland treatment system, one problem which can occur over time – is that the system can become saturated with nutrients. This is like a filter, which eventually clogs up if not cleaned. There are two parts to this problem. Net nutrient gain can occur. The system works by acting as a nutrient sink, that is, it uses more nutrients than it releases. Over time the plant material in the wetland system builds to a point where it actually contributes to the nutrient load in the water. While this is a natural result of a biological system, it is unwanted for obvious reasons. Maintenance of the system requires removal of plant material so that the system continues to use nutrients by growing more plants. Phosphorus tends to stick to sediments, such as clay particles, but the sediment can only hold a limited amount of phosphorus. Eventually the system becomes full, and no more phosphorus can be removed. The sediment trap could use sand and lime to increase the capture of phosphate. From time to time this sand is replaced to remove the phosphorus from the system. An underlying basis of the passive, wetland-based waste water treatment system is that: it is easier to manage solid green waste than invisible nutrients dissolved in water. FENCING THE RETENTION POND The final stage of the treatment system is a retention pond. Some councils may require you to fence the pond or dam. Check with your local council. For smaller systems, an alternative may be to install a tank as the retention pond. REUSING WATER Once you have a system in place to clean the waste water, you will no doubt start to think about reusing the water – especially as water is becoming more expensive. Reuse of water may still require more treatment. Plant pathogens (diseases) may survive in the system, though recent data has shown that Phytophora (a common plant pathogen) is removed in a wetland system. If water needs to be disinfected, there are a number of treatments available including heat, chlorination, bromination, ultra violet radiation and ozone. Jeremy Badgery-Parker, Extension Horticulturist (Protected Cropping), Gosford. NSW Agriculture.
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WETLAND SYSTEM
required retention time depends on the nutrient load of the waste water. Nutrient load is a factor of both the volume of water and the concentration of nutrients in the water. A system with a five day retention period would have a total water volume 5-times the amount of water flowing into the system each day.
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entering the water system. As a result, sometimes the natural system can not cope. One option for the responsible farmer is to use naturally based systems to remove sediments and nutrients before the water leaves the farm. The wetland is nature’s filter and has been shown to be effective in removing nutrients and sediments from water. The use of wetlands has increased a lot in recent years as an effective and friendly method of treating waste water. The objective is to construct a simple wetland system that is effective and feasible for the small, intensive farm. Furthermore, even wetlands need maintenance so they need to be constructed with this in mind.
So you want to produce peppers? Peppers have become a popular ingredient in salads, baked filled with meats or other condiments to adorn the plate. Apart from tomatoes, cucumbers, peppers is very much part of this major three-option product that is grown in greenhouses in South Africa.
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ipe bell peppers are one of the most popular greenhouse crops because the yield and quality can be higher than field-grown crops. It is a slower-growing, more generative crop than other popular greenhouse fruiting crops, like tomatoes, cucumbers, and eggplants. It is important to match a plant’s growth habit, vegetative or generative, to the type of structure in which it will be grown. Greenhouses fitted with highly technological equipment use a lot of heat and extensive climate control to optimize the growing environment. This type of environment grows peppers as fast as possible for the highest yield and promotes vegetative growth - therefore more generative varieties are used to keep the plants balanced and setting fruit over a very long season. Peppers are pruned to two or four stems and grown up a string trellis to make the best use of vertical space. Growing peppers on a two-stemmed plant will result in larger peppers than those grown on a four-stemmed plant. Two-stemmed plants will be more resilient under hotter-than-ideal conditions. In simpler greenhouses with less extensive climate control, conditions cannot be optimized as much, and plants are likely to experience heat, cold, and other stresses more often. Stressful conditions tend to reduce a plant’s vigour, but peppers bred for simpler greenhouses are more vigorous. Good advice is to use field varieties and production techniques, such as a basket-weave trellis or other simple trellis, for production in low-tech greenhouses in short-season areas.
PROPAGATION Sow pepper seeds in a desired grow medium 6–8 weeks prior to trans planting. Maintain a constant, 27–32°C soil temperature to achieve an ideal germination percentage and uniformity. When the first true leaves
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All peppers are green when they start to grow. Only just before harvesting they discolour to red or yellow, if their strain is not green only.
show, transplant the seedlings into cell-type containers or blocks. Containers 5cm or larger will produce larger, stronger root systems; 10cm grow blocks are the standard for hydroponics. Grow plants at daytime temperatures of 21–23°C and during night time at 20°C. Fertilize with a complete nutrient solution (EC 1.5–2, pH 5.2) or equivalent as needed to keep plants dark green and healthy. When transplanting the pepper seedlings into the greenhouse, maintain temperatures of 23°C during the day and 21°C at night during the first week to ensure rapid vegetative growth and root establishment.
FERTILIZING When growing directly in soil, perform a soil test using the saturated media extract test designed specifically for greenhouse growing, and amend to the recommendations provided. If you are growing a long-term crop that will be in the ground for four months or more you will not be able to provide all the necessary nutrients from pre-planting fertility. Side dressing or fertigation with extra nutrients will be necessary. Use plant tissue testing to monitor the health of the plants and add extra nutrients when necessary. If growing hydroponically, consult the manufacturer of your nutrients on an appropriate fertility plan for peppers.
TRANSPLANTING or SPACING
Trellising a pepper plant.
To grow two-stemmed plants, use a plant density of 3–3.5 plants (6–7 stems) per square metre. For four-stemmed plants, maintain the same 6–7 stems/ square metre spacing, but with half as many plants. One common row spacing to achieve this density is to use a double row of plants, trellised to two parallel overhead wires 60cm apart with walkways 90cm wide. Each To page 9
From page 8 PEPPERS
stem is anchored 15cm or so from the next one. Some pepper growers prefer to use four wires with a second set of two more wires 20cm in from the first set of wires because this allows spacing the pepper stems out 30cm from each other on each wire. Sweet Peppers are naturally slowgrowing and need high tempera tures for fast growth. Therefore 7–10 days after transplanting in the greenhouse, lower night tem peratures to 17–18°C and main tain a daytime temperature of 23–24°C. Night time tempera tures may be increased as high as 19°C if more vegetative growth is required. Lower night time tem peratures promote generative, fruit ing growth whereas higher night time temperatures with a flatter temperature profile encour age vegetative, leafy growth. Do not go below 16°C. Peppers have difficulty setting fruit at night time temperatures above 20°C, hence in warm summer nights it is impor tant to get the temperature below that level.
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CLIMATE
Note the spacing and trellising of the peppers.
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Cultivating effective growth with Greenhouse Technologies
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Remember; peppers grow as a one-stemmed plant until the first fruit is set, when the plant branches for the first time. Remove the initial pepper that is set in the first split before it develops. This will give the plant time to develop adequate leaf cover to support a fruit load. It is also recommended to remove the flowers at the second and third nodes, but if all conditions are optimized some growers allow fruit to set after removing just the first one. Every node after the initial split will result in one leaf, one pepper, and two branches. Field peppers may sometimes form
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Onto the overhead wire tie strong twine at the desired spacing and anchor the other end to the base of the plant with a loose knot. Twine made of natural materials tends to degrade and break under greenhouse conditions. If the knot is tight it will cut into the plant as it grows and girdle or even kill the plant, and may form a wound where pathogens can enter. Twist the stem of the plant around the twine or clip with trellis clips every two weeks to keep it supported and growing up the twine. Make the twine from the wire to the base of the plant fairly taught; peppers will not perform well with a lot of slack in the twine.
Is natural ventilation enough? RESULTS FROM GREENHOUSE CLIMATE EXPERIMENTS
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outh Africa has four main climatic zones. To prevent the typical overheating in green houses have to be specifically designed to suit each area. Due to the lack of available scientific South African information, a research project was done to predict the performance of different greenhouse structures and cooling systems when it comes to the internal micro-climate for different external agro-climatic conditions in South Africa. The study ultimately applied mathematical models to predict the internal micro-conditions of a naturally ventilated green house. Experiments were done for data collection as part of the study. These experiments were done on microcli matic conditions such as the temperature and relative humidity of two greenhouses, located in Pietermaritzburg, KZN. The greenhouses used for this study included a naturally ventilated greenhouse fitted with insect nets on the roof vents (NVG) and a naturally ventilated greenhouse fitted with fog ging (NVFG). The NVG had fixed single-sided roof vents, and the NVFG had adjustable single-sided roof vents, both of similar dimensions and both designed with a maximum ventilation area of 22%. Both greenhouses were also filled with crops. The results from the experiments are presented in the two graphs below. Figure 1 and 2 show the average hourly internal and external day-time temperature and relative humidity recorded respectively.
These results show that for the naturally venti lated greenhouse (NVG) with no cooling installa tion, temperatures were significantly higher than external temperature and often reaching internal temperatures up to 10˚C higher than outside. It often reached a peak temperature of 36 ˚C. On the other hand, the fog cooled greenhouse often reached temperatures lower than the external measured temperature (although not visible on the graphs). RH conditions in NVG were low and often dropped lower than the external RH during the day, where the RH for NVFG increased to between 80% and 90% when the fogging was switched on. The results show that for greenhouses installed in warmer climates, without additional ventilation and
cooling systems installed in a greenhouse, unde sired internal temperature and relative humidity conditions will be experienced. The following can be applied to improve the greenhouse microclimate under hot conditions: 1. Increasing the ventilation capacity to at least 30% of the greenhouse floor area as recommended for most South African conditions. Insect netting reduces the airflow efficiency by 20-30% and this has to be incorporated when designing the greenhouse. 2. Since global solar radiation had the biggest impact on internal temperature of greenhouses, it is also possible to use appropriate screening systems that control the amount of radiation entering the greenhouse. 3. Installing an evaporative cooling system. High pressure fogging cause a more uniform humid ity and cooling effect when compared to other systems such as pad & fan systems. A pad and fan system, if not installed in combination with a natural ventilation system, has to run continu ously to ensure airflow through the greenhouse, and is more energy intensive. E du Plessis: erna@renlyn.co.za
Thrips in greenhouse crops - biology, damage and management
The adults are weak fliers, usually taking short flights from leaf to leaf or plant to plant. Nevertheless, they disperse rapidly throughout the greenhouse. Adult thrips can be transported on wind currents and will enter the greenhouse through vents and doorways. At all stages they may be dispersed on workers' clothing and on infested plants, growing media or farm implements.
DAMAGE The adult and larval stages feed by piercing the plant surface with their mouthparts and sucking the contents of plant cells. This causes white or brown spots on the leaves where the plant cells have been destroyed. These spots are also speckled with dark fecal droppings from the thrips.
Figure 3. Pupal stage of western flower thrips.
VEGETABLE CROPS Figure 1. Comparison between adult western flower thrips (right) and adult Echinothrips (left).
LIFE CYCLE The life cycle consists of five stages: egg, larval, prepupal, pupal and adult. Female adult western flower thrips live up to 30 days and lay 2-10 eggs per day. At 20°C, development from egg to adult takes approximately 19 days. At 25°C, it takes 13 days. The eggs are inserted into soft plant tissues, including flowers, leaves, stems and fruit. In sweet pepper, egg hatch gives the leaves a speckled appearance, with the degree of speckling corresponding to the number of hatched eggs. The larval stage (see Figure 2) consists of 2 instars that feed and develop on the leaves, flowers and fruit. The pre-pupal and pupal stages often complete their development on the ground or growing medium, but pupation can also take place on the plant. The pupa (see Figure 3) is a nonfeeding stage during which the wings and other adult structures form.
Figure 2. First and second larval instars plus adult of western flower thrips.
In cucumber (see Figure 4) and tomato, thrips damage is noticed first on the lower leaves. In sweet pepper (see Figure 5), it is evident in the upper youngest leaves. Heavy infestations reduce the ability of the plants to photosynthesize, reducing the yield. On vegetable flowers, thrips feeding creates silvery white streaks on the petals. Fruit damage varies according to the crop. For instance, in cucumber fruit, feeding creates severe distortion and curling as well as white streaks (see Figure 6). Feeding on sweet pepper (see Figure 7) causes silvery or bronze streaks or spots on the fruit. Thrips also feed on the calyx, causing it to turn up and expose the fruit to bacterial infections. On tomato, thrips may lay eggs in the fruit, creating ghost-spotting (see Figure 8). Ghost-spotting can also occur with sweet pepper and cucumber.
MANAGEMENT Monitoring
Monitoring the population levels of western flower thrips is critical for successful pest management. In vegetable crops, monitoring should begin during propagation and continue after transplanting. In floriculture crops, thrips can be present at damaging levels year-round, although populations are usually smaller during winter. Commercially available blue or yellow sticky traps can be used to monitor the population densities of adult thrips (see Figure 10). Blue traps are more attractive to western flower thrips, although yellow traps are more attractive to other pests such as whiteflies and aphids. Your choice depends on how many pests you need to monitor, the susceptibility of
Figure 4. Thrips feeding damage on cucumber leaves.
Figure 5. Thrips feeding damage on pepper leaves.
the crop to thrips and/or tospoviruses and your need to detect thrips populations at low levels. When setting up a monitoring program, use 1 trap per 100-200 m2. The exact number will depend on the layout of the greenhouse. A large open range will require a lower total density of cards than a greenhouse made up of a several smaller areas. Place the sticky cards in a grid pattern throughout the greenhouse. Check the traps weekly and record the average number of thrips per trap. Be aware that this is not an absolute measure of the population; rather, it measures increases and decreases in thrips numbers throughout the year. As you become more aware of how the numbers on sticky cards relate to the population in the crop, you can use the monitoring data to help you make pest management decisions. To page 12
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dult western flower thrips are approximately 1-2 mm in length and generally yellowish-brown in colour. Identification to the species level is difficult (especially among western flower thrips, eastern flower thrips and onion thrips) because they are so small and their colour varies. Adults are the only stage that can be identified to species. Identification should be done by specialists.
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Thrips can become a major pest of greenhouse crops. A number of thrips species are commonly found including western flower thrips (Frankliniella occidentalis), eastern flower thrips (Frankliniella tritici), onion thrips (Thrips tabaci), and Echinothrips. However, western flower thrips is the predominant species and the most difficult to control.
From page 9 PEPPERS
multiple branches per node, but greenhouse peppers are bred to form two even branches. At each node after the initial split, choose the stronger of the two branches to continue forming the stem. Cut the other branch after it has formed one leaf. This involves cutting off the flower and two other branches at the first node of each lateral branch. This leaves one leaf to develop, called the flag leaf. This leaf will protect the peppers from sunscald and help prevent blossom end rot. Do not prune within 20cm of the tip of the plant. Prune every two weeks, or after about 15cm of growth since the last pruning. Pepper plants will set 4–5 fruit before aborting the next few flowers. This is normal, for the plant to set fruit in “flushes” and not set every single fruit. Remove fruit if they are deformed or unmarketable to allow the plant to put the energy into setting another fruit further up the plant.
DISEASES AND PESTS
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Use crop rotation or change the media to reduce incidence of soil-borne disease. Regularly schedule releases of beneficial insects to control pests. Companies can advise you on the appropriate beneficial organisms based on the timing and square footage of your crops. Minimizing the amount of time with temperatures below 18°C will reduce the amount of botrytis. It is important to have a footbath at the entry and exit to the greenhouse where peppers are grown. Good hygiene practices in any greenhouse should be a stern rule to follow.
HARVEST
Harvest peppers when they are 80% or more final ripe colour. They will reach full coloration in storage. Using hygienic pruners or a knife, cut the fruit off flush with the main stem of the plant. Make sure not to leave a stub on the plant, as this can be an entry point for pathogens. Harvesters should also be dressed and capped with hygienic clothing to avoid any pathogen transferred from another greenhouse or plant.
STORAGE
Peppers can be stored at 7– 8°C in the cold room. Do not store them with ethylene-producing vegetables like tomatoes. Transferring the boxes with peppers to a market or the cold rooms of a chain store should take place with the least loss of temperature. The more evenly the product is transported in terms of handling and temperature, the longer shelf life it will offer the consumer. Researched from various sources: JS
Maarten D Koppenol – RIP The well-known Maarten D Koppenol of Soil Fertigation Services (Pty) Ltd passed away on 2 November 2016. The direc tor and staff of Undercover Farming will particularly miss him at the Expo and Conferences where he exhibited but also as a dear friend of the industry. In the May/ June edition 2016 an editorial appeared on the important services he offered to greenhouse operators. We offer our sincere condolences to his wife and family and will for sure miss his expertise in the industry.
Cultural control From page 11 THRIPS
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Figure 6. Thrips feeding damage on cucumber fruit.
Figure 8. Thrips egg-laying scars on tomato
Figure 9. TSWV symptoms on pepper fruit.
for a rapid increase in the density of thrips popu lations.
Physical control
An influx of outside pests, including thrips, can overwhelm your greenhouse IPM program, making it difficult to plan ahead. To prevent this, use screens to restrict the movement of insects into the greenhouse.
Chemical control Figure 7. Egg-laying scars and feeding damage on sweet pepper.
Sanitation is the first and most important step in implementing an effective pest management program. Effective sanitation will reduce or even eliminate thrips as a pest problem. For example, in cut roses, removing all flower buds (including non-marketable flowers) can significantly reduce thrips populations in that crop. Cultural control measures also include maintaining a healthy crop and an optimal greenhouse environment (such as 80% relative humidity), creating less favourable conditions
Chemical control of western flower thrips can be difficult. They are resistant to most pesticides and feed deep within the flower head or on developing leaves. This makes them a difficult target for insecticides, so thorough coverage is essential. If you use pesticides to control thrips, follow these general guidelines: • Begin applications early, before the thrips population grows too large. Thrips are more easily managed when population levels are low. • Although it is important to rotate chemical classes, use only one chemical class for the duration of the thrips' life cycle. This gene
Figure 10.
rally means using a different class every 2-3 weeks, depending on the time of year. • Apply pesticides in early morning or late afternoon, when flight activity of thrips is at a peak. This increases exposure of the thrips to the pesticides. Speak to your greenhouse advisor or contact a manufacturer of pest control applications if you are not sure which Thrips specie you find in your greenhouse.
By: Graeme Murphy, Greenhouse Floriculture IPM Specialist
Scouting regularly is of essence and is part of good horticultural practice. When even a slight awareness of Thrips is observed, be quick to take action!
Speedline offers top quality of synthetic monofilaments to greenhouse farmers
Agen, South of France
The ISL range covers all agricultural needs and different applications:
- As a trellis system for vineyards, orchards, kiwifruits, tomatoes, cucumbers or berries - As a support for your net house or inside your greenhouse structure - As a fence, ISL is also manufactured in white for use with horses. It is very important that ISL monofilaments are correctly installed under tension. This process is very easy and once installed the line will only need a minimum amount of maintenance over the lifetime of the product. TECHNICAL DATA FOR PET RANGE Diameter (mm) 1,8 2,2 2,6 3 Meters/Kg (approx.) 280 188 135 101 Breaking Load (Kgf) 140 214 291 389 “Our core business is to manufacture the line, but we want to be a long term supplier for the farming industry, that’s why we also provide the installation tools in order to allow the installer to tension the line correctly, this is critical to ensure the best life expectancy. These products are not made from steel and must be installed the right way. Even if we are working as a manufacturer, we are always looking to suit the needs of the producer both technically and practically” said Matthieu Gallician, Product Manager from Speed Line South Africa.
Application examples:
The South African office is in Pietermaritzburg, KZN.You can find more information on www.isl-line.com or contact directly Matthieu Gallician at matthieu.gallician@isl-line.com.
GREENHOUSE & NETS Shade curtains Shade house Hail nets Tunnels TRELLISING Vineyards Orchards Tomatoes Berries FENCING Horses
Tzaneen, Limpopo, South Africa
For tomatoes and cucumber plants the ISL support system is easy to install and nearly maintenance-free for years. It is UV protected and wire-free. It does not rust and it is suited for high humidity indoor applications. Also, ISL has a smooth shape to avoid damage to the young shoots and to your plastics. Utilised on berries, the ISL trellising system offers a product which does not rust and will not release noxious substances into the environment. It is specially designed in white for indoor applications and it offers better visibility to avoid cutting during harvest.
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ounded in the heart of the Beaujolais in France during the late 1970s, Speed Group is a global manufacturer of extruded synthetic monofilaments. With manufacturing facilities established in South Africa for almost 15 years Speed Line South Africa is able to meet all customers’ needs around the country with rapid lead times, reduced freight costs, and the elimination of import duties. Speed Group is also present in the United States and Chili. Research and development around a suitable range for the Agricultural industry has resulted in the ISL brand, “Innovative Support Line”, with interesting benefits for both farmers and their plants: - Light, ISL monofilaments are 5 to 7 times lighter than steel, easy to install and manipulate. - They are designed to keep their tension over their life span. - Smooth, ISL monofilaments are non-abrasive to the installer, your structures, crops or your livestock. - Metal-free, ISL monofilaments will not rust. - UV resistant, ISL monofilaments are designed to handle harsh outdoor conditions. They can withstand temperatures from -40°C to +70°C.
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Speed Group pride themselves in producing ISL trellising monofilament lines using only the best grade resins and virgin raw materials. Their agricultural monofilaments are designed to suit producers of tomato, berry, table grapes and vine producers needs in trellising, shade curtains, greenhouse, or fencing applications.
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UNDERCOVER FARMING EXPO & CONFERENCE 7-8 March 2017
Pretoria, South Africa
Contact: Suzanne@pop.co.za
New ways to extend shelf-life of produce
LANGER RAKLEWE Vars produkte en blomme word ryp, word oorryp en gaan dan af weens hul natuurlike produksie van etileengas. Navorsers het produkte ontwikkel wat hulle ‘etileen-antagoniste’ noem (in chemie is ‘n ‘antagonis’ ‘n substansie wat ander prosesse verhoed). Die gevolg is dat vrugte en groente langer vars sal bly en blomme langer sal neem om hul blare te verloor. “Die uitwerking van hierdie stowwe is eenvoudig dat dit nie etileenproduksie verminder nie, maar dit verhoed dat vrugte en groente blootgestel word aan etileen en dus ‘n langer raklewe kan geniet,” volgens een van die navorsers, Dr Payne.
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he process has the potential to help reduce the billions of tonnes of food that are wasted worldwide each year. In effect, it also represents a new weapon in the fight to help feed the world’s growing population, estimated to reach more than nine billion people by 2050. Making food last longer and reducing waste will help feed more people, compared to alternative strategies of having to increase food production. The process was developed by horticultural researcher Professor Zora Singh and organic chemist Dr Alan Payne. Food and flowers ripen, and then over ripen and spoil, due to their natural production of ethylene gas. The researchers have come up with compounds they’ve dubbed ‘ethylene antagonists’ (in chemistry an antagonist is a substance which inhibits another process). The result is that fruit and vegetables stay fresher for longer, and cut flowers take longer to drop their petals. “The way these compounds work is that they don’t reduce the production of ethylene, they prevent the fruits, vegetables and flowers from perceiving ethylene,” says Dr Payne. “Every fruit has a receptor that ethylene binds to." “What we’re doing is we're masking those receptors.” Prof Singh says up to 44 per cent of fresh food and produce spoils before it reaches consumers, and that half of this is due to ethylene production. Professor Singh has been working in the food research area for more than two decades and several years ago approached Dr Payne. “I started to think how could I make a compound that’s easier to make, easier to use and I came up with these compounds that Zora was happy to test on his fruits and flowers,” says Dr Payne. The pair says their ethylene blockers are more versatile than current methods and can be used pre- or post-harvest as a solid or liquid by spraying, dipping, waxing or fumigation. “The beauty of these compounds is that we can apply them in the production phase, when the food is growing,” Professor Singh says. “We tried to make them more user friendly, because it was already being used by the industry." Their work won a recent Curtin Commercial Innovation Award. The researchers and Curtin University have filed a patent and are seeking potential partners to commercialise the technology. From: ScienceNetwork
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Two of Curtin University’s researchers have come up with a way of extending the shelflife of vegetables, fruit and flowers by slowing down the process that leads to them spoiling.
The South African - Dutch Horticultural partnership:
A bird’s eye view of the Horti Business Platform Past, present and future The RSA-NED Horti Business Platform was established in 2013 with the ideal of bringing together the Dutch and South African undercover farming industries to achieve the development of a strong horticultural cluster in South Africa. With food security, safety and economic growth in mind the stakeholders of the platform set out to exchange knowledge and encourage projects in horticulture with focus on sustainability, productivity and an efficient supply chain.
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s a result of this partnership, many projects were implemented viewing the growth of all stakeholders. Some examples include the SMART project with Klein Karoo (Innovative technology), the Knowledge Sharing and capacity building project with ASNAPP and ARC, the Solidaridad Chain Development Project and the New Generation Cooperatives implemented by the Dutch Embassy. The Platform also worked as a base for a Stakeholders Network, giving space for communication between all parties involved, organizing training sessions at different activity centres, arranging workshops and conferences, initiating cooperation projects and overall connecting stakeholders to projects. The Platform also encountered many challenges with projects which were delayed and projects that were not implemented. The main reasons behind these disappointments were lack of funding and communication gaps between Dutch and RSA companies. Other difficulties included the South African drought and the country poor exchange rate. South African farmers also identified that the Dutch technology did not always matched their needs, they were often too advanced and expensive. In October at the 2016 Undercover Farming Conference in Cape Town, the new Dutch agricultural counsellor Mr Jack Vera met with invited stakeholders to evaluate the Platform successes and failures and to determine its future. At the meeting it was highlighted by all participants their interest to continue supporting the goals of the Platform and to work together towards the South African undercover farming industry improvement and sustainability. A concept paper will be developed to set out the way forward. Renewed plans
Suzanne Oosthuizen, director of Undercover Farming at the word during the Westerbn Cape Conference. To her right is Elton Jefthas, SA lead; RSA-NED Platform and on his right Jack Vera, new Agricultural Councilor, Kingdom of the Netherlands Embassy.
include options on how to obtain funding for further project implementation as well as demonstration sites in South Africa (Kwazulu-Natal, Gauteng and possibly Western Cape) where Dutch technology will be demonstrated in a South African environment. For more information or to give inputs into the concept note you can contact Elton Jefthas: ejefthas@sun.ac.za or Suzanne Oosthuizen: Suzanne@pop.co.za
Nanotechnology: Engineering better building blocks for agriculture Nanotechnology has been heralded as a new industrial revolution – as in the 18th and 19th centuries, nanotech has the potential to bring about drastic changes in the agricultural industry. The development of new nanotech-based tools and equipment may help to increase efficiency and overcome challenges faced by the agricultural industry.
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ome of these challenges include the increasing threats to agricultural production and risks of plant-related diseases. The agricultural sector will benefit greatly from nanotech-based tools to detect diseases in a rapid manner, improve the ability of plants to absorb nutrients and promote molecular treatment of diseases. The power of nanotech is the ability to engineer items from bottom up. It is believed there are big opportunities for nanotech in agriculture – nanopesticides, nanofertilizers, nanovaccines etc. Commercially available agricultural nanotech products are slow to develop, however. It’s hard to find a simple definition for the science of nanotechnology. The key word is small – super small. To get a handle on just how small, if we compare a nanometre to a metre, a nanometre would be a marble. A metre would be the size of the earth. The power of this science is the ability to engineer items from the bottom up. Instead of building or using existing components or molecules to engineer products or devices, nanotechnology is used to create building materials at the molecular level with optimal features for the task at hand. Existing examples include lighter, stronger tennis rackets and golf clubs, sunscreen lotions, stain-resistant clothes and carpet, and packaging to keep food fresh longer. There are hundreds of nanotech products we are using daily without knowing it. There are big opportunities for nanotechno lo gy in agriculture. Nanopesticides could be more environmentally benign and provide more effective and targeted control of weeds, diseases and insects. Nanofertilizers are being developed to minimize leaching, control the release of nutrients and improve the uptake of nutrients by plants. Nanoparticles could also
be used to administer vaccines or animal health products more effectively with less potential for resistance. Nanosensors work by detecting electrical changes in the sensor materials. There is ongoing research to create nanosensors to closely monitor plant health and growth. The information could be delivered wirelessly to smartphones to alert farmers if plants are under stress of any kind. Nanosensors can also be built to detect bacteria and viruses. This is already used in food-processing scenarios and could be applicable for livestock operations. The potential for nanotech in agriculture is significant, but to date, commercially available products have been slow to develop. The problem is return on investment – the development costs are significant and the benefits can be difficult to measure. The United States Department of Agriculture recently announced an investment of $5 million to support nanotechnology research at 11 universities. Auburn University proposes to improve pathogen monitoring throughout the food supply chain by creating a user-friendly system to detect multiple foodborne pathogens simultaneously, accurately, cost effectively and rapidly. Mississippi State University will research ways nanochitosan (a polymer used extensively in the medical field) can be used as a combined fire-retardant and antifungal wood treatment that is also environmentally safe. Experts at the University of Wisconsin will work to develop nanoparticle-based poultry vaccines to prevent emerging poultry infections. While nanotechnology has been slow to emerge in mainstream agriculture, the research is under way and we will see nanotech products in the near future. By Peter Gredig @Agwag
The purpose and advantages of a screening system
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or those producers who still are not clear on screening systems this editorial discuss what is known as energy screening systems. An energy screening system can be used for heat retention or for keeping out heat, and this depends mostly on the type of cloth used. The cloth can also be chosen to supply a good balance between heat retention and cooling. It is therefore necessary to decide where the most return on investment for a screening system will be. Will it be saving on heating costs? Will it be saving on cooling costs? Or will it be a fair amount of each? Most commercial growers in Europe have two screening systems operating together: one to keep heat in, and one to keep heat out of the greenhouse. Some even have three … This grower can switch between screens, depending on whether he wants to keep heat in or heat out, and according to the time of year or the type of day. It is important to note that a screening system needs to be flexible, i.e. one must be able to open or close it at will. This gives the grower some control over fluctuating conditions like light intensity, temperature and humidity. The difference between a screening system and shading, by whitewashing or shade-netting over the roof, is that the screen is extractable and can be opened on a cloudy day to let in more light, or closed during bright days (to shade) or at night time (to keep heat in). This affords the grower more control. Also, the shade-netting and whitewash have very little heat-retention capabilities and will not be of much help in winter times.
REASON FOR A SCREENING SYSTEM To save on heating expenses
Saving on cooling expenses If one take the example of a pad-and-fan greenhouse of 10 bays of 9,6 m x 60 m with the pad being 60 m from the fan. In a pad and fan greenhouse, it is accepted that the temperature gradient should not exceed 4 °C. In other words, the temperature should not be more than 4 °C higher when it exits through the fan than when it enters through the pad. This is in order to have a uniform temperature climate in the greenhouse. For a greenhouse with the above-mentioned dimensions, without an energy screen, in order to have a temperature gradient of 4 °C you will need 26 x 1,5 Hp extractor fans. For the same size greenhouse with an energy screen to have the same temperature gradient, you will need only 22 extractor fans. That is a saving of 15% on the capital outlay of the fans and also a saving of roughly 15% on the running costs of the pad and fan system. To page 18
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Greenhouse plastic has a U value of 5,8 W/m².°K, which means it loses 15 times more heat than for example a brick wall with a value of 0.37 W/m².°K. With the cloth most often used in an energy-screening system you will save
57% on energy expenses for heating the greenhouse. This energy saving is due to the facts that very little heat escapes past the screening material, and that it reduces the area to be heated by up to 33% because it is installed just beneath the gutter of the greenhouse. It is proven that when using a good screening system, a saving of 11 kg of coal per m² per year will on average be achieved (when heating only in the coldest months). At the current price of coal this amounts to a saving around R100 000 per year. At the current price of a good-quality screening system this means that the screening system will have paid for itself in 7,5 years. The screening material should last more than 10 years before it needs upgrading and the mechanism a lot longer. This means that after 7,5 years, the savings of say, R100 000 per year will be extra money in the grower’s pocket simply because he installed a screen.
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A screening system is a special cloth that is installed in the greenhouse that can be automatically or manually opened and closed, as well as the mechanism required to do this. The aim could be to save heating energy, help cool the greenhouse by shading, or shorten the day for instance with chrysanthemum (blackout screen) growing.
Ask for the best Haifa’s advanced plant nutrition solutions help you get top yields, season by season. With our pioneering products, expertise and know-how you are always ready for the challenges of tomorrow. Please contact us for your nearest distributor: Haifa South Africa P.O.Box 1409, Brackenfell, 7561, South Africa Tel: 021 982 0309, Fax: 021 981 7637, E-mail: Gerrit.Burger@Haifa-group.com www.haifa-group.com
Seed Company is celebrating their 15th year of business… Established in 2001, Alliance Seeds prides its self in being the only private seed company entrusted to distribute, promote and develop Clause vegetable seeds in South and Southern Africa during this period.
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Carrots
Peppers
Melons
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lause is built upon more than 200 years of experienced dedicated vegetable seed breeding, through advanced seed technology, resulting in quality, high yielding disease resistant hybrid varieties and supplying seed to over 100 countries across five continents. Alliance Seeds is founded on good relationships, personal service, and technical support to growers. Thorough knowledge of local conditions and market needs is the key to their success.
Alliance Seeds, one of the market leaders in Sweet Peppers, supplies a large percentage of the pepper market in South Africa. Top varieties include Red Jewel and Springbok, both suited to open field and net-house production; they offer extensive disease resistances and top quality fruit. Royal Red and Cayman are open-field varieties, offering a more compact plant with exceptional leaf cover and disease packages to match.
Tomatoes
Alliance Seeds has a thorough understanding of the various specialised segments of the tomato market and is a major player in the industry. Offering a range of indeterminate tomato varieties, such as Candela, a very versatile variety, suited to open field, net-house and greenhouse production. CLX 37532, CLX 37574 and Oasis are varieties becoming very popular
amongst growers and markets alike. Alliance Seeds also provides a number of speciality tomatoes including saladettes, cocktails, and mini plums. Alliance Seeds is steadily entering the carrot arena, with some very competitive varieties such as Phoenix, Brutus and Santorin in the range. Extensive countrywide adaptation trials have proven their suitability to various conditions, seasons, and disease resistances, particularly to alternaria. Alliance Seeds continues to provide market leading orange melon varieties such as Melon Pegaso, which was the preferred melon variety of the processing market. The company has introduced very successful improved varieties, such as Fargo and Sucro, improving yields dramatically, offering better disease resistances, improving shelf life and providing for both the processing and fresh markets. Alliance Seeds offers an extensive range of other vegetable seeds which include Baby Marrows, Broccoli, Cauliflower, Cabbage, Beetroot, etc.
For further enquiries contact ALLIANCE SEEDS on 013 750 0575, e-mail info@allianceseeds.co.za or visit www.allianceseeds.co.za
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From page 17 SCREENING SYSTEM
Reduce radiation on the plant Another interesting point that is being practiced in Europe on a daily basis and has been given serious thought in past years in South Africa is, as a rule of thumb it is accepted that a plant (this varies slightly between different plants) stops growing/producing when the radiation per m² exceeds 800 Watts. This is an important factor in Europe, because during certain months they use artificial lighting and in order to be cost effective they don’t want to provide more light/radiation than what the plant needs for optimal growth. On a normal autumn day in Johannesburg, the radiation per m² will easily be sitting at 1 200 W/m² from 10:00 to 16:00. This means that most plants will every day be spending more energy transpiring than growing for the better part of the day. In summer, this will be even worse. In our climate plants are under stress for most of the day. It is therefore probably also a
good idea to use an energy-screening system to reduce the radiation per m² and to get the growing conditions for your plants as close to optimal as possible. You want your plants to produce optimally throughout the day, not only in the morning and in the late afternoon.
Install a quality screening system
One could probably get away with buying a greenhouse from a lesser known supplier because, even if it takes too long to erect and there are some problems, once the greenhouse is up and standing it is normally relatively hassle free. This is not the case with a screening system. A screening system has thousands of moving parts and moves every day and it must continue to do so with minimum trouble for ten or more years. It is therefore very important to make sure that the screening system invested in has a good, reliable To page 19
A letter from a visitor to a prospering young greenhouse farmer
From page 18 SCREENING SYSTEM
supplier backing it up with maintenance service, and a reputable and proven mechanism. If not, the producer is buying years and years of trouble. From the abovementioned subject on return on investment, it is clear that a screen should last at least ten years before needing upgrading, or else the capital outlay cannot be recovered, even if it were the cheapest screening system on the market. A screening system needs to be properly installed and designed or one will not get the savings and benefits from the system that you calculated.
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Amongst other things, a badly designed system will not save as much energy because after some opening and closing it will not seal properly. Another important subject to consider is that not any cloth can be used in a screening system. The cloth needs to be very durable and also needs to be able to fold back into a very thin pocket, or else there will be wide bands of dark shade over your crop when the screens are supposed to be open. It is a good idea to visit growers where a screening system has been operating for a couple of years before making a decision on which system to buy. JS The subscription fee for six bi-monthly issues amounts to R 180.00 (VAT & Postage included, S.A. only). Foreign subscribers: R 340.00 per annum (VAT & Postage included)
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CODE: CONTACT NUMBER: ACCOUNT NAME: Nufarmer cc Trading as Undercover Farming: Bank: First National Bank, Kolonnade BRANCH CODE: 25 10 37 • ACCOUNT NO: 62007699806
19 NOV • DES/DEC 2016
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Dear Kobela, am writing this with a lot of gratitude. Truly thank you for allowing me to use your time so that I can learn from you. In my language, there is a saying that goes "kuphunzira sikutha". This means "we are continually learning"... we learn every day! Who knew that I would have the privilege of learning a new way farming at my age! I have shared my story of my visit with two young men back home... my son, Zai, and another young farmer who inspires me, Harris. They are just as excited about this as I am. It is my hope that I can in the not so distant future, send my son to come and see for himself. He keeps reminding me how young you are and that he has no doubt he can do well as well. I can only wish you well in your business. I promise to "START". That was you advice – the most important thing is to start. This Harris that I have mentioned above was in Kenya where he learnt about hydroponics; and apparently he has ordered his equipment from India. Of course he got funding from Norway to start a demo farm. So I am excited that at Kobela Mokgohloa explains his growing technique to a visitor at Korema Farm. least someone in Malawi is set to do this. I can't wait to see anything concrete can be achieved. So I will take you up on your word... what he will do. It's a long journey but every journey starts with to report on our progress. a single step. Angela Mpando (Mrs), Malawi I will definitely be in touch. I know the hiccups are many before
U N D E R C O V E R F A R M I N G
When one hears of the readiness of successful farmers who reach out to beginner farmers even from other countries it fills you with pride. Kobela Mokgohloa, a young greenhouse farmer from Hammanskraal, Pretoria on which Undercover Farming recently reported had such a visitor from Malawi. This following is an account of her visit after which she wrote to Kobela.
U N D E R C O V E R F A R M I N G
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