Undercover
farming
ucf
I
november/december 2019 volUme 16 no 6
I
I r40.00
crop prodUcTIon
Food SecUrITY
prodUce
prodUce
The incredible journey of Go Gourmet page 4
managing waste water page 6
physiological disorders in lettuce page 10
Hydroponically grown tomatoes page 14
WISHInG YoU Well over THe FeSTIve SeaSon; everY SUcceSS For a bUmper 2020!
A complete range of lettuce
Varieties developed for all growing systems Iceberg and leaf lettuce for open field and hydroponic growing systems.
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All year supply We offer Iceberg and leaf lettuce varieties for all seasons.
About Enza Zaden At Enza Zaden we develop new vegetable varieties that are grown, sold and consumed all over the world. So, it’s very likely that you’ll often find our tomatoes, cucumbers, sweet peppers, lettuce or other vegetables developed by us on your plate. We produce and sell the seeds of those vegetables worldwide.
enzazaden.co.za
GreenHoUSeS I SHade neT I HYdroponIcS I aqUaponIcS
MAIN ARTICLE
PROPRIETOR I ADVERTISING SUZANNE OOSTHUIZEN 012-543 0880 I 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 ADDRESS PO Box 759, Montana Park 0159 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. COPYRIGHT Copyright is reserved and the content may only be reproduced with the consent of the Editor. SUBSCRIPTION Online subs: Email to suzanne@axxess.co.za If you subscribe on-line, e-mail your deposit and address details to: magazine@axxess.co.za. More information from Suzannne Oosthuizen: 012-543 0880. Subscription form available on inside back page. VISIT US AT I BESOEk ONS BY
A CHRISTMAS MESSAGE
“For the Child within her has been conceived by the Holy Spirit. And she will have a Son, and you shall name Him Jesus (Saviour), for He will save His people from their sins. Matthew 1:20-21 (Abbr)
Contents 4 6
The incredible journey of Go Gourmet
8
Haifa Chemicals is pioneering the future of calcium nitrate Nutrigation™
10 11
Coping with physiological disorders in lettuce
12
Managing powdery mildew – common disease on sweet peppers
14
Hydroponically grown tomatoes: yield and quality response to growth medium
16
Increasing fruit and plant brix requires nutrient program adjustment during winter months
17
How UV Technology for disinfection of run-off water works
19
Overhasty public consultation on Section 25 Amendment slammed
19
Subscription form
FronT paGe: The even quality of lettuce grown with utmost care at Go Gourmet. InSeT pHoTo: chris rolfe, the owner of Go Gourmet behind his desk. See page 4.
Managing wastewater from intensive horticulture: a wetland system
INSIDE ...
Thresholds on private power generation curtails agri businesses
11
12
14 16
CHRISTMAS WISHES The director of Undercover Farming, staff and all participants in publishing the magazine, wish to express their sincere gratitude to all our readers, advertisers and correspondents over the Festive Season and wish all a Prosperous 2020!
A
lthough we, as an undercover farming industry pride ourselves in using less water than our fellow open land farmers, we still need this natural commodity very much. Even bore holes dry up and if there’s no rain, our industry suffers to a great extent as well. Therefore, looking at the weather maps of recent, we are thankful for the abundant rains coming down of late over a large part of the country. Still, there are many farmers in dire need of rain and our prayers and hope is gathered with good faith that they will soon be blessed with rains. The economic pinch is felt by all beings in the country, especially those who are making a living for themselves like our farmers. It is written; “Man must eat,” therefore every producer of food has his/her eye on the market and work hard on land and in greenhouses to produce a good quality product to maintain good price levels on the market. With the rand as low as it is, exporters of foodstuffs are able to do well for themselves and add good money to the GDP of the country. Just a pity that government portrays a one sided view on land reform. According to Agri SA, who really stand up for farmers of all backgrounds in the country, their plea for passing the bill on Section 25 in the New Year was not heeded to. In this edition there is a short press release from them outlining the basic facts of how this action will influence our country economically and obviously, socially. Let us never forget to pray for our government and the important decisions they have to make for the benefit of our country’s inhabitants! We wish you and yours a Blessed Festive Season and excellent cropping.
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GreenHoUSeS I SHade neT I HYdroponIcS I aqUaponIcS
Go Gourmet is a Hydroponics Farm situated in Pretoria-East that has been the talk of the town since they sold their first lettuce to Tshwane Fresh Produce market.
The incredible journey of Go
T
he general apathy for nature, the environment, plants and trees led Go Gourmet’s 26-year old Director, Chris Rolfe, to study Environmental Sciences while he attended Agricultural and Botany classes as well. This experience stirred a spirit for Horticulture and a keen interest in feeding people as well as growing different products; not only lettuce, but plants and organisms in general. “I have always loved and respected nature. Growing and maintaining plants has been my favourite past time since I can remember,” Chris Rolfe explained. The name of his business ‘Go Gourmet’ was established two years ago. The logo contains two ‘G’s’ which form a mushroom as the original journey started with exotic mushrooms, especially oyster mushrooms. Chris took a couple of courses, learnt how to grow them and then started to identify markets. These markets soon not only showed barriers of entry, but also limited income, making it an unfeasible investment at the time.
A very proud Chris Rolfe among his neat rows of leafy greens.
5
A shade net covered production house at Gro Gourmet.
“I have always loved and respected nature. Growing and maintaining plants has been my favourite past time since I can remember,” Chris Rolfe. From right to left, Chris Rolfe of Go Gourmet, Phia le Roux and their greenhouse assistants.
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Chris then researched further and well with the iceberg lettuce heads, and investigated strawberries and blueberries then after a tremendous hail storm at the and again, not wanting to jump in with end of 2018, which affected many of the his eyes closed, he highlighted potential open land producers, Go Gourmet found obstacles that would prevent him from there was a major demand as they had reaching the quality and volumes he plenty of lettuce grown under protective intended to supply. cover. Fresh produce retailers flocked to the farm in dire need of greens. Since The next avenue Chris followed was then, their stocks were basically sold the Aquaponics industry which led him out. “We have an excellent production to Hydroponics. He was attracted to system, and it really functions very well. Hydroponics due to its environmental We also receive a benefits and how he realized he Chris was attracted to Hydroponics lot of compliments regarding the could be more due to its environmental benefits quality of our socially responsible, and how he realized he could be produce.” Chris without more socially responsible, without proudly adds. compromising on quality or business compromising on quality or The entire 7ha viability. property can be business viability. covered with “I really enjoyed greenhouses, Hydroponics having which is the business plan on table - but done a bit of chemistry at University - it currently one hectare is undercover. Soon made a lot of sense to me and I did not another almost identical construction of really battle to understand fertilizers, a hectare will go up and production will the oxygenation processes in plants increase. and essentially all the basic principles of Hydroponics production. Then, I Chris further said; “We decided to started doing small trials at home with become as environmentally friendly as a small home-built system I constructed we possibly can on the farm. We run off a You-tube design, and it eventually the whole farm on solar power and we developed to what I have here today.” collect rain water on the farm. With a Chris explained. decent rainfall in about 15 minutes, we collect enough water for the next day’s Go Gourmet’s journey started off irrigation. It is about 20 000 litres that we supplying the Tshwane Fresh Produce collect in 15 to 20 minutes.” market in Pretoria. The business did fairly
The farm utilizes an electronic fertigation system that maintains the correct pH as well as the fertilizer mixes for the produce in the greenhouses. The water is recycled and filtrated to be clean before fresh fertilizer is added and is pumped through the system. Irrigation schedules are based on solar rays, eliminating water and fertilizer waste. In summer, Go Gourmet can produce up to 5 tons of lettuce (spread over 10 different varieties) off the one hectare greenhouse a week. They are running on a 4-week growing schedule at the moment and plant utilizing the Hydroponics system throughout. Go Gourmet make use of three different Hydroponic Systems combined to optimize it for their specific lettuce specifically. The water flows from the produce and is recycled by running into a reservoir, before being filtered and soluble fertilizer added to be used in the production area. Also, any rainwater collected off the plastic roofs or gutters and walk-ways is caught up and flows into an underground tank. If this reservoir is full, they have a 150 000 litres tank outside that they also fill up to save every possible drop. During January/February 2018 with all the rains for a good couple of weeks, they did not use any borehole water at all. The production was done just with harvested
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The one hectare Go Gourmet production shade net house.
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GreenHoUSeS I SHade neT I HYdroponIcS I aqUaponIcS
Managing wastewater from intensive horticulture: a wetland system Wastewater or ‘run-off’ from intensive horticulture usually contains a high level of nutrients – and possibly some sediments and plant pathogens.
D
escribed 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. Solid matter and sediment in wastewater originate from soil-based production systems and may include organic matter as well as sand and clay particles. Hydroponics 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.
Nitrogen and phosphorus 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
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irrigation can result in crop damage. In the environment, high levels of TDS can impact on aquatic organisms.
SOIL PRODUCTION 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 soil-based 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 flow-through hydroponic systems – often called ‘run-towaste’ – 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,
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applying more water than the plant uses can prevent the 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 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. 7
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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. By: JB Parker (NSW) 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 developments – can lead to a higher level of nutrients 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.
Occasionally they will obtain the services of one or two external workers to assist if there are above average orders. They are fully GLOBALG.A.P registered which opens doors to supply various well-established markets and clients. Their online system is able to manage everything from an app. Electronic observation devices are fitted in different locations on the farm in order to view reservoir levels, the site surrounding the greenhouses and then inside the greenhouses in order to scan every aspect of movements in the production site at any At Go Gourmet, the seedlings for leafy greens are time on a smart phone. produced in-house to have full control over quality. Harvesting commences early rain water. Of interest; the farm uses 20 morning, sometimes up to 000 litres a day against a conventional midday and produce is delivered straight farm of the same size which uses about into the cold room to leave very little 90 000 litres per day. Thus, undercover space for losing quality. Many farmers farming water savings are huge. have trouble with the excessive heat, but Go Gourmet is run by only 7 people. on this farm, the movement of produce
and management of temperature in the greenhouses offer little variation in temperature during planting, production or harvesting times. Go Gourmet raises its own seedlings, obtained from various seeds suppliers, in order to have full control over quality from seed to supply. For Go Gourmet, optimum productivity is key and is possible with their technologies at hand and staff that are proud to be a part of Go Gourmet and its mission as stated on their website: ‘Our mission is to hydroponically grow the most nutritious, quality produce in South Africa. Our whole team has grown a real passion and respect for the production of healthy, real, clean foods. They are proud to be a part of the Hydroponics Industry and what its aims are. Go Gourmet is a fairly new fresh produce business which is run by management and workers in a most orderly, hygienic and businesslike fashion and will go from strength to strength, especially with the new expansion envisaged.
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. 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 Go GoUrmeT
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WETLAND SYSTEM 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. 10
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Haifa Chemicals
is pioneering the future of
Calcium Nitrate Nutrigation™ All greenhouse growers will know that calcium (Ca2+) is an element that is required in large volumes by most plants. These include tomato, pepper, lettuce and cut flowers etc.
H
owever, calcium can be a very delicate nutrient to manage, not only in the nutrient solution, but also in the plant itself. Calcium is specifically known to cause chemical interactions with other nutrients when present in high concentrations, e.g. phosphates and/ or sulphates, within the same nutrient solution stock tank. Furthermore, certain growing systems and environments tends to create abiotic conditions that predispose a potential calcium deficiency within the plant or fruit. Selecting the correct fertilizer product for your unique farming system will ensure that your plants have the best possible fertilizer which promote nutrient uptake and results in optimal yield and quality. Haifa Cal™ Prime is the new improved and concentrated calcium nitrate fertilizer from Haifa South Africa. Haifa Cal™ Prime is 100% water soluble and is setting new standards with its near zero ammonium (N-NH4+) level. Standard calcium nitrate typically contains between from 1.1 – 1.5% ammonium nitrogen. Haifa Cal™ Prime contains 0.3% N-NH4. This unique property becomes very important when growing soilless crops, especially in NFT or soilless systems which have low buffering properties. Research by Kafkafi (1990) has clearly shown that elevated N-NH4+ levels and subsequent plant uptake becomes dangerous and detrimental within the plant at high temperatures and radiation levels. These challenging growing conditions, coupled with a dry/ low humidity
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potential toxic effect thereof within the plant. Haifa Cal™ Prime is highly concentrated and offers a 10% increase in nitrate (N-NO3-) contents and 24% increase in calcium compared to other calcium nitrate products. The higher level of nitrate nitrogen (N-NO3-) further promotes the uptake of other important cations, including Ca2+, Mg2+ and K+. The superior solubility compared to other calcium nitrate products, makes Haifa Cal™ Prime extra convenient to apply Haifa Cal™ Prime is by Nutrigation™ or foliar spray. Further the new improved and improvements concentrated calcium with regards to nitrate fertilizer from hygroscopicity Haifa South Africa. also ensures that Haifa Cal™ Prime is Haifa Cal™ 100% water soluble Prime remains dryer for longer and is setting new when exposed standards with its to air. These near zero ammonium characteristics make (N-NH4+) level. Haifa Cal™ Prime the ideal option when needing to supply you crop with climate, are typical to most of South the best source of water-soluble calcium Africa’s production areas. With elevated nitrate on the market. plant transpiration and subsequent water uptake, it is even more important to ensure a nutrient solution with near zero levels of N-NH4+ to reduce the
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Contact your closest Haifa distributor for details about this unique product offering.
NEW
Haifa Cal™ Prime Concentrated Calcium Nitrate + More calcium + More nitrogen + Near zero ammonium Haifa's new prime grade of calcium nitrate offers multiple benefits for growers who seek the most precise results in challenging growth conditions. With high concertation and near zero ammonium level this new product sets new standards of calcium nitrate.
Ideal for soilless grown crops and hydroponics
Haifa South Africa
Recommended for zones of high sun irradiation
P.O.Box 1409, Brackenfell, 7561, South Africa Gerrit Burger | 082 8008766 | gerrit.burger@haifa-group.com Michael Koch | 083 2314516 | michael.koch@haifa-group.com www.haifa-group.com
Extra convenience in handling
GreenHoUSeS I SHade neT I HYdroponIcS I aqUaponIcS
Coping with physiological disorders in lettuce Lettuce is an increasingly important vegetable in salads, especially in urban areas. It is a cool season crop, very sensitive to high temperatures, and grows best within a temperature range of 17°-27 °C during the day and 3 °-12 °C at night. Cool nights are ideal for good quality lettuce.
L
ettuce grows best in areas having mild summers and mild winters. Night temperatures below 3 °C can retard growth rate. Lettuce does not suffer from light frost and winter cold, except near maturity. Severe frost before harvest can scorch leaves and heads. Matured crisp head lettuce can get frost damage if not harvested immediately. During the hot summer months of South Africa, lettuce has poor head development or loose heads, a bitter taste, and physiological disorders such as ribbiness, bolting, multiple-heads and high internal stem growth. At temperatures above 27°C, most of the cultivars do not germinate. Under higher temperatures lettuce quality will deteriorate with the accumulation of bitter latex in the veins and leaves becoming tougher. These conditions also promote premature seed stalk development, i.e. bolting. Cultivar selection is important when growing lettuce during summer in soilless conditions. The research conducted at ARC-VOPI in a 40% black and white shade net house showed that good yield manaGInG WaSTeWaTer From HorTIcUlTUre
7
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
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Martin Maboko
Bolting
of high quality crisp head lettuce can be obtained when grown in a GFT system during the summer season. Generally, the internal stem should not be more than half the head height, i.e. it should not be more than 0.50 core ratio (stem height to head height). If the core ratio is more than 0.50, it indicates that the plant is not growing in a favourable environment. Cultivars that have a short internal stem generally indicate resistance to bolting. Long internal stem height indicates that the plant is about to bolt. Cultivars with a protruding growth of the midrib caused by ribbing are considered unmarketable. This is because the 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
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prominent midrib is easily snapped when wrapping crisp head lettuce. This results in an unattractive discolouration of the affected area due to damaged respiration cells of the affected area.
Bolting Bolting is a serious physiological disorder caused by the formation of an elongated stalk with flowers and, subsequently, develops seed. Bolting in lettuce causes the leaves to be bitter and tough. It occurs under conditions where plants are exposed to high temperatures during the early stages of growth. Author: Martin Maboko, researcher. the water in the system. That is, the time taken from when the water enters the system to when it exits. The 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.
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
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Thresholds on private power generation curtails agri businesses While the current regulations on private power generation (embedded energy generation) have aided many agriculture operations to cut their energy costs significantly, the imposed threshold on small-scale embedded generation (SSEG) is excluding many larger agricultural businesses from meaningfully utilising renewable energy.
M
anie de Waal, CEO of Energy Partners Solar, explains that the existing legislation allows private organisations to generate their own electricity with a total installed capacity of under 1 Mega Volt Ampere (MVA). Installations over 1MVA are allowed, provided that they are awarded a generation license by NERSA. “There are a lot of opportunities for larger energy-intensive agricultural operations to cut their electricity spend and become more efficient through the use of renewable energy. Dairy farms and abattoirs, for example, are prime candidates for photovoltaic (PV) systems larger than 1MVA in size, owing to the fact that they require constant energy for heating, cooling (refrigeration) and milking
every day of the year,” de Waal said. However, he notes that the requirement that these systems need to be licensed is a major impediment. “NERSA has put procedures in place for businesses to apply for generation licenses, but we know from
experience that these are almost never granted.” De Waal adds that this limitation placed upon SSEG systems (larger than 1MVA) also seems quite arbitrary. “We have seen grid-tied PV systems
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greenhouses I shade net I hydroponics I aquaponics
Managing powdery mildew –
common disease on sweet peppers The consumer wants a quality product and in the production of quality sweet peppers, Powdery Mildew is the most common disease and of vast economic importance. The only effective way to control Powdery Mildew is to have a holistic approach in the production of sweet peppers.
P
owdery Mildew in peppers grows within the leaf and can be latent in the plant for 21 days before it becomes obvious as having already infected the crop. It can result in defoliation of the plants, from which recovery is exceptionally slow. Hence, it is essential to monitor a crop carefully and react quickly. During its infection of the plant, powdery mildew utilizes nutrients from within the plant, interferes with photosynthetic processes, increases transpiration, impairs growth, and increases leaf drop and flower loss. Generally, a 10% infection/ infestation will result in a 10% yield loss. Conditions that encourage the growth of powdery mildew include 15.5 to 27°C, although powdery mildew can survive at temperatures as low as 4°C. Low light intensity and powdery mildew has the ability to even germinate in the absence of water. On the other hand, suppressive conditions include water on the plant surface for extended periods of time, day temperatures above 32°C and night temperatures above 18°C, direct sunlight or high pH conditions on the leaf surface. As part of a preventative mechanism, the plant produces papillae which attempt to isolate the infection within the leaf. However, the production of these papillae is very dependent on the availability of vital nutrients to the plant. Magnesium is required for energy production in the building of the papillae. Calcium is required for material formation, whilst the manganese is necessary for biochemical processes and as a cell-defence response. The consumption of these nutrients by the plant does lead to a reduced availability of these nutrients to normal plant processes resulting in reduced growth and development. The management of the fertigation and irrigation system is essential in controlling the infection. Pulsing has been found to be a highly effective irrigation technique that results in creating a low water tension in the soil medium and consequently increasing yields. Frequency of application is more important than the amount of fertilizer being applied, and this can be
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Well-maintained humidity and climate control offers good quality peppers.
directly related to the increased availability of phosphorous and manganese. The importance of light in pepper production is little considered, particularly with regards to field pepper production. Fields obtaining large amounts of afternoon sunshine are less susceptible. Air movement in the tunnel or in the field is also important and planting in the direction of the prevailing wind for field production will also be advantageous in reducing disease incidence. Good soil preparation also assists in the control of powdery mildew infections. A soil analysis is essential in ensuring that the balance of the nutrients in the soil is correct as this will increase the resistance of the crop. The control of soil pathogens is also an important part of this process, particularly with regards to Conditions nematodes. It is that encourage essential to apply the growth of powdery mildew 3 applications of include 15.5 to nematicides to 27°C, although catch all the phases powdery mildew can survive at of the growth of temperatures as the nematodes. It is also important to plant your seedlings correctly. Seedlings should be planted only
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low as 4°C.
as deep as the top of the plug. Transplanting of younger seedlings is better as it allows for better root development. Direct seeding should also be considered as it eliminates transplant shock. Oxygen in the root zone is extremely important, it assists in energy production, produces a healthy root system (longevity, health and yield), assisted by the incorporation of organic matter at planting, minimal compaction of the soil and prevention of over irrigation. Fungal sprays and spray management are an integral part of your powdery mildew preventative program. Preventative sprays are really important, start early. Use only registered products, benlate. Bicarbonates of sodium or potassium have been found to be effective as have neem oil and sulphur burners. Systemic sprays should be followed by contact sprays. For the right variety to suit your purpose talk to your seed supplier to supply you with a suitable variety and provide the necessary technical know-how to produce top quality sweet peppers. Source: Tech. info from various seedsmen.
greenhouses I shade net I hydroponics I aquaponics THreSHoldS on prIvaTe poWer GeneraTIon
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much more effective way to generate the maximum amount of electricity. Entering into a PPA would see a dedicated service provider owning and managing the PV system on site, while selling electricity to the client at a guaranteed lower rate. PPA providers are also well equipped to get the necessary approvals from the local municipality in the shortest amount of time.” Next, he says that other energy-related solutions are also needed. “For a business to be truly energy efficient, it should review its total power usage and develop a holistic energy efficiency strategy. Stateof-the-art energy management coupled with outsourced power (solar), cooling (refrigeration) and heating solutions can help to reduce the operation’s overall energy footprint, while an experienced service provider can also assist by negotiating special tariffs with local municipalities.” De Waal adds that getting these services from a single provider is advantageous. “Energy Partners provides a host of
outsourced utility services: power (solar), cooling (refrigeration), water and heating (steam). We have extensive experience, having coordinated integrated energy strategies underpinned by key outsourced utilities for a number of large Sub-Saharan companies.” In closing, De Waal says that there is a serious need for government to review the limits that it has placed on independent energy generation. “The country’s economy is underperforming and the agri sector cannot afford to lose money on needlessly expensive energy tariffs. We believe that if NERSA does away with the 1MVA cap, it will allow these operations to become more selfsufficient, lower the cost of their products and increase employment significantly. “However, until that happens we would encourage all agri businesses to partner with service providers who have a proven track record of finding innovative solar energy solutions that reduce their clients’ monthly electricity spend,” Manie de Waal From: MSL concludes.
10 lime to increase the capture of phosphate.
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. By: JB Parker (NSW)
much larger than 1MVA (commissioned before the introduction of the licensing requirements in 2018) run smoothly, without causing any disruptions to either the client or the national grid. In our opinion, requiring businesses to apply for a nearly-unattainable licence before they can become more self-sufficient is an unnecessary barrier for growth.” With this in mind, De Waal hopes that the Minister of Energy reviews the existing energy regulations and removes this limitation in the near future. “In the meantime, we believe that the best option for South Africa’s large agri businesses is to get the most out of SSEG systems (smaller than 1MVA). This only requires approval from the local municipality, which is fairly straightforward to attain” Firstly, he advises that the business enter into a power purchase agreement (PPA) with a capable service provider. “There is nothing that stops an agri business from installing and operating its own PV system. However, outsourcing this function is a manaGInG WaSTeWaTer From HorTIcUlTUre
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
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. OTHER ISSUES 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.
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Hydroponically grown tomatoes:
yield and quality response to growth medium Crop production in intensive plant production units requires cost-effectiveness and productivity to be economically viable. A popular growing media (soil-less substrate) often used in the South African greenhouse industry is fresh pine sawdust-shavings. But this substrate is biologically unstable and resources become limited.
T
he greenhouse industry has been investigating alternative organic substrates such as coco peat, which is more stable and in a state of decomposition, although relatively expensive compared to pine sawdust-shavings as well as biological inactive mediums such as sand and/or perlite, to improve productivity. The main objective of a comprehensive research study at the University of Stellenbosch, was to compare the growth, yield and quality of hydroponically grown tomatoes in response to different growth mediums in combination with nitrogen source, irrigation frequency, period of substrate use and liming. From the results it became clear that all these factors influenced the root environment (drainage water) and subsequent growth and quality of tomatoes. Due to different substrate characteristics, crops grown in coco peat may have different cultivation requirements. Coco peat produces the highest number of marketable fruit and yield per plant, but it is important to treat the substrate with lime prior to planting to prevent the development of BER (blossom end rot) and a low drainage water pH during the
growing season. Lime can assist in BER prevention. Irrigation scheduling is very important when coco peat is used. The high cation exchange capacity of coco peat creates an opportunity for the build-up of fertilizer salts during conditions with high temperatures and when insufficient water volumes are applied per irrigation cycle. Leaching of salts need to be done. Coco peat substrate produces a high number of marketable fruit and yield per plant, over pine sawdust-shavings and sand in the first season of substrate use. Growers also need to be very careful with the use of NH4+-N in coco peat as the phytotoxic effect seems to be more severe, especially in the second season of substrate use, compared to pine sawdustshavings. Decomposition, nitrogen immobilization and waterlogging conditions seem to be some of the biggest A healthy truss of tomatoes.
problems in the second season use of pine sawdust-shavings. Sand produces the lowest marketable yield and the highest percentage of fruit affected by BER. Further research into increased effectiveness and productivity of tomato crops in intensive plant production systems were conducted during a series of experiments in greenhouses at the Welgevallen experimental station at the University of Stellenbosch. During three years in succession the effect of three growth mediums, three irrigation frequencies, three nitrogen source ratios, two periods of substrate use and four lime application levels were evaluated.
Tomato plants in a hydroponics unit, planted in bags in a mixed medium of cocopeat and perlite.
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Growth and fruit yield The stem diameter of tomato plants
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Increasing fruit and plant brix
requires nutrient program adjustment during winter months Most people have noticed the poor taste and sweetness of fruit during the winter months; this is by no surprise for the following reasons.
D
uring the winter months / cool seasons, plants require less water (which contains nutrients) due to lower air and soil temperatures, which reduce transpiration and slow the “metabolism� of the plant in general. Shorter days further limit water and nutrient uptake, exacerbating the above-mentioned problems. Most elements required by plants exist in an elemental form such as K+, Mg2+, Ca2+, but others such as phosphate and boron only exist in a compound form. These compounds are longer and slower moving than those elements in the elemental form and thus phosphate and boron are often deficient and limit growth and production in winter / cool conditions. As these elements are slower moving and there is less flow within the soil / media due to reduced transpiration, these tend to limit plant growth and productivity severely in winter. Phosphate and carbohydrates from photosynthesis are responsible for the energy of the plant (ATP & ADP). Testing the plants stem or petiole sap with a portable refracto-meter will be indicative of the phosphate status. Calcium is a rather large ion and uptake is dependent on high transpiration rates to get translocation within the plant. An adverse climatic condition that reduces transpiration such as excess cloud cover, humidity or even wilting due to excessive heat or transpiration will negatively affect calcium uptake. Thus the low transpiration rates in winter will result in low calcium levels. Calcium uptake is also impeded by excess magnesium and by moderate levels of ammonium (NH4) in the soil or media. Calcium and boron work together synergistically and should always be applied together. Calcium deficiency is the cause of bitter pith in apples, blossom end rot in tomatoes, black rot seen on the flower end of watermelons to name a few. Using a refracto-meter, test the calcium levels by using plant stem / petiole sap again, a blurry line indicates good calcium levels.
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Testing brix with a refractometer.
calcium deficiency in watermelon and sweet melon. Potassium is the macro-element used in greatest amounts, especially during the flowering and fruiting stage. As uptake is reduced in winter, this is likely to be the element that is most limiting, hence the small fruit seen in winter as potassium is key in the expansion of plant / fruit cells and ultimately fruit size. A refractometer kit.
Take note: The microbes that convert ammonium to a nitrite and then to a nitrate are virtually inactive in the winter months and thus nitrates must rather be used. Sandy soils / hydroponic substrates with low organic matter content / humus are not conducive for soil microbe proliferation and thus ammonium use on these soils is not recommended, or should be in moderate amounts i.e. 5 to 10% of the total nitrogen application. This is one of the main contributors of blossom end rot in tomatoes and
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Low fruit brix is mainly the result of low potassium and boron! Plant sap with a low brix is the result of low calcium and phosphate! There seems to be a correlation between the plant sap brix and fruit brix and thus one must address all four of these elements as a safeguard. By increasing the plant brix, a grower can reduce the incidence of frost damage as the higher the brix, the lower the freezing point within the plant.
GreenHoUSeS I SHade neT I HYdroponIcS I aqUaponIcS
How UV Technology
for disinfection of run-off water works The UV technology is both the oldest and one of the very latest technologies used to disinfect fluids. The method is based on the natural disinfectant action of the sun’s rays. Low-pressure UV lamps imitate the disinfecting rays of the sun.
T
he reaction time between the UV irradiation and the organism to be killed is very short and does not create any by-products at all. The water quality, both physical and chemical, remains identical before and after treatment using the low-pressure UV technique. UV disinfection can therefore take place at any conceivable and necessary place in a system. Due to the low operating costs, these installations are very efficient economically. Their compact structure allows the installations to be set up in the smallest spaces. No chemicals need to be stored. The system operates without problems and is completely hazard-free. There are no undesirable by-products. Before examining the technologies and methods used, one needs to understand the underlying concepts, like “What is UV?” UV rays are energy-rich electromagnetic rays that occur in the natural spectrum of sunlight. They are in the invisible shortwave light band.
UV radiation gives rise to a photochemical reaction in the DNA, which leads to the formation of dimers, preferably at the level of the thymine bases. This prevents the naturation (bonding) of the adenine bases, and as a result further cell multiplication and metabolism is interrupted.
UV rays are divided into the following categories:
The radiation range below 200 nm consists of ionising ozone-generating or hard rays. The low-intensity lamps used for UV disinfection have their maximum capacity at 254 nm and therefore cover almost the entire absorption curve of DNA.
also means that the disinfectant effect is reduced as the radiation lessens. Transmission is the capacity of a substance to allow UV light (± 254 nm) to pass through it, as measured across 1 cm of liquid. Here are transmission values for a few types of water (transmission through 1 cm): Type
In this way micro-organisms are deactivated and rendered harmless. No by-products are formed in this process which could give rise to a change in the water or have a negative impact on the taste of drinking water.
TRANSMISSION When light shines through water, the water stops part of the radiation. This
Transmission value (%)
Spring water Osmosis water Mains water Rain water Ditch water Waste water after biological
Vegetables Flowers Ornamental Plants Chicory
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96 96 90-96 80-96 60-80 60 Horticultural water 15-30 15-45 25-40 20-55
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Radiation doses The radiation dose is a measure of the biological effect of the UV irradiation. The effect depends on the organism needing to be killed. The measurement is expressed in mJ/cm² and/or J/m². The disinfectant capacity is dependent on: • The capacity of the UV lamp • The soiling of the quartz tube • The transmission of the fluid • The thickness of the fluid layer • The fluid flow rate
It goes without saying that whenever maintenance and/or repairs are carried out on the pipe network, full disinfection is required. The main components in the installations are the lamps that produce UV rays. The artificial production of UV radiation is almost always achieved using Mercury-Amalgam-Indium gas-discharge lamps. Gas-discharge lamps consist of a (usually elongated) discharge reactor. The gas (vapour mixture) inside such a lamp is sealed off from the outside world by an airtight seal. The electrodes are situated at both ends of the glass tube. In principle a distinction is made between two types of mercury gasdischarge lamps:
What UV dose is needed? mJ/cm² Coliform bacteria, legionella, faecal bacteria, streptococci, nematodes (eelworms) and yeasts etc. Pathogenic fungi, such as fusarium, pithium, Phytophtora, etc; Viruses such as cucumber virus, olpidium, cholera, etc.
• Medium-pressure UV lamps • Low-pressure UV lamps
3 to 40
HDUV Medium-pressure UV lamps have certain disadvantages. Systems fitted with them have higher operating costs. Since operating costs are usually a very important if not decisive factor when it comes to water disinfection, low-intensity UV lamps are used almost exclusively.
30 to 120
60 to 250
Avoid re-infection Experience has taught us that reinfection does not constitute a significant problem. Customers confirm that reinfection does not occur if the inlet and outlet pipes are kept clean and if the UV installation is able to function under perfect conditions. HYdroponIcallY GroWn TomaToeS
The main disadvantages are: • • • •
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decreased in pine sawdust-shavings and coco peat when the NH4+-N content of the nutrient solution was increased from 0% to 40% in the first season of substrate use. However, no difference was recorded when only NO3--N and 20% NH4+-N was used. In the second season of substrate use, stem diameter decreased significantly when 20 - 40% NH4+-N was used in sand and coco peat, but plants grown in pine sawdustshavings only indicated a decrease in stem diameter when 40% NH4+-N was used. A similar trend was observed between the first and second season of substrate use. From these results it is clear that plant growth in pine sawdust-shavings was not as severely affected by the addition of NH4+-N as coco peat and sand. The number of marketable fruit and yield decreased with an increase in NH4+-N content in the nutrient solution during production in warmer, summer
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High operating costs Low energy efficiency Short lifetime Rapid dirtying of the quartz tube due to high radiation density and high
conditions. Contrary to these findings, production in cooler, winter conditions recorded high yields when only NO3--N or 80% NO3--N: 20% NH4+-N was applied. It might be that 20% NH4+-N is less toxic during cooler, winter conditions. However, marketable yield was significantly reduced with increasing NH4+-N levels in the second season of substrate use. The addition of NH4+-N decreased fruit mass. Fruit quality Increasing levels of NO3--N as nitrogen source in the nutrient solution, reduced weight loss and increased the loss of fruit firmness of tomatoes during storage. Increasing levels of NO3--N also increased fruit pH and reduced total titratable acidity as a result of the negative correlation that exists between these parameters. However, 100% NO3--N was responsible for the highest increase in fruit pH during storage. NH4+-N nutrition could be
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surface temperature • Rapid overheating when water is not moving • Due to the high proportion of long-wavelength UV rays, recovery mechanisms in the cell are activated: this leads to less effective disinfection capacity • Breakdown of nutrients and conversion of nitrates into nitrites (horticulture)
LDUV It is true that low-pressure UV lamps can only work at relatively low power, but they do score more highly in terms of efficiency. This is because they produce a higher percentage of UVc light (up to 40%). The LDUV lamp is a: • Low-pressure lamp with a Mercury indium amalgam filling. • The UVc capacity of this lamp is only slightly dependent on the water temperature • This lamp can achieve high efficiency and a long lifetime when combined with a modern electronic pre-selection switch Low-pressure UV has many advantages over medium-pressure UV lamps: • Safe and low priced • User-friendly • No chemical changes in the disinfected water. Source: Research on UV filtration. toxic if applied at very high levels and therefore might reduce the uptake of water and calcium to the fruit, hence reducing shelf life. The application of NO3--N does not restrict growth and therefore allows fast development of the fruit with a fruit cuticle that is thinner and more elastic. It is important to note that careful balance in nitrogen source needs to be taken in the planning of tomato production in greenhouses. All interacting aspects have to be taken into account to obtain an optimal yield. Therefore, planning before planting is essential to ensure that all the relevant interactions (a combination of factors, including the type of substrate that is used, irrigation and fertigation practices, and the growing season of winter vs. summer) are taken into account to obtain an economic high yield and quality crop of tomatoes grown in greenhouses. Source: SU Horticulture
GreenHoUSeS I SHade neT I HYdroponIcS I aqUaponIcS
Overhasty public consultation on section 25 amendment slammed Agri SA is disappointed in the decision by die Ad Hoc Committee, tasked with the amendment of Section 25 of the Constitution, to not allow for proper consultation and public participation. The Ad Hoc Committee discussed the draft Bill to amend the property clause on 3 December 2019. Agri SA requested that the publication of the amendment Bill be postponed to after the December festive period. The request was, however, disregarded.
A
gri SA deems it problematic that the Committee has rejected a fair request to allow for proper public participation over such a controversial and potentially far-reaching step as amending an internationally recognised fundamental human right.
The Constitutional court held that: “It is not the Constitution, nor the courts, nor the laws of the country that are at fault. It is the institutional incapacity of the Department to do what the statute and the Constitution require of it that lies at the heart of this colossal crisis”.
There has not been proper “Agri SA has maintained throughout that engagement with the impact that there is no need to amend the property this amendment will have on South Africa’s international obligations, clause. It will have a massive impact on of international the economy and law and the on job creation that “Agri SA has maintained possible economic will eventually lead throughout that there is impact in general. to food insecurity,” no need to amend the De Chavonnes said Willem de property clause. It will has cautioned that Chavonnes, Chairman have a massive impact on South Africa is staring of Agri SA’s Centre of the economy and on job down a fiscal cliff. Excellence for Land.
creation that will eventually “The economy is in “The problem is lead to food insecurity.” a technical recession not section 25 of with spiralling the Constitution unemployment levels and a dangerous and this has been confirmed in various debt GDP ratio and the currency court cases and most recently by the reacting negatively to the news that Constitutional Court in the Mwelase the country’s economy has shrunk judgement.”
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by 0,6 % in the third quarter. We are concerned that international investment treaties will be in jeopardy where payment is not based on fair market value. The banking sector’s exposure is approximately R180 billion to the sector and lending are based on the underlying security of property.” Agri SA and its affiliates are engaged in large scale transformation projects and has shown their commitment to address the skewed land ownership pattern in South Africa. Agri SA is considering all available legal options to ensure the protection of property rights for all South Africans. Source: Agri SA
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