19 posts in this topic
В теплицах для предупреждения закупоривания системы капельного полива используют фильтры, ОЭДФ как постоянную добавку к маточным растворам, азотную кислоту для стабилизации по pH поливочного расствора. Капельницы работают без засорения 7-8 лет. Ортофосфорная менее удобна в использовании
Я знаю, что подобное тут уже обсуждали, но хочу подискутировать не на предмет того, как сделать из подручных средств, а того, как сделать правильнее без переплаты "за бренд".
Заодно, это мой способ разобраться в самой малопонятной для меня части технологии малообъёмки.
Имею цель кормить огурец на мин плите, для эксперимента, в мини-теплице.
Форум читал, итоги того, что усвоил, воплотил в схему ниже.
Идея работы следующая:
1. Имеем исходную воду с температурой 5-17С (в зависимости от сезона) и давлением до 3,8кгс.
Анализ воды пока не делал, но заранее предполагаем превышение ПДК по каким-либо элементам.
Чтобы решить эту проблему, устанавливаем обратный осмос с подмесом исходной воды в пропорции, которая определяется по результатам анализа.
Пропорцию контролируем по счётчикам G1 и G2, и если что, добавляем очищенную осмосом воду исходную, через клапан V1.
2. Полученная вода с допустимой концентрацией солей льётся в пластиковый бак, где поддерживается нужный диапазон уровней по датчикам Lv, L^.
Там же контролируем температуру, и если что, греем воду через ПТО и Р1 до нужного значения (пусть, 22С).
3. При необходимости полива включаем нагнетающий насос Р2, вода проходит через УФ-облучатель, и далее - на набор пассивных подмешивающих насосов, а также
байпасную линию. V2 используем для полива "простой" водой, V3 - для подкормки.
На выходе контролируем значения EC, pH, T.
Вопросы к аудитории:
1. Что скажете по поводу схемы -правильно ли я всё понимаю?
2. Какие датчики ЕС, pH на практике используются?
3. Какие фильтры обратного осмоса малой пропускной способности из доступных на рынке действительно работают?
Система приготовления и подачи питательного раствора в теплицу (растворный узел, миксер) своими руками.By Pyotr
Здесь продолжу описание идеи дозирования маточных растворов в воду для полива растений (способ приготовления питательного раствора) начатое в теме про растворный узел .http://greentalk.ru/topic/3538/?do=findComment&comment=51522
Данный принцип дозирования не нов и реализуется на распространённых и доступных комплектующих, но применён несколько нестандартный подход к составу и размещению удобрений и кислот в маточных баках и регулированию пропорции дозирования.
Является альтернативой механическим пропорциональным дозаторам.
Узел дозирования может готовить раствор в количестве от сотен л/час до десятков м*3/час и даже более при соответствующем подборе комплектующих.
Пропорция дозирования (МР/раствор) может составлять от 1/10 до примерно 1/500. Для нашего случая пропорция 1/200 -- 1/350 позволит использовать баки с МР небольшого объёма.
Для составления МР используются только простые соли (хелаты МЭ содержащие в комплексных удобрениях выпадут в осадок в данном случае), азотная кислота и хелаты МЭ:
Микровит К-1 хелат железа 3% DTPA
Микровит К – высококонцентрированный водный раствор хелатов микроэлементов Mn, Zn, Cu, Mo на основе ОЭДФ
Органо-Бор – высококонцентрированное удобрение бора.
В баке А кальциевая и калийная селитры и азотная кислота. рН очень низкий, ЕС очень высокая.
В баке Б сульфаты, фосфаты, нитраты и азотная кислота. рН очень низкий, ЕС очень высокая.
В баке М (микроэлементы) три вышеназванных раствора МЭ. рН = около 5, ЕС = 1-4 мСм/см2.(зависит от ЕС воды и пропорции дозирования). При таких условиях МЭ очень стабильны и выпадения в осадок не наблюдается.
Баки А и Б и трубки подачи этих мат. растворов могут быть прозрачными - при таких значениях рН и ЕС "цветения" не будет и от солнечного света там разрушаться нечему.
Бак М и трубка подачи обязательно непрозрачные.
В моём случае все баки по 20 л.
Фото по теме в альбоме http://greentalk.ru/gallery/album/495-система-приготовления-и-подачи-питательного-раствора-в-теплицу/
Так выглядит узел дозирования у меня. Видны два датчика уровня, которые следят за наполнением и поддержанием заданных уровней чистой воды (левая бочка, БАК_1) и раствора (правая бочка, БАК_2). Видны 2 фильтра МР (автомобильные). В подающих трубках вставлены иглы от мед. шприца - они ограничивают подачу МР. На остальные железки/провода не обращайте внимания.
На ФОТО 2 показано ограничение дозирования с помощью капельницы.
РИС.1 На этом рисунке изображена схема работы всей системы.
На этом фото можно посмотреть подключение фильтров и капельницы, которая выступает ограничителем дозирования МР.
При значительном расходе воды через ИВ на его входе образуется разряжение Р1 порядка минус 0.6-0.9 атм. За капельницей давление зависит от высоты водяного столба до уровня МР в баках и составляет менее минус 0.1 атм. Капельница открывается при перепаде давления вход/выход около 0.3 атм. и закрывается при падении до 0.2 атм.
Сетчатый фильтр лежит на дне баков с МР.
Конструкция простая и понятная, осталось расчитать сколько-чего-куда лить-сыпать, чтобы в БАКЕ_2 получился раствор с нужными рН и ЕС.
Доброго времени суток!Прошу совета.За копейки досталась теплица по "Митлайдеру" размером 60 на 12 метров,высота 4.5 метра.На оборудование теплицы имеется бюджет 1,6 млн рублей.Вопрос-как лучше выращивать томат,огурец,зелень в грунте или попытаться на указанный бюджет оснастить теплицу системой гидропоники или чем-то ещё???Имеет ли смысл в такую сравнительно небольшую теплицу устанавливать такое дорогое оборудование?
РН и ЕС можите понятно объяснить что от чего зависит, как посчитать, что хорошо что плохо? Я понимаю что это очень важные параметры, помогите разобраться. Больше всего интересует ЕС раствора и почвы. Как с ним считаться при минеральном питании? Как его посчитать, какие допустимые пределы? Все для песчаного грунта.
By Ольга Толмачева
Я не знаю, что вы имеете ввиду, говоря о раздельном дозировании. Если речь идет о голландской схеме, когда фермеру привозят все удобрения уже в растворенном виде, то нет. У нас стандартные растворные узлы, много лет успешно производимые нашей компанией Фито. На каждом растворном узле по две пары баков А и Б и кислотный плюс используем термически обработанный дренаж. Дезинфектор тоже наш Фито.
На растворном узле 6 каналов. Шестой применяется для микродозации биопрепаратов.
Уважаемые коллеги, интересует вопрос о расходе воды для выращивания килограмма продукции.не важно томат это,огурец или перец.да хоть цветы.так же интересует длительность оборота и наличие искусственного освещения..например для выращивания кг огурца в зимне весеннем обороте с искусственным освещением необходимо n литров воды.помогите с информацией
В зависимости от выращиваемой культуры, марки минваты, климатических и световых условий и вообще технологии выращивания.
Aligning energy and root zone management strategies for sustainable tomato cultivation 3/5
Aligning energy and root zone management strategies for sustainable tomato cultivation 2/5
We only feed our plants when they really need it
Aligning energy and root zone management strategies for sustainable tomato cultivation - Part 1/5
Adjusting drain volumes
Improving the Quality of Young Tomato Plants - Part 4/4
Improving the Quality of Young Tomato Plants - Part 3/4
Improving the Quality of Young Tomato Plants - Part 2/4
Less drain is good for plant and profit
Improving the Quality of Young Tomato Plants - Part 1/4
Recycling Drain Water: Improving the Efficiency of Water and Fertiliser Use
Crop rotation with an eye to the Water Framework Directive
Improving Tomato Fruit Quality
Water and EC management
Steering the root zone environment
Understanding Substrate Design
Reusing stone wool slabs is a risky business even in tough economic times
Movement of Water Through Plants
Aligning energy and root zone management strategies for sustainable tomato cultivation 3/5Article published in Practical Hydroponics and Greenhouses October 2013
Aligning energy and root zone management strategies for sustainable tomato cultivation 2/5Article published in Practical Hydroponics and Greenhouses June 2013
We only feed our plants when they really need itPeter Aarts started a company with his brother Willy and their father in 1990. In 1996 he continued the company with his wife Janine in a partnership. The company expanded from 1.5 hectares to 11 hectares. The cropping plan changed this year from two crops of cucumbers followed by tomatoes grown in autumn, to three crops of cucumbers. The decisive factor was the availability of virus-free cucumber varieties, plus the lowered margins for autumn-grown tomatoes.
The cucumbers produced by 't Bleekerven are marketed by growers' association Kompany. Two sales representatives ensure that the produce is supplied to the customers directly or via traders. “Through our marketing organisation we try to anticipate the needs of our customers as well as possible. Sustainable production is one of our spearheads.”
Aarts switched to using PRO blocks from the start of the latest crop. This was a conscious step taken after running a few trials and seeing the positive results at fellow growers. Critical to the choice for PRO blocks was the good initial crop development and the root growth. “The plants are slightly heavier, fruit set appears to be a bit faster and there is less fruit abortion. This was certainly apparent in overcast conditions, such as this spring. In the trial rows no fruits were lost, contrary to the other rows. In the PRO block the roots are well distributed through the block. This encourages the plant to root sooner and better in the slab. And that is vital, as the roots are the engine of the plant”, says Rudi Lenaers. He is responsible for cultivation and climate management at ‘t Bleekerven. Aarts adds: “The plant has a more vigorous appearance above ground. But it's still up to the grower to convert all these benefits into extra production.”
Since he started his company in 1990, Aarts has grown on stone wool substrates from GRODAN. In the intervening period he used perlite for two years, and for a number of years also used other types of stone wool. "We were attempting to find a slab that gave better moisture distribution so that enough air was retained at the base too.”
The downside of other slab types was the reduced resaturation capacity. The new GROTOP EXPERT slabs, which are being used by the grower for the third year running, distribute moisture better and re-saturation stays good throughout cultivation.
Aarts did not choose the slabs on his own, but with his two brothers- who both have vegetable growing companies. They purchase all their growing materials jointly.
Rudi Lenaers enjoys growing on the GROTOP EXPERT slabs. He drains the slabs to approximately 70%. At night, he lets them drain to 55 to 60% to activate the roots. The next day he can re-saturate the slabs back to 70% without any problem. “The slabs are easier to steer. That means you can irrigate until the evening and don't have to take any action until about half past ten to eleven o'clock the next morning in spring, and until between eight thirty and nine around the longest day in June. The slab is sufficiently saturated again by around midday. This makes plant management easier. You only have to irrigate and provide nutrients at the moment the plant becomes active and demands nutrition. Plus, the upper layer does not dry out. Thanks to the excellent capillary working of the slab it can be fully wet through and through.”
And of course it's an added bonus that the materials and the properties of the new PRO block are a good fit with the GROTOP EXPERT slabs.
The grower closely monitors new developments and is a keen innovator in many aspects of cultivation, such as a cleaning unit to clean the various sections, and a machine that can quickly lift cucumbers. 't Bleekerven is also innovative in irrigation practice and operates in line with the GRODAN vision, namely only watering and feeding plants at the moment the plant needs it. “You can only make that a success if you have all the right tools. As far as that goes we are making great progress.”
Kwekerij Peter Aarts
Aligning energy and root zone management strategies for sustainable tomato cultivation - Part 1/5Article published in Practical Hydroponics and Greenhouses March 2013
Adjusting drain volumesArticle published in Greenhouse Canada march-april 2013
Improving the Quality of Young Tomato Plants - Part 4/4Article published in Practical Hydroponics and Greenhouses March 2013
Improving the Quality of Young Tomato Plants - Part 3/4Article published in Practical Hydroponics and Greenhouses March 2013
Improving the Quality of Young Tomato Plants - Part 2/4Article published in Practical Hydroponics and Greenhouses November - December 2012
Less drain is good for plant and profitArticle published in: In Greenhouses October 2012
Improving the Quality of Young Tomato Plants - Part 1/4Article published in Practical Hydroponics and Greenhouses May - June 2012
Recycling Drain Water: Improving the Efficiency of Water and Fertiliser UseIntroduction
Inclement weather conditions impact massively on water uptake by the crop and therefore directly impact on the amount of irrigation water that is required (PH&G, Jul/Aug 2009). To allow the grower to exert total control of the root zone environment Grodan® substrates are now engineered so that WC Water Content) and EC (Electroconductivity) can be steered accurately, whilst at the same time using water and fertiliser efficiently. In this way day level EC and WC can be managed according to the prevailing weather conditions, plant balance and energy input into the greenhouse (PH&G, Nov/Dec 2009). However, as with all things horticultural, there is no ‘magic button’ that you can press to ensure success, you need an overall plan, which meets both marketing (size and quality) and production (kg/m2) goals (PH&G, Jan/Feb 2010). The plan should be robust enough to enable the crop to cope with extreme temperatures and facilitate strong and regular growth even in the darkest periods of the year. With the support of the climate computer and measuring tools such as the WCM (Water Content Meter), continuous informed decisions can be made in respect to the (irrigation) strategy to steer the crop on a daily basis (PH&G, Mar/Apr 2010). The benefits that this knowledge can provide and how it can be used to improve the financial returns to the company by optimising fruit quality were subsequently addressed in the last article (PH&G, May/Jun 2010). In this, the final article of the current series, I will outline how growers can become more efficient at using water and fertiliser by recycling the drain water, demonstrating what is possible with current technology. I will also provide some useful tips on how mundane operations such as cutting and positioning of the drain hole can impact significantly on substrate functionality and water use efficiency.
How much water and fertiliser do you use and what does it cost?
Most growers when asked can tell you exactly how much they spent during the last cultivation cycle on labour and energy, but very few can actually tell you directly how much irrigation they applied per hectare and what it cost. The cost can be significant. The average water use for a tomato grower using Grodan stone wool substrate in Europe is approximately 1.25m3/m2 per year (2.85mL per joule) with 25% drain (0.312m3). The cost of fertiliser is close to €0.5/m3/EC unit. With an average EC of 3.0mS the total cost to the grower in this example would be €1.88/m2 or €18,800/ha.
3.0mS x €0.5/m3/EC unit x 1.25m3
Recycling drain water
In the above example recycling the water would reduce the fertiliser bill to approximately 1 Euro/m2. This excludes disinfection cost, which for a Priva UV Vialux system is approximately €0.15/m3. Recycling the drain water in a ‘closed system’ should therefore be a ‘no brainer’, simply based on the costs savings that can be made year on year. In addition, recycling also presents a positive company image and will most likely play a significant role in any company’s external sustainability message towards its customer.
Figure 1: Advised standard graphic to illustrate the development of WC and EC in the substrate in respect to incumbent weather conditions.
Water, of sufficient quality, is already a scarce resource even in areas of Northern Europe where the annual rainfall is abundant. However, greenhouse growers can be proud of the fact that they already use water more efficiently compared to open field production. Greenhouse operations recycling their drain water in The Netherlands consume approximately 15 litres of water per kilogram of fruit produced. This compares to 60 litres of water per kilogram of fruit in an open field situation in southern Spain. The scarcity of water is of course more acute in most areas of Australia. It is therefore important that you use water as efficiently as possible. This can only be achieved with good irrigation management practices, drain water collection and recycling systems. Do not underestimate the importance of the substrate. This should be of uniform quality allowing you to steer WC and EC accurately. Key functionalities are the ability to steer water content on a low day level (40-45%1) in winter and a higher level (75-80%1) in summer, whilst at the same time being able to change or refresh EC quickly in periods of changeable weather. In this respect the climate computer should allow you to implement flexible irrigation settings (PH&G, Mar/Apr 2010) in combination with providing good graphics (Figure 1) as this will enable you to make informed decisions regarding any necessary adjustments to the settings on the computer.
Worldwide, growers are also coming under increasing legislative pressure related to the emission of water and nutrients from the greenhouse, particularly in the countries making up the European Union and more recently Ontario, Canada. Within Europe the Dutch Government has gone one step further, due largely to the concentration of horticultural holdings, and announced the Kaderrichtlijn Water, 2010 (Water Directive, 2010). In essence, this directive has the goal of realising zero emission of fertilisers from the greenhouse by 2027. The goal is extremely ambitious and will not be achieved unless technological advances in nano-filtration, in-line ion measurement, and precision dosing
technologies can be commercialised. However, there are many things that can be implemented today based on current technology to help reduce environmental emission,
even if legislation is not yet forcing the issue, notably:
Adequate rain water storage (i.e. a pure source of water with no Na+ contamination) in Northern Europe based on an annual rainfall of 800mm (80m3/ha) dictates 500m3/ha. Adequate drain water storage (in Europe, specification dictates 40m3/ha). Accurate application of water and fertiliser. Accuracy within the distribution system (i.e. uniformity dosing equipment and drippers). Re-using first flush. (First flush describes water emitted from the substrates following the action of cutting the drain holes.) Minimal drain per cent during the cultivation with more accurate steering of WC and EC in the root zone combined with regular monitoring and adjustment of nutrient levels. Table 1 illustrates the levels of emission reduction that can be achieved with drain water recycling and implementation of a structured irrigation strategy to minimise the drain volume.
Table 1: Theoretical emission on N (Kg/ha) from commercial greenhouses Strategy Nitrogen emission (Kg/ha) 1. 100% run-to-waste ‘open system’ realising 30% drain 945 Kg/ha 2. 85% re-use and realising 30% drain 142 Kg/ha 3. 85% re-use and realising 15% drain 71 Kg/ha Data assumes a water application of 1250 l/m2 with an average N application during the cultivation 18mmol/L.
In Holland, a survey of 46 tomato growers by Guus Meis (LTO Glaskracht) found that the average N emission was 115kg/ha, which is very close to the figure 85% re-use and 25% drain. There are a number of reasons why with current technology drain still required (Table 2).
Table 2: Reasons to run-to-waste during the production cycle Reason Possible causes Uniformity of greenhouse design Hot spots and cold spots resulting in differences in water uptake by the crop – (i.e. heating in winter/pad and fan in summer). Unbalanced nutrient solution Start of the crop (i.e. flushing coco slabs).
Infrequent slab/drain analysis.
Adjustment of drip solution. High sodium content in drain water Quality of primary water supply.
Quality (purity) of fertiliser. Equipment limitations and/or failure No reverse osmosis unit.
Insufficient drain water storage capacity.
Failure of disinfection equipment (i.e. T10 values of drain solution). Subjective grower opinions/observations ‘Fear factor’ of re-using first flush.
Grodan is a pioneer in precision growing, providing root zone solutions for its customer base worldwide. In this respect Grodan has committed its Application and Development program to generate knowledge that will assist growers apply water and fertiliser more efficiently, reducing costs and minimising emission. This is the number one precondition for environmentally friendly horticulture today and in the future. One way to reduce emission within the confines of current technology is to optimise what you apply from day one.
Initial saturation of the substrate
At the start of the cultivation cycle Grodan stone wool is saturated with a complete nutrient solution. The drain holes are then cut and excess nutrient solution drains from the slab. A standard slab configuration (133 x 15 x 7.5 cm) will require 15 litres of nutrient solution for complete saturation, with approximately 6000 slabs per ha. This equates to 90m3/ha water and fertiliser. For maximum steering in the WC control range for your chosen slab type, Grodan advise one drain hole per 133 cm slab length (see side panel tips for drain hole cutting). This should be cut at the lowest point in the slab (Photo 1a and Photo 1b) and be ideally positioned at least 20cm from the nearest dripper. This will allow maximum irrigation efficiency (i.e. it will generate minimal drain volumes whilst providing excellent EC refreshment in the slab (Figure 2).
Photo 1a (left): Drain hole positioning Example a.
Photo 1b (right): Drain hole positioning Example b.
Figure 2: Effect of drain hole location to the proximity of the dripper on EC in the drain solution. A higher drain EC = higher irrigation efficiency as more substrate solution is replaced.
Tips for drain hole cutting and positioning
One drain point is required per 133 cm slab. For slabs longer than 133cm in length one or two drain holes can be cut, based on the preference of the grower. Please note more drain holes will make it harder to re-saturate the water content in the slab in spring. Also, more drain will be required to level the EC in the slabs. The closest distance between first dripper and drain hole defines the water behaviour in the slab. The greater the distance, the more refreshment and re-saturation can take place in the slab. In the Next Generation assortment the advice is at least 20cm. The cut should be made at the lowest point at the end of the slab in the direction of the slope. In case of an uneven profile, extra drainage holes will be required once the slabs have settled at the lowest point. Never make the drainage holes directly below a propagation block or irrigation pin. Managing emission at the start of the crop
When the drain holes are cut approximately 2 litres of drain solution will be realised (12m3/ha). Grodan stone wool is chemically inert. As such, what you apply in the drip is what you receive back in the drain (Figure 3a). If this solution is allowed to run-to-waste it can result in significant emission, particularly N to the environment (Table 3). In some circumstances, one reason for not re-capturing 100% of this solution is that the drain volumes created can cause the hanging gutters to overflow. If this is the case, to manage the flow the drain holes can be configured in two stages (Figure 4).
Table 3: N emission (kg/ha) from first flush using standard feed
recipes for tomato, pepper and cucumber. N emission (kg/ha) Tomato Pepper Cucumber N emission Grodan based on first flush 12 m3* 3.95 2.86 3.53 N emission Coco based on first flush 24 m3 7.90 5.72 7.00 * Only if first flush is allowed to run-to-waste.
Figure 3a: Analysis of drip, slab and drain solutions during initial saturation of Grodan slabs.
Figure 3b: Analysis of drip, slab and drain solutions during initial saturation of coco slabs.
Figure 4: Managing the flow of drain solution by two-stage cutting of the drain holes.
However, it is perfectly safe to reuse the first flush from Grodan slabs, provided that the drain basin is free of chemicals used during the clean-up of the old crop, a strategy that would result in zero emission (Table 4). Conversely, our research indicates for a like-for-like substrate volume, coco realises twice the initial drain volume (i.e. 24m3/ha) and, therefore, twice the N emission based on the application of the same nutrient solution (Table 3). However, as coco is not chemically inert the drain solution is not balanced (Figure 3b) and would require blending (EC 1.0mS) prior to reuse. However, due to the tannin content in the drain solution, this is not possible (Photo 2b) as the T10 values are not at acceptable levels until at least 60 l/m2 (600m3/ha) water has been applied (Figure 5), equivalent to the volume that would be required in the first 8-10 weeks of a winter crop
grown on Grodan.
Photo 2a: Colour of first flush from Grodan is clear, permitting immediate and effective use of UV sterilisation systems and, therefore, reuse of first flush.
Photo 2b: Colour of first flush from standard coco is brown due to tannins. Use of UV sterilisation is not advised due to inadequate T10 values.
Figure 5: Amount of flushing on coco required to achieve acceptable T10 values for effective drain water disinfection with a UV system.
The potential difference in N emission during the first flush and flushing period of coco is huge (Table 4).
Table 4: Potential emission (N kg/ha) from Grodan and Coco slabs for a tomato based on volume of 1st drain and volumes required to
reach acceptable T10 values for recycling the drain water. 1st drain Flushing Total Grodan 0 kg/ha 0 kg/ha 0 kg/ha Coco 7.00 kg/ha 59.20 kg/ha 67.10 kg/ha
Managing water and nutrient supply during cultivation
Emission reduction during the main cultivation period is achieved by recycling and working with minimal drain volumes (Table 1). Taking the example for a tomato crop further it is also possible to reduce the N-NO3 levels in the initial feed solution to 8-10 mmol/L for more ‘generative’ start to the crop, and then add 1 mmol/L per cluster until standard feed levels (16-18 mmol/L) are reached (Source: Groen Agro Control, The Netherlands). However, it is only possible to impact the desired crop response if you structure the irrigation strategy to target zero or very low drain volumes in the initial weeks of crop development. This is due to the uptake concentration of N-NO3 by the crop. That is, the more irrigation you apply (i.e. to flush the substrate), the more the crop lives from the drip solution and the effect of low N-NO3 feed minimised (Figure 6).
Figure 6: Slab and uptake concentration of N-NO3 at different drain volumes. (Source: Groen Agro Control, The Netherlands)
For winter planted crops the strategy would see the substrate EC increase and the WC fall (Figure 7). When the crop requires approximately 2 litres irrigation per day the EC can be stabilised at a lower level as first drain volumes are realised.
Figure 7: Development of EC and water gift at the start of a winter planted tomato crop in northern Europe.
For additional detail on how to structure an irrigation strategy to provide the level of control illustrated in Figure 1 refer to the article Water and EC management (PH&G, Mar/Apr, 2010), remembering the key triggers in the decision making process, notably:
Transpiration then irrigation. Drain by 400 J/cm2 or 600 W/m2. First drain in line with EC refreshment. EC refreshed and stable in line with global radiation during peak solar hours. Stop irrigation in relation to plant activity for a stable decrease in WC. It is also worthy to note that on the dark days in winter to maximum rest time will drive the total volume of water you give (assuming start and stop are correct). The values provided in Table 5 are a useful indicator related to radiation (W/m2).
Table 5: Guides for maximum rest time settings in line with light
intensity (W/m2). Number irrigations per hour Radiation (W/m2) 0-1 200 1-2 400 2-4 600 4-6 800
During the main cultivation period when the crop is growing quickly it is also important to take regular analysis (7-10 days) of the slab and/or drain solution because the balance of nutrient elements will change quickly. Regular adjustment will allow you to target fertiliser input more accurately and potentially recycle the solution for longer. In this respect remember that your drain may only be 25%, but that the drain solution may account for 33% of the nutrients you apply, due to the EC pre-setting on the computer (Table 6).
Table 6: Proportion of drip and drain solution used to irrigate the crop EC % Drip EC 3.0 mS Drain EC 4.0 mS Drain % 25% EC pre-setting 1.0 mS Proportion of new feed solution 33%
Managing emission at the end of the crop
Continuing with the example of the tomato crop planted in winter, the goal is to have the drain basins empty by the end of the cultivation, in effect using all the fertiliser you paid for. Implement the strategy about 4 weeks from the end of the crop (Figure 8). Start by increasing the EC pre-setting to 1.5-2.0mS so that you use proportionally more of the drain solution to provide the new feed, and work on lowering the drain volumes by decreasing the slab WC. This will result in less solution coming back to the drain basin and they will gradually empty. The reaction in the substrate will be lower WC and higher EC (Figure 9a and Figure 9b). Fruit quality should not be affected as all of the remaining clusters will be in the ripening phase of their development.
Figure 8: Managing drain towards the end of the crop. In this example the heads were removed in week 38. WC decreased and slab EC increased approximately 4 weeks from the end of the crop.
Figure 9a: Slab WC and EC are significantly reduced in the week prior to removal of the crop.
Figure 9b: Slab WC is reduced to minimal levels before the end of the crop. This practice not only minimises fertiliser use but also enables easier handling during turnaround as the slabs are lighter.
This article has highlighted the cost to the business of water and fertiliser and how these inputs can be minimised via drain water recycling. Sustainable growing means minimising water and fertiliser input whilst maximising output and quality. To move towards totally closed systems will require technological innovations, which are currently not commercially viable. However, recycling from day one, working with a structured irrigation strategy, and frequent nutrient analysis during the cultivation cycle to reduce the volume of drain required, will all help minimise the environmental impact in the short term. This was the last, albeit delayed article in the current series. I hope you found the content of each article interesting and the discussions they generated informative. All at Grodan wish you every success in the coming cultivation.
About the author
Andrew Lee works for Grodan as Business Support Manager for North America and Export Markets. He is a PhD graduate from the University of London, England, and has been working for Grodan® over the past 10 years providing consultancy and technical support for its customer base worldwide.
Article published in Practical Hydroponics and Greenhouses September - Ocotober 2010
Crop rotation with an eye to the Water Framework DirectiveCleaning and disinfecting
A new cultivation begins with cleaning and disinfecting the entire greenhouse. This also includes cleaning the entire irrigation system, from emitter through to the drainage collection system. It is important, for the successful start of the new crop, that this se is then rinsed and is completely free of cleaning agents before the new stone wool slabs are laid as residue from bleach or other products could inhibit the growth of the young plants.
Check the watering system
During crop rotation also take the opportunity to check how uniformly the emitters deliver water as an. uneven delivery system can result in uneven growth of the plants... In order to check how uniform your irrigation system is check the volume of water delivered by f number (i.e. 20) emitters in each irrigation section. If the delivery rate varies by more than 10%, we recommend that you take measures to address the problem.
The new slabs
After everything has been cleaned and checked, the new stone wool slabs can be laid. The film on the slabs indicates which side of the slab should face upwards in order to make the best use of the slab’s properties. This is particularly important for Grotop Master and Grotop Master Dry as these slabs have a unique patented dual density structure.
After the slabs have been laid, saturate them with a balanced nutrient solution and leave them at least 24 hours. If necessary, warm the slabs slowly while filling or before planting so as to prevent the young plants going into “cold shock” and subsequently falling behind in controlled uniform growth.
The drainage holes
After the slabs have been saturated and allowed to stand for at least 24 hours, the drainage holes can be made. Take care when deciding where to place a drainage hole. Grodan advises one drainage hole per linear slab meter. The best position for the drainage hole is at the lowest point of the slab, preferably as far from the emitters as possible, as this provides the best control of the substrate Ec. Please note that the number of drainage holes you make at this stage will have an influence on the resaturation capacity of the slab, i.e. the more drainage holes you cut, will influence the maximum re-saturation in Phase and 5 of cultivation.
Saving the first litres
Take your time when making the drainage holes, so that you can collect the water which is released from the slab. Each linear metre of slab may release as much as two litres of water. Take care that the drainage gutters do not overflow. One way to solve this problem is to first make a small hole, and once most of the “free water” has drained from the slab, make the complete cut. The cut should not impede the flow of water from the slab. It is absolutely safe to reuse the initial drain water. Remember the stone wool substrate is chemically inert this means that the water which drains from the slab has exactly the same nutritional balance as the water used to saturate the slab And because of this it can be used immediately, without blending to fill the slabs in another part of the greenhouse or to irrigate the young crop as required after planting. This is an extremely important benefit of Grodan substrates in light of the stricter regulations regarding the emission of fertilisers from greenhouses.
Table 1: Nutrient samples from irrigation water first drain in mmol/l EC pH NH4 K Na Ca Mg NO3 C1 S HCO3 P Si Irrigation water 2,8 6,1 0,5 7,0 1,1 7,7 2,2 19,9 0,7 1,8 0,2 2,18 0,25 Drainage water 2,9 6,1 0,5 7,5 1,2 7,8 2,2 19,5 0,8 2,0 0,1 2,12 0,26
Table 2: Nutrient samples from irrigation water first drain in μmol/l Fe Mn Zn B Cu Mo Irrigation water 17 12 12 83 1,6 0 Drainage water 16 13 12 80 1,7 0 More informatie
Themato recirculates all its water!
Improving Tomato Fruit QualityArticle published in Practical Hydroponics and Greenhouses May - June 2010
Water and EC managementArticle published in Practical Hydroponics and Greenhouses March - April 2010
Steering the root zone environmentArticle published in Practical Hydroponics and Greenhouses January - February 2010
Understanding Substrate DesignArticle published in Practical Hydroponics and Greenhouses November - December 2009
Reusing stone wool slabs is a risky business even in tough economic timesArticle published in De Groenten en Fruit week 43
Movement of Water Through PlantsArticle published in Practical Hydroponics and Greenhouses July - August 2009