Growers using containers to produce vegetable crops have options when it comes to growing in plant-based substrates.

Small- to medium-size growers of vining vegetable crops including cucumbers and tomatoes have traditionally used Dutch buckets filled with perlite as the growing substrate. While some growers may be concerned with the sustainability of perlite because of disposal issues, there are options when it comes to using alternative plant-based substrates.

Improving sustainability of controlled environment production

Uttara Samarakoon, who is associate professor and program coordinator for greenhouse and nursery management at Ohio State University, CFAES Wooster, has been studying ways controlled environment growers can improve sustainability of containerized vegetable production. Samarakoon is working with Teng Yang, a post-doctoral researcher at Ohio State University, CFAES Wooster, and James Altland, research leader Application Technology Research, USDA-Agricultural Research Service in Wooster. Their research is being funded by USDA-ARS.

“The main theme of my research program is on sustainability for controlled environment agriculture,” Samarakoon said. “The research we are currently doing focuses specifically on high wire crops, including cucumbers and tomatoes, produced in Dutch bucket systems.

“My experience when visiting small- to medium-size vegetable growers is that many of them are using perlite as the substrate in Dutch bucket systems. In addition to concerns with disposal issues for perlite, it also has a low water-holding capacity resulting in higher rates of leachate. I have been using perlite in my research for some time because that is the traditional substrate for Dutch buckets.”

Dutch buckets are not the common production system used in most large-scale controlled-environment vegetable operations.

“Large-size vegetable operations tend to use hanging gutters with rockwool or coir slabs for high wire crop production of cucumbers, tomatoes and peppers,” Samarakoon said. “Recirculation of the fertilizer solution occurs primarily with large-scale commercial growers. Most small- to medium-size growers don’t have the capacity to do recirculation.”

Identifying alternative substrates

Although Dutch buckets are primarily used for growing vining crops, Samarakoon said this method of production  is very similar to other types of containerized crop production. Even though the alternative substrate trials she conducted used Dutch buckets, she said the findings from her studies can be applied to any type of containerized crop production.

When Samarakoon was selecting substrates to compare with perlite she considered both sustainability and availability. In the first trial with cucumber, the researchers chose plant-based substrates, including sphagnum peat moss, two different grades (medium and course) of pine bark, coir and wood fiber (HydraFiber). All of these substrates were trialed against perlite, which was used as the control.

For the study, Dutch buckets were filled with 100 percent of each of the substrates.

“Our key finding was growing cucumbers in Dutch buckets, the amount of leachate can be significantly reduced with any of these plant-based substrates compared to perlite,” Samarakoon said. “The sustainability of this production system can be increased by using any of these alternative substrates. Although the substrates we trialed were not certified organic, there is the potential for growers to use similar substrates that are certified organic.”

The researchers found there was no difference in terms of time to fruiting and number of cucumbers produced regardless of the substrate trialed. One difference that occurred with medium-grade pine bark was an increase in fruit weight compared to perlite. However, the fruit weight of plants grown in medium-grade pine bark was similar to the other plant-based substrates.

Tomatoes in alternative substrates

Based on their success with cucumber, Samarakoon and the other researchers looked to repeat the study with tomatoes grown in the plant-based substrates. For these trials the Dutch buckets were filled with 100 percent sphagnum peat moss, medium-grade pine bark or wood fiber with perlite again as the control under two different irrigation regimes. The response was similar to cucumber with the number of fruit and individual fruit weight in plant-based substrates compared to perlite. Irrigation rates used did not influence the yield except in peat.

“The leachate rates were different among the substrates throughout the crop production with perlite having the highest amount of leachate,” Samarakoon said. “Therefore sphagnum peat moss, medium-grade pine bark or wood fiber can replace perlite without any yield reduction and the added advantage of reduced leachate for both cucumber and tomato.”

The tomato trial ran for 20 weeks until the plants reached the top wire support.

“We did not grow the tomatoes beyond that stage because it would have required lowering the vines and that could affect the type of data we collected,” Samarakoon said. “In our next tomato trial we will be using the same substrates but growing the plants in a nine-month production cycle. We will be lowering the vines and training them to continue growing for a nine-month production cycle in order to determine how the alternative substrates sustain the plants. We are also focused on optimizing the propagation of vine crops when using alternative substrates.”

For more: Uttara Samarakoon, Ohio State University, CFAES Wooster; samarakoon.2@osu.edu; https://ati.osu.edu/uttara-samarakoon-phd.

This article is property of Urban Ag News and was written by David Kuack, a freelance technical writer in Fort Worth, Texas.

Carson, CA — NovaCropControl, an industry-leading research and testing centre based in the Netherlands, has completed its independent study evaluating the impact of chemical-free nanobubble enriched irrigation water on tomato fruit growth, pathogen control, and nutrient uptake.

In a side-by-side study, NovaCropControl irrigated plants with technology provided by Moleaer, the global leader in nanobubble technology. Plants irrigated with Moleaer’s nanobubbles had:

• More efficient nutrient uptake and water usage
• Improved capillary root development
• Increased resilience to high heat
• Reduced Pythium levels of up to 80%

The study also showed plants irrigated with Moleaer nanobubble enriched water produced a 9% increase in fruit weight without sacrificing nutrient content or BRIX value (grams of sucrose). 

Tomatoes provide a rich source of vitamins A, C, K, and minerals, including iron and phosphorus, making them one of the most popular and valuable crops grown in greenhouses. 

Moleaer’s patented nanobubble technology is installed at over 200 horticulture facilities, enabling growers to enhance existing irrigation water, promote beneficial bacteria, suppress pathogens and diseases, and increase nutrient uptake.

Moleaer delivers these results by providing a consistent flow of nanobubbles to the plant’s roots to maintain high oxygen levels in irrigation water and deep water culture (DWC) systems. Increased root zone oxygenation through nanobubbles increases plant nutrient uptake. The outcome is healthier, more resilient plants, increased crop yields, and decreased time to cultivation.

“We know that improving water quality through increasing sufficient oxygen levels are important for plant health and crop resilience. Our trial confirmed that Moleaer’s oxygen-filled nanobubbles are a very efficient method of delivery,” said Koen van Kempen, Consultant, NovaCropControl Research Center.

“Nanobubbles are a complex science, but this latest third-party research demonstrates in the simplest of terms the value nanobubbles provide to our food supply by enhancing water quality, without using chemicals, to improve plant health and resilience to environmental stress, which ultimately leads to increased crop yields,” said Nicholas Dyner, CEO of Moleaer.

For more information, please visit moleaer.com.

About NovaCropControl

NovaCropControl is a research and test centre specializing in plant sap analysis. NovaCropControl aims to provide insight into the plant‘s nutrient uptake with a fast and accurate service based on low cost. To reach that goal, NovaCropControl uses plant sap analyses and, if necessary, in combination with (ISO-17025) accredited drip, drain or substrate water analyses. To learn more, visit: www.novacropcontrol.nl/en/method

About Moleaer

Moleaer^TM is an American-based nanobubble technology company with a mission to unlock nanobubbles’ full potential to enhance and protect water, food, and natural resources. Moleaer has established the nanobubble industry in the U.S. by developing the first nanobubble generator that can perform cost-effectively at municipal and industrial scale. Moleaer’s patented nanobubble technology provides the highest proven oxygen transfer rate in the aeration and gas infusion industry, with an efficiency of over 85 percent per foot of water (Michael Stenstrom, UCLA, 2017). Through partnerships with universities, Moleaer has proven that nanobubbles are a chemical-free and cost-effective solution to increasing sustainable food production, restoring aquatic ecosystems, and improving natural resource recovery. Moleaer has deployed more than 700 nanobubble generators worldwide since 2016. To learn more, visit: www.Moleaer.com 

About nanobubbles

Nanobubbles are tiny bubbles, invisible to the naked eye and 2500 times smaller than a single grain of table salt. Bubbles at this scale remain suspended in water for long periods, enabling highly efficient oxygen transfer and supersaturation of dissolved gas in liquids. Nanobubbles also treat and eliminate pathogens and contaminants of emerging concern as well as scour surfaces to break apart biofilm matrices, creating a powerful, sustainable, and chemical-free disinfectant (Shiroodi, S., Schwarz, M.H., Nitin, N. et al., Food Bioprocess Technol, 2021). 

By Jim Lauria, Mazzei Injector Company

In indoor crop production systems, water is vital for crop growth, handy for delivering nutrients and other inputs…and a major cost. As a result, managing every drop of water—and every ounce it carries, whether it’s a biodynamic compost tea or a conventional crop protection product—is critical to maintaining a healthy bottom line.

As closed-system farms become ever more precise, their owners are assessing their choices with an eye toward maximizing precision and efficiency. That has led many to struggle to choose between water-run pumps and venturi injectors for dosing and mixing inputs into their water.

Comparing Technologies

Both water-run pumps and venturi injectors operate on long-established technologies. Water-run pumps use pressure from irrigation flow to lift an injector piston, drawing in a known dose of fertilizer or chemical before it is forced back down by a spring and delivers the dose into a sealed chamber. Injection rates are calculated as a ratio to the flow of irrigation
water through the main line.

Venturi injectors use line pressure to constrict flowing water in a conical inlet chamber, then release it into a cone-shaped outlet port. As the flow expands in the outlet port, it creates a vacuum that draws in nutrients, chemicals or air and mixes it thoroughly. Injection in venturi systems is measured in percentages, parts per million, or gallons per acre.

While water-run pumps require regular replacement of seals and springs, venturi injectors contain no moving parts, so there is minimal wear and virtually no maintenance. The difference is apparent in both acquisition cost and maintenance cost, says John Petrosso, agriculture sales engineer for Mazzei Injector Company.

“A greenhouse can put in four pumps with a manifold, or they can put in venturis for the cost of the rebuild kits the pump manufacturers recommend buying every 12 months,” he explains. He adds that venturi injectors may be specified in sizes ranging from 0.5 inches to four inches, allowing growers to precisely size their venturi injection system to their needs.

Petrosso points out that venturi injectors blend injected materials more evenly than pumps do—a huge advantage in improving precision and reducing physical footprint.

“With a pump, every time that piston goes up, it’s sending out a pulse, where with a venturi you have a more homogeneous mixture that’s going out into that irrigation system,” he explains. “That’s why you’ll also see that water-run pumps usually require a mixing chamber or static mixer. It’s also why pumps can be incompatible with biological products like compost teas or microbial pesticides—the pistons can exert a lot of force and tear up microbes.”

Aeration Excitement

One of the most exciting applications of injection systems is aerating the crop root zone. Petrosso says a recent study at the Center for Irrigation Technology at California State University, Fresno and Memorial University of Newfoundland, Canada, suggested that AirJection® improved nitrogen use efficiency, lowered the potential for NOx production, and created an aerated environment that tipped the soil’s microbial population toward aerobic bacteria that correspond with crop vigor and growth.

“Most urban and indoor farms aim to set a higher standard for food quality and sustainability,” Petrosso says. “Venturi injectors take those benefits a step further as the ultimate complement to sustainable systems. They allow growers to fine-tune their input use, gently and efficiently mix even the most sensitive biological products, and they literally go with the flow, minimizing energy consumption.”

It is said that managing irrigation is a bit like being married. No matter how hard you try, you never do it right. But it is because we try that we succeed in having a happy marriage.

Plants need water and fertilizer to grow. In the hi-tech glasshouse industry, we apply both at the same time. A fertilizer injection system provides the fertilizer, and the drip irrigation system distributes the water evenly to the plants. How hard can it be? When I was a student studying Chemistry, I was never interested in Agriculture. You plant a seed, add water, fertilizer, sunshine, and a little while later, you harvest. How hard can this be? A lot harder than I could have ever imagined.

We base irrigation strategies on the measurements from the day before. Then we look at today’s weather and try to adapt the irrigation strategy to suit. As a result, we are always one step behind. It is why it is so hard to get the irrigation right every day. 

The Tools We Need

There are some basic tools that we need to collect the right information. A scale or moisture content sensor is important. If they are not available, a manual drain station such as pictured below is a must. Even if a scale or moisture sensor is available, a manual drain station is still recommended. Use at least one slab and collect all the days drain water in a bottle or bucket. Be sure also to measure the volume irrigated per dripper. It is a good check to know if the volume of irrigation water calculated by the climate computer is the same as the measured dripper volume.

The key components we want to measure are the %dry-down, the EC in the drain, and the timing of the first drain. The dry-down is the loss of moisture from maximum saturation during the day to a minimum just before the first irrigation in the morning. The dry-down tells us if we are steering the plant into a vegetative or generative direction. The EC of the drain indicates whether we give the right amount of water. The timing of the first drain tells us if we have the growing medium hydrated enough so the plant can transpire at a maximum rate.

Now that we have the right tools in place let’s look at what are the most important rules in irrigation. 

1. A healthy, mature tomato plant uses approximately 1.7 ml/Joule/M². 

Light determines about 80-90% of the water uptake. Therefore, triggering irrigation based on light sum deserves preference. The Humidity Deficit of the glasshouse air determines the remaining 10-20%of the water uptake. Many growers open the vents in the spring so that plants get used to low humidity. It is a fallacy because a plant that can handle a high light intensity does not need to take up much more water to deal with low humidity. A healthy root system is the most important.

2. The drain percentage emerges from the desire to maintain a certain EC.

I get often asked how much drain should be achieved. It is an irrelevant question. The desired drain EC is the key parameter; the percentage drain is how the EC is controlled. If the desired drain EC is 4.5 and it reaches 5.0, the best way to lower the EC is through irrigating more. The best time to irrigate more is through the middle of the day. If the EC in the drain is too high, increase the frequency of the irrigation between 11 am and 2 pm. If the drain EC is too low, decrease the frequency of the irrigation between 11 am and 2 pm. Some growers use light intensity to decrease the Drip EC during the middle of the day. I’m not a great fan of this, as I don’t think it helps the plants transpire more easily, and it creates imbalances in the nutrient concentrations, especially when recirculating. 

The following guidelines can be used to generate a drain that maintains a steady EC, based on a drip EC of 3.0 and a drain target EC of 4.5.

              Less than 500 Joules;       0-10% drain

              500-1000 Joules;              10-20% drain

              1000-1500 Joules;            20-30% drain

              More than 1500 Joules;   30-40% drain

The important message here is that the drain percentage itself is not what should be         targeted. The EC in the drain is the best indication of whether the plant gets enough water. The values in the table above change considerably if the grower targets a higher drain EC. 

Decreasing the EC by irrigating more on a dark day is not a good strategy. On a dark day, we must reduce the amount of water significantly. The trigger for irrigation should still be light. It keeps the growing media dry, and the roots are encouraged to “find” water elsewhere.

3. The desired dry-down determines the timing of the last irrigation.

Generally, a dry-down of 10-15% is recommended. A 10% dry-down is a vegetative action, whereas a 15% dry-down is a generative action.  If the desired dry down is 10% and the sensors show 9%, the timing of the last irrigation needs to be earlier and vice versa. I prefer to be careful with the last irrigation. If the weather becomes cloudy during the late afternoon, the desired dry-down cannot be achieved. As it is impossible to take one irrigation away, it is better to be careful, and if it the dry-down is looking like it becomes too large, night irrigations are always an option.

In days where the light sum is only a couple of hundred Joules, there is no need to achieve drain. If we consider a day of 300 Joules, then the amount of water the plant uses is 300 Joules x 1.7ml/Joule/M²= 510 ml/M². Most standard slabs contain 10-15 liters of water, so there is no danger of the plant running out of water. If we irrigate twice at 0.25 liters/M2, the slab is saturated. It means that we have driven most of the oxygen out of the slab, which creates an ideal environment for soil diseases. One or no irrigation is a better option. It also means that during dark days, the saturation point on the moisture content meter is never achieved. As a result, the difference between the maximum and minimum moisture content is less. On these days, the dry down should be measured as the difference between the minimum moisture content of that day and the maximum saturation point of previous days. 

Roots are like muscles; if you don’t use them, you lose them. Three days of less than 500 Joules per day results in dying off of the root system. It is important to keep the above calculation in mind. Saturating the growing medium on these dark days results in Pythium and root dieback. In the graph below, you can see the irrigation strategy of a sunny day followed by a cloudy day. In this case, a scale was used. The maximum weight was 36.6 Kg (dark blue line). The minimum weight the next morning was 33.0 kg. The dry-down was (36.6-33.0)/36.6 = 9.8%. The next days’ light sum was 432 Joules. The maximum weight increased to 35.4 Kg, so the saturation point was not achieved. No drain was achieved, which allowed for oxygen to remain in the root zone. The last irrigation was at 3 pm, and the weight decreased to 33.14 Kg by the next morning. It means that the timing of the last irrigation was perfect. It is a good way to manage the irrigation on a cloudy day. Also, note that the EC (light blue line) is rising. It means that during the next sunny day, the irrigation frequency has to be increased during the middle of the day to decrease the EC.

4. The first drain should be achieved at 500 watts or 1.2-1.8 ltr/M2

During periods of high transpiration, we want to make it easy for the plant to take up water. The growing media should be saturated, and the EC becomes lower as the drain increases. Therefore, it is important to have the first drain at 500 watts. This rule of thumb can be applied regardless of where in the world you are. The second rule that can be applied is that the first drain should be achieved at 1.2-1.8 ltr/M2. This value depends on the desired dry down. If a dry down of 10% is required, the drain should come at 1.25 liters per square meter. At a dry down of 15%, the first drain should come at 1.8 liters per square meter. If the drain starts before that, the frequency in the morning is too fast.

During low or no radiation, we want to make it more difficult for the plant to take up water, so the roots are encouraged to spread through the growing media, looking for moisture. It is why we want to achieve a minimum dry down. In general, the plant sends assimilates to the warmest part of the plant. During the late afternoon, the growing media often is the warmest part. Having enough air in the growing medium at a time when the assimilates are directed to the roots results in optimum root growth.

The above strategies help implement the four key parameters for irrigation; a start time, drain time, the total amount of irrigation water, and stop time. By following these rules of thumb, the grower creates an environment for the roots where they are kept healthy and aerated so that they can perform at maximum transpiration when required.

Figure 2 shows a typical rootzone temperature, moisture content, and EC graph. In the morning, the moisture content is quickly brought up to the saturation level, and the drain starts at the 8^th irrigation (cycle size 0.2 ltr/m2). The EC decreases quickly during the day and starts rising again after the last irrigation. At the same time, the moisture level decreases, meaning air is entering the root zone. Moisture measurement within the slab has greatly enhanced the understanding of the irrigation requirements of plants. It is important to remember that the measurement needs to be representative of the whole irrigation zone. One measurement per hectare doesn’t seem enough to represent one hectare. However, using one measurement for multiple irrigation zones in the same glasshouse for the same variety gives a better statistical average. It is especially true if the electronic data is backed up by a manual drain station. It is recommended to perform manual EC measurements of the surrounding growing media to verify that the single points of measurement are valid representations of the irrigation zone. It is also important to make sure that the slabs of growing media contain a representative number of plants. When the planting density is increased, it can happen that the measured slab does not have the right amount of plants. Equally important is that any equipment that is used is maintained to a proper standard. It includes the EC and pH meter.

While manufacturers of moisture meters claim that their meters are compensated for temperature, the reality is often different. In the graph above, it appears that the moisture content is increasing. That is not true. The increase in water content is caused by an increase in temperature and EC over the three days of measurement. It complicates the interpretation of the data. However, the most important information from the moisture content meter is the difference between minimum and maximum. This difference is less prone to fluctuations. 

If no moisture content measurement is available, we can still get the dry-down information from manual drain stations. By physically checking the manual drain stations for the first drain every day, we can backward calculate the dry-down. For instance, if we know at which irrigation cycle the first drain arrived, we know the volume of water added to the slab at that time. If we know the saturation weight of the slab, we can calculate the dry down that was achieved. For instance, if the drain arrived at the 5^th cycle and we give 100 ml per cycle, there are four drippers per slab, and the slab saturation volume is 15 Liters, we can calculate that it took 5 x 4 x 100 = 2,000 milliliters to re-saturate the growing medium. We should allow for the water uptake for the plant during that time as well. If the first drain came after 200 Joules, then we can calculate the water uptake from the plant as 200 x 1.7 ml/Joule/M2 = 340 ml/M2. If the dripper density is 2,5 plants/M², the four plants on one slab have taken up 340 x 4/2.5 = 544 ml per slab. The real dry down is (2,000-544)/15000 = 9.7%. It seems like a lengthy calculation, but the only variables are the number of irrigations before the first drain, and how many joules have passed at the first drain. If the grower in the above example wants to maintain a 10% dry-down, he only has to make sure that the first drain comes at the 5^th irrigation at 200 joules light sum. If he wants to increase dry down to 15%, the first drain must arrive at the 7^th irrigation at 200 joules.

Different Strategies for Different Stages of the Crop

A tomato crop has 5 distinct periods that require a different approach to irrigation. I discuss the best strategies for each period, for a crop of tomatoes grown in a high light climate.

Propagation

In high light climates, young plants tend to grow vegetative. The block can be dried down to 40-50% of the saturation weight when the roots emerge from the bottom. Usually, a 10 x 10 x 7.5 cm block weighs about 500 grams when it is saturated. It means that the block can be dried down to 250-300 grams. The irrigation must be given in the morning so that the blocks are not too wet at night. When the plants suck water out of the blocks, air replaces it, providing the roots with necessary oxygen. The EC in the block can run up to 12 applying this practice, which makes the plant more generative and encourages the roots to fill the block. It also prevents the long, stringy roots that form when too much water is applied, and puddles form on the surface.

Planting to Flower

Most growers in warm climates do not have access to nurseries that can deliver a plant at flowering stage. When the plants arrive from the propagator and the plants are still small, the grower needs to complete the propagation cycle. When there are conditions of high light and low humidity, it causes the plant to make large leaves to cool itself. There are no fruits on the plant that function as a sink for assimilates. If allowed to grow without intervention, this plant grows very vegetative. The grower must give generative impulses that force the plant to flower and fruit. One well-known aspect of fruiting plant species is that threatening environmental conditions causes the plant to act reproductively. Most growers make use of this fact by not allowing the roots of the plant to grow into the growing media. An example of this is shown in Figure 8.10 and 8.11. The green sheet prevents the roots from going from the block into the slab with more volume.

By doing this, the volume of the growing media is restricted. Even a little plant can suck the moisture out of the block, which gives the grower control over moisture and salt content of the root zone. Drying down the weight of the block to 50% of its saturation weight is a generative impulse through which the plant starts producing hormones that steer it towards reproduction. 

The irrigation must be carefully controlled. Weighing the blocks multiple times per day allows the grower to dry the blocks down to 50% of their saturation weight. The plants should not go into the night with a wet growing medium. If the plants need irrigation, irrigate in the morning when the temperature is still cold. Check those areas of the glasshouse that are warmer or receive more light (wall or gable rows) are not drying out (and wilting) sooner. It is preferred to have the irrigation hoses under the gutter so that the sun does not have a chance to heat the irrigation water.

The EC in the drip should be 4.0. When the blocks are irrigated, the water system can be stopped when the first drain is visible. If it is evident that there is too much variance in EC between blocks, more drain needs to be realized. The EC in the block can rise to EC = 10-16. It creates a generative impulse.

The trend is to use less nitrogen in the fertilizer formula at this time to stop encouraging the plant to become vegetative. It seems low nitrogen also helps in increasing Brix of the fruit.

Flower to Harvest

Once the flowers on the first truss are open, the plastic sheet is removed, allowing the roots to grow into the larger volume of root space. The longer this action can be postponed, the better it is for the generativity of the plant. However, not allowing the plants to root into the slab makes them unstable, and they might fall over, even when tied up to the string. By the time the roots are allowed into the slab, the EC in the block is 10-16. The slab must be filled with EC=4 irrigation water. This difference in EC forces the roots to go into the slab very quickly. A nice truss such as shown in Figure 8.9 is a sign that the plants are generative. Notice the extreme curl in this cherry truss. If the irrigation is given too late in the afternoon, or the growing media is kept too wet, the trusses become more elongated and stick up, as shown in figure 4.

Now the plants have access to the almost unlimited water supply in the bag. It is a dangerous situation as the availability of so much water creates a vegetative impulse. To reduce this effect, apply the following rule of thumb; restrict the irrigation after planting and reduce the moisture content in the slab by 1-2% per day. It means that after 10 days, the water uptake of the plants creates a dry down of 15%. The decrease in water content must be realized with zero drain. After two to three weeks, the drain starts, and the EC in the drain from the slab is at 6-10. From this time on, reduce the drain EC by 0.5-1.0 EC unit per week. The EC should be at EC=4.5 by the time harvesting commences. Bring the drip EC down gradually to EC = 3.0.

Three weeks after allowing the roots into the slab, the dry down is 20%, and it should remain above 20% until one week before harvesting or earlier if the plants show a more generative appearance. Achieve this by stopping early with the irrigation and giving more water during the day between start and stop times to control the EC. Late irrigations have an extraordinarily strong vegetative impulse, causing trusses to stick up straight (see figure 5) instead of the nice curl shown in figure 4. If it seems the dry-down is too much overnight, night irrigations are a better choice. But in most cases, it is better to stop early. You can always give extra irrigations, but you cannot take one away after its given. The grower has an essential input in irrigation management. The weather is different every day, and the stop time of the irrigation varies as a result.

Harvest and Beyond

If everything went right, we should have a well-balanced plant, loaded with fruit, ready for harvest. The highest fruit load on the plant takes place approximately one month after harvesting begins. At maximum load, the plants required nurturing. The grower must make it as easy as possible for the plant to grow. The majority of the assimilates that the plant makes are used for fruit production. Nurturing the plants helps stimulate vegetative growth and guarantee a future harvest. Now is the time to switch from generative to vegetative actions. The focus switches from the plant making fruits, to making leaves.

Irrigation

The dry-down of the slab must quickly decrease to 10% or less. It means irrigating later into the day. By now, the EC in the drain should be 4.5, while the drip should be at EC = 3.0. With less light, the plants require less irrigation. The following rule of thumb can be applied;

The last irrigation should come at 200 joules before sunset. If the dry down is too high, night irrigation can be given between 9 and 11 pm. It is important to remember that the guidelines above emerge from a desire to maintain the correct EC. In other words, keeping the right EC is the prime directive. The drain percentage is a means to achieve this. If the EC is too high, Some companies put a high priority on Brix and believe that they can achieve a higher Brix by maintaining a higher EC. 

Topping

About 6 weeks before the end of the crop, the growing point is removed. The remaining seven to eight trusses ripen one by one over the next 6 weeks until the plant is empty. Removing the growing point results in the plant needing less assimilates for growth, making leaves and roots. The majority of assimilates that the plant creates are used for fruit growth. Due to the decreasing fruit load, the plant has a smaller buffer to direct water to the fruits when root pressure is high. Therefore root pressure must be reduced. We do this by increasing the EC and dry-down. The dry down can be increased slowly from 10% at topping to 25% at last harvest. The EC can be increased to 8. Due to the reduced fruit load, there are more assimilates available for the last couple of trusses. Even with a high EC, the fruit size up properly. 

Irrigation is a very important tool in the arsenal of a grower. 

If you like to be copied in on future articles or would like to know more and have questions, follow me on LinkedIn, Godfried Dol, or email Godfrey@glasshouse-consultancy.com or go to my website; http://www.glasshouse-consultancy.com. You can also download previous posts from this website.

This comprehensive summary is an essential information for indoor farming! February Indoor Ag Sci Café focused on water quality and biofilm for indoor production.

Dr. Fisher discussed characteristics of different source water and their potential issues (alkalinity, chlorine, salinity, and pathogens) as well as mitigation measures. Key steps of biofilm management was introduced and efficacy of different commercial products was discussed.

Indoor Ag Science Café is an outreach program of our project OptimIA, funded by USDA SCRI grant program (http://www.scri-optimia.org). The café forums are designed to serve as precompetitive communication platform among scientists and indoor farming professionals.

The Café presentations are available from the YouTube channel. Contact Chieri Kubota at the Ohio State University (Kubota.10@osu.edu) to be a Café member to participate.

Registration is free. For more information, go to https://greenhouse.uconn.edu/webinars/

University of Florida Greenhouse Training Online courses 

Our last Greenhouse Training Online courses for 2019!

Weed Management

Earn CEUs

An intermediate level course that teaches all aspects of weed management in nurseries and greenhouses, including weed identification, developing herbicide programs, and the latest non-chemical methods of weed control that work.

Irrigation Water Quality & Treatment

An advanced level course that helps interpret water quality tests for irrigation of greenhouse and nursery crops, select appropriate water treatment technologies, and design a water treatment and monitoring system.

Both courses run from November 4 to December 6, 2019, are offered in English and Spanish, and include a personalized certificate of completion. Weed Management has been approved for CEUs in several States. Each course has a cost of $US199 per participant, with discounts if you register 5 or more. The last day to register is November 11, 2019. Over 4 weeks, there are streaming video lessons, readings and assignments, which can be accessed at any time of day. Click here to register (http://hort.ifas.ufl.edu/training/).

For more information, including discounts for registering multiple staff, email us at greenhousetraining@ifas.ufl.edu, or visit http://hort.ifas.ufl.edu/training/.

Nursery and greenhouse growers comprise an important sector of United States agriculture that is uniquely situated to conserve water while growing plants that provide many social and environmental benefits. In order for Extension professionals to effectively help growers use water conservation technologies, it is important to understand the knowledge level and adoption rates growers have surrounding different water conservation techniques. It is also important to understand how grower perceptions of water conservation strategies relate to their adoption. In this publication, we present results of a study designed to understand the knowledge level, adoption rate, and levels of continuance associated with eight water conservation technologies among nursery and greenhouse growers. We also examined whether five characteristics of these technologies (trialability, complexity, compatibility, relative advantage, and observability) predicted grower adoption.

Click here to read the publication: https://www.cleanwater3.org/research.asp

Pleasant work attitude

Fritz Meier explains briefly how the mobile gutters system works: ‘First we pot the plants on tables, after which they are transported all the way to the back of the greenhouse. There, we transplant them to the gutters, which then automatically slide through the greenhouse so we can harvest at the front again. Because all gutters and tables move through the greenhouse automatically, our people no longer actually have to lift anything other than plants and lettuce. So, we can operate it with very little manual work.’

Favorable for the environment

Advantages of the gutter system include a very easy work posture for employees, strong performance and environmental benefits. Fritz Meier tells: ‘We use about half of our water and much less pesticides and fertilizers. And nothing goes in the environment that doesn’t belong there. That is very important to us as a company.’

Codema is a company we like to coorporate with

The Gebrüder Meier has been working with Codema for quite a few years. Fritz Meier explains: ‘When we decided to install a gutter system, we asked Codema for help. We looked at the possibilities together with them so they could build a system for us on this basis.

Together with Codema we visited different companies in the Netherlands and Belgium and we have seen what Codema is capable to design, such as sophisticated transport systems for flowers. As a company, we are always happy with customers who are satisfied and who continue to work with us, and that’s how we want to deal with suppliers: we also consider a supplier who does a good job for a next project.’

This is taught at an advanced level, designed for an experienced grower or technical manager. Lessons are offered in English and Spanish, and are taught by professors from six universities in the United States.

The course runs from November 5 to December 7, 2018. It costs $US 199 per participant, and includes a personalized certificate of completion. Over 4 weeks (no classes over Thanksgiving week), there are streaming video lessons, readings and assignments. The 3 to 4 hours of lessons and activities each week can be accessed at any time of day. Bilingual PhD instructors are available via discussion features. Click here to register (http://hort.ifas.ufl.edu/training/).

For more information, go to http://hort.ifas.ufl.edu/training/, or contact Greenhouse Training, Environmental Horticulture Dept., University of Florida, USA, by emailing greenhousetraining@ifas.ufl.edu.

This course is supported by the Specialty Crop Research Initiative project ‘‘Clean WateR3 – Reduce, Remediate, Recycle’’, #2014-51181-22372, from the USDA National Institute of Food and Agriculture. Spanish translation is supported by a grant from the American Floral Endowment.

Irrigation Water Quality PDF Flyer

Big Tex Urban Farms wanted to incorporate an innovative solution that would help them grow more food per square foot to provide more produce to their local community. After evaluating several options, they chose Moleaer’s nanobubble generator. The generator boosts the deep-water culture’s dissolved oxygen content through oxygen-enriched nanobubbles. When roots are exposed to oxygen- enriched nanobubbles combined with elevated dissolved oxygen content, they can absorb nutrients more effectively, translating into higher yields and ultimately, more food for the local community.

When Big Tex Urban Farms lost power, temperatures in the greenhouse soared above 110 degrees Fahrenheit. The nanobubble-infused water was able to mitigate the effects. Nanobubbles are unique because they are neutrally buoyant and remain suspended in water for long periods of time. In this capacity, they act like a battery, maintaining dissolved oxygen in the water beyond the point of aeration. When the farm lost power, the nanobubbles saved the crop by keeping the plants healthy until power was restored. The tank that did not incorporate a nanobubble generator experienced significant losses, demonstrating a unique benefit of nanobubbles in high-temperature applications.

“Big Tex Farms State Fair Project is all about growing, harvesting, and donating produce. We give everything that we grow away to the local community,” said Drew Demler, Director of Horticulture at the State Fair of Texas. “We are trying to feed people and we think that the Moleaer nanobubble system is going to be a big part of how we can get more fresh produce to South Dallas.”

About Moleaer

Moleaer (Latin for tiny air) is a Los Angeles based company that develops industrial scale nanobubble generators to enhance a wide range of processes. Nanobubbles do not float, have immense surface area and stay suspended in water for long periods of time resulting in an unprecedented high rate of gas transfer. These extraordinary properties are proven to help farmers grow more food, oil and mining companies recover more valuable resources and operators treat wastewater more cost effectively.

This tool interprets the quality of a water source to irrigate plants in greenhouses and nurseries, and is available in English and Spanish.

Link to the WaterQual Tool

Clean WateR3 is a federally funded Specialty Crops Research Initiative grant focused on research and outreach to help growers Reduce, Remediate and Recycle irrigation water. The grant team is managed by Dr. Sarah White at Clemson University and includes many research collaborators.

Clean WateR3 – Reduce, Remediate, Recycle

Our projects focus on developing sustainable remediation technologies to encourage use of alternative water resources, especially recycled irrigation runoff, to decrease dependence on potable water, and enhance long-term economic viability. This is possible thanks to an award from the National Institute of Food and Agriculture Specialty Crop Research Initiative, and the involvement of 22 researchers in 9 universities. The objectives of this project are to:

• Reduce contaminant loading into recycled water sources via treatment technologies and improved water management strategies.
• Evaluate treatment technologies (physical and biological) to Remediate pathogen, pesticide, and nutrient contaminants.
• Provide online and published information to help growers successfully Recycle water.

Real-world application

Hort Americas installed the 50-gallons-per-minute (GPM) nanoBoost in in its hydroponics demonstration greenhouse in Dallas, Texas, to improve the production of leafy greens and culinary herbs during the summer months when warm summer temperatures make production more difficult.

“Our thought was that if we enhance and maintain higher dissolved oxygen levels, we should be able to improve crop health and ultimately improve yield,” said Chris Higgins, general manager at Hort Americas. “We observed dissolved oxygen levels of 29 parts per million in water temperatures of roughly 90ºF. Not only did we achieve our highest level of dissolved oxygen, but our crop yields increased between 20 and 50 percent.”

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Improving nutrient uptake and plant transpiration

The self-cleaning nanoBoost Nanobubble generator, which has no moving parts, produces oxygen-enriched nanobubbles that efficiently oxygenate an entire body of water and provides a reserve of oxygen encapsulated within the bubbles.

The generator delivers billions of nanobubbles with 200-times the inter-facial surface area when compared to micro bubbles, making them far superior in transporting valuable oxygen to the plants’ root system. The surface of the nanobubbles is negatively charged, attracting nutrient salts and enhancing nutrient uptake. Nanobubbles also increase the mobility of water molecules, potentially improving plant transpiration.

The generator is available in various flow rates and is fully encased in a durable, NEMA4-rated weather-tolerant PVC shell. The unit is self-cleaning and features plug-and-play installation with no moving parts, thus ensuring long-lasting durability with minimal maintenance. The generator can be configured with an integrated pump or retrofitted with a customer’s existing pump to maximize energy efficiency.