The speakers and topics are:

Dr. Jim Owen, USDA-ARS, Water in Ohio – nursery use and return including reservoirs

Dr. Sarah White, Clemson, Reservoir water quality and management

Dr. Jeb Fields, LSU, Substrates and water management

Dr. Jake Shreckhise, USDA-ARS, Irrigation frequency and container color affect substrate temperature and controlled-release fertilizer longevity

Dr. Garrett Owen, OSU, Basics of substrate pH and soluble salts sampling and monitoring

Dr. Raul Cabrera, Texas A&M, Managing soluble salts in nursery and greenhouse production

Dr. Amy Fulcher, UT-Knoxville, TBD

Click here to enroll: https://cfaesosu.catalog.instructure.com/courses/water-management-and-quality-for-greenhouse-and-nursery-crop-production

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.”

Press Release – Resource Innovation Institute Executive Director Derek Smith previewed the forthcoming Cannabis Water Report as part of MJBizCon’s 2020 Associations Day on Tuesday, Dec. 1. The presentation provided information about past and current cannabis cultivation water usage and shared a sneak peek of proposed conservation benchmarks that will be relevant to cultivators, industry leaders, supply chain members, policymakers and media representatives. 

Water is a critical component of the cannabis industry, used for treatment, storage, fertigation and other non-cultivation activities like heating and cooling processes, fogging for humidification, pest-management, cleaning activities and more. The expansion of legal markets and increased consumer demand has driven huge cannabis production surges and increased water needs. 

“We live in an era of climate change where droughts are increasingly common,” Smith said. “A significant portion of cannabis cultivation is located in Western states, which will continue to be affected by water scarcity. It has never been more important to understand how our industry can improve efficiency. Previously, a lack of data stymied efforts to quantify water usage, but the transition to legal production provides a unique opportunity to establish new standards and key performance indicators that will help us do better in the future.” 

Whereas old data and press narratives based on the illicit market represented cannabis as an extremely “thirsty” crop, the new report notes that the regulated, legalized cannabis industry uses significantly less water than other major agricultural crops in California including cotton, tomatoes, wheat, and corn. 

“A portion of our research was focused on understanding why cannabis had received such notoriety as a water-intensive crop,” said Christopher Dillis, Postdoctoral Researcher at the Berkeley Cannabis Research Center. “We need to educate people about what is happening now, in the legal industry, and separate that from the old narrative around the illicit industry.

The report reveals that water use practices are highly diverse in the new regulated cannabis industry, and we hope that this new data leads to well-tailored regulatory policies that are responsive to this diversity.” The report also establishes that it is nearly impossible to normalize water usage per plant because it can vary so widely between indoor and outdoor cultivation, and depending upon location, growing techniques and other factors. As such, the report recommends that evaluation of future cannabis water efficiency be based upon canopy square footage, not plant count, as it has in the past. 

A partnership between Resource Innovation Institute, New Frontier Data, Berkeley Cannabis Research Center and members of RII’s Water Working Group, the full Cannabis Water Report is scheduled to be published in February 2021 and will establish a scientific understanding of how, and how much, water is used for cannabis cultivation. It will provide cultivators with insights, clarity and strategic recommendations for how to be more water-efficient, and ensure industry leaders, governments and media are accurately informed about the range of water practices in today’s dynamic and highly regulated cannabis market. 

To learn more about the 2021 Cannabis Water Report findings or to schedule an interview with Smith, please contact Shawna Seldon McGregor at 917-971-7852 or shawna@themaverickpr.com. 

The video is hosted by Dr. Paul Fisher of University of Florida IFAS Extension for the Five Tips for Horticulture series on the UF/IFAS Greenhouse Training Online channel (tinyurl.com/ufgto). The series highlights technical topics from university and industry experts. The channel is sponsored by the Floriculture Research Alliance (floriculturealliance.org).

For related training on this topic, see our Greenhouse Training Online certificate courses for growers at https://hort.ifas.ufl.edu/training, including the Irrigation Water Quality and Treatment course that will be offered in 2021.

The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. ifas.ufl.edu | @UF_IFAS

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.

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/.

If you are growing crops hydroponically in deep-flow or raft systems, one of the last things you want to see is an unusually low or empty tank. It is not uncommon for nutrient solution levels to be reduced by evaporation and transpiration, but when levels decrease rapidly, there may be a larger issue.

A common issue in nutrient film technique (NFT) or with drip systems is a leak from the tube delivering the nutrient solution. Another possibility is a crack in a tank or tube. However, what could be the cause if you do not see a leak? A less-intuitive issue that may occur is siphoning.

Watch out for siphoning if you are using air stones or tubes for oxygenation in deep-flow or raft systems or reservoir tanks. Siphoning may happen if the air pump is not supplying air flow due to a broken tube or the power going out. If the nutrient solution is siphoned into the pump, damage to the pump may occur. Siphoning may also be a result of air stone tubes breaking or coming loose from the air pump.

To prevent this issue, position air pumps higher than the nutrient solution reservoir. This will stop siphoning from a pump or power failure. However, if the tubing becomes loose, cracks, and falls outside of the tank beneath the water level siphoning may still occur. If feasible, consider installing in-line back flow prevention valves. Be aware this may be a problem and, if the nutrient solution is suspiciously low, check for siphoning.

About the Author:
Kellie Walters and Roberto Lopez Assistant Professor and Floriculture/Controlled Environment Extension Specialist(Michigan State University), and PhD candidate (Michigan State University), Roberto G. Lopez is an Assistant Professor and Floriculture/Controlled Environment Extension Specialist at Michigan State University. He has an appointment in research, teaching and extension. His area of expertise is; controlled environment specialty crop production; Lighting applications for greenhouses and indoor vertical production; light-emitting diodes; young plant propagation.

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