2023 Trial: Impacts of Soil Fumigation of Tobacco

In our last post we covered the Impacts of Fall & Spring Fumigation of Tobacco.

Based on the findings from those trials in 2021 and 2022 TriEst wanted to take a deeper look at finding unique application and timing solutions to better meet a grower’s nematode and disease pressures. The 2023 trial focused on sampling depths to map location of pests, dual depth applications to place the correct product in the right place, and a variation of treatments to proof out these concepts.

We prepared different application levels to best place TELONE™ and Chloropicrin where nematode problems were the previous season at depths of 12” to 18” due to cool soil temperatures in early spring driving nematodes down to more temperate soil levels. In the Fall, nematodes are up high in the soil profile due to warmer soil temperatures and available food sources from crop roots being grown through the summer. Fall is a challenging application time for tobacco growers due to harvest of tobacco along with rotational crops and timing of crop contracts for the next season. In most cases, growers haven’t finalized plans for planted tobacco acres for the following season until late Winter. This makes finding a Spring application solution critically important.

Soil samples were pulled monthly throughout the season at dual depths of 0” – 8” and 9” – 16” from both in the row and the row middles. This sampling protocol allowed us to map the movement of nematodes from deeper in the soil profile up into the root system, as well as from the row middles into the row. Shown below in the soil samples. The darker color soil (right) is from the deeper level of 9” – 16”. Note the soil type differences in the soil probe and final sample collection bags, this visually highlights the potential need for dual application, as nematodes in the Spring are concentrated in the deeper soil profile (9-16”) and soil borne pathogens in the shallower soil profile (0-8”).

We designed an application strategy that would place TELONE™ and Chloropicrin within the soil sample zones described above and compared the dual depth application to the grower standard single depth application on the bottom of the shank. All applications were made in-row treating 25% of an acre, with a 12” application zone on 48” row centers. See the picture below, the top outlet is 8” below the soil line and the bottom outlet is 14” below the soil line. At the time of application, there will be an additional 8-10” of soil stacked on top during the bedding process.

Unlike our trial in 2022, this trial didn’t show a late season nematode resurgence. Pre-fumigation root knot nematode levels warranted treatment, but all treatments cleaned up this issue. We expected additional nematode pressure to come from the row middles and to move up from below our application depths, which happened in 2022. Yields were not impacted by nematode pressure; however, they were heavily impacted by Grenville Wilt. The significant differences you see in yield in the chart below between the non-treated check and all other fumigant treatments are due to early season growth responses from Chloropicrin and suppression of Granville Wilt. All fumigant treatments performed well over the non-treated check, with little separation between the grower standard of PIC100 at 50 lbs/acre and the additional treatments including TELONE™. Again, this was a result of lower than anticipated root knot nematode levels from mid-season through harvest. The highest yielding treatment was the dual depth application of TELONE™ and Chloropicrin, likely due to getting Chloropicrin closer to the root system of the plant with a shallower application point than the grower standard treatment.

Guava Root Nematode pressures are rising in sweetpotatoes so we did a similar trial that compared in-row vs broadcast applications at different depths with high/low sampling. Unlike the tobacco trial of 2023 the pests showed up to dinner.

Be sure to subscribe to our blog so you don’t miss the details on the sweetpotato trial and other trials.

If you’d like more in-depth information on our trials and what TriEst can do for your farm be sure to reach out to us. Contact Us Here

You can also view a video from the 2023 Tobacco Field Trial on our YouTube Channel Here.

Impacts of Fall & Spring Fumigation of Tobacco

This project was established in East Central NC originally in 2021 to evaluate the effects of TELONE ™ II and Chloropicrin (PIC) on nematode suppression, Granville wilt suppression, and tobacco yield and quality.

Yield losses from crop “melting” late season have become common in the greater tobacco production regions. This is a complex issue of harvest timing, weather conditions, disease, and nematode pressure. Growers are consolidating and getting larger with same infrastructure, which is putting more pressure on fumigants to protect the crop longer. Companies also want more overripe tobacco, putting more pressure on late season harvests.

In tobacco, maturity windows are critical to management, when everything matures at once and growers struggle to get around the crop and harvest in a timely manner. In 2021, our first tobacco blend study resulted in the grower standard of 200# PIC (#50 BER) being the better treatment overall with more early vigor than treatment blends containing TELONE. The plots with PIC100 showed a 5 to 7 day earlier maturity rate over PIC/TELONE blends, leading us to the question of – is it possible to stagger harvest between the products?

If PIC is maintaining earlier maturity, that needed to be accounted for in harvest planning. We consolidated our 2021 findings into our set of treatments for the 2022 tobacco study with another central North Carolina tobacco grower. Similar to 2021, treatments containing only Chloropicrin (PIC) in the Spring showed the best early vigor, highest lower stalk yields, and overall best plant structure.

Once harvest began, we found that late season nematode pressures resulted in higher wilt levels and caused yield losses. There was not much separation between the Spring PIC100 and PIC60 plots in nematode control (Spring application, cool soil temps, and depth of pest may have played a role). Spring PIC application plots looked best prior to nematode pressure and had the best first and second harvest yields. In instances where Root Knot Nematode isn’t present PIC100 is the most economical solution.

All of the plots where TELONE was Fall applied had a significant impact on season long nematode suppression and resulted in the highest yielding plots overall. While Fall applied TELONE treated the late season nematode problem and protected yields, it didn’t necessarily cause the yield gains. The Spring PIC60 application didn’t solve the late season nematode problem. Knowing nematode levels and location in the field pre-soil fumigation is critical.

Based on these findings TriEst’s intention is to take a deeper look at finding unique application and timing solutions that meet a grower’s needs. We have more trials in the ground now improving on soil fumigation application timing and depths. Our next blog will be on our 2023 trials that focus on sampling depths, the probes, and treatments. In the 3rd blog of this series, we will go over those 2023 trial results.

So stayed tuned and be sure to subscribe so you don’t miss the latest information.

Soil to Substrate: Key Irrigation and Fertigation Ideas for Long Cane Raspberries

The Comparison

Traditional soil production for soft fruit crops is a buffered system that is slow to change, whether good or bad. Fertigation mistakes in a traditional soil system isn’t necessarily going to be detrimental, or result is major pH or nutrient changes. For the same reasons, soil deficiencies or incorrect pH ranges are more difficult to correct in traditional systems.

The difference in a substrate system is significant. It is a low volume potted container area that is essentially fed by an IV nutrient solution, so fertigation changes can result in major nutrient or pH shifts within a matter of hours. So, this situation is both good and bad – you can correct your mistakes very quickly and you can make mistakes very quickly. Think of substrate as a high risk, high reward type system where your attention to detail is very important.

Moving forward with those differences in growing systems pointed out let’s lay out some key ideas for growing.

Plant Nutrition and PH

Starting with the right pH is key in a soil system for berries, or you’ll be fighting it all season long, but impact in season is minimal with the right fertility program. Most soil systems are high volume of fertilizers and water, with low frequency of runs for irrigation and fertigation. Fertility in soil systems are referred to in terms of pounds per acre. The southeast typically has programs of 150-30-200#/acre NPK with 30-50# S and 40-50# Ca. Fertigation is supplied commonly with potassium nitrate/calcium nitrate/UAN style blends (a 5-1-7 with 2% Ca for example). We do a lot of these type blends in traditional soil production of soft fruit, with sulfur being supplied as a supplement.

In a substrate system, the program is the opposite of a soils system. Low volume and high frequency systems run typically for 2-3 minutes at a time 20-30 times daily. Fertigation is driven by PPM (parts per million) to target crops by each stage every irrigation cycle. Fertility isn’t driven by pounds of nutrient applied per acre, but crop demand of a balanced nutrient solution based on irrigation needs. It is also critical to realize that rapid pH manipulation is possible through water treatment and fertilizer selection. Just think about the size of the pot and the tight area the plant is in. So, as a grower, you have to re-calibrate yourself in this type of system to be more targeted and understand how quickly changes can be made.

Water Quality

Water quality is the first factor in determining a proper nutrient and irrigation plan for a substrate crop. Well, municipal, and surface water is variable and should be regularly tested for pH, EC, and iron. Managing pH is very important particularly in substrate systems as highlighted earlier. Making assumptions about your source water can lead to big mistakes, test first.

Injection Systems and Fertilizer Sources

When you look at injection systems to create a fertility base like we’ve been discussing it is generally a two-stage injection system that will allow growers to run one tank that is calcium based and another being sulfur based. Calcium and sulfur don’t play nice as fertilizer concentrates, so this split is the most natural way to begin your fertility program. Both tanks can be run as a diluted mix simultaneously, pending quality and dilution rate.

Nutrient form matters! The form you choose to use can have a large impact on your pH (especially nitrogen). Water-soluble blends are the recommended best option for a substrate system due to the ability for customization. Drip grade liquid fertilizers are an option with reduced labor, but it can’t be customized as much, as the scale for drip fertigation is much larger and is made in greater quantities typically. There are many options to find the same end goal for nutrition, as long as the product form/ratios are correct.

Last Thoughts

There are a lot of factors that need to be monitored in both substrate and soil systems. You can go from a very simple, labor intensive style to monitor pH, water quality, nutrients, and E/C which does work or you can start adding layers of sensors and automation. To learn more you can reach out to our team and they can help you research solutions that will work best for you and your substrate production needs.

Green Beans: Low Rate Fumigation Trial

Green Beans

Building off of our traditional success in tobacco and our more recent watermelon results in 2020-2021, we wanted to trial our low rate system in another crop that fit the specifications outlined earlier; 60-120 day crop, high value, not currently being fumigated as a standard practice. An opportunity was found in Florida with fresh market green beans. After reviewing the economics of green bean production in this region and considering the chloropicrin rate ranges we had seen increased vigor/yields in other crops, the following protocol was set for the trial:

  • Evaluate 85# broadcast (25# BER) and 130# broadcast (40# BER) on fresh market green bean
  • Fumigation was applied bare-ground with a single application shank at a 6” depth while stacking a 12” bed at application. The grower followed this by double bedding immediately following the fumigation pass to increase stack from 12” to 15-18”, resulting in a final application depth of 21-24”. At planting, the bed is knocked down to an 8-10” pressed bed that’s prepared for direct seeding. This results in seed being planted directly into the fumigated zone.

The results of this study were very successful. The crop vigor and uniformity were significantly better in fumigated treatments and had a direct correlation to rate. Both rates resulted in better seed germination, larger root systems, uniform plant populations and enhanced growth versus non-fumigated. Yield results were the following:

The results of this study are quite drastic, but this work was done in a heavily cropped system in tight rotations.  This project was in the third rotation of green bean on this farm, with no previous fumigation on that specific crop and grower standard yields were below average. With that said, we’ve drawn the following conclusions and thoughts:

  • Chloropicrin has the potential to maintain higher than average yields in multiple cropping cycles of green bean
  • Consistent emergence and uniform growth resulted in more yield bearing plants per acre and harvest efficiency
  • Future projects will focus on fresh rotations in both Fall and Spring, to determine ideal timing of applications and efficient use of Chloropicrin

We hope you continue with us on our low rate trial journey. Sign-up for our blogs today to keep up.

To learn more about what soil fumigation can do in your fields contact a sales rep in your area by clicking here.

Part II: A Deeper Look into Grafted Watermelon Production and Management

Harvested Watermelons

In our last blog post we took a deeper look into grafted watermelon production and management by reviewing a 2020 watermelon trial in central North Carolina. In this post we want take you through year 2 results and our findings. The key focus points of the trial were increasing yields and maturity window of grafted plants using chloropicrin.

Trial details for background

  • The trial was on watermelons grown on plasticulture using TIF film since we found the best results the year prior with using that.
  • We made shank applied fumigant application using a Reddick Equipment Company RMC plastic layer 25 days prior to planting.
  • The grower had watermelons on this particular piece of land on a 3 year rotation with sweet corn, small grain, and tomatoes.
  • The land had heavy root knot nematode pressure and low fusarium wilt pressure so the Carolina Strong Back rootstock was used for the grafted watermelon plants.
  • The trial was planted on 8’ row centers x 3’ standard plant spacing (1,815 plants/acre) and 8’ row centers x 4’ grafted plant spacing (1,316 plants/acre).
  • We used 25% pollinators in-row between every 3rd and 4th seedless plant.

Harvest Events

  • The trial fields allowed for 3 harvest events.
    • June 30 (74 DAP)
    • July 12 (88 DAP)
    • July 26 (102 DAP)
  • The Joyride melon used is an 86 day melon.
  • The grafted maturity is the same as the standard Joyride plant maturity, but heavier yields were shifted 5-7 days.
  • We saw a strong yield response to the fumigant applications and vine health remained great all the way through final harvest on July 26th.

In summary, we saw results similar to our findings in 2020.

  • Chloropicrin is increasing yields in both non-grafted and grafted plant production systems
  • Fertility changes and addition of chloropicrin are speeding up grafted plant maturity
  • First harvest of grafted is approximately half of non-grafted, but the second harvest of grafted is much heavier
  • Longer harvest windows are possible with grafted plants, due to increased plant growth and durability to harvests
  • No significant differences were seen in size profiles or sugar content/brix between treatments

We saw comparable results in 4 different trials of similar design across North Carolina, Georgia and Florida in 2022. Some key findings:

Standard plant yields are increasing use of chloropicrin

  • North Carolina – 34% increase
    • Florida – 16% and 15% increase
    • Georgia – 20% increase

Grafted plant yields are increasing with the use of chloropicrin and specific fertility protocols

  • North Carolina – 22% increase
    • Florida – 12% and 23% increase
    • Georgia – 14% increase

Combining grafted plants and fumigation with chloropicrin is providing dramatic yield increases over grower standard practice yields in all trial areas

  • North Carolina – 70% increase
    • Florida – 28% and 44% increase
    • Georgia – 28% increase

To learn more please contact our very knowledgeable team at TriEst and be sure to sign up for the next installation of the TriEst Ag News series.

A Deeper Look into Grafted Watermelon Production and Management

In our last blog we went over the obstacles that growers face in watermelon production and their potential solutions. In this blog and video presentation we will take a deeper dive into why we recommend grafted plants and fumigation as potential solutions to obstacles in watermelon production.

Before we get into the first broad study trial we conducted, I would like to focus on grafted plants as a tool and potential solution to grower obstacles.

Some advantages in grafted plants and differences over standard are:

  • Improved root system, increased vigor, better plant and vine health.
  • Disease resistance. (Fusarium, all races)
  • Nematode resistance. (Rootstock dependent)
  • Reduced crop rotation due to better disease resistance.
  • Prolonged harvest potential and higher yield potential.

A common question about grafted plants is about which rootstock is best for a farm. Rootstocks that Tri-Hishtil offers are the Interspecific Hybrid Squash and the Carolina Strongback. The Interspecific Hybrid Squash is susceptible to Root Knot Nematode while the Carolina Strongback offers resistance.

In a trial we conducted in Central North Carolina we looked at solving some of the problems that growers faced by focusing on grafted plants versus standard, fumigated versus non-fumigated, and standard fertility versus reduced fertility.

At the end of this first trial, we learned that grafted plants with the Carolina Strong Back rootstock had significant yield responses over the standard plants, while also performing better than the squash-based rootstock. We also saw increased yields from fumigation regardless of plant type (grafted or standard) and regardless of plant spacing. Lastly, we discovered that reduced plant populations within 20-30% did not result in yield loss when using grafted plants.

Chart description of end field performance results of non-grafted, squash-root grafted, and Carolina Strong Back on different row spacing.

Lastly, we learned from this trial that early fertility reduction would control vine density and promote earlier flowering in grafted plants; however, fertility decreases after fruit set resulted in yield loss. This information has led to specific fertility programs for grafted plants that increase yields, decrease costs and result in earlier harvests.

The 4 beds marked R have Reduced Fertilizer. The 4 beds marked F have typical fertilizer program.

To learn more please contact our very knowledgeable team at TriEst and be sure to sign up for the next installation of this blog. We’ll be going over more trial data and results from the field!

Overcoming Obstacles in Watermelon Production

Sustainable crop production is a complex issue that every farmer faces each season. All crops present their own challenges and specific needs for maximizing yields and profitability. Let’s focus on discussing a few key impacts for watermelon production in the Southeastern US. The production issues for watermelon are not limited to those listed here by any means, but the following are the focal points of ongoing research that will be discussed over several blog installments in the coming months.

  • Soil borne pests – fusarium wilt, which can be devastating as crop rotations become limited and “new ground” isn’t an option
  • Nematodes – root knot nematode, a widespread issue across the Southeast US
  • Viruses – significant impacts on certain markets and very difficult to control
  • Crop rotation – ability to produce and market crops that aren’t a disease host for watermelon
  • Land availability – decreasing availability in almost all major melon production areas
  • Cultural production system – plasticulture vs bareground under many different styles of irrigation methods (drip, overhead, seep, flood etc)
  • Plant type and variety selection – Use of grafted plants for fusarium wilt control and/or use of tolerant varieties
  • Harvest windows – Watermelon markets are hyper sensitive to timely harvest events by geography. It is critical to understand how production system practices can impact these windows
Fumigated grafted plants (center) and grower standard plants (either side)
20 days after planting – fumigated melons on the left and non-fumigated on the right.

The task for every farmer is to find the balance between these challenges and potential control measures for each, while staying profitable. Solving this problem has to be taken one step at a time and our first step was to identify the products we had available to bring the farming community solutions to these problems. TriEst Ag Group and its affiliates are dedicated to providing soil solutions for the agricultural industry, so let’s take a look at the tools we’ve used to solve this puzzle in watermelon production.

  • Soil fumigation – TriEst has a variety of fumigants and product combinations that can be used for managing a wide range of soil borne pests and nematodes. In addition to managing pests, we have results to indicate that at low rates certain fumigates can be used to improve soil health and increase crop vigor in watermelon crop production. The right product is dependent on the specific pest and disease pressures of an individual farm. In our research we have used multiple products and we will discuss the pros and cons of each in this series.
  • Grafted plants – Like fumigants, there are several options for rootstocks available for grafted plants. Choosing a rootstock is also specific to the issues faced on an individual farm. The primary focus for grafted plants is fusarium wilt control and increased yields.
  • Cultural practices – There are many different cultural practices that are used in watermelon production. Each different scenario can impact the efficacy of fumigation, grafted plant performance, water availability and fertility. We focus on multiple cultural practices in our research, trying to find the best system possible and understanding how each changes the other products involved.
  • Fertility – Soil fertility and fertilizer use has a major influence on crop production. When looking at an overall system for control, fertility has to be considered. Fertility programs should change when they’re used with fumigation and grafted plants. The cultural system being used impacts timing and rates. Details on this will be outlined as we move forward in the series.

Over the past two years, with crops located all across the Southeast, we have worked to develop effective production systems using these tools. We will bring these results and concepts forward in this watermelon crop series, month to month. Next blog, we will take a deep dive into grafted plant production and the impact of fumigation in that system. Stay tuned!