How Do You Maintain the Health – Quality – Productivity of Soils in Your High Tunnel(s)?

Growers are increasingly impacted by and/or interested in learning how to prevent declines in the health, quality, or productivity of soils in their high tunnels. More are experiencing or aware that various biotic and abiotic issues threaten crop yield and quality and farm income. As some have learned, increases in nematode populations, disease inoculum, salinity, nutrient deficiencies/excesses/imbalances, and/or compaction or reductions in soil structure can be troublesome. Thankfully, a comprehensive effort is underway to help understand and address soil health/productivity-related challenges in high tunnel production. Sponsored by the USDA Specialty Crops Research Initiative and coordinated by Dr. Krista Jacobsen of the University of Kentucky, researchers with different expertise and extension specialists are documenting grower concerns and practices and charting a path leading to greater grower success. The OSU and five other universities are also currently involved. Team members recently hosted a focus group of eight growers from the Great Lakes (including Ohio) and will hear from more in other regions soon. Growers in the recent focus group represented a range of experience, size of operation, crops grown, typical number of annual production seasons (1-4), and overall farming approach (conventional, organic). Collectively, they shared concerns with issues referenced earlier and gave special attention to others such as the effects of high tunnel soils going extremely dry fall-to-spring unless watered (with or without also being cropped). Interestingly, this observation and concern lines up with the view shared by Dr. Bruce Hoskins of the University of Maine that high tunnel production is like “irrigated desert production in the west and southwest,” and that “failing to realize or take steps to address potential problems because of this” can be detrimental (see VegNet article Feb. 20, 2021). In any case, the recent conversation with growers was a reminder of: (1) potential causes of declines in (high tunnel) soil productivity (examples are listed below), (2) innovative steps growers and researchers are taking to limit the problem, and (3) benefits of addressing the complex problem through partnerships. It also prompted me to ask myself what I am doing to maintain the productivity of soils in my high tunnels. Maybe it will do the same for you!

The health-quality-productivity of soils used in vegetable production, including in high tunnels, can decline for many reasons. Some major ones are listed below in no particular order.

1. Repeated or excessive use of a potentially narrow range of fertilizers, various chemicals, and other soil amendments.
2. Vegetable plants often having relatively small and shallow root systems (compared to other annual crops) and crops returning relatively little residue to the soil.
3. Short rotations with few crops.
4. Placing frequent pressure on and aggressively disturbing soil, especially when it is wet.
5. In high tunnels, relatively unique and potentially extreme temperature and moisture profiles.

Re-Introducing The Vegetable Beet and Re-Thinking Transplant Production

Re-Introducing The Vegetable Beet

The Vegetable Beet is a live weekly interview and discussion focused on vegetable production challenges and opportunities coordinated by the Great Lakes Vegetable Producers Network. Callers participate live and others listen to session recordings when convenient. See https://www.glveg.net/listen for details and recordings (24 and counting).

On 3/17/21, Dr. Judson Reid of Cornell University shared excellent observations on and suggestions for initiating warm season production in high tunnels and open fields. Among other core principles, Jud emphasized routine soil testing, high quality seed and transplants, and tailoring fertility management to crop setting and other factors. We also discussed a range of issues related to using high tunnels for warm season crops only or warm and cool season crops (i.e., harvesting and marketing one season per year or year-round).

Drs. Mohammad Babadoost (University of Illinois) and Francesca Rotondo (The OSU) will be featured guests for the session on 3/24/21 and discuss seed selection, treatment, and starting, including for transplant production.

Please contact me or another program coordinator directly or use greatlakesvegwg@gmail.com to suggest topics and guests for future sessions of The Vegetable Beet (or VegNet Newsletter!).

Re-Thinking Transplant Production

Some recall when bare-rooted seedlings (often produced outdoors) were the norm. That era was replaced by the one we are currently in featuring, for example, soilless rooting media, foam or plastic trays varying widely in cell shape and size, and highly soluble fertilizers. We also rely heavily on greenhouses for transplant production — that has many important implications for everyone involved since those greenhouses can be ours or someone else’s. Regardless, for many, transplant production has become so familiar and routine that it can be overlooked relative to other issues and stages in crop production. The general impression may be that transplant production is “all figured out,” that today’s overall approaches need little improvement. However, as successful businesspeople, you know that taking a fresh, hard look at the familiar and routine can spark innovations and reveal changes offering real returns on investment. So, as transplant production moves forward this season, consider how your system could be fine-tuned. Seed handling and starting practices, rooting medium and tray selection, temperature, light, and humidity control, fertility and irrigation management, and more are options.

Limiting Bird Damage in Sweet Corn

Bird damage in sweet corn and other specialty crop production can be significant and those affected by it need different types of effective solutions. Some are described in articles and publications such as https://vegetablegrowersnews.com/article/some-tips-to-curb-bird-damage-in-specialty-crops/, https://ag.umass.edu/vegetable/fact-sheets/preventing-bird-damage, and https://rvpadmin.cce.cornell.edu/uploads/doc_691.pdf. Still, the search for additional farm-ready ‘tools in the toolbox’ continues. A team led by the University of Rhode Island is working with growers in the Northeast and other regions to better understand the extent of the problem and success of current control measures. Consider completing their very brief (5-minute) survey at https://uri.co1.qualtrics.com/jfe/form/SV_8qBBeU2HAIwcKYl to help inform and get the most from the team’s work.

 

Soil Sampling and Analysis for High Tunnel Production

Installing a stationary high tunnel (HT) is a significant, long-term commitment to the parcel of soil beneath it, especially if the crops will grow directly in that soil. Maintaining, and preferably enhancing, the health, quality, or productivity of that soil for as long as possible should be a high priority beginning at HT installation.

Soils in HTs are less well understood than uncovered soils in “open sky”/open field production. However, the HT farming, extension-research, and industry communities are aware that HT soils are prone to specific issues and require specific care to remain commercially viable. These issues and preventative or reclamation tactics are the subject of much research and extension. Therefore, HT growers are encouraged to stay tuned for more information, including on how they can participate directly in identifying concerns and developing solutions. Examples of concerns and working solutions were summarized in a recent presentation (https://www.youtube.com/watch?v=XpUl0IwaDFI). Choosing one concern, in a summary of a presentation given at the 2013 New England Fruit and Vegetable Conference (https://newenglandvfc.org/sites/newenglandvfc.org/files/content/proceedings2013/Hoskins%20High%20Tunnel.pdf), Bruce Hoskins of the University of Maine’s Analytical Lab and Soil Testing Service mentions that the buildup of nutrient salts over time is “one of the most common problems in a continuously covered HT system,” that HT soil management can be similar to “irrigated desert production in the west and southwest,” and that growers familiar with open-field production can “fail to realize this potential problem or take steps to remediate it.” He also mentions that nitrate may carryover from one HT crop cycle to the next more readily than in open field production.

We heard from Bruce Hoskins and John Spargo during recent conversations about HT soil management. They direct soil testing and analytical labs at the University of Maine (https://umaine.edu/soiltestinglab/) and Penn State University (https://agsci.psu.edu/aasl), respectively. Each of these labs receives soil samples from hundreds of HT growers (conventional, organic) each year and have been actively helping improve soil management recommendations and cropping outcomes for HT growers. They have been joined in that work by others, including farmers, across the Northeast and Mid-Atlantic regions for years.

Take-aways from these recent conversations include that routine soil testing is essential, along with accounting for potential nutrient salt buildup when collecting soil samples. Normally, samplers: 1) use a soil probe or spade to retrieve a column of soil about twelve inches deep, 2) drop the soil in a bucket, 3) repeat the process one or more times from other areas, 4) mix the soil in the bucket, and 5) submit a portion of it for analysis. Listening to testing and other experts, the best approach appears to include “stratified” sampling; that is, submitting samples taken from 0-4 inches deep (upper layer of the rooting zone) separately from samples taken from four inches and deeper (lower layer of the rooting zone). Salts tend to accumulate in upper layers, especially if soil is heavy-textured and irrigation is frequent but brief. So, standard “mixed” samples may either: (a) underestimate salt levels in upper layers of soil experienced by roots of transplants and more mature plants or (b) overestimate salt levels if samples include only the upper level. Stratified sampling, mindful that soil characteristics can change with depth, equips growers and others with information to better manage HT soils. Regarding the costs of soil testing, especially of stratified samples, input from soil testing labs suggests that few of the growers they work with mention it as a significant concern. Instead, most growers appear to have done their math and concluded that soil analysis offers a significant return on investment, given that its cost is more than offset by gains in crop yield and quality in the current and subsequent years.

Grafted Plants: What They May Offer You and How to Obtain Them

Grafting creates physical hybrids between seedlings of at least two varieties. The rootstock variety is used for its root system and traits and the scion variety is used for its shoot and fruit traits. Grafting is providing growers with an expanding list of key plant traits more rapidly and in different combinations than standard hybrid variety development. These traits include resistance to specific soilborne diseases (e.g., Fusarium, Verticillium) and the ability to overcome various abiotic stresses (e.g., salinity, drought, low fertility). Plant growth at low soil temperatures, improved fruit quality, and/or greater fruit holding ability on the vine may also be possible in specific cases. Among grafted crops, field and high tunnel acreage of tomato and watermelon are greatest, although interest in and acreage of grafted pepper, eggplant, cucumber, and melon are also rising.

Resources to help growers make the best use of grafting are also increasing and improving. The most important resource is growers who have experimented with grafted plants and share their experiences and views. Online resources (e.g., http://www.vegetablegrafting.org/) can also be useful. For example, one site (http://graftingtool.ifas.ufl.edu/) helps growers “run the numbers” on grafting’s potential impact on their bottom-line. That decision-support tool improves as information from farm-level tests of grafting is added.

Growers also ask how they can obtain grafted plants. The number of operations supplying Ohio and the U.S. (http://www.vegetablegrafting.org/resources/suppliers/) is rising. I have personal experience with the three suppliers listed below in alphabetical order. Contact them soon if you are interested in receiving grafted plants for use in 2021.

1. Banner Greenhouses (Nebo, NC; ph. 828-659-3335; https://www.bannergreenhouses.com/).
2. Re-Divined (Bainbridge, PA; ph. 717.286.7658; grafted@redivined.net; https://redivined.weebly.com/).
3. Tri-Hishtil (Mills River, NC; ph. 828.891.6004/828.620.5020 – Chris Furman; sales@Tri-Hishtil.com; http://www.trihishtil.com/).

Grafted plants can also be prepared by the same person or farm that uses them in the field or high tunnel. Many guides describing how to graft vegetables are available. The following are a small number of examples.

1. https://u.osu.edu/vegprolab/grafting-guide/ and other resources at https://u.osu.edu/vegprolab/research-areas/grafting-2/.
2. http://www.vegetablegrafting.org/resources/grafting-manual/.

Please contact me if you need additional information.

Improving Success with Soil-less Rooting Media

Researchers representing the USDA and six universities are spearheading an effort to improve both soil-less rooting media used in specialty crop and transplant production and peoples’ success using soil-less media. Their research focuses on grower concerns and their extension/outreach will include a North American Soilless Substrate Summit. The team’s work is supported by the USDA Specialty Crop Research Initiative  (Grant # 2020-02629). Learn more about it by contacting Dr. James Owen in Wooster, OH (jim.owen@usda.gov; 757-374-8153) or Dr. Jeb Fields (jsfields@agcenter.lsu.edu; 985-543-4125). Just as important, help steer the team’s research by completing a 5-minute survey at https://bit.ly/2ZLNIkn.

Grafting, In-row Spacing, and Seasonal Nitrogen Application Rate Effects on Watermelon Yield and Quality

Growers, consultants, seed company representatives, and others have questions about watermelon management protocols, especially when grafted plants are used. The three panels below provide background on and summarize preliminary findings from two experiments on this topic completed in Wooster in 2020.

Please contact me at kleinhenz.1@osu.edu or 330.263.3810 for more information.

High Tunnel Site Selection Tips

High tunnel production is important to an increasing number of vegetable farms in Ohio and many are installed in the fall. Installing a high tunnel is a major commitment, beginning with the one made to the soil that will be covered by the tunnel for decades to come (regardless of whether the high tunnel is moveable). The video at the link below summarizes factors to take into account when selecting sites for high tunnels. More input is available on the overall topic and each factor — just ask or look for follow-up publications, programs, and more!

high tunnel site selection primer

Optimizing Plant Spacing (Population) and Seasonal Nitrogen Rates in Grafted Watermelon Production

Data collection on fruit taken from two “grafted watermelon” experiments being completed at the OARDC in Wooster,OH has started. These experiments were outlined in VegNet posts on June 6 and July 11 and they are described in the image below, too.

Harvest 1 occurred on 8/19/20 with ‘Jade Star’ fruit harvest and analysis. The first harvest of ‘Fascination’ will be the week of 8/24 and a second harvest of each variety from both experiments is also planned. We assess the maturity of each fruit and its readiness for harvest using these criteria: a) yellow belly, b) dry vine tendril, c) developing longitudinal ridges, and d) white stripes brightening and widening (‘Fascination’). Occasionally, fruit weighing less than 8 lb meet one or more of these criteria, so they are harvested and photographed along with all other fruit from the same plot. Fruit weighing less than 8 lb are later separated from the group of fruit weighing more than 8 lb (marketable). In all pictures below, fruit are shown on a blue tarp slightly larger than 7 ft wide x 4 ft tall.

Pictures below are representative of what was observed in replicates 1-3 but conclusions should not be drawn from them. Data from Harvest 2 are needed to complete the picture and all data from 2020 must be analyzed along with data from previous years of the research (2018, 2019). On 8/19/20, in the “density” study, we observed that all four plots containing grafted plants produced a total of 12 fewer fruit than the four plots containing grafted plants at an in-row plant spacing of four feet. However, the situation was reversed at an in-row plant spacing of five feet since the four plots containing grafted plants produced a total of thirty-five more fruit than the four plots containing ungrafted plants at the same spacing.

The last planned fertilizer application (fertigation) in the “fertility” study was completed on 8/21/20. Two days before, the number of fruit taken from all twelve plots containing grafted plants was greater than the number of fruit taken from the twelve plots with ungrafted plants, regardless of seasonal nitrogen (N) rate. The difference in fruit number was greatest, moderate, and least at 75%, 100%, and 50% of the normal N rate, respectively. The pictures below are an example of the difference in fruit number at the standard N rate developed for watermelon production using ungrafted plants.

The experiments are being completed with USDA-SCRI program support and we look forward to sharing the results when the work is complete. In the meantime, please contact us (kleinhenz.1@osu.edu; 330.263.3810) for more information.

Rotation Crops in High Tunnel Production

Many growers establish cash and non-cash rotation or cover crops each main season with the percentage of land in cash and non-cash crops varying farm to farm and year to year. Non-cash rotation crops are established to help maintain or improve soil health and nutrient levels, suppress weed growth, break pest and disease cycles, and provide other benefits. Despite these benefits, typically, high tunnel vegetable growers can be understandably reluctant to devote high tunnel space to non-cash crops in summer (main season). Perhaps as a partial consequence, soil health challenges (e.g., declines in organic matter and increases in nutrient imbalances, salt accumulation, compaction, and disease and pest pressure) are increasing in high tunnel soils. Anecdotal reports mention declines in crop yield and/or quality and increases in costs to maintain productivity. It is reasonable to expect that these trends could be be slowed or reversed through the consistent use of non-vegetable rotation crops in high tunnel production much like they have in open field production. However, few conclusive high tunnel-based experiments have been completed on farms or research stations.

This situation was not necessarily front of mind when the VPSL established cowpea, pearl millet, and sorghum sudangrass in many of its high tunnels at the OARDC in Wooster in early summer. Rather, the decision was primarily pandemic-related as vegetable experiments planned for the tunnels were suspended. That said, a summer including non-cash rotation crops is providing us with the opportunity to observe and learn about them and their potential value going forward. Currently, we consider cowpea, pearl millet, and sorghum sudangrass as just three of many potentially useful ‘alternative’ high tunnel crops for main season plantings, regardless of whether their use is planned or unplanned. The pictures below are examples of what we have observed to date. Please contact us (kleinhenz.1@osu.edu; 330.263.3810) if you would like to discuss the plantings or the “high tunnel rotation” question further.