Recognize and Mitigate Crop Heat Stress

Recent conditions in some areas (soaked soil, fog- and dew-filled mornings, high daytime humidity) can give a different impression about the season so far than weather data at https://www.oardc.ohio-state.edu/weather1/ and various forecasts. Temperature, rainfall, and other data are collected around the clock at OSU vegetable (and other) research sites in Fremont, Celeryville, Wooster, and Piketon and have been for decades. So far in 2021, these four locations have accumulated less precipitation and more growing degree days (GDD) than their historical averages. Also, climate and weather authorities reported on June 11 that the Upper Midwest, including Ohio, is set to experience hot, droughty conditions. Most agree that a dry year is less problematic than a wet one — provided irrigation is possible. However, it can be difficult for vegetable growers to escape the unwanted effects of excessively high temperatures. A way to separate potentially minor, moderate, and severe heat stress, example effects of moderate-severe heat stress, and main strategies for mitigating heat stress during production are summarized below.

Five Major Factors Influencing Whether Heat Stress is Minor, Moderate, or Severe

  1. Crop and variety (sensitivity 1). All crops and varieties have a range of temperature in which they perform best. A crop’s genetic past (i.e., heritage/Center of Origin) and level of improvement through breeding matter. Individual crops and varieties are thought or proven to be relatively heat tolerant or intolerant.
  2. Timing (sensitivity 2). When high temperatures occur in the crop cycle is key. Crop plants can tolerate high temperatures more reliably at some stages than others. Even relatively tolerant varieties can be impacted by temporary spikes in temperature at the “wrong” time.
  3. Intensity. The extent to which actual temperatures exceed the crop’s and variety’s optimal range is important … 5 degrees? 15 degrees?
  4. Duration. The length of time the temperature was consistently above optimal. Short periods of intense stress can be problematic although the effects of prolonged moderate stress typically accumulate.
  5. Mitigation: were steps taken to lessen the stress?

Combinations of these five factors represent common scenarios. For example, for vegetables for which pollination is required, excessively high temperatures lasting only hours can disrupt pollination or trigger flower or fruit drop or interruptions in normal developmental patterns. The result can be loss of a “set” (dip in production) and/or malformed or misshapen units to be harvested (e.g., pods, fruits, roots, stems, leaves, tubers). Longer periods of above-optimal temperatures can speed (e.g., bolting) or delay (e.g., prolonged vegetative state) maturity depending on the crop and when they occur in the crop cycle. Heat stress is also implicated as a contributing factor in fruit ripening and physiological disorders (e.g., blossom-end rot). Above-optimal temperatures can also trigger changes in the chemical composition of plant tissues, possibly affecting the color and/or taste of marketable units. Similarly, prevailing temperatures can influence a crop’s tolerance to typical inputs and protectants.

Irrigation and shading are among the most common strategies for mitigating the effects of excessively high temperatures in field and high tunnel vegetable production. Irrigation is essential for the obvious reason that evapotranspiration is the crop’s primary means of cooling itself. A warm period or season calls for the best irrigation (scheduling) practices, not just pouring water on because, as we know, excessive irrigation (soil moisture) disrupts water uptake, compounding the heat stress problem. Circumstances allow some growers to shade the crop (e.g., in high tunnels) as they attempt to reduce the temperature around it.

At this time, 2021 has not earned the label as a “hot or heat stress” year. Let’s hope that remains true even as we remain aware of factors contributing to heat stress and ways of addressing it. In addition to proper irrigation, shading (if possible), and careful application of inputs and protectants, consider tracking variety performance closely to aid in variety selection going forward.

What are You and Others You Hear from Willing to Pay for New Farming Technology?

Technology surrounds us and is often defined as: “the application of scientific knowledge for practical purposes, especially in industry” and “machinery and equipment developed from the application of scientific knowledge.” Whether by definition or experience, it’s clear that vegetable production requires a lot of technology. Hybrid varieties and clean lots of true-to-type seed, seed coatings and treatments, the many crop inputs (e.g., fertilizers, protectants), small and large pieces of machinery and equipment … the list is long and growing. Each technology growers rely on has its own characteristics and pros and cons of use. Therefore, it’s important to be clear on what you are willing to pay for a technology and what others (e.g., advisors, educators) say about it. Helping develop and people to use new technology effectively is a big part of my job. In recent years, I have tested and advised people on high tunnel, grafting, microbe-containing crop biostimulant, and other technologies. So, what growers like and dislike about these and other technologies and are willing to pay for them is important to me, too. Growers and others provide key information, sometimes in scientific reports. A report describing peoples’ perspectives on biodegradable mulch (BDM) caught my attention recently. It is useful in two ways. First, it includes important information on BDM, an emerging technology. Second, it can help guide similar evaluations of other technologies and, perhaps, products.

The report was published by a team of investigators led by Kuan-Ju Chen (University of Guam) and including partners at Washington State University, Colorado State University, and Massey University (New Zealand). The report is available at https://doi.org/10.21273/HORTTECH04518-20 or from Dr. Chen or me by request.

The team’s specific objective was to assess peoples’ willingness to pay (WTP) for BDM characteristics. More broadly, they wanted to understand how ‘green’ technologies affect agricultural production when they are introduced into the market. Using input from farmers, educators, advisors, and others, the team assessed the WTP for adopting BDMs and peoples’ rankings of the relative importance of different BDM characteristics. The input indicated that study participants were willing to pay a statistically significant premium for healthy soil and a lower fraction of plastic residue left in the field after harvest. The data also indicated that farmers and others ranked the attributes of BDMs differently. In this case, attributes included cost, soil health, plastic residue, and consumer premium.

People interested in BDM may wish to examine the report closely or contact me, the authors, or BDM experts about it. People considering investments in a technology (new or old) or advising people on one may wish to review the report as an example of how willingness to pay assessments are completed.

Irrigation Water Quality Testing

The active irrigation season is underway, so let’s pause briefly to review why irrigation water quality testing is important, the value of proper sampling, and what to look for in test results.

Links to seven resources on the topic follow this brief summary. Reviewing those and similar resources is a good idea.

To summarize, irrigation water can:
1. Have a mineral or chemical composition that damages soil, irrigation plumbing and equipment, or crops directly. That same composition may also lower the effectiveness or complicate the use of other inputs such as fertilizers of crop protectants.
2. Contain plant pathogens.

Of course, using the same water source to wash produce and/or fill spray tanks can raise additional unwanted possibilities.

Regardless, the bottom-line is that irrigation water quality affects growers directly and indirectly and in the short- to long-term.

Testing the chemical and particulate (nonliving) composition or characteristics of water used for irrigation is relatively straightforward when major recommendations are followed. Keep the “garbage in-garbage out” principle in mind and collect, handle, and submit your water samples carefully. Also, be mindful that special steps are required for sampling surface (pond, stream/river) versus well water. Consult your testing service for specific guidance, if needed. Testing for plant and/or human pathogens is also important and consulting a plant pathologist and/or human health and food safety specialist is recommended. As you know, Drs. Sally Miller, Melanie Ivey-Lewis, and Sanja Ilic with The OSU are experts in these areas.

Test results of the chemical characteristics will often include the levels of: pH, total alkalinity, hardness, electrical conductivity, total dissolved solids, and multiple elements. The importance of and acceptable ranges for each are outlined in resources linked below and other publications.

Soil and plant testing are common – consider testing irrigation water, too!

Related Resources

https://extension.psu.edu/interpreting-irrigation-water-tests

https://njaes.rutgers.edu/FS793/

http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-4630/L-323–2013.pdf

https://cfgrower.com/testing-irrigation-water-for-pathogens/

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1160&context=anr_reports (focused on nursery and greenhouse crop management but also a good reference for vegetable growers)

https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_033068.pdf

Knott’s Handbook for Vegetable Growers (https://www.amazon.com/Knotts-Handbook-Vegetable-Growers-Maynard/dp/047173828X) also has five pages of handy reference tables on irrigation water quality, including regarding crop tolerance to various characteristics of irrigation water. Contact me for more information, if needed.

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.