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.

Optimizing Soil Moisture in Drip-irrigated Soils

When a lot must get done and crop needs for water are high, fine-tuning irrigation is usually an afterthought. Still, consider a few issues when working to get the most from drip-irrigated crops. This is one thought that came to mind when I returned to an article published by Drs. Michael Dukes, Lincoln Zotarelli, and Kelly Morgan of the University of Florida. The article is available at https://journals.ashs.org/horttech/view/journals/horttech/20/1/article-p133.xml?rskey=f046lk. Do not be thrown by the title, there is something for Ohioans and others to gain from the summary. Sections on verifying and optimizing soil moisture distribution in drip-irrigated soils (especially within plastic-covered raised beds) are one example.

Of course, distribution is influenced by soil type, irrigation frequency and duration, loss (ET, drainage), and other factors. Sampling using a soil probe or other approach can reveal unexpected and, possibly, damaging surpluses and deficiencies which is a first step in correcting them. My team and I have experienced this firsthand many times over the years, including this season. Taking 10-15 minutes to pull soil samples has told us we can or cannot afford to delay an irrigation and where it is least or most important relative to crop need, weather, other tasks, etc. Also, the article from the Univ of FL includes pictures depicting desirable and undesirable distributions of soil moisture and effects of under-and over-watering. For example, the team used dye to track the movement of water and fertilizer through and outside the rooting zone. Seeing the pictures helps illustrate what is rarely seen (so must be imagined) but can be seen with a spade or shovel and a little time and care.

The Dukes, Zotarelli, and Morgan article (Use of irrigation technologies for vegetable crops in Florida; HortTechnology 20(1):133-142) is highlighted here. However, there are many other similarly excellent irrigation guides and resources. All contain bits of information we can act on. I am also glad to help resolve irrigation-related questions; just let me know if I can help (kleinhenz.1@osu.edu; 330.263.3810). Regardless of how you proceed, recall that in addition to the sunlight, air, nutrients, and protection crops require, the right amount, timing, location, and quality of water is also very important. As far as nutrients are concerned, recall that fertility experts often say root zone moisture strongly influences whether their levels, etc are optimal.

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

Growers, seed, grafted plant, and fertilizer suppliers, extension-research personnel, and others are interested in identifying if, where, and how grafted plants may fit in vegetable production toolboxes. Those questions can be answered reliably only after the performance of grafted plants is documented under a range of management schemes because it is possible that standard production practices may need to be altered to account for the influence of rootstocks. Plant spacing (i.e., population density per acre) and fertilizer application rates (e.g., total seasonal nitrogen applied) are two variables likely to influence (grafted) plant performance; therefore, they have many peoples’ attention, including ours.

With USDA-SCRI program support, we began studying these variables at a preliminary level in 2018 and more thoroughly in 2019. Experiments started in 2019 are being repeated in 2020.

Data collection begins with tracking crop development and concludes with laboratory analyses of fruit quality. The experiments provide an opportunity to analyze fruit yield and quality as influenced by grafting, scion, spacing, and N level. In 2019, soilborne disease did not appear to be a factor and grand mean total cumulative fruit yield (ton/acre) values were: a) 32.5 (ungrafted ‘Fascination’), b) 25.0 (ungrafted ‘Jade Star’), c) 42.6 (grafted ‘Fascination’), and d) 47.7 (grafted ‘Jade Star’); these values include data for all density and N rate treatments. Analyzing data collected in both study years more thoroughly will provide a more reliable assessment of the influence of grafting, in-row spacing (4 or 5 ft), and total seasonal N application (100, 120, or 142 lb/acre) on watermelon fruit yield and quality.

Water Needs and Supplies, and Delivered during Typical Drip Irrigation Events

Warm, dry weather can lessen some production challenges, but it clearly increases the need to irrigate. Not surprisingly, growers are currently working overtime to meet crop water demands. Some forecasts call for high water demand conditions to continue, important because many crops are entering particularly “thirsty” stages uniquely sensitive to water deficits. Therefore, as one step in overall crop water management, consider taking stock of how much water is delivered during typical irrigation events. Doing so helps compare water supplies to expected irrigation demands and prioritize irrigation across plantings if rationing becomes necessary, in addition to providing other benefits. Of course, in the big picture, crops differ in their sensitivity to even temporary periods of sub-optimal soil moisture. Just as relevant, the production cycle for each crop includes stages in which sub-optimal soil moisture has a greater or lesser impact on yield and quality. The June 28, 2016 VegNet article (https://vegnet.osu.edu/sites/vegnet/files/imce/newsletters/VegNet/6-28-16%20VegNet%20Vol%2023%20Issue%2011_0.pdf) outlined this issue briefly for cabbage. In addition to the yield and head size differences shown there, laboratory and taste panel tests revealed: (a) that irrigation program (timing) influenced cabbage flesh chemical properties and (b) that panelists could differentiate cabbage samples from different treatments by taste.

Installing and recording information provided by a flow meter is a simple, relatively inexpensive, and, importantly, direct method of measuring system flow. Using charts, tables, and other references such as the one below also helps. They remind us that irrigation system factors, especially bed or row spacing and emitter flow rate, typically set the baseline system flow rate, although actual flow rate is impacted by leaks and plugs. Leaks, plugs, etc are another reason to both include a meter in the line and check the system frequently. Ultimately, keeping and reviewing irrigation and crop records can be useful in optimizing irrigation practices as a major step in maximizing yield and quality.


Source: Knott’s Handbook for Vegetable Growers (5th ed.; D.N. Maynard and G.J. Hockmuth)

Factors Influencing Measures of °Brix (Soluble Solids), an Indicator of Potential Crop Quality

°Brix readings continue to interest and confuse farmers and others. Collecting a reading is far easier than making decisions based on it. In fact, it takes just moments to obtain a °Brix (soluble solids) reading in the field, packing shed, or elsewhere; the major steps include collecting a small drop of plant sap or juice and placing it on a properly maintained and used refractometer, a handheld instrument that fits easily in your pocket. A reading typically can be in hand in less than two minutes. However, making proper use of the °Brix value requires effort and experience for reasons outlined below.

The sugar sucrose is perhaps the most prevalent soluble solid in plant juice. Therefore, many vegetable-based °Brix (refractometer) readings are set primarily by the number of sucrose molecules in the sap or juice used as the sample (unless the sample is contaminated). Within a crop, these sucrose levels are, in turn, influenced by:
1. Variety;
2. Plant population/density;
3. Irrigation or soil moisture status;
4. Nutrient management or soil fertility status;
5. The plant part sampled (e.g., root, stem, leaf, fruit) and exact portion of it;
6. The age (maturity, position) of the plant part sampled;
7. Time of day of sampling;
8. Temperature and light conditions;
9. Post-harvest conditions; and
10. Other factors.

Not surprisingly, experienced refractometer users understand that it is essential:

1. To use a standardized, consistent approach involving sampling the same plant part (and portion) at the same development stage at the same time of day, etc. That way, comparisons based on other factors are more reliable.
2. To obtain and record many values (the process is nearly free minus small initial investments). Much like measures of blood sugar, cholesterol, heart rate, etc, the worth of one °Brix reading in decision-making is often based on comparing it to readings collected previously and the conditions under which they were collected.

We have measured °Brix levels in vegetable crops grown on Ohio farms and at OSU research stations for nearly twenty years using protocols explained in fact sheets at https://u.osu.edu/vegprolab/research-areas/product-quality-2/ and taking factors listed above into account. The data below were collected in July-November 2011 by Dr. Natalie Bumgarner (then a graduate student at The OSU and now with Cooperative Extension at the University of Tennessee). Note the variation within and across crops.

Contact Matt Kleinhenz (330.263.3810; kleinhenz.1@osu.edu) for more information.

Grafted Plants, Suppliers, and Experiments


Growers typically convert to using grafted plants (e.g., tomato, watermelon) primarily because they can be much more productive when specific soilborne diseases are present (and the correct rootstock is used). In addition, however, grafted plants are often more vigorous than ungrafted ones of the same scion (fruiting variety). Grafted plants may also use water, fertilizer, and other inputs more efficiently. Therefore, it is necessary to optimize cultural and fertility practices for grafted plant-based production. Two experiments will be completed in this 1+ acre parcel in 2020. One experiment tests alternative fertilizer rates and the second experiment tests in-row spacings (plant populations/acre). All grafted plants are supplied by Tri-Hishtil in Mills River, NC.

Tri-Hishtil (http://www.trihishtil.com/) is one among a constantly-lengthening list of commercial grafted plant suppliers. Others include Banner Greenhouses (https://www.bannergreenhouses.com/), Grafted Growers (https://graftedgrowers.com/), and Re-Divined (https://redivined.weebly.com/) in the eastern U.S. and others based in the west. Local suppliers are also operating in Ohio and some farmers are preparing their own grafted plants. Commercial suppliers continue to ramp-up their capacity to meet the needs of vegetable growers, regardless of the size, location, or type of their operation (field and/or high tunnel; conventional and/or organic). Also, grafted plant costs are increasingly competitive. Overall, access to grafted plants is strong and increasing and no longer a reason for being unable to test the performance of grafted plants on your farm. The Vegetable Production Systems Lab at OARDC can also assist, if needed; we teach people how to graft and, in 2021, we hope to resume preparing small numbers of plants by request.

One empty and three filled cells of a 128-cell tray holding grafted watermelon plants prepared by Tri-Hishtil. Note roots are visible on the surface as healthy white ‘threads’ with smaller root hairs near the tip, creating a bottle-brush appearance. Slotted cells (as shown at the bottom-left) contribute to this root condition and morphology.

Hand-grafted watermelon plants from Tri-Hishtil in Mills River, NC.
Plant at left is Jade Star and plant at right is Fascination, both grafted to Carnivor rootstock.
Clear and green clips show the location of the graft union and supports (white sticks) will be removed at planting (scheduled for 6/8/20).
Root systems are well-developed, stems are sturdy, and the plants pull easily. Roots are not spiraling, partly due to the larger size and special shape of the cells.
Clips can be removed at planting or allowed to be forced off naturally by stem growth.

Contact Matt Kleinhenz (330.263.3810; kleinhenz.1@osu.edu) and see updates at this blog for more information.