soils

Ohio State soil researchers Steve Culman and Christine Sprunger have analyzed soil health and management data from around 900 Ohio farm soil samples. The samples were collected during various on-farm research projects in the last few years, including about 200 from organic operations.

The Culman and Sprunger labs have looked for relationships between soil health metrics and the corresponding soil type, sampling depth, and management practices. Below are a few quick highlights and opportunities to learn more.

Management Impacts on Soil Health

The study suggests that the most effective way to increase microbial activity and other soil health indicators was to include perennials in the crop rotation, especially for multiple years.

Organic growers will be happy to hear that, so far, cover crops appear to be a better soil health building strategy than no-till. That’s not to say that tillage is good for soil health. More complex crop rotations and increased tillage showed a negative effect on organic matter and microbial activity.

Culman cautions that this is “noisy” data based on observation, not a side-by-side controlled study, nor is it a comprehensive sampling of soils. More work is definitely needed. Some of this future work will look at aggregate stability (a measure of soil physical health), compare the soil health impact from different types of tillage, and compare organic vs. conventional practices (for example, the effect of organic vs. synthetic fertilizers). The researchers are also interested in ways to decrease tillage passes in an organic system.

BELOW: Results from Ohio soil samples survey. The blue trend lines show how years in no-till or years in cover crops related to soil health metrics that measure organic matter, microbial activity, and soil structure. Source: Soil Health Survey Across Ohio Farms, Ohio State eFields Report 2020, pg 224.

Emerging Tests for Soil Health

As farmers and consumers focus increasingly on soil health, there is a growing need for better soil health measurements. Data from these on-farm soil surveys is helping to further this goal as well. 

Standard soil tests include a total organic content measure, but most organic matter in the soil is not available to plants. Recent research also suggests that total organic matter changes very slowly over time and is probably not the best tool if you want to track how new management practices are impacting soil health.

Ohio State’s soil labs have been evaluating soil health tests for accuracy, for their value in management decision-making, and for cost and turn-around time. The goal is to recommend useful tests to commercial labs so that these can be offered directly to farmers, along with information about state averages, ranges, and how the test values vary with soil type.  

Get Involved

It's important that organically managed soils continue to be part of this sampling project. Ohio State will collect soil samples again in 2021 as part of eFields – an agronomic crops program to conduct and share on-farm research. Contact your local extension educator or email digitalag@osu.edu for more details on getting your soil sampled for this statewide study. Individual soil test results will be shared with participating growers.

Learn More

• Management Practices That Impact Soil Health and Organic Matter 
  March 17 Sprunger presentation (45 minutes) - part of Ohio State's 2021 Winter Organic Webinar Series
• Using Research and Data to Improve Soil Health 
  February 25 presentation, Steve Culman & Elizabeth Hawkins - part of Ohio State's 2021 Soil Health Webinar Series
• eFields report 2020 - see page 224 for Soil Health Survey report.
• eFields program

Biostimulants are not exclusive to organic systems, but they are a common input for organic growers. Ohio State vegetable production specialist Matt Kleinhenz has spent many years studying microbial-based biostimulants (MBBS). Few agricultural input markets have seen the kind of explosive growth that has occurred with MBBS.

“These products are widely available, relatively inexpensive, are said to offer interesting and appealing benefits, and rarely put users at significant risk, unlike some other products,” says Kleinhenz.

Nicole Wright, program coordinator for the Vegetable Production Lab’s MBBS project, also attributes market growth to increased interest in microbiology.

“I think growers are applying them and thinking about soil and soil microbiology,” she says, “They are thinking ‘everything I hear says that having healthy soil means having lots of living things in them and if I can contribute to that, it’s a good thing.’”

With a constant stream of products entering and exiting the market, Kleinhenz and his team are less interested in testing specific products and more interested in answering the bigger questions surrounding this subset of agricultural inputs. Their research has focused on identifying which factors are important to product efficacy, such as the effect of timing and application rate.

Kleinhenz and Wright have this advice for growers interested in or already using MBBSs on their crops:

• Do background research. Just because a product is OMRI-listed does not mean it’s been found effective. Set aside time to read up on the product. Take a critical look at label instructions. What details are provided about the timing, application rate and application methods? What can the manufacturer tell you about mixing it with other products or using it in specific conditions or crops?
• Be wary of claims that seem exaggerated. Most of these products create modest, gradual, and/or inconsistent yield improvements. Growers should have realistic expectations for MBBS products.
• Product consistency can be an issue with MBBSs. If a product only works some of the time, the cause may be related to the user, the manufacturing process and product itself, or production conditions. For example, environmental factors like soil fertility, pH, or cropping history might influence  the product’s effectiveness.
• Use storage and handling procedures that acknowledge these are living products. Avoid temperature extremes and chlorinated water, for example.
• Track what happens. Referrals from other users of the product are valuable. But remember that their success won’t necessarily be repeated in your farm’s unique conditions. When trying a new product or practice, maintain a similar untreated part of your field to compare. Do your own experiments with rate and timing. Keep records on what you applied, where, and take notes on any differences you see in growth, yield, quality, etc.
• Use good cultural processes to increase microbials in your soil too. Wright likens MBBS products to taking a vitamin vs. eating healthy foods. Cultural practices that favor soil biodiversity, organic matter, and good drainage are also needed to provide food and conditions that allow microbial life to thrive.

Change is coming

So far, these products are largely unregulated. For the first time, the current farm bill includes language defining a biostimulant--an important first step in creating better uniformity in the industry, says Kleinhenz. Some manufacturers are concerned about the overall image of MBBS products and are pushing for a more narrow definition along with efficacy testing.

Kleinhenz feels regulation will usher in increased product consistency and better information for consumers, but regulation may also limit the number of products available. Testing product efficacy requires time, expertise, and/or expenses that smaller manufacturers may find challenging.

He also questions if it is truly appropriate to apply the same efficacy standards used for many mainstream agricultural inputs. Based on averages and standard, proven statistical analysis, a comparison of treated and non-treated plots failed to show that inoculation (product use) significantly influenced yield. However, the Vegetable Production Systems Lab team observed many times when a MBBS did increase yield (and a few times when it lowered it).

“If you went out to your truck and it only started half of the mornings, you’d be pretty annoyed and conclude it’s unreliable, that it’s not working,” Kleinhenz says. “However, if you apply a product to your crops or soils and see measurable improvement say, 30% of the time, you might still find the application worthwhile if the costs and other risks were low. Our goal as a team is to provide growers and others with information they can use to distinguish worthwhile from unwise investments and practices.”

There are many additional practical questions to answer that could involve microbiology and decision-making. For now, Kleinhenz and his lab are enjoying the conversation and questions stimulated by this growing and changing industry. 

Read more at: https://u.osu.edu/vegprolab/research-areas/vegebiostimsferts/

This research is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Organic Transitions Program under award Number 2016-51106-25714 and also under award number 2016-38640-25381 through the North Central Region SARE program under subaward number LNC16-380.

The Ohio State Soil Balancing Team is concluding a five-year project examining the beliefs, practices, and effects of soil balancing. Soil balancing involves the use of high calcium amendments to manipulate the ratio of calcium, magnesium, and potassium in the soil. For decades, proponents have claimed that the right balance of these cation nutrients will improve field conditions and yields, but none of these effects have been replicated by modern university research.

Through interviews, surveys, and literature reviews, the team gained a better understanding of why and how soil balancing is used by farmers and how it had been studied by researchers. The group found that while most researchers and university educators viewed soil balancing as an ineffective fertilization program; farmers and consultants who use soil balancing view it as a holistic method for improving soil health.

With input from a farmer advisory committee, the team designed long-term field experiments situated on organic farms and university research sites. The field trials found some evidence that changes in Ca:Mg ratios were associated with changes in soil structure and weed populations. However, the team was unable to document consistent effects on these characteristics, or on soil biology, crop quality, or yield.  

Based on the overall project findings, the Ohio State team recommends further investigation of how soil balancing’s effectiveness is impacted by specific site conditions such as cation exchange capacity (CEC), clay content, or management practices. Meanwhile, the team has issued the following recommendations for anyone using or considering soil balancing. 

Recommendations.

Soil test data is critical to making informed decisions about managing Ca:Mg ratios.

Watch your pH if using lime. Gypsum is a better choice to change your Ca saturation ratio without affecting pH, and it also provides sulfur.

Soils with a CEC below 10 meq/100 g may develop K deficiencies. In soils with a low holding capacity for cations, excess Ca can quickly lead to deficiencies of K, and possibly Mg. We did observe this in on-farm sites.

Consider economic factors. On soils with higher CEC, more time and amendments will be needed to increase the Ca:Mg ratio. Depending on the amount of change needed and the value of your crop, using soil balancing may be cost prohibitive.

Any time you try a new practice, monitor the results. If possible, try using the new practice on only part of your farm and compare it with a similarly managed area to see if the new technique is making a positive contribution over time.

Further Reading.

Additional Resources and Information are available at https://offer.osu.edu/soil-balancing/resource including summary reports, articles, and presentations. 

Use of compost and a mixed species hay crop are recommended.

For farmers transitioning from a conventional to an organic farming system, decisions made during the three-year transition period can influence important factors of future production, such as soil-borne pathogens, soil fertility, and soil structure. In this study, compost incorporation strongly affected physical, chemical, and biological soil health factors and, overall, the soil food web. Using a mix of perennial hay during the transition was most successful in reducing disease-causing pathogens in the soil. Highest available N and yields occurred in the plots using high tunnel vegetable production.

Materials and Methods

A three-year study was conducted in Wooster, Ohio, to evaluate four common rotational strategies used during transition from a conventional to an organic farming system. The four organic transition strategies evaluated were: 1) tilled fallow, 2) a single planting of mixed species perennial hay, 3) low intensity open field vegetable production, and 4) intensive vegetable production under a high tunnel.

Each transition strategy plot was split in half with 15,000 lbs./ac composted manure applied each year to one half.

At the year of certification, the fields were planted to tomato, with two smaller plots of soybean.

Key Findings

• Compost treatment increased organic matter of soils in all treatments, lowered bulk density, and increased NO₃-N, and microbial biomass-N.
• The addition of compost boosted plant vigor for tomatoes for all transition strategies, but had an inconsistent effect on suppression of soil-borne diseases.
• Transition cropping strategy was the main factor influencing bacterial community structure in the soil and the rhizosphere.
• Bacterial communities involved in disease suppression were more abundant in soil previously cropped with hay compared to tilled fallow and low-intensity vegetable production. This was true for both tomato and soybean crops.
• Overall, the mixed hay was the most effective in decreasing damping-off for both tomato and soybean crops.
• Tomato yield during year four was much higher in the high tunnel plot. The hay treatment also showed better yield than the tilled fallow and open field vegetable production.

Why Researchers Think the Hay and High Tunnel Treatments Did Better

Disease suppression might happen in two ways. One involves specific action against pathogen populations. For example, brassicas (cauliflower, kale, turnip, radish, cabbage) suppress soil-borne diseases by exuding sulfur-rich substances that are toxic to many pathogenic soil organisms. And certain species of nematodes eat bacteria and fungi that cause plant diseases. Disease suppression can also occur from high competition for available resources. In both cases, the disease suppression is associated with the overall composition of the microbial community (bacteria, fungi) present in the soil and the rhizosphere.

The hay crop used in this experiment was a combination of Festulolium (a rye fescue hybrid) under-sown with alfalfa, red and white clover, timothy, chicory, orchardgrass, and plantain in equal proportions. Researchers concluded that the above-ground diversity of the hay mix supported an increase in beneficial soil organisms that compete or interfere with pathogens, thus, reducing incidence of disease in future crops.

The highest yields in this study were from the high tunnel plots. While some of the increase resulted from extending the growing season, soil analyses also found a higher level of available N in the high tunnel plots. Researchers think this was a result of maintaining the soil food web in a biologically-active state during the cold early spring months in northern Ohio. The monthly mean soil temperature inside the high tunnels was warmer by 35–41°C from January to May while from July to September it was marginally lower than the outside soil temperature. (Based on top 4 inches.)

For more information on using tunnels in vegetable production, visit the Vegetable Production Systems Laboratory’s Crop Enivronments page.

Prepared by Louceline Fleuridor and Cassandra Brown

Based on summaries of the following papers:

Benítez, MS; Baysal, F.; Rotenberg, D.; Kleinhenz, M.D.; Cardina, J.; Stinner, D.; Miller, S.A.; Gardner, B. B. 2007. Multiple statistical approaches of community fingerprint data reveal bacterial populations associated with general disease suppression arising from the application of different organic field management strategies. Soil Biology and Biochemistry Volume 39, Issue 9, September 2007, Pages 2289-2301

Briar, S.S., Miller, S.A., Stinner, D., Kleinhenz, M.D., & Grewal, P.S. 2011. Effect of different organic transition strategies for peri-urban vegetable production on soil properties, nematode community, and tomato yield. Applied Soil Ecology, 47, pgs 84-91.

Baysal, F; Benitez, MS; Kleinhenz, MD; Miller S.A.; Gardner B.B. 2008. Field management effects on damping-off and early season vigor of crops in a transitional organic cropping system. Phytopathology, Vol. 98, No. 5.