written by Andrea Leiva Soto, Horticulture and Crop Science
Ohio State researchers compared an organic system to a conventional one, looking at several soil quality indicators such as bulk density, organic matter content, and nematode populations. After four years, the organic system had fewer harmful nematodes, especially during the hay phase of the rotation. Mineral nitrogen was more abundant in the conventional system, while microbial nitrogen prevailed in the organic system. Soil bulk density did not differ between systems, even though intensive tillage was done in the organically managed fields. However, despite the high carbon inputs added to the organic system, organic matter was only slightly higher compared to the conventional system.
Nematodes have a bad reputation for damaging crops and garden plants, but some can be quite important for plant growth. Certain kinds of nematodes eat bacteria and fungi that cause plant diseases. Others decompose organic matter, providing plant nutrients. Studies indicate that nematodes supply 27% of the soil nitrogen that is available to plants. Today, nematodes are increasingly used as an indicator of the status of the soil food web. The soil food web is a complex network with organisms that provide services to the farm ecosystem like regulating pests, nutrient recycling, modifying soil structure, or even breaking down man-made chemicals.
Organic matter additions have been shown to influence nematode populations. Adding green manure cover crops or decomposed animal waste can decrease root-feeding nematodes. Additionally, organic amendments are known to increase soil nitrogen, organic matter and microbial biomass, and reduce soil bulk density, leading to less soil compaction. As a result, roots explore deeper and have more oxygen available leading to more vigorous growth.
However, the intensive tillage practices used to incorporate amendments or control weeds, disrupt the soil ecosystem, affecting the populations of beneficial microbes and nematodes. Synthetic fertilizers, insecticides, and soil compaction can also cause similar undesirable effects.
To better understand these kinds of interactions and develop insights into how best to manage them, a study at the Ohio Agricultural Research and Development Center (OARDC) in Wooster, Ohio, compared conventional and organic farming systems and how soil characteristics, nitrogen cycling, and nematode populations are affected by each system.
The conventional system used chemical fertilizers, herbicides, and reduced tillage in a corn–soybean rotation. The organic system incorporated fresh straw, beef manure, poultry compost, and intensive tillage in a corn–oat–hay rotation. Soil samples were taken in the spring before soil inputs, and in autumn after crop harvest. Samples were taken from between and within the crop rows. Then for each sample, the nematodes were counted and identified, and soil bulk density, organic matter, and nitrogen were measured.
Results: After four years, the organic system had fewer harmful nematodes, especially for the hay phase of the rotation. Mineral nitrogen was more abundant in the conventional system, while microbial nitrogen prevailed in the organic system. Soil bulk density did not differ between systems, even though intensive tillage was done in the organically managed fields. And despite the high carbon inputs added to the organic system, organic matter was only slightly higher compared to the conventional system.
Take Home Messages
- When you are transitioning to organic, it is important to reduce synthetic inputs gradually. The soil system needs time to build different sources of nutrients to be sustainable in the long-term. It is known that after the transition period, organic farms have more nitrogen in the soil compared to conventional farms, mainly due to a build-up of the microbial nitrogen pool, but these benefits will not be available immediately.
- Organic amendments and crop rotations can decrease harmful root-feeding nematodes in the soil. And by including hay in the rotation cycle, you can decrease these nematode populations even more.
- Intensive tillage can reduce the soil-related benefits of organic farming. On the other hand, organic inputs should significantly increase soil organic matter and decrease soil bulk density. In the organic farming system discussed above, the benefits of the large organic inputs were diminished by the intensive tillage routine. Rather than seeing a decrease in compaction level, the soil bulk density remained the same. And there was only a minor boost in soil organic matter. Decreased use of tillage in organic farming would better take advantage of the benefits that an organic system can provide.
Read more about it:
This study was conducted at Ohio State in the early 2000s. Published results are availabe online.
Briar, Shabeg S.; Grewal, Parwinder S.; Somasekhar, Nethi; Stinner, D.; Miller, Sally A. 2007. Soil nematode community, organic matter, microbial biomass and nitrogen dynamics in field plots transitioning from conventional to organic management. Applied Soil Ecology 37: 256-266.
Read more news and information on organic agriculture research at offer.osu.edu.
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.
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.
Additional Resources and Information are available at https://offer.osu.edu/soil-balancing/resource including summary reports, articles, and presentations.
Recordings are available from the 27th Annual Conservation Tillage and Technology Conference, held in Ada, Ohio, in March 2019. This two-day event brought together speakers in a variety of subject areas – many of which will be of interest to organic farmers.
Videos are available on the conference’s You Tube Channel.
Here are some of the offerings:
Cover Crop Panel: Addressing Cover Crop Seed Issues
Sarah Noggle, OSU Extension, Paulding Co., Moderator; Jay and Ann Brandt, Walnut Creek Seeds; Don Grimes, Ohio Seed Improvement; Cody Beacom, Bird Hybrids
Protecting Identity Preserved Crops In The Field:
Managing Pollen Drift to minimize contamination of Non-GMO Corn
Dr. Peter Thomison, OSU Extension Corn Specialist
Enhancing Mycorrhizae And Metarhizium Fungus
Jim Hoorman, USDA-NRCS, Soil Health Specialist
What Management Practices Most Influence Soil Health In Corn Production?
Dr. Christine Sprunger, OSU Assistant Professor, SENR
Enhancing Beneficial Insects With Pollinators
Dr. Stephanie Frischie, Xerces Society Agronomist / Native Plant Materials Specialist, Plymouth, WI
Can Weeds Be Managed With Calcium Amendments?
Dr. Doug Doohan, OSU Professor, HCS, and Andrea Leiva Soto, OSU PhD Student, HCS
Elephant In The Room: Why Do So Many Farmers Practice 'Soil Balancing' Despite The Lack Of Scientific Evidence?
Dr. Doug Jackson-Smith, OSU Professor, SENR, and Dr. Caroline Brock, OSU Senior Research Associate, SENR
The Effects Of Manipulating Ca:Mg Ratios On Ohio Crop Yields And Soil Health
Dr. Steve Culman, OSU Assistant Professor, SENR, and Will Osterholz, USDA-ARS
Weather Pattern Effects On Conservation Practices
Dr. Aaron Wilson, OSU, Byrd Polar and Climate Research Center
Return On Investment With Using Gypsum
Dr. Subbu Kumarappan, OSU Associate Professor, ATI
Gypsum Is More Than Calcium: Summary Of Ohio Field Crop Responses To Sulfur
Louceline Fleuridor, OSU MS student, HCS
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.
- 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.
"Soil balancing is complex, it's prevalent, and it's shown the capacity to endure. It also raises very interesting, and sometimes difficult to answer, questions. All of those are reason enough for us to chat, but as we address those questions we’re also very likely to learn about soils, about crops, about farms and farmers, and the people who advise farmers and supply them."
- Matt Kleinhenz, Ohio State, vegetable production specialist
Below are a few notes and quotes from our first two Soil Balancing call-in conversation. Recordings of both calls are available at our website, go.osu.edu/SB-call-in, where you can also find details about our final call-in event on December 12, 2018, 1:30-3:00 p.m. eastern time.
What We Think Soil Balancing Does
“The physical and biological aspects of the soil have more impact on an ultimate yield than actual N, P, and K does. So we're in working with these heavier clay soils. Our main goal is to minimize stress and duration of stress on the crop, so we're trying to preserve yield, because we continually stress this crop and most of the stress on those clay soils comes from water.“
- Joe Nestor, Nestor Ag, LLC (November call-in)
Joe Nestor works as an independent crop consultant in Ohio, Michigan, Indiana. He estimates about 70% of the soils he works with are heavy clay. His main goal using soil balancing is to improve water infiltration for less stress on crops.
“As we reduce flooding in the fields, we end up with a healthier crop in many cases -- a crop that survives, versus a crop that dies out under flooding conditions, and as a result, fewer weeds. When the crop dies or when the crop is not vigorous what grows in those in those areas of the field are weeds primarily. And we've all seen those dead areas in the field that come up in foxtail and other weeds.”
- Doug Doohan, Ohio State, weed specialist (October call-in)
Doug Doohan theorizes that soil balancing might affect weed populations indirectly through improved soil structure and infiltration. He cautions that there is no hard data on this yet, but it’s a research question be is studying based on conversations with farmers.
What Soils Does SB Work Best On?
“I think guys that have promoted the Albrecht balance have kind of given people the idea it works in any soil and that's really not the case. And so I think some of that has drifted into the research facilities in thinking that it works in all situations and that's not the case.”
- Bill McKibben, consultant, Soil Tech, Inc. (October call-in)
Although McKibben says he grew up as an “Albrecht guy,” i.e., focused on the 65% Ca, 15% Mg base saturation recommendations, his experience has shown him this technique is much more effective on clay soils.
However, by growing and incorporating a mixed species cover crop into his soils, vegetable grower Bob Jones reports significantly increasing the CEC on his sandy loam soils. He also uses compost teas and mineral applications, rotating fields in and out of production. He feels this increase of organic matter combined with increasing his Ca:Mg ratio has led to improvements in soil and crops.
“We're raising the CEC, we're raising the organic matter levels, we're getting the calcium up in that seventy to seventy-five percent ratio with magnesium in line with that of 7:1 and that seems to be— We seem to be seeing a very marked improvement in the quality and the shelf life of the product that we're growing.”
- Bob Jones, The Chef's Garden (November call-in)
Focus on the Crop, not Just the Numbers
“The number one goal, the number one objective, needs to be to grow a really healthy crop…. So in terms of priorities sometimes the lab report might indicate that we have a soil that is severely out of alignment and we need to make major adjustments, but the budget doesn't exist and it's not possible to make that happen. In those cases, the priority always needs to be to grow a really healthy crop first and then fix the soil over time as we're able to.”
- John Kempf, consultant, Advancing EcoAgriculture (October call-in)
Other consultants chimed in, saying it’s important to get out in the field and see what’s happening. Both Kempf and McKibben recommended a Paste Analysis test to examine how nutrients are moving into the soil solution and becoming available to plants.
"I can only say what works on our farm. Going back to the question of the truth, what's the truth on your farm? Then go with that. And you can only do that by experience. My father told me a long time ago that the best fertilizer you can put on a field comes from the soles of your feet and that means walking through the field and seeing what's going on and listening to the plant. The plant’s the best test mechanism we have. Does the plant look healthy?"
- Bob Jones, The Chef's Garden (November call-in)
On-Farm Experience vs. Research
“If the universities have a different opinion than the farmers, I normally go with the farmer opinion. They may not know why something is working, but they do know that it does work. And maybe the researchers…. they may not have the whole system, where a farmer would.”
- Will Glazik, organic farmer, Cow Creek Organic Farm
Glazik spoke in detail about how he applied soil balancing on his fifth-generation family farm: how his inputs changed over time and what improvements he saw. He looks to researchers to answer questions about ‘why’ something works, which helps him replicate a practice at his own farm.
“Scientists, I think, legitimately, have a healthy skepticism about what they might consider anecdotal reports of things that people say, especially when it comes…with the sales interest in mind, and they want us to validate that. On the other hand, farmers have a very healthy skepticism and legitimate skepticism of science, and the degree to which scientists’ work is directly as applicable or useful in their work, and that's why they turn to farmers often and legitimately to get advice and counsel.”
- Doug Jackson-Smith, Ohio State, natural resources and rural sociology specialist
Doug Jackson-Smith says that if soil balancing is to move forward, farmers and scientists must work together and bring the on-farm experience to science, and science to the on-farm experience.
Why Aren’t More Universities Studying Soil Balancing?
Steve Culman said many scientists feel this topic has already been decided. But his review of published literature and farmer input, made him think there was more to study. Other panelists theorized that Soil Balancing was an unpopular topic for study because there were few products (and sales revenues) tied to it or because previous research was done on soils poorly suited for the technique.
“I think that the beauty of science is that we… claim to be a self-correcting enterprise. It might take a year or two, it might take ten years, it might take decades. We believe that truth is the foundational thing that we're after, and that, if we have it wrong now, that in time and with additional evidence, we're going to change the way we think about things.”
- Steve Culman, Ohio State, soil fertility specialist (October call-in)
"You're asking, should we be doing more research and generating more numbers. I think so in this regard, because it is a question that I get at almost every soils talk I give. Can I improve my drainage by increasing the calcium-magnesium ratio?"
- Josh McGrath, University of Kentucky (November call-in)
Join the Conversation
- Read more details about future Call-ins
- Register for December call-in.
- Read about the basics of soil balancing and Ohio State's project.
- Listen to full conversation (below).