Effects of regenerative, organic, and conventional soil management and glyphosate on crops’ chemical composition

Progress report for FNC21-1309

Project Type: Farmer/Rancher
Funds awarded in 2021: $9,000.00
Projected End Date: 01/31/2023
Grant Recipient: Sumner's Farm, LLC
Region: North Central
State: Missouri
Project Coordinator:
Dr. Walton Sumner, II
Sumner's Farm, LLC
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Project Information

Description of operation:

Sumner's Farm LLC maintains an 80 acre farm just north of Hillsboro, MO, in the Sandy Creek watershed, with 40 acres of woods, 40 acres of hay production, and an experimental area for conducting trials of soil management looking for changes in crop composition as the main outcome. The farm has been using large amounts of compost made on site, some cover crops, and berms and swales to stop water erosion. The soils in the experimental area are silt loams (Useful and Horse creek).


My 2019 SARE FRG explored crops’ nutrient density as a function of soil management. An intense, expensive program to restore trace elements and soil organic matter unexpectedly decreased nickel content across diverse crops, and decreased several heavy metals in amaranth leaves and seeds, compared to conventional fertilization. Effects on selected nutrient compound densities were muted. Weed control using physical methods was challenging.
High dietary nickel probably exacerbates Systemic Nickel Allergy Syndrome (SNAS), and may contribute to other common diseases. Heavy metal exposure should be minimized.
Other SARE-sponsored reports suggest that no-till management allows soil microbiomes to supply major and trace elements to annual crops. Concerns exist that glyphosate (Round Up) and chemical fertilizers injure the soil microbiome.
This proposal will compare 8 crop species grown in 5 soil and weed management conditions (no till field, no till sheet mulch, tilled, tilled with fertilizer, and tilled with fertilizer plus glyphosate), each in two fertilizer conditions (organic versus conventional). Outcome measures include heavy metals in amaranth and nickel in all crops. The main hypothesis is that no till strategies reduce input costs while achieving crop quality comparable to balanced organic amendments: this ecologically sound practice could improve economic viability and social health.

Project Objectives:

1. Estimate net profit for each crop in the different weed and fertilizer management strategies (no till, sheet mulch, till, till+glyphosate x organic, conventional fertilizer).
2. Describe how different weed and fertilizer strategies affect:
a. dietary nickel exposure from diverse crops.
b. dietary heavy metal exposures from amaranth leaves and seeds.
3. Quantify dietary glyphosate and aminomethylphosphonic acid (AMPA) exposure following use for weed control.
4. Share results in peer reviewed professional publications, conferences, a site tour, and social media.


Materials and methods:

The experimental area comprises 5 strips, each having two halves that have been similarly managed except for soil amendments. We propose dividing each of the ten 60’x~20’ half-strips into four 15’x~20’ summer plots for individual USA or global staple crops (amaranth, sweet corn, cowpeas) and regionaly important companions (okra & sweet potato), while planting winter cover crops in full length (60’) companion rows of radish, pea, and wheat. We will use Round-Up in one tilled strip (#5). We will fertilize half of each strip using Organicalc recommendations, and half using conventional Extension guidance, adapted to the weed management plan.
Current Organicalc recommendations typically include compost (adjusted for NPK), CalPhos or soft rock phosphate, gypsum or elemental sulfur, Biomin copper, Borax, sodium molybdate dihydrate, cobalt sulfate heptahydrate, and AZOMITE. Crop specific University of Missouri extension recommendations typically include only CaCO3 and NPK, generally without recommending zinc or sulfur amendments. We will calculate, mix, and apply amendments for deep fertilization half strips in separate batches. Surface fertilization will use complete organic or conventional vegetable fertilizer.
The half-strip management will provide data for three way ANOVA models, with independent variables for weed management (No-till; Sheet mulch; Till; Till + Round-Up), fertilizer type (Organic, Conventional), and crop:
Strip 1: No till, surface fertilization
Strip 2: Till, surface fertilization
Strip 3: Sheet mulch, row surface fertilization
Strip 4: Till, deep fertilization
Strip 5: Till + Round-Up, deep fertilization
We will harvest, dry, grind, and submit to the OSU STAR laboratory samples of crops for complete element profiles, including nickel (main dependent variable). We will pursue expensive glyphosate and AMPA testing only in triplicate wheat, corn, and amaranth samples from strip 5. We may assay wheat protein, amaranth riboflavin, and sweet potato beta-carotene, and retail produce, at our expense if 2020 crop results confirm previous observations.

Interim report: Strip 2 was mistakenly fully fertilized prior to tilling, rather than being treated at a surface fertilization rate of 1/3. This means that Strip 2 is effectively a replicate of strip 4, and the "Till, surface fertilization" combination and associated analyses are not possible. 

A neighbor's local farm store had a large excess of "Better Boy" tomato plants that they were giving away. None of the experiments at Sumner's Farm LLC have focused on any Solanaceae plants, which are commercially very important. Therefore three of these tomato plants were planted on each side of each strip. The conventional side of strip 5 was extremely slow to produce red tomatoes, so some green tomatoes were collected from strips 4 and 5 for comparison. Eventually red tomatoes did mature in strip 5C. Grinding dried tomatoes to dust was very challenging and actually damaged some equipment that had worked well for okra. Eventually I had to use a Vitamix blender at high speeds to convert dry tomatoes to dust.  

Sweet potato production in no-till strips was particularly poor. I opted not to analyze the sweet potatoes and instead analyze the tomatoes. 

Strip 3 control was treated with a general purpose vegetable fertilizer, which contains a number of trace elements, and a mixture of urea and other N sources. This seemed like a better simulation of a commercial market garden than a simpler NPK fertilizer. 

Research results and discussion:

Interim report: 408 samples were collected, dried, and ground during the spring and summer growing seasons and were submitted for elemental analysis in mid November, 2021. We also submitted 78 samples from related pilot and follow-up studies, for a total of 484 samples. These results are still pending, partly because the laboratory is upgrading a microwave sample drying system, and had about 1,000 samples in queue before receiving nearly 500 samples from this study. 

Strip 1 production was mostly modest to poor in both conditions. This strip was treated with 1/3 of the fertilizer that would have been used with 6" tilling, and a 1/4" layer of compost on the organic side. Winter daikon radish and pea crops did well, but daikon radish tubers were mostly above ground. Spring radish and spinach crops were poor. Amaranth is adapted to disturbed ground, which the no-till strip was not, and struggled on both sides. Sweet potatoes also did not grow well at all in strip 1, presumably due to dense ground. Corn, cow peas, and tomatoes were fair, and okra rather poor. 

Strip 2, which was mistakenly fully fertilized, was extremely productive in both organic and conventional conditions. 

Strip 3 production was mostly good in both conditions, but generally better in the control condition. This is the sheet mulch strip that received either standardized "complete organic fertilizer" or a commercial vegetable fertilizer. However, okra production was much lower on the organic side than the conventional side. 

Strip 4 was a lot like strip 2. 

Strip 5, which was drenched with the maximum allowed dose of glyphosate, showed a dramatic difference between conditions. The conventional side became dry with large cracks in the soil surface, small plants, and low yields, and significantly underperformed the conventional side of strip 4. The organic side of strip 5 was similar to the organic side of strips 2 and 4, if not more productive. Fertilizer (and compost on the organic side) were tilled into the strip well after the glyphosate application. The pattern suggested that glyphosate without compost resulted in a microbial dead soil, but that adding compost fully compensated for the loss. Of course, we are waiting for a number of analyses to see how this affected the crops.

Although not part of the SARE study, a post season soil analysis showed that the organic side of each strip has reached 5% soil organic matter, while the conventional sids are consistently just above 2%. This sampling occurs about 8 months after the last compost application and tilling. Small year-over-year increases in the SOM on the conventional side of each strip might be due to cover crops and debris left on the plots. 

Participation Summary

Educational & Outreach Activities

3 On-farm demonstrations
1 Webinars / talks / presentations
1 Other educational activities: Educating immigrants about temperate zone gardening and farming

Participation Summary:

3 Farmers participated
2 Ag professionals participated
Education/outreach description:

The farm hosted had three harvesting tours in which local farmers and investors get to explore the conventional and organic sides of the different strips, meet unusual crops like amaranth, and take produce home. About 13 people have been involved in these tours. 4 of these are local farmers, and 1 is collaborating on a follow-up SARE FRG application involving livestock. 

Two farm professionals have visited the farm and learned about the unexpected nickel results that we are exploring. 

I founded a non-profit research and education entity, Argillic Horizon, which has published two videos related to the previous SARE grant on YouTube late in 2021. The short abstract video has had 23 views and the longer, quite detailed vide, which explores the rationale behind the current set of experiments and findings to date, has 33 views. Jennifer Betit Yen, a New York actress who has a blog and a significant dietary nickel sensitivity, added a link to the longer video in her blog. Argillic Horizon will be producing and publishing more videos as new data arrives. 

Methods developed at the farm have been shared with refugee and other immigrant families and children in Saint Louis through a local church ministry called Harvest. We have introduced families to amaranth (some already know about it), and perhaps most importantly started introducing them to frost covers and cover crops. Harvest has introduced frost covers to about 20 immigrant high school students and 3 families, and interacts with about a dozen families. 


Learning Outcomes

3 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Lessons Learned:

A strong distinction between organic and conventional methods may obscure some hybrid methods that would be extremely effective. Two of these seem likely from our current observations. First, new compost may largely offset soil microbiome or other damage caused by glyphosate. This semi-organic method could be a very useful combination given the substantial difficulty that organic growers face controlling weeds. Second, sheet mulch with conventional fertilizers may be as productive as any fully organic strategy, and more productive than "complete organic fertilizer" with sheet mulch. Again, the decomposing sheet mulch or its microbiome may be able to repair damage caused by urea or other components of conventional fertilizer. 

Project Outcomes

1 Farmers changed or adopted a practice
1 New working collaboration

We submitted a follow-up SARE FRG proposal to follow nickel and other metals through the food chain into animals. Also, by focusing on a few crops and selling surpluses, I am getting closer to being able to support human studies: nickel sensitivity with different foods would be a good first topic. 

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.