Progress report for FW22-404
Project Information
Testimony from producers in our networks and research presentations by Dr. David Johnson suggest that New Mexico producers can save water, improve soil health, and reduce fertilizer expenses—without sacrificing crop yields—by adopting mixed-species cover cropping and Johnson-Su microbial inoculations. However, the current lack of published field trials leaves this promising combination of approaches as just that: promising.
To produce reliable evidence that could hasten the adoption of mixed-species cover cropping and Johnson-Su microbial inoculations if their promise is confirmed, we have designed and begun a six-year, on-field trial at Pata Viva farm, using a modified split plot research design. There are three experimental variables--mixed-species cover crops, Johnson-Su microbial inoculations, and fertilizer inputs (progressively decreased over the duration of the study)--and four dependent variables: soil health metrics, plant nutrient data, plant yield data, and water use (controlled and monitored by an automated irrigation system triggered at a threshold soil moisture content).
Based on the experiences of other producers in our networks (see letters of support) and the credible but non-peer-reviewed research of Dr. Johnson, we expect the field trial to provide compelling evidence that cover cropping and Johnson-Su microbial inoculations can provide environmental benefits (reduced water use and improved soil health) and save producers money through reduced inputs (water and fertilizer). By publishing the experimental results and by presenting them to producers in the Soil Health Champions network, the Seeding Regenerative Agriculture project, and other groups, we plan to foster the broader adoption of these (potentially) environmentally and economically favorable practices.
In lay terms, our research objective is to investigate whether New Mexico producers can save water, improve soil health, and reduce fertilizer expenses—without sacrificing crop yields—by adopting mixed-species cover cropping and Johnson-Su microbial inoculations.
Our education objective is to increase awareness of mixed-species cover cropping and Johnson-Su microbial inoculations by sharing the results of our on-field trial through virtual presentations to the New Mexico Soil Health Champions network and through in-person demonstrations through the Seeding Regenerative Agriculture project.
| Year | Farm Management Plan | Data Collection/Outreach | ||
| 2020 | Set up research plots & sample. | Y0: Baseline soil sample | ||
| 2021 | Till, level, lay water lines. | No data collection | ||
| Fall: plant cover crops. | ||||
| WSARE | 2022 | Fertilize, roll cover crops. Plant summer veg., harvest. Plant winter cc. | Y1: Soil sample; plant nutrient and yield data collection. Field day. | |
| GRANT | 2023 | Fertilize, roll cover crops. Plant summer veg., harvest. Plant winter cc. | Y2: Plant yield data collection. Field day. | |
| Activities | 2024 | Fertilize, roll cover crops. Plant summer veg., harvest. Plant winter cc. | Y3: Soil sample; plant nutrient and yield data collection 2. Field day. | |
| in Bold |
2025 | Fertilize, roll cover crops. Plant summer veg., harvest. Plant winter cc. | Y4: Plant yield data collection. Field day. | |
| 2026 | Fertilize, roll cover crops. Plant summer veg., harvest. Plant winter cc. | Y5: Soil sample; plant nutrient and yield data collection. Field day. | ||
| 2027 | Write and publish article. |
|
Cooperators
- (Researcher)
Research
Our research objective is to employ an on-field, split-plot design to investigate how mixed-species cover cropping, Johnson-Su microbial inoculations, and progressive reductions in applied fertilizer affect water use, plant biomass, crop yields, and indicators of soil health (physical, chemical, and biological).
Research Design:
Plots are arranged in a split-plot design with Cover Crop Mix vs No Cover Crop Mix as whole plots and Johnson-Su Compost vs No Johnson-Su Compost as subplots (Figure 1). There are 2 replications of the whole plots, and plots will be maintained for 5 years (or for as long as funding for soil testing is available) while soil test data (field and lab) are collected. Whole plot size: width equals three 6-foot beds per row (18’ per row) by 72 feet long. A tilled border will occupy beds to the north and south of the plots.
Figure 1: Plot Treatment and Replication Layout
All plots are managed similarly with respect to conservation tillage and fertilizer; while the cover crop vs. non cover crop treatments may require different levels of irrigation. Cover crops will be terminated by roller crimping.
Within each replicated subplot, four crops are sown east to west as follows: pepper, okra, tomato and squash. Each year, the crop is planted one subplot over (eastward) until on the fifth year, the crops are planted in the same location as the first year (Figure 2).
Figure 2: Subplot Details
Peppers and tomatoes are transplanted; okra and butternut squash are direct seeded. Varieties are as follows: Peppers- Carmen Organic and Escamillo Organic, Tomato- Estiva, Okra- Clemson Spineless Organic, Butternut squash- Butterscotch Organic. Planting dates are April-June.
The project uses compost created via the Johnson-Su Bioreactor method, which is an aerobic, no-turn process in which the compost matures 12 months and tends to produce a microbial species-rich, fungally dominant compost.
The cover crop mix is sown every fall and terminated in the spring by roller crimping. Seeding rates and species vary based on actual planting dates with a priority of maximizing diversity, cycling nutrients and water thriftiness.
Fertility Plan
All plots receive the same fertilizer and rates, as follows:
- 2022: 700 lbs/ac
- 2023: 300 lbs/ac
- 2024: 150 lbs/ac
- 2025 & 2026: no fertilizer application
Fertilizer (The Farm’s Choice poultry meal, 10-0-0) and liquid nutrients are banded at approximately 3" deep in the planting row . Timing of application is early to mid-April, or when cover crop plots reach about 18" tall. Non-cover crop plots are fertilized at the same time. Rates are reduced each year, with no applications in year 4 or 5.
Given the farm’s history of micronutrient deficiencies, a pre-plant liquid fertilizer blend is applied as well. This is band applied with the poultry meal. Rates are as per acre. Fertilizer is from Advancing Eco Agriculture: Rejuvenate (3 quarts), Forage Foliar (1 gallon) and HoloCal (1 quart). Rates are reduced by one third of the original value each year, with no applications in year 4 or year 5.
Data Collection
For water use monitoring, we have established separate irrigation systems between cover crop and non-cover crop treatments. Each system has a water meter and soil moisture sensor. Moisture sensors are integrated with the irrigation controller that automatically turn irrigation on and off based on a soil moisture thresholds. Total water applied is tracked by manual water meter readings.
Soil health is monitored through lab tests including Haney, S-11 Salinity, POX-C, PLFA, and S-5 Complete Routine + B, as well as through field tests including earthworm counts, soil surface and subsurface observations, and infiltration rate. These tests are performed according to NRCS guidelines.
Soil samples were collected in fall 2020 for baseline measurements. Additional samples were collected in fall 2022 and will be collected in fall 2024, with final soil tests in fall 2026 to compare with the baseline. Soil samples are taken equally from all vegetable plots and aggregated into one soil sample per treatment subplot (T1-T4). Soil samples are collected at a depth of 0-6”.
Soil cores within one treatment subplot are collected in a bucket, mixed well, placed in ziplock bags, and labeled with sample IDs that identify treatment, replicate, date, and farm name. Care is taken to use clean buckets and tools from plot to plot to avoid cross-contamination. All soil samples for lab analysis are shipped on ice via the fastest possible method to Ward Labs, except for the Total Elemental Nutrient Analysis, which is sent to New Mexico State University.
Cover crop biomass is measured as net primary productivity before rolling. Three samples are collected from each cover crop plot as shown by the green squares in the subplot detail image above. Biomass is clipped at soil level within an 18" x 18" frame, collected and air dried. Samples are then oven dried at 220 °F for 3 hours. Vegetable crop yield is measured as weight at harvest. These data will be gathered from 2022-2026.
Plant tissue/nutrient data for peppers is measured through P-2 Routine Plant Tissue Analysis. Crop yield and plant tissue/nutrient data collection areas are limited to the center 10’ of the middle rows of each subplot (see Figure 2). Collection of plant tissue/nutrient data will be conducted in 2022, 2024, and 2026.
### Results by Dr. Stricker, Dr. Johnson, & Hui-Chun Su-Johnson
Notes on Materials and Methods
The experimental design was carried out as planned in the 2022 growing season, with the notable exception of the cover crop plots. There was a delay in the planting of the cover crop mix, which was planted on March 25, 2022. The resulting cover crops did not die off as expected in summer heat, and they suppressed the growth of most vegetable crops in the cover crop plots. The cover crops and the few vegetable crops that came up in the cover crop plots were terminated by mowing followed by cultivation on July 18, 2022, with the intention of replanting a summer cover crop; however, rains made the fields unworkable during the summer cover crop planting window, so the cover crop plots were fallow from July 18, 2022, until winter cover crops were planted on November 27, 2022.
For measurements in subsequent years, we intend to collect additional data on 1) cover crop biomass and 2) soil microbial community composition through visual microscopy of soil microbial communities (using the Soil Food Web method). 9
In the 2023 growing season, delayed planting due to extreme pest pressure (False Chinch Bugs, Nysius raphanus), combined with record heat (approximately 130 days at or above 100 °F), severely reduced plant stands and yields in all plots. Tomato and pepper crops were both lost.
Notes on Results
The year one and two results are preliminary and may primarily reflect baseline field conditions.
Year One Preliminary Results
Infiltration rate
Compost alone tended to increase infiltration rate 116% compared to control (main effect X2 = 2.79; P = 0.094), other treatments had intermediate infiltration rate values (cover crop main effect X2 = 0.00, P = 0.984; interaction term X2 = 3.70, P = 0.054).
Figure 1. Infiltration rate in 2022 (1 year after treatments were imposed) by compost and cover crop treatment levels (n = 3). Boxes show the median, and the first and third interquartile range, whiskers extend to the largest value no further than 1.5 * interquartile range, and points indicate outliers beyond the whiskers.
Bulk Density
Bulk density tended to be lower (4%) in the cover crop plots than controls (X2 = 3.03, P = 0.082), but no effect of compost or the interaction (P values > 0.1).
Figure 2. Bulk density in 2022 (1 year after treatments were imposed) by compost and cover crop treatment levels (n = 3). Boxes show the median, and the first and third interquartile range, whiskers extend to the largest value no further than 1.5 * interquartile range, and points indicate outliers beyond the whiskers.
Vegetable yield
There was no significant effect of production per plant by compost treatment in 2022 (F3,16 = 0.55, P = 0.652).
Figure 3. Total yield of different vegetable products through time in 2022 by treatment (treatment was imposed in September 2021; n = 3).
Figure 4. Yield per plant in 2022 (1 year after treatments were imposed) by compost treatment (n = 3). Boxes show the median, and the first and third interquartile range, whiskers extend to the largest value no further than 1.5 * interquartile range, and points indicate outliers beyond the whiskers.
Slake test
Plots with a cover crop had 25% higher aggregate stability than plots without (X2 = 7.44, P = 0.006) but there was no effect of compost addition or interactive effect (P>0.10).
Figure 5. Aggregate stability in 2022 (1 year after treatments were imposed) by compost and cover crop treatments (n = 3). Boxes show the median, and the first and third interquartile range, whiskers extend to the largest value no further than 1.5 * interquartile range, and points indicate outliers beyond the whiskers.
Total microbial biomass (from PLFA)
Figures 6-7. Total microbial biomass (top) and fungi:bacteria ratio (bottom) through time by treatment (treatment was imposed in September 2021; n = 3).
There was no effect of the treatments or interactions on total biomass or fungal:bacterial ratio in 2022 after 1 year of treatments (all P > 0.10).
Haney test results
The cover crop treatments overall led to higher pH (8.12 compared to 7.93; F1,8 = 6.72, P = 0.032), but there was no effect of compost or their interaction (all P > 0.10).
There was no effect of compost or cover crop treatments on respiration rate, organic N, phosphorus, or potassium after 1y of treatment (all P > 0.10).
Figures 8-9. Total CO2 respired (top) and total organic nitrogen (bottom) from Haney tests through time by treatment (treatment was imposed in September 2021; n = 3).
Compost alone tended to increase organic C 9% compared to control (main effect F1,8 = 3.70; P = 0.091), other treatments tended to have intermediate organic C values (cover crop main effect F1,8 = 0.02, P = 0.879; interaction term F1,8 = 4.00, P = 0.080).
Figure 10. Organic carbon in 2022 (1 year after treatments were imposed) by compost and cover crop treatment levels (n = 3). Boxes show the median, and the first and third interquartile range, whiskers extend to the largest value no further than 1.5 * interquartile range, and points indicate outliers beyond the whiskers.
Year Two Preliminary Results
Data collection in 2023, year two of the study, comprised measurements of vegetable yield (Figure 11), aboveground dry weight cover crop biomass (Figure 12), and irrigation water usage (Table 1). Preliminary results are below.
Vegetable Yield
Figure 11. 2023 Vegetable Yield
Aboveground Cover Crop Biomass
Figure 12. 2023 Aboveground Cover Crop Dry Weight Biomass
There was no significant difference in aboveground biomass by treatment (P = 0.80).
Irrigation Water Usage
Table 1. 2023 Irrigation Water Usage
| Cover Crop | No Cover Crop | |
| Total Gallons Used | 152,870 | 79,540 |
| Gallons Used by Vegetables | 101,597 | 79,540 |
Research Outcomes
None yet, pending future results.
Education and Outreach
Participation Summary:
We established three educational objectives for this project:
- Publish the final experimental results in a peer-reviewed journal by the end of 2027, within one year of the experiment's completion;
- Train producers and agriculture students in field measurements and testing and share preliminary results through field days at Pata Viva Farm, coinciding with each field data collection scheduled; and
- Inform producers, agricultural scientists, and other stakeholders of preliminary results through digital publications and at least one presentation annually over the project period.
We anticipate that the first objective will be accomplished on schedule at the end of the project, and we have successfully carried out objectives two and three over the first two years of the project.
We established three educational objectives for this project:
1. Publish the final experimental results in a peer-reviewed journal by the end of 2027, within one year of the experiment's completion;
2. Train producers and agriculture students in field measurements and testing and share preliminary results through field days at Pata Viva Farm, coinciding with each field data collection scheduled; and
3. Inform producers, agricultural scientists, and other stakeholders of preliminary results through digital publications and at least one presentation annually over the project period.
We anticipate that the first objective will be accomplished on schedule at the end of the project, and we have successfully carried out objectives two and three over the first and second years of the project.
In years one and two, objectives two and three were accomplished through field days at Pata Viva on October 9, 2022, and October 28, 2023, as well as by soil and plant tissue sampling on October 10, 2022. Twenty-four participants attended the field days, and in post-event surveys, 100% of attendees reported that the workshop increased their knowledge of sustainable agriculture. In optional comments, participants elaborated on these impacts. Responses included special appreciation for “the chance to do some hands on field testing. Its really easy for people to explain something, but allowing us to actually get on the farm and try some things was really wonderful.” In another response, another participant reported, “I learned a lot of interesting details about making Johnson-Su compost that I didn’t know before. I also learned about diversity in cover cropping and why that’s important.”
Objective three was also advanced on May 18, 2022, when Bryce and Shelly Richard presented at Quivira Coalition’s soil health workshop in Columbus, NM hosted by James Johnson of Carzalia Valley Produce. Bryce discussed the WSARE research project objectives to 25 attendees including farmers, the general public, and staff from NRCS, SWCD, NMACD, and NMSU.
Outreach, advertising & promotion for the fall 2022 and fall 2023 field days was conducted by the Seeding Regenerative Agriculture Project, Quivira Coalition, Cruces Creatives, and New Mexico Healthy Soils through organization websites, email list-servs, and social media.
Success Stories and Participants
Four participants at the 2022 Pata Viva Farm field day–a group of nonprofit administrators, conservationists, and researchers–applied the knowledge they gained through the field day to a composting project in Silver City, New Mexico, which is using Johnson-Su composting bioreactors to make compost from school food waste and slash from the Gila National Forest.
Education and Outreach Outcomes
In surveys on the impacts of our education and outreach activities, participants expressed special appreciation for “the chance to do some hands on field testing." They also elaborated, "Its really easy for people to explain something, but allowing us to actually get on the farm and try some things was really wonderful.”
Responses such as these, combined with the data point that 100% of survey respondents reported learning more about sustainable agriculture through the field day, strongly suggest that hands-on learning and knowledge sharing is an effective approach for sharing information.