Compost application on rangeland in the semi-arid southwest for increased soil C storage and forage production

Progress report for FW20-363

Project Type: Farmer/Rancher
Funds awarded in 2020: $19,981.00
Projected End Date: 04/01/2023
Host Institution Award ID: G355-20-W7900
Grant Recipient: Polk’s Folly Farm
Region: Western
State: New Mexico
Principal Investigator:
Zachary Withers
Polk’s Folly Farm
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Project Information

Summary:

In the semi-arid Southwest, rangeland restoration is needed to ensure economically  viable agricultural operations in light of historical mismanagement of rangeland and climate change. Compost application to croplands and rangelands in mesic environments has proven successful to increase forage production and soil carbon storage, essential for soil water-holding capacity. Here we propose leveraging current compost production at Polk’s Folly Farm to assess the efficacy of compost application to rangeland for increased forage production and soil carbon storage at two semi-arid sites in New Mexico (annual precipitation ~ 460 mm). Polk’s Folly Farm and Sol Ranch collaborated with the Quivira Coalition and New Mexico Tech to assess this method at two sites with native plant communities using three application rates and a control. After one year, ranches saw improved aboveground biomass, methane uptake, and infiltration rate with compost addition. In order to provide a comprehensive picture of project efforts to producers, Polk’s Folly Farm created an economic case study of on-farm compost production. Additionally, the team held two field-days featuring the experiments and Polk’s Folly Farm and Sol Ranch discussed their experiences on Quivira Coalition’s podcast. Results were presented at the annual REGENERATE conference, where the largest attendee group is producers. Assessing the efficacy of this nationally recognized method for increasing soil carbon storage and forage production in semi-arid sites will inform producers, agencies, and technical service providers’ management decisions.

Project Objectives:

Objective 1: Determine best methods and economic feasibility of compost production on Polk’s Folly Farm

  • Produce compost with a C:N >11 appropriate for rangeland application [4,6]
    • Polk’s Folly Farm, Eva Stricker (technical advisor), Benjamin Duval (researcher)
  • Open-source, free economic case study of compost production
    •  Polk’s Folly Farm, Eva Stricker, Benjamin Duval

Objective 2: Determine appropriate compost application rate 

  • Establish 3 application rates (1/4, 1/2, and 1") and a control plot in experimental plots
    • Polk’s Folly Farm, Sol Ranch, and Eva Stricker

Objective 3: Determine compost application effect on soils and plant communities

  • Soil sampling and analyses at pre-treatment (year 1) and years 2 and 3. Plant community monitoring at pre-treatment and years 2 and 3. 
    • Lead: Eva Stricker, all team members participate
  • Analyze and interpret data for presentation at 2021 and 2022 REGENERATE Conference
    • Eva Stricker and Benjamin Duval

Objective 4: Producer focused engagement in experimental setup and the WSARE grant application process

  • Experimental design and compost application field-day
    • Eva Stricker, Polk’s Folly Farm, and Sol Ranch
  • Podcast about WSARE Farmer/Rancher Research and Education Grant process for producers
    • Polk’s Folly Farm and Sol Ranch 
  • Presentation of results at 2021 and 2022 REGENERATE Conferences
    • Eva Stricker, Polk’s Folly Farm, and Sol Ranch
Timeline:

Please see the link below to the pdf of our timeline:

Timeline

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Emily Cornell - Producer
  • Dr. Benjamin Duval (Researcher)
  • Eva Stricker - Technical Advisor
  • Zachary Withers - Producer

Research

Materials and methods:

Polk’s Folly Farm (2035 m) in central New Mexico experiences average annual precipitation of 431 mm with an average daily temperature of 6.9˚C [7]. Experimental blocks will be located in degraded rangeland dominated by snakeweed (Gutierrezia sarothrae) and blue gramma (Bouteloua gracilis), on an aridisol with a very fine sandy loam profile (5 to 9 % slopes) [8]. This pasture was continuously and intensively grazed by horses from 1976 through the late 1990s. The pasture was fallowed until 2014 and mowed annually. In 2015 the pasture has been intermittently grazed by cattle using temporary electrical fencing to move herds ranging in 2-8 head through small paddocks. 

Sol Ranch (1890 m) in northern New Mexico experiences annual average precipitation of 413mm with an average daily temperature of 6.9˚C [7]. Experimental blocks will be located in a dry grassland on aLa Brier silty clay loam (0-3% slope) [8]. Before the 1950s, the land was used year-round for grazing sheep, after which it was used to graze cattle annually.  

Compost Production and Testing

Polk’s Folly Farm will be responsible for compost production; they already have an established composting operation. Primary feed stocks for the compost are food scraps and wood mulch. Additional feed stocks are horse, pig, and chicken manure, cardboard, and straw. About 25,000 lbs/week of expired fruits and vegetables are sourced from Road Runner Food Bank and deposited onto a bed of C-rich material, where it is physically mixed with swine manure. When a suitable mixture and moisture level are achieved, the compost is mounded in windrows. Windrows are temperature tested daily and turned or aerated with a skid steer as needed. A minimum of 131˚F is maintained for at least 3 days on each pile, most piles sustain temperatures of greater than 160˚F for more than 5 days, and are turned at least 5 times. When piles begin to cool they are consolidated and allowed to cure for a minimum of 30 days. Once cured, the compost will be tested by commercial labs to determine that the C:N is > 11, as this is the most appropriate ratio for dry rangeland application [6]

On-site compost production and testing will allow us to address objective 1, and is essential for completing objectives 2 and 3.

Block Plot Compost Application

Polk’s Folly Farm, Sol Ranch, and Eva Stricker will be responsible for establishing the experimental plots. We will rely on Polk’s Folly Farm’s hydraulic dump trailer to deliver compost to Sol Ranch. 12 plots will be established on each site. Plots will be assigned to one of 4 treatments (1/4", 1/2", 1" compost application rates and control) that are ~5m x 10m, with 5 m alleys between the plots. Within each plot, a 1 m exclosure will be established to test for effects of grazing x compost. Compost will be applied in August/September 2020, during the primary growing season. 

This experimental design will allow us to address objective 2, determining the appropriate compost application rate. 

Soil and Plant Testing and Monitoring

Polk’s Folly Farm, Sol Ranch, Eva Stricker, and Benjamin Duval will all be involved in soil sampling and plant monitoring, and Benjamin Duval will be responsible for soil analysis. In August 2020 and then  annually for two years, we collected soil samples to characterize the physical and chemical properties of the soils. We sampled each plot in triplicate at at 0-10cm for the following physical and chemical properties: pH, texture, water-holding capacity (field capacity and wilting point), TOC, TN, C:N, infiltration rate, water stable aggregates, and soil C storage (density fractionation for free light and occluded light, and heavy fraction). At each block plot we also collected bulk density at 0-10 cm to convert C and N concentrations to content (mg C or N ha-1). 

To determine the effects of compost addition on forage production, we monitored above-ground net primary productivity as with line intercept transects and with clip plots/root cores. 

Additionally, we partnered with Los Alamos National Labs to assess greenhouse gas fluxes in the compost and control plots using a Licor. 

Research results and discussion:

Baseline data available so far revealed that the 12 plots at each site were initially quite similar in soil physical properties (bulk density (g/core) at Polk's = 248.44 +/- 3.48SE; Sol = 291.04 +/- 3.84SE; aggregate stability at Polk's = 2.22 +/- 0.17; Sol = 2.48 +/- 0.13) and biological properties (aboveground biomass (g/m^2) at Polk's = 44.7 +/- 9.9; Sol  = 118.3 +/- 2.17; Respiration rate from Solvita kit; CO2 evolved at Polk's = 1.875 +/- 0.24. 

After one year, there was an 86% increase in biomass compared to control with 1” of compost addition, and at Sol Ranch, there was 150% higher biomass inside than outside the livestock exclosure (Figure 1). There was a 30% increase in aggregate stability at Sol ranch but no difference in aggregate stability at Polks with upto 1” of compost, but for both sites, infiltration rate decreased by at least 5 minutes for the second inch of water with 1” of compost (Figure 2). 

As expected, compost additions led to higher respiration and therefore higher CO2 emissions and both Polks and Sol saw decreased emissions or enhanced uptake of methane with upto 1” of compost (Figure 3). Nitrous oxide fluxes, however, varied by site and compost addition (Figure 3), which is points to microbe-microbe interactions of host site soils with the compost (which was the same initial pile for both sites).

We did not find strong differences in air temperature or humidity (at surface level) between compost and non-compost sites (Figures 4, 5), which was surprising given the rancher observations that snow persisted longer on top of compost plots than on controls. This points to added moisture or decreased temperatures, but we did not find strong evidence using ibuttons for prolonged differences in these physical properties above the soil.

Participation Summary
2 Producers participating in research

Research Outcomes

4 Grants received that built upon this project
3 New working collaborations

Education and Outreach

4 Consultations
1 Curricula, factsheets or educational tools
1 Online trainings
1 Published press articles, newsletters

Participation Summary:

Education and outreach methods and analyses:

We toured the Sol Ranch compost sites in July 2022 as part of the “Improving Water Availability and Conservation for Livestock & Wildlife on New Mexico’s Rangelands” workshop hosted by NRCS and Bat Conservation International (note that the Agenda has the wrong name for the Presenter and also the wrong title of the section - should be “Compost and rangeland soil health - Eva Stricker, Quivira Coalition”). We also toured the Polk’s Folly compost sites in July 2022 as part of the Composting workshops. While staff and contractors used heavy machinery to set up an aerated static compost pile, the participants and Quivira staff observed the compost experiment. At both sessions, we discussed the healthy soil principles and how compost additions align with those principles. We verbally discussed initial results and visually noted that there was more biomass in exclosures in the compost plots than in the control plots. People also observed that while much of the biomass was annual plants, there were some useful plants (eg. Kochia which is palatable to livestock), and no one noted noxious weeds besides what are already found on the landscape (eg. tumbleweed). 

In fall 2020, the project was featured in the Quivira Coalition’s monthly e-newsletter (https://mailchi.mp/quiviracoalition/august-enews). 

The Quivira Coalition co-produces the Down to Earth podcast with Radio Cafe.  Both Polk’s Folly Farm farm manager Zachary Withers and Sol Ranch’s Emily Cornell were interviewed on the podcast to discuss the WSARE Farmer/Rancher Research and Education grant. The podcast ran in January of 2022 https://quiviracoalition.org/dte-episode-108/.

 At the 2022 REGENERATE conference, Eva Stricker presented the preliminary results of the WSARE experiment. Producers (ranchers and farmers) are the largest single attendee group at the REGENERATE conference  (in 2018 40% of 590 attendees), which makes this is an ideal venue for sharing information about the project and its findings with producers. 

Eva Stricker provided an outline of grant application process as a webinar in June 2021 (https://youtu.be/vVX0-rLtrUw) aimed at producers and other technical service providers. Eva has also been conducting one-on-one consulting with producers and TSPs about grant writing.  

2 Farmers intend/plan to change their practice(s)
2 Farmers changed or adopted a practice

Education and Outreach Outcomes

Recommendations for education and outreach:

A key aspect of the experimental design that was added was that an exclosure has been constructed on each plot to enable comparison of grazed and ungrazed plants; we anticipate preferential grazing on plants in compost addition plots. 

Some concern has been expressed that the plot sizes were small relative to what will be useful in a true operation scale; luckily, sol ranch is engaged in both this research as well as on-ranch trials so we can compare the differences qualitatively in things like edge effects or amount of land treated before a change in vegetation is observed. An additional concern relates to how little we know about compost additions in dry rangelands: what is ideal timing of deployment (growing season vs. after spring windy season).

We have not yet engaged in in-person educational outreach but have shared the video on newsletters and social media and the previous version has been viewed over 250 times since October 2020. We intend to facilitate peer-to-peer learning about how compost can relate to soil health, leveraging existing region-appropriate content such as the Soil Health Workbook (https://quiviracoalition.org/soil-health-workbook/)

2 Producers reported gaining knowledge, attitude, skills and/or awareness as a result of the project

Success Stories

    Success stories:

    Sol Ranch received the Excellence in Range Management in Feb. 2021, partially due to willingness to engage in research and outreach as well as hosting an apprentice (8 months) interested in learning more about agricultural enterprise. 

     

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.