Our farm believes strongly in our use of cardboard mulch as a critical component of our no-machinery/no-till/minimum imported amendment cultivation of our market gardens. Over the years we observed a rapid conversion of sod from recently logged thin forest soil into deep rich friable soil. The remarkable abundance of earthworms in our beds led us to speculate that their actions were the main agent of change in our soil.
This grant proposed to investigate these questions:
Is there a difference between cardboard and other mulch in attracting earthworms?
How do the mulches affect soil temperature and moisture?
With no other inputs than transplant compost, how does the the soil change?
With no fertilizer or mineralizers, what will produce quality be?
The results show that:
Cardboard mulch performs better than newsprint, and mulch hay was less effective at regulating and moderating soil moisture and temperature.
Cardboard beds had the highest earthworm populations, closely followed by newsprint mulch. Mulch hay alone did not differ greatly from bare ground.
Cardboard beds were weed-free throughout the growing season, newsprint weeds increased at the season progressed where seams appeared, mulch hay at the coverage we provided was ineffective at controlling weeds.
Soil tests followed this pattern – cardboard mulch beds showed the most change in their soil chemistry, followed by newsprint and mulch hay. Organic matter, available nutrients and micronutrients and pH all rose to varying degrees. The relative rapidity of this rise is probably due to the “tillage” action of the earthworms moving the applied compost throughout the beds and their deposition of castings in the topsoil.
Plant sap pH, Brix, and chemical plant tissue analysis were more difficult to interpret in terms of mulch, but did provide some intriguing information about vegetable quality grown in a no-till/minimal input method.
The Seeds of Solidarity 30 acre site is located on Chestnut Hill Road in Orange, Massachusetts. The goal of the farm is to supply restaurants, coops and markets, demonstrating intensive food production through soil building, season extension in the Northeast, and renewable fuel and energy for farm and home. Two acres are intensively cultivated, including five greenhouses. Current crops are salad greens, cooking greens, tomatoes, hot peppers and tree fruit. The farm is located on recently logged, non-agricultural land. An unusual feature of the farm is that it is operated without any machinery (tractor/implements), and is 100% off-grid solar-powered. Farm vehicles are powered exclusively with vegetable fuels. During the grant period, the focus has changed from delivery to regional restaurants and grocers to more local vendors and an on-site farmstand. During the 2010 growing season, two full-time farm apprentices were on-site; part of the farm transition was to not hire any additional labor or apprentices during the 2011 growing season.
Ricky Baruc, Farmer
Rachel Scherer, Data collection and analysis
Christopher Picone, Fitchburg State College, was intended to be the scientific consultant on this project but was unavailable during the grant period to provide on-site assistance. He did provide phone and email support.
We are grateful to the following technical advisers for their assistance during the grant period:
Ruth Hazard, UMASS extension
Tracey Allen, UMASS Experiment Station
Pat Larsen, North Quabbin Energy for video production assistance
This project seeks to describe the properties of the soil and the plants grown in it when cardboard mulch is used, and whether there are any characteristics unique to cardboard or if comparable amounts of newsprint or hay mulches generate the same soil and plant properties.
To maintain our commitment it community education about the role of no-till methods for sustainability, the project includes a strong educational component, that will be enhanced by adding quantitative information to the anecdotal observations that have fueled our interest in cardboard mulching.
A 50’x36′ area ( Figure 1), was divided into 12 plots, (3) each of four test conditions:
undisturbed soil (Figure 2)
12” mulch hay (Figure 3)
1” newsprint + 12” mulch hay (Figure 4)
1/4” corrugated cardboard + 12” mulch hay (Figure 5)
Seedlings were transplanted into the plots by creating holes in the mulch using a dibble, removing approximately one quart of dirt, and replacing it with fully composted chicken manure. No seedlings were grown in the “undisturbed soil” plots. (Figure 6)
The initial soil tests were performed prior to dividing plots and setting out mulch on top of the existing vegetation.
Subsequent soil tests were pooled from the plots of each experimental mulch. Soil tests were done in April 2010, December 2010, June 2011 and December 2011.
Soil moisture and temperature readings were recorded twice weekly during the 2010 growing season at 3 places in each plot marked by flags so the same place was used each time. (the pink marker flags can be seen in figure 6)
Soil pH was measured monthly at these same locations.
The NE corner of each plot’s mulch was lifted,(Figure 7) and earthworms apparent at the surface were counted weekly during 2010. In the 2011 growing season, a one-cubic-foot earthworm count area was established for each plot, and counted monthly.
Tissue samples of the plants were tested for plant sap pH and Brix in 2010, and submitted to the UMASS plant and soil science laboratory for Plant Tissue analysis at the end of the 2011 growing season.
Soil samples were analyzed at the start and end of the project(Table 1)
Consultants were skeptical about the possibility that this degree of change could occur in only two seasons. The compost used to transplant into, and the layer of earthworm castings found under the mulch (The dark brown material seen under the pulled-back mulch in Figure 2) were also analyzed in order to compare components and try to estimate the contribution of each to the final soil analysis. (Table 2)
Our interpretation is that the end soil analyses (Table 1) reflect a mixing of the compost into the starting soil, along with a substantial amount of earthworm castings, and that this mixing must be the result of earthworm activity since no other tillage was employed. We also believe that the incremental differences in the changes between mulch types corresponds to the initially larger population of worms under cardboard (Table 3). The spatial arrangement of interspersed square plots probably did not permit isolation of earthworm populations under only one type of mulch, so that ultimately, all the soil was “tilled” by the worms to some degree. It is interesting to note that in Sub-Saharan Africa, the Fertility Tree System has a similar basis: instead of spreading prohibitively expensive chemical fertilizers over large acreages, small amounts of organic fertilizers are applied co-locally with interspersed tree plantings. The spreading root system of the tree and the attracted microbial and microfaunal life serve to spread the nutrients into the surrounds of the trees, improving the soil and sustaining other plantings (e.g., : International Journal of Agricultural Sustainability, Sustainable intensification: increasing productivity in African food and agricultural systems , pp. 129-136(8).
The health of the plants in the beds is also protected by the ability of the mulch layers to moderate soil temperature and conserve moisture in the root zone (Table 3,4).
Plant sap monitoring in SARE plot 2010 was limited to small (non-quantitative sample sizes, cardboard mulch plants only):
A balanced level of nutrients in the leaf of the plant will show an ideal pH level of 6.2-6.4., according tot he late agronomist and proponent of Biological Farming, Bruce Taino.
Tomatoes (salad and paste) basil, summer squashes, pumpkins
A lower than ideal pH level will indicate a deficiency in the following minerals: Calcium, Potassium, Sodium or Magnesium.
Lacinato and curly kale, brussel sprouts
A higher than ideal pH level will indicate a deficiency in the following minerals that act in the opposite direction:
Phosphates, Nitrate Nitrogen, Sulfates and trace minerals
(none in this category)
While these tests were qualitative rather than quantitative, they are especially interesting in light of the 2011 plant tissue tests done at the UMASS plant and soil testing lab. These results (Table 5) show that in all the mulches, nutrients are present at satisfactory levels compared to standards, with two exceptions: Calcium and Boron. This is of great interest from the biological farming perspective for two reasons – first, the plant sap pH tests also suggest lack of Ca; and second, it is widely disseminated that Boron is the micronutrient most closely tied to making Calcium available to the plant.
It is also interesting to note that relative levels reflect the same “hierarchy” as all the other measured parameters: cardboard; newsprint; mulch hay. We propose that this is further evidence the the action of the earthworms, which populate the cardboard first and most highly, then newsprint and mulch hay in decreasing order, is responsible for the conversion of the initial soil into the final one, amply supplied with nutrients, and possessing a friability unimaginable at the start of the project. (Figure 7: Soil Appearance at start of project, Figure 8: Soil appearance at end of project)
Earthworms appeared under the cardboard mulch within 48 hours, and continued to populate those areas at twice the rate of newsprint, and three-four times the rate of mulch hay alone for several months. By the end of the season, numbers of earthworms under the newsprint area were roughly equal to the cardboard, but still 2-3x more than mulch hay alone. Earthworms were almost never seen at the surface of the undisturbed beds, and the number of worms below the surface was always in the lowest range.
The quantity of worms under the mulch and in the bed corresponds to the increase in nutrients and micronutrients in those beds as shown in the soil analyses, and to a lesser extent, in the plant tissue samples. This is a combination of the physical mixing of the added compost by the earthworms movement through the beds, and their deposition of castings. It makes sense that the highest increases would occur where there are the highest amount of worms, and that over time, it would all be mixed together as the worms were not subject to a physical barrier between the bed types.
There have been discussions to the effect that the hide glue used to bond the cardboard layers attracts the worms as a protein source. We cannot confirm or deny that, but since we did observe that the equivalent thickness of newsprint also attracted worms more than just a mulch hay layer, that some quality of these mulch types was responsible.
The answer may be in a simple observation – the birds – primarily robins, do not prey on the worms for food through the cardboard, or, in the early part of the season, through the newspaper. The cardboard, since it is laid on top of existing vegetation, now provides a predator-proof cover over an organic matter food source for the worms, it creates a consistently moist environment protected from the sun – all things that are optimal for worm feeding and perhaps more importantly, for mating. As the mulches degraded, there were less worms at the surface but the subsurface numbers remained consistent. It would be really interesting to get a worm specialist to design some controlled experiments in a situation where the subsurface counting would be more rigorous than we could perform.
In addition, the extreme amount of rainfall in 2011, when we attempted to do more rigorous counting, prevented us from maintaining the count squares in fixed locations, and when the soil became saturated so that even new holes would be waterlogged just a few inches below the soil surface, we could not do scientific counting.
The robin observations may have been the most useful part of the exercise, and it would be also useful to consult with a bird behavior specialist to find out more about their hunting preferences.
The use of biological farming assessments was disappointing, in that we could not obtain reference materials to guide our sampling or analysis without incurring large consulting fees that had not been written into the budget. Some of the tests we used (Brix and plant sap pH) are described above. Other testing of the soil was of minor use to us in formulating the results of the project – We submitted soil samples for Formazan testing, a measure of biological activity in the soil, and we had soil bacteria and fungi counts performed by the Soil Food Web laboratories in Oregon, but we were unable to establish a context for the numbers reported.
The most important aspect of this system is that it enables our farm to run with no machinery and the labor of only one full-time farmer. It is worth considering that the method virtually eliminates weeding (Figure 1,2: cardboard mulched commercial kale, pumpkin beds) and minimizes watering (see Results section for data on soil moisture).
What follows is a comparison of logged time for the cardboard method vs estimates of time necessary with more conventional small-farm methods:
In YEAR 1 of the cardboard method, sod is converted into a useable bed by covering with cardboard and then planting into compost-filled holes cut or dibbled through the cardboard layer.
As an example, consider a bed containing tomatoes, stagger spaced at 3′ in two rows for 68 plants/bed
Time (one person) logged:
Lay cardboard: 30 mins
Cut and dig holes: 1hr 42 mins
Compost into holes and set seedlings: 1 hr 8 minutes
Cover cardboard w/ mulch hay: 10 mins;
Total time 2hrs 4 mins
It is important to note that -0- time is required for weeding in the cardboard mulched bed.
In comparison a conventional technique requires: (time estimated)
Spring rototill 30mins
Sod breakup 30 mins
Cover bed w/ compost 45 mins
Holes for planting 11 mins
Mulch application 10 mins
Weeding 4x 30 mins/season = 2hrs
Total time 4 hrs 5 mins
We have not estimated equipment costs/maintenance/fuel
total bed prep time 3hrs 11 mins (additional time logged in creating raised bed on top of previous years bed)
Total time 4hrs 35 mins (additional time for creating raised bed)
Raised beds in place so time decreases to
Total: 2 hrs 3 mins
time remains the same
@4hrs 35 mins
The economic benefits of cardboard mulch, demonstrated by the research results, are:
Free or low cost source of mulch for moisture conservation
Adds organic matter at low/no cost
No weeding (really!) and no bringing up new weed seeds with tillage
No need to wait for weather/field conditions to permit machinery on field, cardboard can be laid at any time under any condition. Additionally, do not have to wait for cover crop or sod to break down, can plant through cardboard at any time.
No equipment/maintenance/fuel costs – and no pollution.
Less time and energy input into watering
Low cost of soil amendments – import over time decreases as opposed to conventional repeat applications yearly. This is due to the “tillage” action of the earthworms, who distribute the added compost throughout the soil in the bed, and add their castings at the same time as they improve drainage and aeration.
The two growing seasons during which this study was conducted presented many challenges. 2010 brought an extremely wet spring, periods of unusually high temperatures in the early part of the season, followed by long very dry periods and unusually high temperatures for longer than usual duration. The research plot experienced severe repeated predation by herbivores destroying most of the crops. This limited the plant-based testing to qualitative results, as we did not have enough plants in reproducible conditions to generate sample sizes for statistically significant data.
2011 was another season of unfavorable conditions for conducting the research. We had planned to focus more on the monitoring of the earthworm population, but the record setting rainfall added complicating factors of earthworm behavior into the mix. The resulting data was useful descriptively, but would not be statistically significant.
- Table 1: Soil Test Results
- Dark brown granular castings under degraded mulch
- Table 2: analysis of other components
- Table 3: Temperature under mulch
- Figure 7: soil at beginning of project
- Cardboard mulched commercial kale beds
- Cardboard mulched commercial pumpkin beds
- Table 4: Soil Moisture under Mulch
- Table 5, plant tissue analyses
- Figure 8: Soil at end of project
We had outstanding attendance at our on-farm workshops, and the attendees were always impressed by the tours of the research plots and discussions of how earthworms contribute to soil health, and thereby, human health. These tours generated a lot of new awareness of the existence and purpose of SARE.
The farm operates in coordination with The Seeds of Solidarity Education Center, a nonprofit organization providing people of all ages with the inspiration and practical tools to use renewable energy and grow food in their communities. During the grant period, “The Cardboard Method” was part of the material presented to a large number of school groups and health provider organizations in our community. We are very proud of the resulting implementations. That work is documented at:
Education & Outreach Activities and Participation Summary
June 12, on-farm workshop “No-Till For Life: The Cardboard Method”
3 hrs/40 attendees
July 2, Omega Institute Rhinebeck NY, 4hrs/60 attendees
July 9, on-farm workshop 3hrs/12 attendees
August 12, on farm, 25 teachers starting gardens at schools
October 2,3 Garlic and Arts Festival, Orange MA: 4 workshops each day
30mins,~20 people at each.
October 23, on farm workshop, 3hrs, 50 people
January 15, NOFA-MA Winter Conference, 1.5hrs/50 attendees
May 12, Presentation to Mt Grace Land Trust Community Gardens Project, 2 hrs, 20 persons
June 4, on-farm, 3hrs/40 people
June 17,19 Omega Institute, Rhinebeck NY 4hrs/50 people
July 8, on-farm, 3hrs /15 people
Aug 12, “Grow Food At Schools” cardboard method workshop
Oct 1,2: Garlic and Arts Festival, 4 demos per day/30mins/20 people
Oct 29: on-farm – 3hrs-45 attendees
No Till Farming for Life
Excerpt from a 28-minute video aired on AOTV, the local public access station.
A handbook for workshop attendees is in production.
Lancaster Farming Article (attached)
We did some research into how a farm set up for row cropping might make use of the cardboard method. I have applied cardboard I get from appliance/furniture stores to fields of 200 foot rows, but looked for a method for even larger scale uses, utilizing machinery.
Rolls of one-faced corrugated cardboard can be purchased locally from Mt Tom Box Company. For example, a 36″ wide roll to cover a field with raised beds costs $45 for 250 feet, a cost of about 18cents/foot.
The roll cardboard could be put on the field with the same type of rig used to apply plastic mulching.
It would be interesting to hear from larger scale farms whether this could offset their labor/machinery costs for weeding which is eliminated, and with lowered fertility import costs if this were applied following a cover crop on the beds to provide organic matter for the attracted earthworms to till into the soil.
The cardboard mulch will definitely continue to be the main method for growing cooking greens, summer and winter squash, onions, leeks, field corn. There was no reason presented to incorporate it into the greenhouse methodology, and it has not proven advantageous for root crops.
The extensive soil and plant testing revealed previously unknown to us aspects of our cultivation methods. The soil is high in calcium, yet plant sap and tissue test showed calcium deficiency. We will investigate use of household borax as a soil amendment to increase Boron availability, and thereby increase calcium mobility.
Secondly, we will investigate if the high P content of the soils after a year or two of this cultivation method presents any concern for groundwater by conferring with water quality experts.
The method was demonstrated to be successful in relation to other mulching options. However, the investment of the beds created under continuous cardboard covering does not allow the rotation of cover crops into the system. I will be looking into ways to create these rotations on my farm.