Evaluation of efficiency and efficacy of a method for managing the nutrient cycle on a bio-intensive micro-farm

Problem/Solution

We are always seeking methods, tools, and philosophy with the potential to make our farm more productive, more sustainable, and more efficient. The natural nutrient cycle dictates that a farm, which strives to operate within the constructs of nature, return as much plant matter to the soil as possible. Of course for this plant matter to be converted back into useful nutrients takes time, and space, two commodities often in short supply on a tiny vegetable farm. In order to be profitable on a micro-farm we must plant a new crop in place of the old as quickly as possible once the bed is harvested out. This leaves us little opportunity to let beds rest, or go fallow, and no opportunity to allow crop residues to decompose in place. Coarse crop residues are moved to a compost pile for later return to the soil and fine residues are incorporated with multiple passes of the rototiller. Then finished compost is moved to the bed, other amendments are added and the bed is tilled again to prepare a suitable seed bed.

What all this means is we spend a lot of time moving things to and from the bed, and erode our soil structure through repeated tillage in order to effectively recycle plant nutrients. If we can encourage our crop residues, cover crops, and green manures to rapidly decompose in place, we can drastically reduce the labor and tillage required to return nutrients to our soil. Jean Martin Fortier is a Canadian micro-farmer who authored the book “The Market Gardener”, which was published in English earlier this year. In this book he lays out methods, which I believe could solve many of the challenges micro-farmers face with regard to green manures, cover cropping and reduced tillage. When a bed is harvested out, Fortier uses a 30” flail mower on his walk behind tractor to finely shred the crop residues. He then covers the residues with a tarp, creating conditions in which de-composing microorganisms thrive. A couple days later the tarp is removed, any required amendments are spread, and a shallow horizontal tillage is performed with a power harrow. Finally the bed is replanted. The use of the flail mower creates small particles and greater surface area, which allows for accelerated decomposition of the residue. Because the material is finely chopped, and well on its way to decomposition when the tarp is removed the deep tillage of a rototiller is not necessary, and the soil structure may be spared by the shallow horizontal bed preparation of a rotary harrow. These practices do not appear to be in wide use and we believe it would be valuable to have a farm in our area demonstrating the techniques for fellow farmers, as well as up and coming farmers. We would like to implement, evaluate, and demonstrate these strategies within our farming community.

Introduction:

PROJECT BACKGROUND

Urban Roots Farm is a Certified Naturally Grown micro-scale commercial vegetable farm. We grow around 40 types of vegetables across 90 varietals.  On average we harvest approximately 500 pounds of produce per week. This produce is sold primarily through our CSA, and wholesale accounts.

We refer to Urban Roots Farm as a micro-farm because of its tiny footprint. The farm sits on a 1.7-acre parcel in a residential neighborhood, and currently utilizes only ½ of an acre for production. We maximize our yields from this small area through the use of 3 mobile high tunnels for four season growing, bio-intensive crop planning and successions, and careful soil management. While our footprint is small, our output is not.

Urban Roots is Owned and operated by Adam and Melissa Millsap. When we applied for this grant in 2015 both Adam and Melissa worked full time on the farm. Since then Adam has taken a full time job off the farm, and Melissa continues to manage the farm.

Urban Roots Farm is a Certified Naturally Grown farm, and we have held sustainability as a primary motive from the farm’s inception. From the start we have utilized all natural practices, used no chemical pesticides or chemical fertilizers, used conservative irrigation practices, worked to decrease the farm’s dependence on petroleum products, and worked to maximize passive heating and minimize fossil fuel heating of our growing structures. Like any farm we have room for improvement with regard to sustainability, and continue to strive to reach new goals.

PROJECT DESCRIPTION

GOALS: The goal of this project was to demonstrate and evaluate a system in which a flail mower is used in conjunction with opaque plastic sheeting and a rotary harrow to cycle nutrients, purge weed seed from the soil and prepare beds for successive planting.

This system is described in a book authored by Jean Martin Fortier titled “The Market Gardener”, and we felt it would be valuable to evaluate the system and demonstrate its practice, as the system is not currently in widespread use.

PROCESS

This system is cyclic, and could be described starting at any point in the cycle but is perhaps best explained starting with the plastic sheeting. The steps and purposes are as follows.

1. The crop area is covered with opaque plastic sheeting. The primary purpose of the sheeting is occultation, or to starve the area of light. The area that is covered is warmed through passive solar capture, starved of light, and kept moist by the prevention of evaporation. This warm, moist and darkened environment encourages decomposition of organic material that is on the surface as well as the germination of weed seeds that are stored below the surface. When the weed plants emerge from the soil they are met with an inhospitable dark environment in which they perish and decompose.  This cycle continues as the soil is warmed to deeper levels, hopefully resulting in a weed free seedbed.
2. When satisfactory results are observed in the covered area, the sheeting is removed and the area is prepared for planting. Previously it was our practice to till the area in preparation for planting, but the soil inverting rotary action of a tiller is likely to move weed seeds from deeper levels, and increase the likelihood, and volume of weed growth after the bed is planted. Instead of rototilling, this system employs a rotary harrow, which has a rotation like that of a clock laid flat on the soil. This blade rotation allows the loosening of only the top layer of soil while leaving the un-germinated seeds down deep, where they are less likely to germinate. The harrow is infinitely adjustable from zero penetration to about five inches of penetration, and is adjusted to the shallowest setting, which will allow for seeding (usually 1-2 inches), or transplanting (usually 2-3 inches) of the incoming crop. If the crop calls for it we also spread a layer of compost and chicken manure based fertilizer.
3. The next step is many steps in one. The crop is tended to and harvested as prescribed by the farm’s methods. It is of course critical that weeds that persist in the bed are destroyed, and preferably at very early growth stages, but certainly before they produce seeds. Otherwise the cumulative weed pressure reduction, which is a benefit of this system, will not be realized.
4. After the cash crop has been harvested the vegetative residue is pulverized with the flail mower. Flail mowers have a horizontal shaft from which L-shaped blades are hinged. Because the blades are hinged they rarely receive permanent damage upon striking hard material such as stones, and the operator can feel confident mowing very near soil level. The discharge is adjustable allowing materials to be circulated and thoroughly pulverized. The pulverized residues seem to decompose more readily, and the low mowing height allows the bed to be covered without stalky materials holding the plastic sheeting above the soil, or puncturing the plastic.
5. The process then continues through crop successions. When the bed is cover cropped the process is the same, and the cover crop is mowed and covered for decomposition. The plastic sheeting is also very effective in killing down a cover crop if it is necessary to plant the space before the cover crop is at an easily killed stage (for instance if a bed is needed before winter rye is at pollen drop)

PEOPLE

Urban Roots Farm personnel conducted the bulk of the work in this project. Melissa Millsap who is in charge of day-to-day operations on the farm decided which beds would be covered and when. She and other farm personnel performed the tasks necessary to execute this system on a daily basis over the course of two years. Initially this system was put to use in one plot for evaluation, but as the benefits became clearly illuminated the system was instituted everywhere on the farm except in the control plot.

Involved personnel included:

• Melissa Millsap – Farm owner and operator
• Alyssa Hughes – farm manager
• Bill Schultz – intern for one year during project
• Emilee Blansit – Farm intern for 6 months during project
• Kevin Prather – Farm intern for 2 months during project
• Adam Millsap – Farm owner and grant coordinator

Most of these persons were involved in the execution of the steps of this system on a daily basis. All of them have plans or intentions of farming in their future.

RESULTS

Initially this system was set in motion in one 30’ X 48’ test plot and a similar plot of identical size was allocated as a control plot in which we would continue our traditional cycle. We selected the plots because they had similar soil conditions, and similar weed pressure.

In the control plot we continued to move residue from previous crops to the compost pile, spread compost and fertilizer, and till the bed before planting.

In the test plot we initiated the system as outlined in the project.

Soil Testing

We took soil samples in both plots and had them analyzed in the MU soil laboratory prior to the project commencement, and throughout the project. We did not see significant differences in the makeup of the soil in the two plots. We expected to perhaps see some improvement in the organic matter content of the soil in the test plot, but both plots remained fairly consistent across all measured parameters.

Soil Structure

The structure of the soil was a different story all together. While our measurement of this characteristic was less formal and less quantifiable, we observed significant improvements in the test plot. The soil structure in the test plot became significantly less compacted, and required less and less soil work prior to planting. In fact it became common for us to simply spread a thin layer of finished compost on a bed before direct seeding with our 6-row seeder or our 1 row precision seeder. This was possible because the soil was loose even without tillage, and there were very few small stones near the surface, as they were not brought up by tillage. Even when we used the harrow to loosen the surface soil fewer and fewer stones were exposed as the cycle count increased. Previously we had to rake stones from the bed after tilling and prior to 6 row seeder use, because even small stones make use of that tool very difficult.

In the control plot we observed that our soils seemed very loose and fluffy directly after rototilling, but very quickly returned to a compacted state which often appeared to settle at an elevation below that observed prior to tillage.

Weed pressure

Reduction of weed pressure was readily observed in our test plot. The change was large in scale and almost immediate. In beds where plants were previously competing with heavy weed pressure almost before emergence, there were very few weeds germinating before the crop. While beds in the control plot continued to be plagued with green carpets of emerging weeds, the beds in the test plot saw a steady reduction in the density of weeds with every cycle. For us this proved to be the most valuable prospect of this system, and it is what convinced us very early on to put the system into use in all our plots but the control plot. Within a single growing season this system changed our weed pressure from levels, which left us, feeling utterly hopeless to levels we believe will allow us to progress toward consistently clean beds.

Reduction of Labor

This system has without question reduced labor for bed preparation. Before, coarse crop residues were moved to a compost pile for later return to the soil and fine residues were incorporated with multiple passes of the rototiller. Then finished compost was moved to the bed, other amendments were added and the bed was tilled again to prepare a suitable seed bed.

Now the bed is flail mowed, covered and allowed to rest for 1 to 3 weeks, then top-dressed with compost and fertilizer and depending on conditions, planted or harrowed then planted.

The trade off is that our beds are potentially not re-cropped as quickly, but we have found that with the reduction of weed pressure, and reduction of prep time required for planting we are actually likely to have a larger percentage of beds in production at any given time as we have time to plant them as soon as they are ready. We also anticipate the need to cover the beds to become less frequent as the bank of weed seeds in our soil is depleted, so it is possible we will have shorter intervals between harvest and planting in the future.

Yields

While we did not measure change in yield; the relationship between yield and weed pressure is well established. We grow large volumes of cut greens and it has become significantly less common to give up on a greens bed due to the impracticality of sorting the greens from the weeds. Additionally labor has been reduced as we spend much less time sorting out the weeds when it is not an option to abandon a greens bed due to sales commitments.

DISCUSSION

I believe our reported observations make very clear that this system is advantageous to an operation such as ours. The system, which we set out to analyze and demonstrate, has significantly improved our labor situation, our yields, and our soil conditions. As expected we saw reduction in the labor of moving materials around, but were pleased to find additional gains were to be had in reduction of time spent managing weeds, preparing products for market, and preparing beds for planting.

The only aspects of this system we are not thrilled with is the introduction of more plastic (petroleum dependence) into our operation, and the increased interval between harvest and planting, but we purchased high quality silage tarps which should last many seasons, and we expect to see a reduction in the required frequency of covering the beds as the weed bank is further depleted.

Our farm is plagued with Bermuda grass, which is an invasive weed, which spreads by rhizome. For six years we have desired to reduce tillage on our farm, and with it the undesirable effects it has on soil structure and health, but we have not seen a feasible path prior to implementation of this system. We now believe that through use of this system and cover cropping we will vastly reduce tillage in the coming years.

It would not be an overstatement to say this system is revolutionizing our operation.

OUTREACH

During 2015 we had 3 interns, a farm manager, and 2 full time farmers who participated in the implementation of this system, and countless discussions about how it was working out. We also had around 12 volunteers who observed the system throughout the year.

During 2016 we had 1 intern, a farm manager, and 2 full time farmers who participated in the implementation of this system. We also had around 10 volunteers who observed the system throughout the year.

We had many conversations with CSA member, from our 75 family CSA, who were curious about the plastic sheeting on the beds when they came by for their weekly share.

 In 2015 and 2016 we hosted 2 farm tours with about 20 fellow farmers, 3 college level tours with around 20 students each, 3 elementary school tours with approximately 80 total students, four cocktail nights with tours including around 20 people, and two farm-to-table dinners with tours including around 40 folks each night.  Anytime we give a tour we are sure to mention this system and its perceived benefits as it has become an important part of our farming system.