Evaluation of efficiency and efficacy of a method for managing the nutrient cycle on a bio-intensive micro-farm
In the 2015 season we purchased all budgeted items designated in the grant. We chose two plots of similar character as our test plot and our control plot. Unfortunately in the spring of 2015 we did not have a well established cover crop on these plots (as we had planned) due to having planted the cover crops a bit too late in the fall of 2014. This meant there was not much residue to speak of on either test plot prior to spring planting in 2015. One plot was covered with black plastic, and the other was left uncovered. Soil samples were sent in for analysis from both plots.
As the season progressed we continued as planned in one plot: planting, harvesting, flail mowing covering the beds with black plastic for 2 weeks then using the power harrow for shallow tillage before beginning the cycle again.
And in the other plot: planting, harvesting, moving crop residue to the compost pile, applying finished compost to the bed, rototilling the bed and beginning the cycle again.
Soil samples were taken again in the fall of 2015, and then both plots were planted with winter rye and Austrian winter pea as a winter cover crop.
Results And What Was Learned So Far
In 2015 we learned a lot about the practical functionality of this system. Here’s a list of some of the critical lessons.
Lessons on operations.
- It is critical to thoroughly weight the edges of our plastic sheeting, not only to hold it in place in windy conditions, but also to ensure a good seal with the ground for decreased air flow under the sheet. When air was allowed to flow under the sheet we had limited success in killing and decomposing crop residues, and building enough warmth to encourage germination and kill down of weed seeds in the soil (occultation). On our standard beds (30” x 45’) the plastic needs sand bags at every corner and about every five feet down both edges. It is also very helpful to start at one end of the bed and pull the plastic taut as you place sand bags.
- If you are using the plastic sheeting to kill down vegetation it is necessary to run the flail mower first in order to allow the sheet to hug the ground as closely as possible.
- When the ambient temperatures are lower it takes longer to achieve thorough occultation of a given bed.
- Both the flail mower and the power harrow are VERY heavy pieces of equipment. It’s absolutely necessary to install counter weights on the walk behind tractor in order to make the machines manageable and avoid damage to the handle bar mechanisms of the walk behind tractor. The system would greatly benefit from a counter weight system, which allows for easy installation and removal of the weights when changing back and forth between implements, which do and do not require the weights. The system we used was not quick to remove or install which led us to break the handlebars off the walk behind tractor while using the machinery without counter weights, obviously leading to time-consuming repairs. Even with the counter weights in place our smaller farmers had a hard time maneuvering the machinery.
- In order to avoid soil compaction it would behoove a farmer to install axle extensions on their walk behind tractor to avoid running the tires in the bed while operating such heavy implements.
- We observed accelerated decomposition of most crop residues, which we covered, but stalky and fibrous residues did not decompose enough in the 2 to 3 week coverage to allow them to be incorporated by the harrow, and those beds required a quick raking prior to planting bed preparation.
- The Harrow we use is 30 inches wide, but has a tendency to widen our 30-inch beds by 4 inches or so. There would be less labor involved in bed preparation if a bed shaper could be incorporated into the harrow. It is also important to find the optimal counter weight to prevent the roller behind the harrow from making the seedbed overly dense.
- One of the first and most clear-cut benefits we observed from this system was an immediate decrease in weed pressure in the beds that had been covered, and not rototilled. This benefit was so clear that we began implementing the occultation system into our standard practices in all beds with the exception of our control plot. We have continued to observe significantly less weed pressure in the occultated beds as compared to the control plot.
- Over time we also observed much looser soil in the covered beds than in the control beds. By the end of the 2015 season we began considering that many beds might not require the harrow prior to planting as the soil was already quite loose, and might benefit more from a light application of finished compost for the seeder to run through.
- Because the system requires the bed to be covered for at least 2 weeks we are not able to replant beds as quickly after a crop has finished. Time will tell if improved soil health and decreased weed pressure will increase yields enough to offset these short periods of fallow. It was also clear that there is no set amount of time a bed should be covered. The key is to check the level of decomposition and weed kill under the sheeting and take action only when the desired conditions have been met. This was often closer to 3 weeks than 2.
Summary of observations:
In general we found the system to be very promising. It appeared to have a positive impact on the health of a given crop, to decrease weed pressures, and to improve soil structure.
WORK PLAN FOR 2016
In 2016 we will continue to operate the control plot as prescribed in the grant narrative. The rest of the farm will operate under the new model. We will sample soil in the control and test plot in the spring and fall of 2016, and analyze them for obvious differences. We purchased large silage tarps to use in occultation of adjacent beds when it is convenient. These tarps will cover a full nine bed 30’ X 48’ plot. In May we will flail mow the cover crops and cover the entire test plot with one of these large tarps, and in the fall we will use these large tarps for occultation prior to planting cover crops. We also believe crops residues might decompose a bit faster with a little finished compost thrown on the bed prior to covering, basically inoculating the bed with decomposing organisms. We will also begin harrowing after occultation, only if it is required to produce a suitable seed bed, laying down a light layer of compost elsewhere prior to planting.
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.
We had many conversations with CSA members who were curious about the plastic sheeting on the beds when they came by for their weekly share.
In 2015 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.
Regional Horticulture Specialist
University of Missouri Extension
2400 S. Scenic.
Springfield, MO 65807
Office Phone: 4178818909