My farm is located on a glacial Esker, with a thin organic horizon on top of 1.5-2 meters of sand. To address the lack of organic matter on the farm, I decided to establish a no-till Permanent raised beds (PRB) system to build soil and soil water holding capacity. Anecdotally, the no-till PRB system I have established on my farm has allowed me to effectively build soil organic matter, manage weeds, and increase overall yields compared to the more traditional organic agriculture practices our colleagues have been using. However, I have not formally collected the data necessary to validate these observations.
My research has three main objectives that will provide quantitative data to help improve on-farm productivity, reduce production and management costs, and improve farm viability, while building healthy soils. To better understand how our PRB system works, I will (1) assess effectiveness of weed suppression, (2) evaluate soil health, and (3) calculate production potential for three main crops, strawberries, garlic, and mixed leafy greens. I will conduct the proposed study for two growing seasons in 2018-19.
Permanent raised beds (PRB) are used for various cropping systems throughout the world, but are still not common for commercial, small scale, mixed vegetable production in the Northeastern United States. A PRB system intentionally designates permanent growing space for crops that is cultivated year after year, and often includes tilling the rows while leaving the inter-rows untouched. Forming beds with a tiller or other shaping equipment to mound soil in the rows, makes the beds slightly higher than the walkways or inter-rows. In an ideal system, PRB increase soil water holding capacity, soil organic matter (SOM) formation, and soil temperatures; and reduce soil erosion and nutrient leaching compared to conventional production systems (Govaerts et al., 2007; Gathala et al., 2015). However, there is no scientific, peer-reviewed research available on no-till PRB systems specific to New England agriculture, though it may be a valuable practice for improving soil health, reducing weed pressure, and increasing production capacity.
Many weeds have evolved resistance to herbicides in conventional systems, causing ongoing management concerns (Heap, 2017). Organic production often relies on tilling or plasticulture to control weeds (Kasirajan and Ngouajio, 2012). However, tilling can compromise soil health and disturb the weed seed bank; and plasticulture is costly, requires specialized equipment, and creates disposable waste products. All three weed management methods create annual expenses and require hours of on farm labor. It is not uncommon for direct sown crops (e.g., carrots, leafy greens, beets, etc.) to be outcompeted by weeds, and thus lost income for the farmer. Scientific research on weed management within PRB systems is lacking.
Also, while the number of farmers in New England has risen over the past decade, the number of prime farmland acres in production has decreased (USDA, 2012). As the interest in agriculture increases, but the availability and accessibility of prime farmland decreases, we must explore the possibilities for bringing marginal lands into production, without compromising yields and thus farm viability. As PRB systems have been found to increase SOM formation, these systems could be one means of converting marginal lands into productive agricultural systems.
Additionally, traditional agricultural plantings often spatially constrained to fit farm equipment (e.g., the width and distance between beds is determined by the tractor and attachments for tilling and planting). No-till PRB systems are not limited in configuration, as fossil-fuel powered equipment is not necessary, therefore, farmers can plant more intensively. Given that biologically intensive agriculture has been shown to increase yields compared to traditional organic agriculture (Algert et al., 2014), it is possible that production capacity in no-till PRB systems could be higher than traditional agriculture. In general, previous research, and my own farming experience suggests that no-till PRB system have a “lower barrier to entry”; with decreased long-term capital inputs (e.g., the need for expensive equipment and labor for weed management).
As my PRB systems were established over the course of four years, I effectively have a time series of PRB systems at different levels of “maturity” (figure 1). This time series will allow me to determine how PRB systems change over time and determine if there are differences in weed suppression, soil health, and/or production capacity as the PRB system matures. To build each PRB system, I covered the existing sod with 10 cm of hardwood chips, and constructed each PRB to be 81 cm wide, with varying lengths, using compost, and 46 cm between rows. Crops are rotated between beds within each PRB system several times per season, with a cover crop seeded at the end of the growing season in early fall. Black silage tarp is used for three weeks prior to planting all crops to germinate and kill any surficial weed seeds and warm the soil. Garlic is an exception to this as it is planted in the fall and mulched with 10 cm of chopped maple leaves/saltmarsh hay. We do not till, and do not use any fossil fuel powered equipment in the systems; all farm tasks are done by hand.
I will work with Dr. Richard Smith’s agroecology lab to address each of my objectives. To assess how effective my farm’s PRB system is at suppressing weeds, each week I will pull and collect all weeds found within the four systems. The weed biomass will be bagged, labeled and picked up by a Smith lab technician, who will identify, sort, dry, and weigh all weeds at their lab at UNH. I will also track the number of hours spent weeding each week. This will allow me to quantify the amount of weeds growing in the production areas, and how much farmer time is devoted to weed management. Additionally, an undergraduate lab technician will conduct a weed seed bank analysis at the UNH greenhouses to identify and quantify the density and species composition of the soil weed seed bank. To do this, we will collect soil cores from the rows and inter-rows, from each of the systems at the beginning of the growing season. Three randomly selected soil cores will be taken to a depth of 10 cm from each row/inter-row, mixed, and a 50 g subsample of the mixed sample will be used for analysis. Thus, each composite sample will be representative of a row/inter-row within its respective system. We will then spread the soil sample on a soilless medium in plastic trays, and place the trays in the UNH greenhouse where they will be kept moist.
To determine if soil health differs across the time series, we will collect soil samples from the rows and inter-rows within each treatment, as well as from the surrounding sod. To sample, three randomly selected cores will be taken from each row/inter-row, mixed, and a subsample of the mixed sample will be used for analysis. Thus, each composite sample will be representative of a row/inter-row within its respective treatment. The samples will be packed in a cooler and shipped to the Cornell Soil Lab for a Comprehensive Assessment of Soil Health. These data will be used to understand how my PRB system affects soil health over time and if soils in PRB differ from the unmanaged sod.
To determine production capacity, I will measure yields for three main crops on the farm, strawberries, garlic, and mixed leafy greens. Crops will be weighed using a certified Tor Rey L-EQ series scale. Only marketable yields will be measured each week, as marketable crops are what contribute directly to net farm income. Garlic scapes will be weighed separate from garlic bulbs, as each are distinct salable crops. Leafy greens will be weighed as one category of crop, but will include up to five different vegetables (e.g., spinach, head lettuce, lettuce mix, kale, and swiss chard). Yields for each crop will be averaged per square meter of bed space and compared to yield averages of traditional organic production.
I worked with Dr. Richard Smith’s agroecology lab to address each of my objectives. To assess how effective my farm’s PRB system is at suppressing weeds, we collected weeds in early spring, and mid-summer. The weed biomass was bagged, labeled, and picked up by a Smith lab technician, who sorted, dried, and weighed all weeds at their lab at UNH. This differed slightly from the initial proposal to collect all weeds throughout the season, as we found that this took more time than weeding with a hoe, which is the way in which we would typically manage weeds. Given that we were also collecting data on the amount of time spent weeding each week, we decided to reduce the number of weed collections to two (when weeds are typically most abundant), and add a biweekly weed observation. An undergraduate lab technician came to the farm biweekly throughout the season from late May through the end of August 2018 and noted which weeds were growing in each section (by species), as well as the relative abundance of each. In late May, soil samples were collected for a weed seed bank analysis, which was conducted at the UNH greenhouses. This analysis allowed the technicians to identify and quantify the density and species composition of the soil weed seed bank.
To determine if soil health differs across the time series, on October 31, 2018 we collected soil samples from the rows and inter-rows within each treatment, as well as from the surrounding sod. We took, three randomly selected cores were taken from each row/inter-row, mixed, and a subsample of the mixed sample. The samples were then packed in a cardboard box and shipped to the Cornell Soil Lab for a Comprehensive Assessment of Soil Health.
To determine production capacity, I measured yields for three main crops on the farm, strawberries, garlic, and mixed leafy greens. We weighed crops using a certified Tor Rey L-EQ series scale. Only marketable yields were measured each week from May 21, 2018 to October 11, 2018, as marketable crops are what contribute directly to net farm income. Garlic scapes were weighed separately from garlic bulbs, as each are distinct salable crops. Leafy greens were weighed as one category of crop, but included up to five different vegetables (e.g., spinach, head lettuce, lettuce mix, kale, and swiss chard).
Preliminary results from year one of this two year study indicate that our farm has high weed diversity, but low abundance.
The average time spent weeding was as follows: ~12 hours/month in May & June, ~5 hours/month in July & August, 30 minutes in September, and 0 min in October.
Soil heath data will be analyzed this winter, after test results are received from Cornell Soil Health Lab.
Yield data from year one will be analyzed this winter.
Education & Outreach Activities and Participation Summary
I am planning to present about our research project and share preliminary data from year one at the NOFA NH annual winter conference on March 16, 2019. We will host an on farm twilight meeting next summer 2019. We will also work on publications through UNHCE and peer review journals after the completion of the study.