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Using cover crops and mineral amendments to increase fertility and production on urban farms

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This article comes from the NOFA/Massachusetts 2017 March Issue Newsletter

By Nicole Belanger

Green Team staking the tomatoes in test plot #1

Though the word “farming” is in its name, NOFA does more than just work with rural farmers. Much attention is paid to ways more traditional, production farmers can use techniques like cover cropping and mineral amendments to enhance their yields, but there are few resources and little knowledge for using these tools on smaller scale and urban sites.

NOFA/Mass is partnering with The Trustees Boston Community Gardens and Groundwork Somerville on a three-year project to improve the fertility and production of compost-based soils, funded by the Massachusetts Department of Agricultural Resources (MDAR). Compost is often free and used-widely by many city growers. Though considered non-toxic and safe for growing in, compost does not provide all that soil needs to produce healthy and sustained crop growth.

Staff from organizations including the Bionutrient Food Association (BFA) and USDA Natural Resource Conservation Service (NRCS) are consulting, offering their expertise on cover cropping and mineral amendments on this three-year grant. NOFA/Mass is managing the project. One goal is to develop a knowledge base of skills and best practices in using cover crops and minerals on smaller scales and increasing food sovereignty and access in urban areas. Communities having access to culturally appropriate foods is key; this grant is building technical skills and training to help urban farmers grow and access to food they know and like.

What are the partner sites like?                 

Test plot at South Street FarmSince 2011 Groundwork Somerville has been growing on what eventually blossomed into a 2500 square foot garden site, an abandoned lot a five-minute walk from Union Square. “In Somerville, our focus is on sustainable environmental measures and urban farming. In a very urban city, urban farms are a great way to have green space in the city and also address questions of health equity,” says Groundwork Somerville Program Director and Farm Manager Jess Bloomer. “Our Somerville community has a significant percentage of folks who would be in the environmental justice category; for whatever reason, they are vulnerable in some way,” shared Bloomer.

Local youth play a big part in maintaining and growing food at South Street Farm in Somerville, getting them outside, into meaningful work and providing local, culturally relevant food to residents in the city. All the food is grown in raised beds with imported soil. Groundwork Somerville staff and volunteers provide support and management too.

Tucked in on an unassuming Mattapan street with auto body shops is City Natives, The Trustees’ learning garden and nursery, where their test plots are housed. “It’s an oasis; even people who live in Mattapan might not know it exists if they’ve never been here before,” says Trustees’ Michelle de Lima, Engagement Manager for Boston Community Gardens. They work with young people through their Youth Conservation Corps, as well as with groups of local volunteers.The site has an unheated hoop house and a compost-heated greenhouse, raised and in-ground vegetable beds, an herb spiral, bees, mushroom logs, native plantings, fruit trees and more.

Test plot at City NativesThe first year of the grant, 2016, was a learning year for the farms and with some adjustments they’re ready to hit the ground running in 2017. In 2016 both sites grew mostly nightshades, like Roma tomatoes and peppers like scotch bonnet, ají dulce and cubanelle. The sites each had three tests plots, trying different growing methods in each bed. After using this winter to plan, the farms are poised for enhanced coordination. They have added a fourth plot on each farm, to control for each of the variables being tested. The Trustees will grow the seedlings for both sites and each plans to use better record keeping systems.

The four test plots will use the following variables: 1) conventional organic practices; 2) cover crops being undersown; 3) mineral amendment application; and 4) both cover crops and minerals. To measure their experiments, the farms will take photos, measure yields, test soils and send plant tissue samples to UMass Amherst’s lab. The sites will also switch to crimson clover and rye cover crops, which can be planted and established before frost sets in and turned in come spring, recommended by Tom Akin of NRCS. BFA’s Dan Kittredge recommended many amendments, including basalt rock dust for potassium and a host of other minerals, manganese sulfate, cobalt sulfate (aiding in production of vitamin B12 and essential for soil life), and sodium molybdate to aid with nitrogen fixation.They’ll also grow brassicas and greens this year, instead of nightshades.


Developing appropriate techniques for small and urban growers

“What’s been so cool about this grant,” shared Bloomer, “is that it’s really allowing us to ask the question ‘what are some of the best practices around growing in an urban setting’. Our soil issues are very different from what farmers are working with in peri-urban or rural spaces.”

One challenge of this grant is to apply the tools of cover cropping and mineral amendments used by larger and rural growers in ways that are appropriate for the conditions and situations faced by smaller scale, urban growers. These growers cannot afford to leave a plot fallow for a year, nor can they easily find small quantities of minerals needed for their land. An outcome of this project, in addition to educating local community members, will be compiling existing resources and adding the grant’s findings and best practices into documentation and educational materials that can be shared with other urban growers.

“Sometimes urban growers are faced with trying to interpret texts about soils that aren’t relevant to their land,” says Bloomer. “[We can help develop] applications of these methods that are relevant and accessible to urban growers. We can demonstrate how to get our own soil to be much better and inspire others to do the same.”

Several workshops will take place over the course of the grant, offering local community members and the general public the chance to learn about these techniques and explore the possibilities together. See a list of upcoming workshops at the end of this article.

“I think there’s a lot of desire in Somerville for this knowledge from a wide range of community members,” says Bloomer, “from diverse population of immigrants to young people who recently moved to Somerville who want to have a garden in their backyard.

“The grant has been helpful to bring the focus of soil as the foundation of all our growing practices to our youth, having this set up and the beds we’re been testing. They notice that clover is growing in one bed versus another and ask why. At our end of season gathering they were telling other people why we’re planting cover crops and the value of that. That hands-on focused approach has made our teenagers more aware of the importance of soil. For new growers and young people we can focus so much on a specific plant, and it’s cool to see them asking questions about soil.”

Desired outcomes for the project

Entering year two of the grant, it’s still early to draw many conclusions from the first year. “It’ll take another year or two before we can say much conclusively,” says Michelle. “It’s exciting to try to suss out some different methods that people might use and want to adopt. There are a lot of creative and eager and interested gardeners in the city. If we can give people more information and tools to take better care of their soil that’d be a great thing.”

“We really want to be science based and not just tradition based,” says Clay Larsen, Project Manager & Landscape Design for Groundwork Somerville. “We want to really work with what works by looking at soil tests and really analyzing the sources of materials.” Eventually they’d like to consult in helping to build other Boston farms.

“It’s great to have our community think of our farm as a resource,” continues Larsen. “There’s not a lot of expertise in our area. I’ve been on other farms in Somerville and Everett that have interesting soil challenges… Now I feel like I have an opinion and can say ‘this is why my opinion matters’.”

“It’s really cool to feel like we’re a part of a larger ecosystem of different organizations trying to do urban growing,” says Bloomer. “It feels great to partner with NOFA and the Trustees and bring together the uniqueness of our situations and more, even, the similarities.” “It’s kind of funny,” reflects Clay, “but in America and the Northeast, urban farming is a new thing. In much of the rest of the world, people never stopped. It’s fun to be on the cutting edge of a new thing in the United States and help it grow – literally.”

Urban Soils Workshop Series

NOFA/Mass members and the general public are invited to register for these workshops through NOFA/Mass’s event website. For more information, contact Anna Gilbert-Muhammad at

Biological Systems for Gardeners: An Overview with Dan Kittredge

March 8 | 6-8pm 

Green City Growers | 600 Windsor Place, Somerville 

Seedlings & Inoculations for Biological Systems with Dan Kittredge

March 29 | 6-8pm 

The KITCHEN at the Boston Public Market | 100 Hanover Street, Boston

In-season Management for Biological Systems with Dan Kittredge

July 13 | 6-8pm

South Street Farm | 198 South Street, Somerville

Cover Crops for Small Gardens with Tom Akin 

Aug 10 | 6-8pm

City Natives | 30 Edgewater Drive, Mattapan


The following workshop is free and open to the public:

No-Till Vegetables with Brian O'Hara at the Gardeners' Gathering

March 18 | 1:30-3:30pm (event hours: 11am-5pm)

Shillman Hall, Northeastern University | 115 Forsyth Street

Contact Michele de Lima at for more information.

Cover crops & minerals will be available for sale in garden-size quantities at City Natives & South End plant sales May 13, May 20, September 9:


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