As we get close to the time to start tomato, pepper, and other seedlings indoors, I thought I’d share this picture of my older sister’s seed starting setup from few years ago:
Two desk lamps with compact florescent bulbs. Not traditional, but worked great. Just a reminder that you can get creative when it comes to lighting for seedlings, using whatever fixtures and layout works for your space. The only rules are to use florescent or LED bulbs, not those old fashioned incandescent bulbs which have poor light for plants, and err on the side of more light rather than less to make sure you get compact, healthy plants that will transition to the sunny outside world without drama.
As a beginning gardener I learned that to give plants like tomatoes and peppers more time to grow and produce the largest possible crop, it was best to start the seeds early indoors.
As soon as I learned that, I wondered: Well, if starting my tomatoes 6-8 weeks before transplanting them outside is good, surely 10 weeks would be better, right? Or 12? Or 16?
Turns out, earlier isn’t always better, and here are some of the reasons why.
First, you probably don’t have enough light. If, like most home gardeners, you are starting seeds under florescent bulbs, it is difficult to give sun lovers like tomatoes and peppers enough light. Light intensity drops off rapidly as you move away from the bulbs, so you know to keep the bulbs right above your seedlings. This works great when the plants are small, but as they grow it becomes very difficult to give both the tops and the bottoms of the seedlings enough light. The result is dying lower leaves and spindly, unhealthy growth.
Secondly, you are almost certainly going to get some crappy root systems. If you’ve followed this blog for a while, you’ve no doubt read Bert and Linda talking about all the potential problems with the root systems of container grown trees and shrubs. Well, most of the same problems develop with other plants grown in small containers. The roots start circling and they are slow to grow out of the rich soil of the container and into the native soil around them once transplanted into the garden. The longer your transplants grow indoors, the more likely they are to develop problematic root systems. Keeping transplanting them up to larger and larger containers can help mitigate the problem, but that quickly takes up far more space than most home gardeners have for there seedlings.
How big and impact that circling root system will have on the health of the plant varies by species. My personal experience growing zinnias, for example, is that they handle circling, pot-bound roots so poorly that plants from seeds sown directly in the garden quickly over-take and out-perform plants started weeks earlier indoors.
So follow the recommendations for the timing of seed starting. It really does work better. You should be able to get advice on when to start seeds from the catalogs you are shopping, extension offices, or you can use Margaret Roach’s excellent seed sowing calculator.
If you DO decide that earlier is better, that you can provide the light and generous pot sizes to avoid problems, there’s no harm in giving it a shot. But if you do, try starting a second batch at the later, recommended, time and growing the two side-by-side in the garden so you can really compare and see which perform best in the actual conditions of your garden, and if all that extra time and space under your lights or in your greenhouse was really worth it.
I believe I’ve spent approximately $1,000,000 on seeds over the years. Plant and seed catalogs are usually addressed to “Gullible L. Scoggins.” I really suffer (on many levels) during the darkest days of winter; this makes me highly susceptible to seed catalogs filled with delicious descriptions and enhanced photos.
This spring, I sorted through my massive bin of partially used seed packets and ruthlessly (ruthlessly!!!) chucked everything dated prior to 2012 (like normal people do). A large portion of the expired packets were for squash and zucchini. I love squash of every ilk – glossy dark zukes, gold crooknecks, pattypan-anything. Squash and tomatoes are summer incarnate.
My absolute favorite is the heirloom Italian variety Costata Romenesco with its dense, nutty flesh – it really tastes like something on its own. The huge rambling vines put out relatively few fruit, so not the best for a compact garden.
But variety is the spice of life…so how to try several varieties and not end up with either a mountain of squash (as happened to me a while back) or a bunch of seeds left over? California seed purveyor Renee’s Garden does a very cool thing – one pack of seeds with three (3!) varieties – the “Tricolor Mix”. Brilliant! You get a gold-bar type (Golden Dawn), the dark green one that will go berserk (Raven), and a lovely pale gray-green Clarimore.
The seeds are color-coded with just good ol’ food coloring, so you know what you’ve planted. I got 100% germination (whoops) and a delightful variety and volume of zucchini. And NO LEFTOVER SEEDS – so I will feel completely justified next February when ordering more. Hurrah!
I was checking my eggplants today, and watching the bumble bees getting busy with the large purple flowers. As they flew in, buzzing away, they landed on the flower and kept buzzing — but the note changed, dropping in pitch. The bumble bee hummed away for a while, then flew off to the next flower.
I was watching buzz pollination at work. Egg plants, and a lot of other flowers, don’t leave their pollen hanging out in the open where any ant or fly that happens by could eat it. Rather they wrap them up in little packages that, when vibrated at just the right rate by a buzzing bumble bee, sends the pollen shooting out, so that bumble bees, which pollinate effectively, can access the pollen, but other insects, that would just eat it all, can’t.
In the garden, it isn’t easy to catch a glimpse of the pollen spewing forth, but luckily there are videos. Thank goodness for youtube. Watch it, and next time you are in your garden and hear a bee land in the flower and suddenly change the tone of its buzz, know you are seeing — and hearing — buzz pollination at work.
With drought predicted for the west, southwest, and south through June 2015 (National Weather Service March 2015), many conscientious vegetable gardeners will try to conserve water by using soaker-hoses, those bumpy black hoses that weep water onto the soil through tiny pores.
Soaker hoses are made from fine-crumb rubber, usually recycled from vehicle tires. Research strongly establishes that tire particles leach heavy metals, carcinogens, and mutagenics, among other toxins. Yet soaker hoses have not been studied for potentially increasing the toxicity of edible plants. Are they really safe to use safe on our edible plants?
Soil in the City
Urban soils already contain high levels of heavy metals (Murray et al. 2011) from years of household runoffs—chemicals from pesticides, cars, painting, cleaning, and more. Adding soaker hoses made of crumb tires might exacerbate the problem.
Whether plants take up enough heavy metals to be toxic, however, is a complex equation, depending on a slew of interrelated factors, including:
• Soil pH (Costello 2003) and texture (Singh and Kumar 2006; Murray et al. 2011)
• Temperature (Murray et al. 2011; Lim and Walker 2009)
• The size of the rubber particles (Gaultieri et al. 2004)
• Chemical composition of irrigation water (Singh and Kumar 2006)
Furthermore, the plant species and even the cultivar can affect a plant’s uptake of zinc and other heavy metals (Murray et al. 2009 and 2011).
Growing Healthy Food
If you’re looking for the key to ensuring that your vegetable patch grows healthy food, however, I’m sorry to disappoint you. Too many factors are involved to predict the toxicity of what we grow in our gardens.
A good way to get more information is to contact your local extension agent for a list of laboratories that test soils not only for nutrient composition but for heavy metals. Although this information won’t guarantee you’ll be able to grow heavy-metal-free produce, it’s a step in the right direction while we wait for more research to be done.
Cindy Riskin is a Master of Environmental Horticulture and freelance journalist raising edible plants, an unkempt ornamental garden, and elderly mutts in Seattle, Washington.
NOTE: This article is excerpted from a longer one soon to appear in Cindy Riskin’s upcoming blog, tentatively named Muddy Fingers Northwest. Please contact Cindy Riskin at email@example.com for an advance copy or the blog’s web address.
1. Costello, Laurence Raleigh. 2003. Abiotic disorders of landscape plants: A diagnostic guide. Oakland, Calif.: University of California, Agriculture and Natural Resources. P. 117.
2. Gualtieri M., M. Andrioletti, C. Vismara, M. Milani, and M. Camatini. 2005. Toxicity of tire debris leachates. Environment International 31 (5): 723–30.
3. Lim, Ly, and Randi Walker. 2009. An assessment of chemical leaching releases to air and temperature at crumb-rubber infilled synthetic turf fields. Albany, N.Y.: New York State Department of Environmental Conservation. http://www.dec.ny.gov/docs/materials_minerals_pdf/crumbrubfr.pdf.
4. Murray, H., T.A. Pinchin, and S.M. Macfie. 2011. Compost application affects metal uptake in plants grown in urban garden soils and potential human health risk. Journal of Soils and Sediments 11 (5):815–829.
5. Murray, Hollydawn, Karen Thompson, and Sheila M. Macfie. 2009. Site- and species-specific patterns of metal bioavailability in edible plants. Botany 87:702–711.
6. National Weather Service Climate Prediction Center. March 19, 2015. U.S. Seasonal Drought Outlook. NOAA/National Weather Service National Centers for Environmental Prediction. http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.html.
7. Singh, S., and M. Kumar. 2006. Heavy metal load of soil, water and vegetables in peri-urban Delhi. Environmental Monitoring and Assessment 120 (1-3):1–3.
Once you’ve chosen cover crops that fit your vegetable rotation, management goals, and garden site (See Part III: Selecting Cover Crops for Vegetable Gardens), it’s time to plant! This article contains tips on sourcing seed, and planting and managing cover crops using hand tools.
As I outlined in Part I and II of this series, cover crops can serve many purposes in small-scale vegetable gardens, including soil quality improvement, nitrogen (N) fixation, weed suppression, and habitat for beneficial insects. To achieve maximum benefits from cover crops, it’s important to select appropriate species (or species mixtures) for each garden bed. In this article I’ll highlight promising annual cover crop species for different seasonal niches, management goals, and environmental conditions. Much of this information is based on preliminary results from two seasons of cover crop research in Brooklyn, NY community gardens.1
Vegetable gardeners are turning to cover crops to improve soil quality, add nitrogen (N) to the soil through legume N fixation, suppress weeds, and attract beneficial insects in their gardens. In this article I’ll introduce several groups of cover crops. Cover crop species can be broadly grouped into non-legumes (those that do not fix N, but take up and recycle nutrients left in the soil) and legumes (which fix N). Mixtures of non-legumes and legumes may offer the benefits of both types of cover crops.
Non-legume cover crops
Non-legume cover crops include species in several plant families:
Buckwheat (Fig. 1c, Polygonaceae) is a popular summer cover crop.
Fig. 1. Examples of non-legume cover crops used in vegetable gardens(Photo credits: M. Gregory)
Fig. 1a. Oats (Avena sativa) is a winter-kill cover crop in USDA Zones 7 and cooler. It is usually planted in late August, and dies with the first hard frosts.
Fig. 1b. Winter rye (Secale cereale) is a hardy over-wintering cover crop. It can be planted in September or October, and produces large amounts of biomass by May.
Fig. 1 c. Buckwheat (Fagopyrun esculentum) is a fast-growing summer cover crop, suitable for planting between spring and fall vegetable crops.
Benefits of non-legumes: 1, 2
Prevent erosion – Non-legumes establish and grow quickly, provide rapid soil cover, and have dense, fibrous root systems that hold soil in place.
Build soil organic matter – Non-legumes produce large amounts of biomass, which contributes to soil organic matter.3
Retain and recycle nutrients – Non-legumes take up nutrients left in the soil after vegetable harvest, which prevents them from being leached out of the garden during heavy spring rains.
Suppress weeds – With their vigorous growth and high biomass, non-legumes can successfully compete with weeds, even in fertile soils. Some non-legumes (winter rye, sorghum-sudangrass, and Brassicas) also release chemicals that inhibit weed germination and growth. Residues of grass cover crops also provide a weed-suppressive mulch that lasts much of the growing season.
Disease management — Some Brassicaceae cover crops also release chemical compounds that may help control soil-borne pathogens and parasites(e.g., fungi, nematodes) upon incorporation. Winter rapeseed (Brassica napus) greatly reduced Rhizoctonia damage and Verticillium wilt in potato crops.1, 2
Drawbacks and constraints of non-legumes:
Slow nutrient supply and/or N immobilization — Non-legumes have lots of carbon (C) relative to N during growth, which causes them to decompose slowly after mowing or incorporation. As a result, nutrients in non-legume residues may not be available to vegetable crops quickly. If non-legume residues are incorporated into the soil, they may actually immobilize (“tie up”) N for a few weeks as decomposer microbes take up soil N to balance the large amount of C in the plant residues they’re breaking down.1 For this reason, it’s best to wait several weeks after incorporating a non-legume before planting vegetable crops.
Legume cover crops
Legume cover crops include field peas (Fig. 2a) crimson clover (Fig. 2b), hairy vetch (Fig. 2c), and cowpeas. They provide many of the same benefits of non-legumes, with the additional benefits of nitrogen fixation and feeding pollinators.
Fig. 2. Examples of legume cover crops used in vegetable gardens (Photo credits: M. Gregory)
Fig. 2a.Field peas (Pisum sativum) can be planted as a winter-kill or early spring cover crop. It should only be planted in full sun, as this legume performs poorly in shaded areas.4
Fig. 2b.Crimson clover (Trifolium incarnatum) over-winters in Zones 7 and up, and can be used as a summer or winter-kill cover crop in cooler zones. Crimson clover is a high biomass producer and is quite shade-tolerant.4
Fig. 2c. Hairy vetch (Vicia villosa) is the hardiest legume, and will over-winter in even the northernmost parts of the US. It is an excellent legume for adding fixed N to the soil.4
Additional Benefits of legumes:
Nitrogen fixation – Legume cover crops add ‘new’ nitrogen (N) to the soil through N fixation, which occurs when N-fixing bacteria in legume roots take N from the air and convert it to a form the plant can use. When legume residues break down, this N is added to the soil for food crops.5
Build soil organic matter and soil quality – While legumes don’t usually produce as much biomass as non-legumes, they also help build soil organic matter.6, 7 Legumes are also excellent soil conditioners, because legume roots ooze sugars that stick soil particles together in larger crumbs, or aggregates.8, 9 This helps the particles fit together loosely, making for a soft, porous soil.
Attract beneficial insects – Many legume species provide resources for beneficial insects. Crimson clover provides pollen and nectar for native pollinator bees (Fig. 3), and both crimson clover and hairy vetch host predators such as lady beetles, which eat many pest insects.1
Drawbacks and constraints of legumes:1, 3
Slow growth, lower biomass — Legumes establish and grow more slowly than non-legumes, and usually produce lower biomass.
Less weed suppression — Legumes may not suppress weeds as effectively as non-legumes, particularly in soils with high N fertility. In Brooklyn gardens, legumes suppressed weeds in soils with low to moderate N fertility, but not in soils with high N fertility.4 Legume residues break down quickly, so weed control by legume mulch may be short-lived.
Seed cost — Legume seeds are more costly than non-legumes.
Cover crop mixtures
Mixtures of non-legumes and legumes often combine the benefits of both types of cover crops.
Benefits of nonlegume/legume mixtures:
Produce large biomass and suppress weeds effectively — In many cases, cover crop mixtures provide more complete soil cover, greater biomass production, and more effective weed suppression than plantings of just one species.1, 3 This is because mixtures of grasses and legumes use water, nutrients and sunlight very efficiently due to complementary root systems and growth habits. Grasses (like rye) also provide support for viny legumes (like hairy vetch), which allows the legume to access more light.
Increase N fixation — Planting legumes with grasses may enhance N fixation. Grasses out-compete legumes for soil N, forcing the legume to rely on N fixation. As long as the grass doesn’t suppress legume biomass (see below), this can increase the total amount of N fixed. Promising grass/legume mixtures for N fixation include rye/vetch and Japanese millet/cowpea.10
Optimize nutrient cycling and nutrient supply to crops — Mixtures provide the benefits of N ‘scavenging’ by non-legumes and N additions by legumes.1 At maturity, grass-legume mixtures often have an ideal C:N ratio of 25:1 – 30:1, which promotes a steady release of N for vegetable crop use as the cover crop plants decompose. N-rich legume residues prevent N tie-up that can occur when incorporating pure grass residues, while C-rich grass residues slow the breakdown of legume residues such that N is released at a rate that vegetable crops can use through the growing season.2, 11
Fig. 4. Examples of grass/legume mixtures used in vegetable gardens (Photo credits: M. Gregory)
Fig. 4a.Oats/ Field peas is a common winter-kill or early spring mixture. It should only be planted in full sun. Since oats may suppress field pea biomass and total N fixed,4 try seeding the field peas at a higher rate.
Fig. 4b. Rye/ hairy vetch is an excellent over-wintering mixture. The hairy vetch ‘climbs’ the rye, which allows the legume to access more light. In Brooklyn gardens, rye/vetch mixtures produced the highest biomass of any cover crop combination.4
Drawbacks and constraints of nonlegume/legume mixtures:
Reduced N fixation if nonlegume out-competes the legume – Mixing a non-legume with a legume may decrease the total amount of N fixed if the non-legume suppresses legume growth and biomass. This occurs in mixtures of: oats/field peas,4, 12 rye/crimson clover,4 and sorghum-sudangrass/cowpea.10 Seeding the legume at a higher rate may result in a more even distribution of nonlegume and legume biomass – gardeners can experiment to find the relative seeding rate that works best in your soil.
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Understanding the benefits and limitations of non-legumes, legumes, and mixtures is a great starting point for selecting cover crops to plant in your garden. For guidance on choosing specific cover crops based on your vegetable crop rotation, management goals, and soil and light conditions, see Part III: Selecting Cover Crops for Vegetable Gardens.
(3) Snapp, S. S., S. M. Swinton, R. Labarta, D. Mutch, J. R. Black, R. Leep, J. Nyiraneza, and K. O’Neil. 2005. Evaluating cover crops for benefits, costs and performance within cropping system niches. Agronomy Journal 97(1):322-332.
(4) Gregory, M. M., L. E. Drinkwater. In preparation. Developing cover cropping practices to improve soil quality, nutrient cycling, and weed suppression in urban community gardens.
(5) Drinkwater, L. E. 2011. It’s elemental: How legumes bridge the nitrogen gap. The Natural Farmer, Summer 2011, pp. B-1 – B-6. Northeast Organic Farming Association, Barre, MA: Accessed online at: http://www.nofa.org/tnf/Summer2011B.pdf, 6 December 2014.
(6) Sainju, U. M., B. P. Singh, and W. F. Whitehead. 2002. Long-term effects of tillage, cover crops, and nitrogen fertilization on organic carbon and nitrogen concentrations in sandy loam soils in Georgia, USA. Soil & Tillage Research 63(3-4):167-179.
(7) Kong, A. Y. Y., J. Six, D. C. Bryant, R. F. Denison, and C. van Kessel. 2005. The relationship between carbon input, aggregation, and soil organic carbon stabilization in sustainable cropping systems. Soil Science Society of America Journal 69(4):1078-1085.
(8) Puget, P., L. E. Drinkwater. 2001. Short-term dynamics of root- and shoot-derived carbon from a leguminous green manure. Soil Science Society of America Journal 65(3):771-779.
(9) Haynes, R. J., M. H. Beare. 1997. Influence of six crop species on aggregate stability and some labile organic matter fractions. Soil Biology & Biochemistry 29(11-12):1647-1653.
(10) Drinkwater, L. E. 2011. A holistic view: Leguminous cover crop management in organic farming systems. The Natural Farmer, Summer 2011, pp. B-20 – B-24. Northeast Organic Farming Association: Barre, MA. Accessed online at: http://www.nofa.org/tnf/Summer2011B.pdf, 6 December 2014.
(11) Teasdale, J. R., A. A. Abdul-Baki. 1998. Comparison of mixtures vs. monocultures of cover crops for fresh-market tomato production with and without herbicide. HortScience 33(7):1163-1166.
(12) Schipanski, M. E., L. E. Drinkwater. 2012. Nitrogen fixation in annual and perennial legume-grass mixtures across a fertility gradient. Plant Soil 357(1-2):147-159.
Shawn Banks: Extension Blog Contributor Johnston County Extension Agent/Educator
North Carolina State University
As an extension agent one question I often get asked by new gardeners is, “Where do I put a vegetable garden in my yard?” That leads to a lot more questions, but let’s answer the where question first. There are four basic considerations when selecting a garden site.
The first thing to consider is the need for direct or full sunlight. Most vegetables need a minimum of six to eight hours in order to produce a crop. However, the more sunlight they get the more bounteous the harvest will be. If there isn’t a spot in the yard that receives full sun all day, then the question becomes, is it better to have shade in the morning or in the evening? Morning sun will dry the dew from the leaves, reducing the chance of fungal diseases infecting the leaves.
Speaking of dew, the next consideration is water. How close is the water source to the vegetable garden. Many vegetables need to have consistent moisture. That means a water source should be easy to access to keep the soil moist throughout the growing season. The further the water is from the garden, the less likely it is that the garden will get watered on a regular basis. Have you ever wondered why the tomatoes crack, or the radishes split? One of the most common reasons is that the soil was very dry and then it rained a lot and the plant was trying to store as much water as possible, causing the cracks and splits
Another consideration is airflow. Many foliar diseases are caused by fungal pathogens. Most fungi need water standing on the leaf for eight or more hours before they can infect the leaf. Good airflow will dry the leaves out before the fungi can infect the plant. A hedge, a solid fence, or even a house may obstruct airflow. Another way to obstruct airflow is to plant too close together, but that is a discussion for another time.
Lastly comes the phrase “out of sight, out of mind”. This is very true for a vegetable garden. When selecting where to place the garden, consider ease of access. Many people find that when the garden is way in the backyard, they don’t tend it often enough. The soil dries out. The weeds take over. The crops don’t get harvested in a timely manner. In short, the garden doesn’t succeed. Select a garden site that is close enough that you will see it and want to tend to it.
These four site characteristics are the most important when selecting the location for a vegetable garden. Remember, a vegetable garden site needs a minimum of eight hours of direct sunlight, consistent moisture, good airflow, and easy access. A site with all four of these characteristics will ultimately produce more, have fewer problems with fungal diseases, and be better taken care of because it is visited more frequently and loved.
Keep in mind that if you don’t have anywhere in your yard that works, many options, such as container gardens, can help you have a productive garden anywhere.
Cover crops are close-growing plants sown in rotation with food crops, or inter-seeded between food crops to cover bare ground. They are not harvested, but rather are planted to improve soil quality and provide other benefits for crop production and the environment. Before planting the next vegetable crop, most cover crops need to be cut down. The shoots can be chopped (or mowed) and left as mulch on the soil surface, or incorporated into the soil.
There is a large body of research supporting the use of cover crops on organic and sustainable farms.1 However, vegetable gardeners can successfully plant and manage cover crops with hand tools, and reap the benefits of this practice for their soil and crops.2
Why should I plant a crop that I’m not going to harvest?
Cover crops provide many benefits for future vegetable crop production, and for the garden agro-ecosystem as a whole. Incorporating cover crops in vegetable rotations may:
Increase soil organic matter levels, and therefore improve soil quality. As cover crop roots and shoots decompose, they build soil organic matter. This improves soil structure and water-holding capacity (Fig. 2), and increases slow-release nutrient reserves.3 Fresh cover crop residues also nourish beneficial soil fauna (bacteria, fungi, worms, etc.) that improve soil tilth and aeration, recycle plant and animal wastes, and release nutrients for crops to use.
Provide nitrogen for future food crops through legume nitrogen fixation. Cover crops in the legume family (e.g., beans, peas, clovers, and vetches) add “new” nitrogen (N) to the soil. Legumes host N-fixing bacteria in bumps on their roots, also called nodules (Fig. 3). These bacteria take N from the air and convert it to a form the legume can use . When the plant decomposes, the fixed N also becomes part of the soil organic matter. Eventually, this N is released by microbes for crop uptake.4
Improve nutrient retention and recycling. Over-wintering cover crops take up extra nutrients at the end of the growing season, which would otherwise be lost to leaching (when nutrients dissolve in rainwater and drain below the root zone, making the nutrients unavailable for plants). Over-wintering grasses like rye reduce N leaching by about 70% compared to bare soil.5
Suppress weeds. Growing cover crops reduce weed growth through competition (e.g., for space, light, moisture, and nutrients) and allelopathy (releasing chemicals that inhibit other plants). After , the cover crop mulch can prevent weed seedling emergence through the growing season.6
Attract beneficial insects. Cover crops often provide important resources (such as nectar and pollen and over-wintering habitat) for beneficial insects, including pollinator bees and natural enemies of insect pests like ladybugs and lacewing.1
Increase or maintain crop yields with less inputs. Well-managed cover crops can improve vegetable crop yields, or reduce the amount of fertilizer needed to obtain good yields.7-10
On the left is soil from an urban garden that received a rye/vetch cover crop for more than five years, and therefore has high SOM.
On the right is soil from a garden that never received cover crops, and has lower SOM.
This photo was taken 30 minutes after pouring equal amounts of water through the soils. The high-OM soil held most of the water, while much water drained through the low-OM soil. Since both soils were of similar texture, the difference in water-holding capacity can be attributed to the SOM.
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Vegetable gardeners have a number of cover crop options suited to different seasonal niches, management goals, and environmental conditions. To learn about the main groups of cover crops and how to select cover crops for your garden, see Part II (Types of Cover Crops) and Part III (Selecting Cover Crops).
(2) Gregory, M. M. and L. E. Drinkwater. In preparation. Developing cover cropping practices to improve soil quality, nutrient cycling, and weed suppression in urban community gardens.
(3) Snapp, S. S., S. M. Swinton, R. Labarta, D. Mutch, J. R. Black, R. Leep, J. Nyiraneza, and K. O’Neil. 2005. Evaluating cover crops for benefits, costs and performance within cropping system niches. Agronomy Journal 97(1):322-332.
(4) Drinkwater, L. E. 2011. It’s elemental: How legumes bridge the nitrogen gap. The Natural Farmer, Summer 2011, pp. B-1 – B-6. Northeast Organic Farming Association, Barre, MA. Accessed online at: http://www.nofa.org/tnf/Summer2011B.pdf, 6 December 2014.
(5) Tonitto, C., M. B. David, and L. E. Drinkwater. 2006. Replacing bare fallows with cover crops in fertilizer-intensive cropping systems: A meta-analysis of crop yield and N dynamics. Agriculture Ecosystems & Environment 112(1):58-72.
(7) Abdul-Baki, A. A., J. R. Teasdale, R. Korcak, D. J. Chitwood, and R. N. Huettel. 1996. Fresh-market tomato production in a low-input alternative system using cover-crop mulch. HortScience 31(1):65-69.
(8) Abdul-Baki, A. A., J. R. Stommel, A. E. Watada, J. R. Teasdale, and R. D. Morse. 1996. Hairy vetch mulch favorably impacts yield of processing tomatoes. HortScience 31(3):338-340.
(9) Abdul-Baki, A. A., J. R. Teasdale, R. W. Goth, and K. G. Haynes. 2002. Marketable yields of fresh-market tomatoes grown in plastic and hairy vetch mulches. HortScience 37(6):878-881.
(10) Abdul-Baki, A. A., J. R. Teasdale. 1997. Snap bean production in conventional tillage and in no-till hairy vetch mulch. HortScience 32(7):1191-1193.