Food Gardening

Composting and Climate Change

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Composting is probably seen by most people as good for gardens and the environment. After all, compost helps make our soils and plants healthier and keeps green waste from our yards and kitchens out of landfills.

But is composting good in the context of our climate crisis? Doesn’t the composting process generate lots of carbon dioxide (CO2), the principal greenhouse gas (GHG) that traps heat in Earth’s atmosphere? Can composting also mitigate climate change and make our yards and landscapes more climate-resilient? The answer to both questions is YES. This article will show that composting, at the home, community, and municipal/commercial level, is an important global warming mitigation and adaptation tool. As we’ll see, the ways that humans manage this natural process and use the compost can affect the climate benefits.

Composting basics

We don’t make compost! Huge populations of microorganisms do most of the work and we humans manage the process for our benefit. It’s nature’s way of recycling anything that lives and dies, like plants, animals, and microbes.

The decomposition process produces lots of carbon dioxide (CO2), part of the world’s carbon cycling system shown in this graphic:

illustration of the carbon cycle - plants use carbon dioxide from the air and water from the soil to build carbohydrates
Plants exude carbohydrates through their roots to feed soil organisms. Those organisms release carbon dioxide through respiration. Illustration by Jocelyn Lavallee, Ph.D., Soil Scientist

This CO2 release is considered biogenic (happens through natural biological systems), not anthropogenic (people-made), and is not included in the calculations of greenhouse gas (GHG) emissions that drive global warming and climate change.

The three primary GHGs are:

  • Carbon dioxide (CO2) — 300-1,000 year atmospheric lifetime; 86% of total GHG emissions
  • Methane (CH4) — 84X the global warming potential of CO2; 12 year atmospheric lifetime; 7% of total GHG emissions
  • Nitrous oxide (NO2) — 265X the global warming potential of CO2; 100 year atmospheric lifetime; 6% of total GHG emissions

There are many factors that determine the potential for composting to generate methane and nitrous oxide, like the mix of materials being composted, temperature, moisture, pile size and configuration, and aeration. Compost piles and windrows that are waterlogged and low in oxygen (anaerobic) are more likely to generate these GHGs. Composting is “climate-friendly” when it’s done in the presence of air (aerobic). Home and community composters turn piles by hand to keep them aerated and large-scale composting facilities use mechanical turners and force air into windrows with blowers. Well-managed composting at any scale releases very little methane or nitrous oxide into the atmosphere. 

Direct climate benefits of composting

  • Dumping food wastes and grass clippings in landfills generates large amounts of methane because the decomposition process is anaerobic. Landfills release about 17% of total U.S. anthropogenic methane emissions and food waste makes up 24% of landfill space. Burning organic wastes releases GHGs and toxins. Composting these organic wastes using best practices greatly reduces emissions.
  • Carbon sequestration: Compost continues to degrade after soil incorporation. Some of the carbon cycles through soil microorganisms and some is held tightly to clay particles, protected against decomposition, and becomes part of the long-term reserve of stored carbon.

Indirect climate benefits of composting

The mid-Atlantic climate is becoming wetter and warmer overall, punctuated by localized extreme weather events, like record-breaking rainfall and extreme drought and heat. Intense storms can cause soils and nutrients to wash away and warmer temperatures cause more rapid organic matter decomposition and turnover, especially if soils are tilled and uncovered.

Adding compost to soils makes them more resilient by:

  • Holding more water in the soil during periods of drought and extreme heat
  • Reducing erosion (washing away of soil during extreme rainfall) and nutrient run-off) due to improved soil structure (larger, more stable aggregates or crumbs)
  • Improving plant growth, by slow release of plant-available nutrients
  • Reducing the need for synthetic nitrogen fertilizers which require natural gas for their production
  • Reducing the need for potassium and phosphorous fertilizers (derived from mined mineral deposits that are dwindling worldwide)
  • Binding and degrading toxic metals and pollutants
  • Substituting compost for peat products can help reduce the release of CO2 from commercial peat extraction from wetlands 
illustration of how compost combats climate change - increases water holding capacity - sequesters carbon in soil
Poster by the Institute for Local Self-Reliance

Home composting

Managing and recycling as much yard waste as possible on-site is often the most climate-friendly approach because it reduces GHG emissions from transporting and processing or landfilling organic waste. You can do this by recycling grass clipping (“mow ‘em high and let ‘em lie”), mulch-mowing tree leaves and leaving them in place, or using them as mulch, composting yard and garden waste, and burying kitchen scraps. These practices help to recycle nutrients on-site and increase soil organic matter. Selecting or building a non-plastic composter can also help reduce GHG emissions.

Municipal/commercial composting

This is the next best option for organic wastes that cannot be managed on-site. Commercial and municipal composting operations do create GHG emissions from the trucks and equipment, powered by fossil fuels, that are used to collect, transport, and process organic waste and compost. The closer the source of organic waste to the facility the lower the emissions and the greater the benefits. On balance, composting on a large scale can also help mitigate climate change.

illustration showing that the carbon sequestration benefits of municipal composting outweigh the greenhouse gases generated by transportation, storage, and processing compost

To summarize: aerobic composting reduces GHG emissions compared to the landfilling and incineration of organic wastes. The resulting compost sequesters carbon when mixed into soils and improves soil health and resiliency. Composting at home and in your community is the most climate-friendly approach but commercial and municipal composting is another important tool that helps mitigate climate change.

References

By Jon Traunfeld, Extension Specialist, University of Maryland Extension, Home & Garden Information Center. Read more posts by Jon.

Pepper Report

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Just a quick note from me (Erica) this month to report on some new pepper cultivars I’m growing. These include ‘Lesya’ sweet pepper, ‘Tam’ jalapeño, and ‘Escamillo’ frying pepper.

First, ‘Lesya.’ Wow, I’m in love with this one.

It’s a heart-shaped red pepper, about 3-4 inches long, thick-walled and super-sweet. Those thick walls make it great for roasting, but it can also be eaten raw or cooked other ways. It also just looks terrific growing on strong plants that don’t get leggy and seem pretty disease-resistant.

I bought seed for ‘Tam’ jalapeño because it’s supposed to be on the milder side, but with some spice to it, unlike the ‘Nadapeño’ heatless type I grew last year (which was kind of boring). The first thing I did with the fruits was to make them into refrigerator pickles (sliced), and those turned out pretty hot. So I thought I’d do a taste test comparing ‘Tam’ to other jalapeños. Please note, this was not a scientifically valid comparison; that would involve a lot more testers (instead of just me and my son), a lot more peppers, and many tests over time. Peppers can be more or less hot depending on the weather, the soil the plants are grown in, the genetics of particular plants, and probably lots of other factors.

Anyway, I picked a couple of peppers from the Derwood Demo Garden, and a ‘Tam’ from my own garden.

L to R: ‘Tam,’ ‘Lemon Spice,’ and ‘Jalafuego’ jalapeños

I’ll also note that picking the ‘Lemon Spice’ fully ripe made the comparison even less valid (but it’s so pretty!), and that I should have found a larger and more mature ‘Jalafuego.’ But onwards. Of the three, ‘Lemon Spice’ was definitely the hottest, nice and eye-watering. ‘Tam’ had practically no heat on first bite, and then it crept up on me, but it was definitely milder. ‘Jalafuego’ was weirdly mild as well; I suspect another fruit on another day would have knocked my socks off. So, nothing definitive, but I think if you want a milder jalapeño ‘Tam’ is worth trying.

Apparently this year some people, in some places, bought ‘Tam’ plants that turned out to be sweet banana peppers – all part of the great pepper seed mixup that you can read about on this Garden Professors blog post – but my seed (purchased from Sow True Seed, for the record) turned out to be the real thing.

Finally, this is my second year growing ‘Escamillo’ frying pepper, and I’m very satisfied.

It’s a nice meaty yellow pepper that can easily reach 6 inches or more, ripens up fast, has thick walls for good roasting, and is also great for frying or eating raw.

And that’s the pepper report!

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

Vinegar Acidity for Home Canning: Preserve Your Garden Produce Safely

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The National Center for Home Food Preservation, which is out of the University of Georgia Extension, has been fielding questions about using 4% acidity white distilled vinegar that is available for home cooks on grocery store shelves. People will often use 4% acidic vinegar to help make salad dressings and sauces. However, it is recommended for safety when canning to use 5% acidic white distilled and cider kinds of vinegar. We ask home canners to read the label of the vinegar they intend to buy at the store closely to look for the acid percentage before purchasing and using it for canning purposes.

Vinegar-acidity-level-for-home-canning-1Download

Further questions? Email Shauna C. Henley, PhD at shenley@umd.edu.

Shauna is the Family & Consumer Sciences Senior Agent at the University of Maryland Extension, Baltimore County

Insects: Our Most Under-Appreciated Neighbors

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Why should I want bugs, insects, and creepy crawlies in my yard or green space?

Insects are an incredibly diverse group of organisms, with 91,000 described species in the United States and likely an equal number yet to be described by scientists. Only an exceedingly small fraction of these species ever have negative impacts on humans as “pests” (<1% of species). Often the overabundance of pest species is due to human agricultural and landscape practice choices. The vast majority of insects in shared spaces with humans like yards and parks are going about their own lives. In addition to being fascinating creatures deserving of habitat in their own right, they also often contribute to unnoticed but very important tasks that help humans, termed “ecosystem services.” The next time you see one of these critters in your yard, consider thanking them rather than smashing them.

What are ecosystem services?

Ecosystem services are benefits that humans gain from the environment. Examples of ecosystem services include water filtration, raw material production, erosion control, and pollination. Some ecosystem services, like the maintenance of atmospheric gasses (e.g. plants remove carbon dioxide and produce oxygen that humans breathe), are noticeable and directly impact our everyday lives. On the other hand, services like decomposition may go unnoticed because they indirectly affect us.  

Insects (and their arthropod relatives like spiders and earthworms) play vital roles in many ecosystem services. This is often due to insects interacting with plants in some way, though insects also provide food for many other animals. Below are some examples of the ecosystem services that insects contribute to.

Water filtration

Filter-feeding insects positively affect water quality because they remove particles of dead organic material. Insects retain many of the nutrients they filter out of the water, thus reducing the likelihood of algal blooms, their associated toxins, and dissolved oxygen “dead zones.” This is crucial because clean water provides habitat for other plants and animals like fish and amphibians. It also means less effort is required to purify water for human use. 

Types of insects that improve water quality:

  • Blackflies, mayflies, stoneflies, and caddisflies (Note: the underlined insect groups are not “true” flies in the taxonomic Order Diptera; they are part of other orders.) 

Other types of organisms that improve water quality:

  • Mussels, crayfish, snails

More information: Why Care About Aquatic Insects

an illustration of the diversity of insects in an aquatic environment
Source: https://www.nsf.gov/news/mmg/mmg_disp.jsp?med_id=66886&from=

Biocontrol

Biocontrol is when natural enemies are used to suppress pests and reduce the amount of damage they cause. Natural enemies are insects that are antagonistic to pest insects. There are three types of natural enemies: predators, parasitoids, and pathogens. Preserving natural enemy populations is crucial to reducing our reliance on pesticides because when natural enemies are active, pest outbreaks are less likely to occur in the first place. Predators need food all year, so they also need alternate prey available in order to prevent pest outbreaks. Pesticides eliminate beneficial insects in addition to pests, so they should be used only as a last resort.

Fun fact: Fireflies spend much of the year as larval predators belowground, feeding on pests like grubs in turfgrass yards. If no prey is available in yards, then there will be no display of adult fireflies in the summer.

Types of insects used for biocontrol:

Other types of organisms used for biocontrol:

  • Fungi, birds, amphibians, reptiles, and mammals

More information: Approaches to the Biological Control of Insect Pests.

a tiny black wasp next to insect eggs
Source: https://blog.pensoft.net/tag/parasitoid-wasp/

Seed dispersal

Seed dispersal is when seeds are moved away from the parent plant. Seeds are moved when insects knock them off while feeding or when insects collect and then move seeds to a new location. Seed dispersal is important because it reduces resource competition between the parent plant and offspring plants. It also makes germination and seedling survival more likely, especially in arid climates. 

Types of insect seed dispersers:

  • Ants (most effective), beetles, wasps, thrips, and some moths

Other types of seed dispersers:

  • Fruit-eating animals (frugivores), such as some monkeys, lizards, and bats
  • Unwitting animal dispersers of sticky seeds like this

More information:

Seed Dispersal – The Australian Museum

The Conservation Physiology of Seed Dispersal

Source: https://www.science.org/content/article/don-t-crush-ant-it-could-plant-wildflower

Decomposition & nutrient cycling

Nutrient cycling and decomposition are two important processes that rely on one another. Nutrient cycling is when soil nutrients are taken up by plants, insects eat plants, and then those nutrients are reintroduced into the soil when dead insects and droppings are broken back down into nutrients via decomposition. Decomposer insects help clear dead animals and plants off the ground which would otherwise accumulate everywhere. They also help create soil texture and circulate nutrients back into the soil, which plant populations and productivity depend on.

Types of insect decomposers:

  • Many beetles, springtails, termites, wood cockroaches, and some fly larvae (maggots)

Other types of decomposers:

More information: Decomposers

Source: https://www.atlasobscura.com/articles/flightless-dung-beetles-south-africa

Supporting food webs

Insects are a main source of protein and nutrition for many animals (and even some plants). They play a crucial role in transferring energy from plants to larger animals that eat insects like spiders, birds, frogs, fish, bats, foxes, opossums, and bears. This wide food base that they provide allows for functioning, stable ecosystems that are resilient to disruptions.

Fun fact: By weight, there are roughly 300 times more insects than humans on Earth.
There are so many animals that eat insects, but here are just a few examples:

  • Terrestrial bird species, in particular, feed their babies almost exclusively with insects, and if there are fewer insects, baby birds are less successful at fledging from nests.
  • Popular fish like salmon, bass, and trout eat insects, especially when they’re young.
  • Grizzly bears will eat tens of thousands of moths a day to prepare for hibernation.
chameleon eating an insect
Source: https://a-z-animals.com/blog/what-do-chameleons-eat-16-foods-in-their-diet/

Pollination

Pollination is the transfer of pollen between flowers, resulting in flower fertilization and seed/fruit production. It is an unintentional consequence of pollinators going from flower to flower to feed themselves. Pollination is crucial for human survival, as 80% of plant-based foods and products rely on animal pollination. According to the USDA, pollinated crops are worth $18 billion in the US alone. Foods requiring pollination include apples, blueberries, chocolate, coffee, grapefruit, peaches, peppermint, sugarcane, tequila, and vanilla. 

Fun fact: beetles were likely the first insect pollinators– starting 200 million years ago!
Types of insect pollinators:

  • Bees, wasps, beetles, flies, ants, butterflies, and moths

Other types of pollinators:

  • Birds and bats

More information:

Pollination Basics

What is Pollination?

Why is Pollination Important?

Pollinated Foods

two white and black butterflies on yellow flowers
Source: https://www.technologynetworks.com/applied-sciences/news/pollination-reduced-as-bees-and-butterflies-confused-by-air-pollution-357697

By Yasmine Helbling, Kelsey McGurrin, and Karin Twardosz Burghardt, from the University of Maryland Department of Entomology, Burghardt Lab

Make and Plant a Bucket Garden

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If you don’t have space for an in-ground garden or access to a community garden, planting in 5-gallon containers can be a great option for making a “bucket garden” along a sunny walkway, balcony, or porch. In this video, Extension Specialist Jon Traunfeld demonstrates how to make a self-watering container garden using 5-gallon buckets and a few basic materials. You can get these buckets for free from restaurants, bakeries, and grocery stores. They are used for shipping food products and then they are usually thrown away afterward. This is a great way to give them a second use!

Tomatoes, peppers, and basil are some of the most popular plants to grow in a bucket garden. It is too late to start those plants this season, but in late summer, you can still plant kale and other leafy greens, carrots, beets, and perennial herbs. Use our Vegetable Planting Calendar as a guide.

Instructions for the self-watering bucket garden are also available on the University of Maryland Extension website, on the self-watering containers page.

By Christa K. Carignan, Coordinator, Digital Horticulture Education, University of Maryland Extension Home & Garden Information Center. Read more posts by Christa.

What to Know Before Applying Pesticides in Your Garden

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a man inside of a hardware store reading a pesticide label
Before using a pesticide, read the label. Photo: Oregon Department of Agriculture, CC.

You have a pest problem in your garden – maybe it is hungry insects feeding on your vegetables, or stubborn weeds taking over your flower patch, or fungal diseases killing your lawn. You might consider using pesticides (which include insecticides, herbicides, and fungicides), especially if the problem seems widespread or severe. How do you choose the right pesticides and apply them correctly to support a healthy and thriving garden? How do you ensure your food plants remain safe for consumption and adverse impacts on beneficial species and soil health remain minimal?

Choosing the right pesticide

Home gardeners can generally choose between two types of pesticides: general use pesticides and minimum risk pesticides. Both pesticide types come with labels that explain how to safely handle, use, and dispose of the products. The labels of general use pesticides are reviewed by the Environmental Protection Agency (EPA) and will have an EPA registration number (highlighted by the blue rectangle on Figure 1), typically on the back panel. The labels of minimum risk pesticides are less extensive and are not reviewed by the EPA as they pose minimal risks to humans and the environment. Since these labels lack an EPA registration number, you can verify the product’s authenticity by contacting the Maryland Department of Agriculture’s State Chemist Section (410-841-2721). Alternatively, you can check out this list of approved minimum risk pesticide substances (PDF).

an example of a pesticide label for Houseplant and Garden Insect Killer
Figure 1: First representative label (back panel)

Regardless of the pesticide type, it is important to select a pesticide that has a narrow activity range. If your pest is an insect, you would ideally want a pesticide that targets insects. It would be even better if you could narrow down your insect pest – is it a caterpillar, beetle, or aphid? Some pesticides are more effective against certain pest insects (for example, see the product in Figure 2) and are therefore less likely to harm non-target insects. If you are unable to identify your pest, you can submit questions and photos to the University of Maryland’s Ask Extension service. Ask Extension will help identify the pest and recommend a course of action. 

Another important criterion for pesticide selection is human safety, which can be determined from the signal words on the front panel of the label (see the purple rectangle highlighted in Figure 2). Danger signifies high toxicity, warning signifies moderate toxicity, and caution signifies low toxicity. A pesticide that is virtually non-toxic may have no signal word. Ease of use and application frequency can also help make your choice, as it may not always be feasible to measure and mix or frequently apply the product. This information is typically part of the section on directions for use, often found by peeling open the entire label (see the black rectangle highlighted in Figure 1).

a sample label from a biological insecticide called Monterey B.t. - the caution word on the label is highlighted
Figure 2: Second representative label (front panel)

What else to look for on the pesticide label

Labels also include the following information on the front panel (see Figure 2): product brand name, ingredients, and the statement “Keep out of reach of children”. Other information found typically on the back panel (see Figure 1, which includes the label peel) are precautionary and other hazard statements, first aid, and storage and disposal sections. It is important to read all these sections properly, including the entirety of the directions for use, prior to the use of the pesticide. 

  • The precautionary statement typically includes personal protective equipment that needs to be worn during pesticide applications (for example, full-length clothes, gloves, and eye protection) and informs the period of time during which one must not enter or come into contact with the treated area. The signal words are repeated in this section. 
  • Hazard statements warn of potential hazards to the environment, including soil, water, air, wildlife, and nontarget plants. An example warning statement is “This product is highly toxic to bees”. This section may also include possible fire, chemical, or explosion hazards posed by the product.
  • First aid section recommends steps to be taken in case of accidental exposure or poisoning. The instructions vary in accordance with the route of pesticide exposure (swallowing, inhaling, contact, and eye), and include statements like “sip a glass of water if able to swallow”, and “take off contaminated clothing and rinse skin with water for 15-20 minutes”. Often, there is information on who to contact in case of a medical emergency. If you need to visit an emergency health provider, remember to take the pesticide label with you. 
  • Storage and disposal section provides information on how to store the product (for example, “store in the original container in a cool and dry place” and “protect from freezing”) and dispose of it (for example, “triple rinse the empty container” or “place the empty container in the trash”). The Maryland Department of Agriculture has often had an annual program where one could recycle an empty pesticide container for free. If you would like to dispose of unused pesticides, follow the instructions in the disposal section. Never dispose of pesticides down any indoor or outdoor drain. Many Maryland counties offer options to safely recycle or dispose of household hazardous waste, including lawn and garden pesticides. Current or retired farmers and producers can also avail of a free pesticide disposal program offered by the Maryland Department of Agriculture.
  • Directions of use section instructs how to properly use the product. This section typically includes a description of intended uses, mixing and application methods, use rates, and sites where the product may be used. It can also include application restrictions – this consists of statements like “do not apply if rain is predicted within the next 48 hours” or “do not apply when bees are actively foraging”. In many labels, application restrictions are also found within the hazard statements section. 

Why is it important to follow the label?

A pesticide is any substance that prevents, destroys, repels, or mitigates pests. Thus, by nature, pesticides negatively impact living organisms. Federal law states that the EPA must ensure that pesticides entering the marketplace do not cause “unreasonable adverse effects to humans or the environment”. To carry out this mandate, the EPA assesses a variety of factors, including data on the pesticide’s chemistry, human health effects, environmental effects, etc. These data help inform the label language ̶ if the label is appropriately followed, the pesticide product should not cause unreasonable adverse effects to humans or the environment. For example, if a pesticide is highly toxic to fish, the hazard statement of the label would include a sentence like “Do not allow pesticide to enter or run off into storm drains, drainage ditches, gutters, or surface waters”. Applicators can be protected from unreasonable adverse effects by complying with precautionary statements like “Avoid contact with eyes” and “Wear chemical-resistant gloves”. Pesticide use/application rates are set to prevent hazardous quantities from entering the environment, including the infested plants you would like to consume. 

Given the label’s critical role in minimizing a pesticide’s negative impacts, it is little wonder that the label is the law. Remember, if you use pesticides improperly, you are legally responsible for any consequences that may occur!

References:

U.S. Environmental Protection Agency. Label Review Manual. https://www.epa.gov/pesticide-registration/label-review-manual

American Association of Pesticide Control Officials. FIFRA Minimum Risk Pesticides – 25(b) Product Label Guidance. https://aapco.files.wordpress.com/2018/03/fifra-minimum-risk-pesticides-label-guidance-3-12.pdf

By Niranjana Krishnan, Assistant Professor, Department of Entomology, and Maryland Pesticide Safety Education Program Coordinator

Golden summer: tomatoes and tomatillos

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A few times a year I like to take a moment to assess the vegetables I’m growing, their positives and negatives, and whether I’ll grow them again. This year I’m growing a few varieties new to me, so I’m going to look at those today: two tomatoes and one tomatillo.

Let’s start with the tomatillo. This is not a vegetable I always grow, because it takes up space–two plants are needed for cross-pollination, and they are not small plants–and because I always seem to have insect issues. Both those things are true this year as well, and yet I’m glad to have been tempted by catalog copy and fallen for Chupon de Malinalco tomatillo. It just isn’t like anything I’ve grown before.

The fruits are huge–over two inches long on average–and generally pear-shaped. They ripen quickly to a bright yellow, and the flavor is sweet-tart, great for salsas. The negatives: they’re hard to keep up with, and fall off the plant when fully ripe. Once on the ground, or even when hanging low on the plants, they get eaten. I don’t know by whom, though it could be rabbits, since they get into our community garden all the time. The fruits higher up are not safe either, since fruitworms and other pests get to them, and often I’ve removed the husk to find so much damage it’s not worth cutting away the bad parts. But with these larger fruits, often the damage is minimal and I can save some parts, which is an advantage over the smaller tomatillos I’ve grown before.

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