Farm Queries

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By: Julianna Rennie, DCF student crew member

When I first volunteered at the Duke Campus Farm, I was amazed by all of the weird and wonderful things growing there. Who knew that eggplants come in so many shapes and sizes? Or that okra can get to be a foot long? Or that peanuts grow underground? One of the many reasons I love the farm is because it provides so many learning opportunities. My questions often spark thoughtful and interesting conversations with other people. Now, as a member of the student crew, I look forward to working in the fields because I never know what I will encounter. In the spirit of curiosity, the farm has started collecting and researching questions that arise in the fields. I’m excited to learn alongside my farm family as we continue to explore nature and all of its unexpected joys. 

-  Q: Are ants good for soil?

-  A: Yes (but sometimes they’re bad for crops)! Ants have many benefits for soil. As they build their ground nests, they till and aerate the soil, allowing moisture to reach the plants' roots. Also, ants contribute to decomposition by feeding on organic waste and dead animals. They are pollinators, too! As ants move around, they pollinate flowers and disperse seeds.

A proliferation of ants typically indicates the presence of aphids, mealybug, whitefly or other insects that attack plants. According to the Old Farmer’s Almanac, ants “stroke the insects with their antennas, causing the insects to excrete the sweet liquid.” They then store the substance, called honeydew, in a “special holding stomach called the crop” and bring it back to their nest to nourish the queen and the other ants. Ants will protect and even “farm” these honeydew-producing insects, which may cause the populations of farm pests grow. 

Native fire ants and carpenter ants are typically viewed as pests but won’t harm plants. Nonnative fire ants can wreak havoc, though. They may damage crops, displace the native ant population, and break machinery. (To get rid of ants, you can pour hot water on their nests.)

Some other fun facts about ants: they outnumber all other species combined, with a population of approximately one quadrillion. They’ve been around since the dinosaurs and can be found practically everywhere on Earth. There are also several cool articles about how ants mastered farming before humans.

-  Q: Why do leafy greens have relatively high respiration rates? What does this have to do with harvest protocol?

-  A: Leafy greens are characterized by high respiration and transpiration rates because of their high surface-area-to-volume ratio. They lose water quickly and are highly perishable. Leafy greens have stomata, which are natural openings that regulate gas exchange and water loss. Other types of produce may have stem scars, tiny hairs, or waxy coatings, all of which affect the transfer of gas and water between the plant and the environment.

The rate of water loss from fruits and vegetables is determined by their shape and structure as well as environmental conditions. The surface area available for evaporation compared to the overall volume of the produce is a key factor. For example, potatoes and squash will lose less water than the same weight of spinach leaves or lettuce heads. The most important environmental conditions are temperature and relative humidity. 

Different types of produce have unique thresholds at which water loss affects their quality. For example, leafy greens will wilt after about 3-5% water loss, while other produce can withstand up to 20% water loss. Water loss can affect shelf life and nutritional quality. After harvest, leafy vegetables that experience water loss rapidly lose Vitamin C. 

Water loss can be mitigated by storing produce at cooler temperatures and reducing the time between harvest and cooling. (This article recommends storing leafy greens at zero degrees Celsius.) It’s also important to store produce at a constant temperature to avoid condensation, which can breed harmful microbes.

-  Q: Are citrus peels bad for compost piles?

-  A: No. In moderation, citrus peels (and onions!) are great for compost piles. Some chemicals found in citrus peels have been used as organic pesticides, so people worried that they might kill good soil critters. But those chemicals break down rapidly and don’t affect the health of the compost pile. Citrus peels may take longer to break down, but you can tear them into small pieces or dry them out first to speed up the decomposition process. Also, citrus peels also can ward off scavengers that don’t like their strong smell.

-  Q: Can the human eye visibly see mycelium?

-  A: Sometimes, if the hyphae is big enough! Fungi are made of microscopic, branching threads called hyphae. As the hyphae develop and intertwine, they form a web — the mycelium. If there are enough hyphae bunched together, the mycelium may be visible to the human eye. However, we often don’t see the mycelium of a fungus because it grows underground or inside of other organisms. That’s why fungi are most visible to humans when they create mushrooms, the fruit of the fungi that is responsible for reproduction.