Many urban gardeners know that adding ingredients like compost and mulch to their soil has great benefits. But it can be difficult to know what to add and why. Researchers at Purdue University have collected scientific evidence on a specific soil addition, leaf mold compost, and its benefits for tomato plants.
The degraded soils often found in places like cities and towns can cause vegetables to grow poorly and not produce as much food. In addition, these communities produce many types of waste that can be composted. In this study, the researchers used “leaf mold” compost from the leaves of deciduous trees, a common waste stream found in urban areas.
“Leaf mold compost differs from traditional compost in that it’s not agitated as much,” says Lori Hoagland, professor of soil microbial ecology at Purdue University. “It slows down the time it takes to create compost, but growers claim it generates higher quality or more ‘disease suppressant’ compost. In particular, leaf mold compost should promote greater colonization by beneficial fungi, which we assessed. in this trial.”
The study was published in Journal of Urban Agriculture and Regional Food Systems.
Researchers tested whether leaf mold could help tomato plants produce more tomatoes. They also assessed whether fungal inoculations, often sold to increase tomato yields, were stimulated by leaf mold.
Their results showed that the leaf mold compost they applied improved many important soil properties that affect plant health and productivity. Plants that received leaf mold compost produced significantly more tomatoes and had fewer diseases. They also found that the compost increased the survival of the beneficial microbial inoculant that can help plants resist disease pressure. Although they grew tomatoes in this study, the researchers say they suspect many other crops could benefit from leaf mold compost.
“Our recommendation is that compost generated from urban waste streams can improve urban soils and increase plant productivity,” says Hoagland. “However, it is important to remember that although compost improves the soil and can provide additional nutrients to crops, it should not be substituted as fertilizer. Indeed, excessive application of compost in addition to fertilizers can lead to problems such as building. -too much phosphorus.”
Hoagland adds that it’s important for gardeners to have their soil tested as well. Most standard tests that measure total organic matter and major nutrients like nitrogen and phosphorus are inexpensive, often $10-20 per sample. More detailed tests can be more expensive but also useful. If a gardener is concerned about their soil, they can also have it tested for heavy metals, such as lead, to know that their garden soil is safe.
So how can you make and use leaf mold in your own urban garden? According to growers, gardeners can simply pile the leaves and stir them occasionally, or even once a year. Nature does the rest of the work by slowly breaking down the leaves. In midsummer, consider putting a tarp over the leaf pile to create enough heat to kill weed seeds. Avoid putting diseased plant material in the pile. Compost can be used once the leaves have decomposed.
According to Hoagland, many cities don’t have urban composting programs, so valuable waste like leaves ends up in landfills rather than in the ground. People can ask their city to start a program or find a way to compost themselves. Home gardeners can also compost their own leaves, as well as food scraps like coffee grounds to produce valuable soil amendments.
“What makes the study unique is that we were using local waste streams in a city to help ‘close the loop,'” says Hoagland. “Using urban waste streams in this way can not only help promote urban agriculture, but will reduce municipal costs and protect the environment by keeping this ‘waste’ out of landfills.”
Kyle Richardville et al, leaf mold compost reduces waste, improves soil and microbial properties, and increases tomato productivity, Urban agriculture and regional food systems (2022). DOI: 10.1002/uar2.20022
Quote: Leaf mold compost shows benefits for tomato plants in degraded urban soils (June 20, 2022) Retrieved June 20, 2022 from https://phys.org/news/2022-06-leaf-mold-compost- benefit-tomato.html
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