Plant Litter in the Garden: Soil Scientists Say Just Leave It Be!

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Farmers keep crop residues on their fields for the same reasons home gardeners should consider!  Source: Fabian Fernandez

I’ve never been big on fall clean-up in the garden. I’ve never really seen the point of it After all, Mother Nature doesn’t rake up the roots, stems and leaves of dead annuals and vegetables in the fall and she knows best, right?

However, I’m just a home gardener, and a laidback one at that. My point of view isn’t all that valuable. But what does the scientific community say about it?

Here’s an article giving the scientific point of view from the excellent site, Soils Matter, Get the Scoop of the Soil Science Society of America, a go-to source for valuable and honest information on the soils we garden in.

What is the effect of leaving some of the vegetable crops up over the winter—how does that improve soil conditions?

Intentionally or unintentionally, many gardeners have left plants in their gardens over the winter. This is actually a good thing … and something everyone should consider on a yearly basis!

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Crop being sown into a no-till field in spring. Source: nrcs.usda.gov

Scientists—specifically agronomists and soil scientists—refer to the plant “litter” that remains after a harvest as “residue”. Leaving the residues in place over the winter, instead of pulling them up or tilling them into the soil surface, provides numerous benefits for the soil and your garden.

  • Plant residues reduce erosion and the loss of valuable topsoil. Residues cover soil and protect it during the non-growing season. Crop residues catch rainfall. This reduces the impact that individual rain droplets have with the soil surface. Residues also slow down any flow of melting snow over the soil. Both help protect the soil structure, keeping it intact for next year’s crops and gardens.

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    When there is no plant residue left to cover the soil, it can form a crust. This reduces the soil’s natural ability to soak up rain and snowmelt, and can increase erosion. Credit: Kate Norvell

  • Having plant residues on the soil surface also prevents something called soil crusting. You may have seen that during a very heavy rainfall, the soil won’t absorb any water. Even worse, sometimes little streams form on dry soil, then become larger streams. This carries away the soil and its important nutrients.
  • Residual plant material reduces weeds by covering and shading the soil. Weeds are often early spring germinators, and residues inhibit their growth. They limit the amount of soil that is available for weed germination and growth. Crop residues reduce the resources and space that weed seedlings require to grow.
  • Plant residues provide shade, regulating soil temperature. This keeps soils cooler during the non-growing season to the early part of the next growing season. Cooler soil temperatures provide more suitable conditions for soil microbes. Microbes are necessary for maintaining a productive soil for crop growth.20181010D Ann Fischer.jpg
  • Cooler soil temperatures also aid in the retention of soil moisture, which in turn is favorable for seed germination in the spring and crop growth.
  • Crop residues provide micro-habitats that protect and benefit the germinating plant seeds and establishing seedlings.
  • Plant residues provide a source of organic matter for the soil. Organic matter is essential to soil health. It helps create an environment supportive of crop growth. Organic matter provides an energy source for soil microbial populations, which results in faster decomposition rates, releasing essential nutrients for crop growth. Soil organic matter also helps maintain good structure of the soil itself. This further reduces erosion and improves water infiltration and soil aeration.
Text by Kelley House, Certified Professional Soil Scientist, Duraroot & Kate Norvell, Certified Professional Soil Scientist and Certified Professional Agronomist, North 40 AG, Inc.
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