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!
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.
- 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. (To learn more about soil microbes, read this Soils Matter blog post: https://soilsmatter.wordpress.com/2015/07/14/is-it-true-bacteria-live-in-the-soil-isnt-that-bad/).
- 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. (Read this March 1, 2016 blog post to learn more about plant litter and soil organic matter! https://soilsmatter.wordpress.com/2016/03/01/leaves-left-on-the-ground-really-become-soil/)
Answered by: Kelley House, Certified Professional Soil Scientist, Duraroot & Kate Norvell, Certified Professional Soil Scientist, Certified Professional Agronomist, North 40 AG, Inc.