The Many Benefits Of Mulching Your Soil

*The first thing you must understand is that the health of your soil is what determines the health and productivity of your plants. If you have healthy soil, growing plants becomes easy and rewarding. Mulch is the key to healthy soil.

 Ecosystem Issue

With Mulch ……

With Bare Soil….

Soil Organic Matter (… it is responsible for holding most moisture and nutrients in soil)

Organic Matter is made from decomposed mulch. The Soil Organic Matter under mulch is constantly increasing as microorganisms eat the mulch from below and incorporate it into the soil.

There is no source of Soil Organic matter if the soil is bare. Soil Organic Matter will decrease over time since it is not being replenished. This means less water and nutrients will be held in the soil.

Soil Temperatures

Mulch acts like insulation for the soil, moderating the temperature. The soil is kept cooler on hot summer days, which prevents evaporation and possible burning of roots. The soil is also kept warmer during the winter, which allows the roots to be active and growing which will strengthen the plant the following season.

Soil temperatures fluctuate quickly without mulch. The soil gets very hot when the summer sun is hitting the soil, which kills most life in the top few inches of soil and also sucks out moisture quickly. Soil gets very cold in the winter, which could potentially kill some roots, weakening the plant in the future. Soil temperatures fluctuate widely between the day and night, these unstable conditions are hard for organisms to live in; this reduces soil biodiversity.

Soil Compaction

Mulch provides ample food for the microorganisms in the soil. Microorganisms are responsible for creating non-compacted, airy soils in nature, no tilling required. They create glues and fibers which bind soil particles together into larger particles, these larger particles do not pack as tightly as smaller particles (think of Olives in a jar versus Rice in a jar.) which allows more air and water flow through the soil.

Bare soil provides no food for soil organisms and makes it difficult for them to live. Without microorganisms creating larger soil particles the soil will become more and more compacted as the soil particles break down over time. Tilling is the only option…. which will actually kill even more soil organisms, so the problem of compaction just gets worse and worse each year.

Water infiltration rate and infiltration depth

Water can infiltrate a mulched soil quickly because the soil will be less compacted. When rain falls, all of the falling water is immediately absorbed into the soil instead of staying on the surface where it causes erosion problems. Mulched soil (if the soil has been well managed for several years) will also be loose to a greater depth, which allows rainwater to more easily reach the deep roots of perennial plants. Mulch also greatly reduces the rate of water evaporation from soils. So the water will stay where it is needed, instead of evaporating back into the atmosphere.

Bare soils become more and more compacted over time… especially at the surface layer of the soil. When rain hits the compacted soil most of it will simply stay on the surface and run downhill, instead of being soaked up by the soil. If there is somewhere for this surface water to go it will start to erode the soil (losing soil = bad). If not then it will create puddles. These puddles prevent air from getting to the soil below… this leads to anaerobic (no oxygen) soil conditions which are bad for many reasons(see below). The roots also require oxygen, if there is a puddle over the soil the roots will drown (die). Bare soil allows water to evaporate very quickly. A heavy rainfall on bare soil may be completely evaporated in a day, leaving soil organisms and plants without water.

Soil Aeration (anaerobic vs aerobic)

Mulch, as mentioned above, allows soil microorganisms to naturally loosen the soil. Loose soil is the only place Aerobic (with oxygen) conditions can occur. Under aerobic conditions nutrients remain in the soil, there is no bad smell, soil becomes looser, beneficial organisms dominate the soil.

Bare Soil, as mentioned above, creates compaction over time. Compacted soil quickly becomes Anaerobic (no oxygen). Under anaerobic conditions nutrients are lost as gasses, the soil smells bad, compaction increases, and disease causing organisms dominate the soil.

Other Benefits

Provides habitat for bugs, rodents and other small organisms which are essential parts of any food chain. Without these organisms the soil food web itself would be negatively effected.

Does not provide habitat for many organisms at all. The lack of small insects, rodents, etc will disrupt the balance of the soil ecosystem, leading to poor plant health.

The mulching power of properly managed livestock.
The mulching power of properly managed livestock.


What to use for mulch?

For Annual Plants:

  • Grass clippings, straw, hay and manure are best.

  • Wood chips, sawdust, shredded paper/cardboard and leaves are okay.

  • Never use bark mulch, plastic or cedar wood chips on your annual plants.

For Perennial Plants:

  • Wood chips, sawdust, shredded paper/cardboard and leaves are best.

  • Grass clippings, straw, hay and manure are okay.

  • Never use bark mulch or plastic. Cedar wood chips can be used as a last resort.

One Reply to “The Many Benefits Of Mulching Your Soil”

  1. We have a small in city vegetable garden. After taking off the vegetables I spread out all the garden waste, approximately 150 gallons of compost, and as many used coffee grinds from coffee shop that I can get. By the time it snows I’ll have about 12” of debris on top of the soil. In the past I have had the garden rototill before winter and again in the spring time. If I don’t rototill in the fall, how much will the mulch settle/break down by spring time? Alberta, Canada.

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