Understanding Healthy Soil and Climate Change

Veer Mudambi

Journalist - Writing Green
Feb 28, 2020
Understanding Healthy Soil and Climate Change

Curbing greenhouse gas (GHG) emissions traditionally centers around the reduction of fossil fuel dependence in our society. While arguably the most effective initiative, we cannot ignore our other activities that act as sources of GHGs. We can start by looking at...dirt?

Healthy soil stores up to three times as much carbon as the atmosphere and about four times the amount of carbon stored in all living animals and plants. That’s approximately 2,500 gigatons of carbon safely sequestered and not clogging up our atmosphere.  Depending on its composition, carbon can remain in the soil anywhere from a few days to a few centuries. 

How does this work? We all know that plants absorb and store carbon so when plants decompose and die, this is transferred to the soil.  When their tissues are incorporated into the soil, this organic carbon is broken down into mineral components, which plants then take back up as nutrients through their roots. This means that, under the right conditions, soils can help remove and store carbon dioxide from the atmosphere. Healthy plants absorb more carbon and the cycle continues. 

 However, all that carbon is released by deforestation, erosion, frequent tillage, overgrazing, removal of crop residue, excessive use of pesticides, and heavy fertilizers. These practices have contributed to a situation where soils across the world have lost anywhere from 50 to 70% of their initial carbon content.  Degraded soil leads to poor quality plant growth which does not absorb as much carbon dioxide from the atmosphere and when the soil itself cannot replenish, the carbon is released into the atmosphere exacerbating global warming

So how can we treat our soil right and ensure that its carbon storing capacity is nurtured and enhanced? By proactively monitoring conditions that might lead to deterioration and by working to maintain soil health, which will not only help to remove carbon dioxide from the atmosphere but also allow it to return to the soil. The term ‘regenerative growing practices’ is usually associated with farms and agriculture, but can be implemented even in our own yards, in the form of least disturbance, compost applications, addition of green organic matter and maintenance of soil structure.  Additionally, these practices allow us to reduce our use of costly fertilizers and pesticides.

Basic soil facts

  • Important nutrients

    • Nitrogen is responsible for healthy leaf and stem growth and is made available to plants by nitrogen-fixing bacteria that convert nitrogen into nitrates, a form that plants can use. Nitrogen does not remain in the soil for long since it gets used up by plants and by decaying matter in the soil. It is also water-soluble and can wash out of the soil quickly so may need to be reapplied regularly. 

    • Phosphorus is very important for root growth as well as for producing flowers.

    • Potassium is needed for overall plant health. It keeps the plants growing and supports their immune systems. Like nitrogen, potassium is also water-soluble and needs to be replenished from time to time.

  • Soil texture is a term used to describe how soil handles water and air. An easy test for soil texture is to make a ball of damp garden soil. If it breaks apart easily when you tap it, it's sandy. If you can press it between your thumb and finger and make a flat ribbon-like strip, it's clay. 

    • Soils with fairly large particles are described as sandy. Water, air, and plant roots can move freely in sandy soils but too sandy is not good for plants either - while water drains quickly so plants roots don’t stay soggy, it can also mean that roots don’t get enough time to absorb nutrients. The best fix for sandy soils is the addition of green organic matter - grass clippings will improve soil texture by settling between the large particles of and plugging the spaces in sandy soil.

    • At the other end of the spectrum are clay soils, where the particles are so small that they pack together tightly and have good water retention capabilities.  However, too much clay and the soil will be poorly aerated, leaving little room for water, air, or roots. The best fix for clay soils is also green organic matter and gypsum, both of which improve soil structure and loosen the tightly packed clay particles.

    • Good garden soils are somewhere in between sand and clay and the ideal soil is a form called a sandy loam. It should be light enough to allow for air and water movement, but also have the fine breadcrumb-like texture that occurs when there is plenty of organic matter in the soil known as tilth. You can add grass clippings and other plant debris directly into the garden bed to decompose slowly. Be sure whatever you put down is free of seeds and has not been treated with pesticides or weed killers.

  • PH balance 

    • This information is essential because nutrients in the soil are only available to plants if the soil pH is within a certain range.  The scale goes from 1.0 to 14.0 with 7.0 being neutral. The lower the numbers go down from 7.0, the more acidic the soil. The higher they go above 7.0, the more alkaline the soil.  Generally, the ideal pH range is between 6.0 and 7.0.

    • Most garden soils have a pH between 5.5 and 8.0. If the soil is too acidic, you will need to add ground limestone. If the soil is too alkaline, you may need to add soil sulfur. You should easily be able to find the lime or sulfur that you need at a local garden center but remember that the soil will revert to original PH ultimately. 

In your flower garden, backyard or vegetable patch

You will want to do a home soil test since the first step to improving your soil is to know what’s in it. Soil tests are very simple and will tell you everything you need to know and you can buy a test at your local gardening supply store or on Amazon to accomplish this goal. The soil test kit will also provide you with an idea of the PH balance. Once you know what elements your soil has and what it lacks, you can take steps to compensate. Here are a few tips on how to remedy any deficiencies in your soil:

  • Phosphorus - add bone meal (ground animal bones)

  • Nitrogen - add coffee grounds, blood meal (powdered animal blood) or fish emulsion (industrial leftovers from fish oil production). Coffee grounds are a great addition and are easily available. If you don’t drink coffee, you can typically find a local coffee house that will be more than happy to let you take their spent grounds off of their hands! Don’t just dump the grounds onto your garden but sprinkle them to avoid mold

  • Potassium - add some wood ash

  • Magnesium - add epsom salts

  • Calcium - add crushed eggshells or lime

Along with the right soil texture and nutrients, the biggest priority is letting wet spring soils dry before planting. Digging, walking on, or driving a rototiller over wet soils, particularly those with clays, will compact and damage the soil structure by squeezing the air out and leaving inadequate space for organisms to breathe or roots to grow. A good way to judge when your soil is ready for planting in the spring is to take a handful and squeeze - if water oozes out, hold off any gardening until the soil forms a sturdy ball when molded in your hand.  

To further augment your soil, mix in compost - whether you make your own or buy some, it will help your soil drain better and add a rich, loamy feel. Compost can increase the soil’s carbon content continually, at a rate equivalent to removing about 1.5 tons of carbon from the atmosphere annually.

To make a real difference in our carbon emissions, we need to adopt a multipronged approach.  We can do this by evaluating how we treat the earth beneath our feet, as well as what we release directly into the atmosphere by way of emissions. Undeniably, it is no longer enough to cut back on fossil fuels - humans need to make changes in gardening, agriculture and land use. Starting in our own yards is often the best way to begin making an impact.

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Veer Mudambi // Journalist - Writing Green

Master's in Media Innovation from Northeastern University Freelance journalist and blogger

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