Sadly, the damage doesn't end there. These conditions change weather patterns and impact water supplies. It's no wonder bare soil is another element in global warming. I remember my first-grade teacher discussing an article the class had read in “My Weekly Reader” about farming and the notion of leaving a field fallow for a season or two to rebuild fertility. Such was the thinking in the 1950s, and I thought the notion sounded perfectly reasonable. Of course, nothing could be farther from the truth. Unplanted bare soil degenerates and the carbon cycle stops working.
Alternatively, the process of photosynthesis is a cooling, or endothermic activity as plants make their carbohydrates. There is a net water gain if land has a continuous population of plants. The conventional agriculture practice of tilling renders a net water loss. If the soil is planted with a cover crop, water can keep infiltrating the soil, and life beneath the surface keeps functioning and staying healthy. Legume cover crops like fava beans and clover are good choices because they return a significant amount of nitrogen to the soil. This is achieved when the plants are chopped down and left on the soil. Using fast-growing buckwheat for a cover crop will feed pollinators. Mustard and brassica will fumigate the soil for nematodes. Grass roots hold soil in place and help keep the ground cool. All of them attract beneficial organisms, pull down carbon from the atmosphere and help retain water.
Mulching is another good practice to keep the ground cool. Two inches of compost should first be laid down, then three inches of mulch. Straw is an excellent, organic cover for garden beds. Mother nature can help by using leaves to mulch if we can get past another unuseful habit (besides tilling the soil) of demanding our gardens be perfectly manicured. It's always a good idea to spread compost, but the reason we do it before we mulch is that some mulches, such as wood chips, can leach nitrogen out of the soil. If we apply compost first, the effect will be buffered.
If we follow these practices, we will improve the tilth of the soil, promote soil organic matter (SOM), retain moisture in the ground, prevent leaching of soil minerals, attract soil organisms, and improve the yield and nutritional value of our fruits and vegetables.
Our takeaways are these:
Bare, tilled soil contributes to global warming.
Cover the soil with living plants.
Use cover crops.
When this isn't practical, add compost and mulch.
*This is the fourth post in this series following concepts and information from UC Master Gardeners of Napa County presentation, “Soil is the Solution, healing the earth one yard at a time,” https://www.youtube.com/watch?v=JqA8DqBtRuo . The presentation describes practices we can learn and implement about soil to help slow and ultimately reverse the damage humankind has done and slow global warming. Previous posts were May 24, June 7 and June 28, 2021.
Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143. Volunteers will get back to you after they research answers to your questions.
Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.
Photo credits: Pixabay