Soil and Fertilizer

Gardeners have a wonderful opportunity to help mitigate the effects of climate and habitat loss. A good place to start is with soil management. You don’t need to have hundreds of acres of farmland to make a difference. Many gardens and yards converting to sound ecological practices can have a big impact.

Managing the soil to retain and store carbon is within our reach:

How might this play out in your garden?

During the summer and fall, leaf blowers and rakes are constantly employed in urban and suburban gardens as people “clean up” their garden beds. But there are some great reasons to give yourself a break from this garden task.

Falling leaves and dormant plant material are the beginning of the virtuous cycle of soil health:

  • The soil needs a winter blanket to moderate temperature and keep rain from compacting the soil. This lets oxygen mix with soil particles and nourish the tiny life that keeps soil productive. Leaves from healthy trees do this magnificently. Microorganisms and soil insects continue to mix soil particles, stabilize soil structure, and hold nutrients, even in winter!
  • Here is how they do it: leaf mulch decomposes over time, thanks to microorganisms and fungi. As nutrients and organic matter are released they stay in the soil attached to particles, and in the bodies of soil organisms.
  • Soil-dwelling invertebrates, beneficial fungi, bacteria, and others feed on dead plant material to create humus in the soil. Humus is the product at the end of decomposition that remains in the soil to soak up water like a sponge, store carbon, and hold on to nutrients as rain washes through the soil all winter.
  • Worm and insect holes are important biopores through which water and air can flow into the soil. Air and water together make up about 50% of the soil volume, and are equally important for root health. If rainfall encounters a layer of mulch and a network of pores created by soil organisms, the surface is like a sponge instead of a water slide and it soaks into the soil for storage and slow release.
  • Carbon stored in soil organic matter and humus mitigates the effects of climate change and holds that carbon in soil for decades and even centuries! It also acts as a soil conditioner, making your soil soft, crumbly, and full of nutrients. It protects our waterways from the pollution caused by nutrient runoff.
  • Beneficial insects like bees, spiders, beetles, and many others, find protection in leaf mulch for the winter. There may be eggs, larvae, or adult insects – even frogs and larger animals, that use your mulch and clumps of stems for winter survival. Twig nesting bees may be using dead stems as nests – so wait to cut those back until spring, after bees have emerged.
  • It’s easy to do your part for carbon storage and wildlife. You will produce more pollinators and beneficial insects, water from rain and irrigation will exit your property cleaner and more slowly, and that helps salmon and stream life that need clean water in the right amounts.

I dd not mention fertilizer in this article! Fertility is the product of feeding the soil with organic matter. Fertilizer, although sometimes a necessary supplement, is not necessary for native plants and for very few ornamentals.

*Many of Oregon’s native bees do need some bare soil for nesting. You can leave space open for them by creating areas with bare soil, sand, or a collection of small stones and larger rocks where these bees can make their homes. Removing some leaves in the spring can also free up space for ground nesters. Hollow trees, tall  bunchgrasses, and rodent holes offer bumblebees a good spot for their nests.