The soil itself is a natural system and it is deeply tied to “place”. It is the foundation of life that makes everything else work. Our soils support a mostly invisible and highly complex ecosystem made up of bacteria, fungi, amoebae, mites, worms and beetles. Working in concert, these organisms create humus, which supports plant life by assisting with the transfer of water and nutrients to the plants’ roots. Plants in turn provide nectar and cover for insects, and together they support the vertebrate food chain.
Scientists know, although still cannot fully explain, that soil organisms help protect plants from disease and transfer certain essential nutrients. We know that a humus molecule is made up of negatively charged oxygen ions and these attract and hold positively charged micro nutrients (cations) such as Copper, Potassium, Ammonium (N), Magnesium, Zinc, Manganese and Calcium. In this excellent article on “How Humic Substances Benefit Soil and Landscapes” Michael Martin Meléndrez discusses the science of humus and how it can transform depleted soil, even in harsh physical environments, into healthy, productive soil.
The best way to build humus? Add organic matter. Here in New Mexico, where we are dry, alkaline, and low in organic matter, the task of nourishing the soil is critically important if you want to grow food. The best strategy is to add organic matter and encourage root zone activity with cover cropping. The root zone is where the circus of micro-organisms starts working on new organic matter, breaking it down into successively smaller and smaller particles. The last particles left are humus. For happy plants, humus is your best friend. Here are some great ways to add organic matter to your soil:
- Start a compost pile. Here in the desert, composting can be challenging, but it is possible if you put a source of water on your pile and cover it with a plastic sheet. Due to the arid climate, we are abundant in carbon or “brown” materials and lacking in nitrogen or “green” materials. Good sources of nitrogen include coffee grounds (huge quantities free from coffee shops like Starbucks); all plant based kitchen scraps; poultry manure; fresh grass clippings without herbicides; all your yard waste, clippings, trimmings, weeds, etc. One of the best investments you can make is purchasing a chipper-shredder. Shredded materials compost much faster in our arid climate. Another way to shred your materials is to run them over with a lawnmower. For an excellent composting resource, check out this Soil, Mulch and Compost page.
- Keep all your organic matter on site. Up in the Albuquerque foothills where I live, I laugh every time I see people paying “landscapers” to rake and leaf-blow every last scrap of organic debris and haul it away. I prefer to keep all organic “waste” on site, especially the pine needles that accumulate on the ground from our ponderosa pine trees. I shred everything up and use it as mulch around my garden where I want it. If you prefer to have a clean yard, try asking your service provider to shred everything and apply the waste material as mulch where it’s needed. On the farm, we use a “chop and drop” approach, leaving pulled weeds and mowed grass on the soil as mulch. Note that weeds that have gone to seed should not be used and should be discarded in the trash as the seeds will spread more weeds around your property.
- Cover your soil. This strategy is critically important in the arid West, but it is a smart approach no matter where you are. A thick layer of mulch creates a micro-environment on the soil surface, regulating moisture and temperature and encouraging microbial activity that extends down to the root zone. Your soil and your plants will be much healthier with even moisture and temperature levels.
- Use cover crops. Cover crops are of increasing interest in sustainable farming and the research coming back from the field regarding their use has been overwhelmingly positive. This guide from SARE.org runs through all the major benefits of cover cropping, which are used to restore soil quality and fertility, manage erosion, retain moisture, reduce weed pressure, control pests shelter wildlife and foster biodiversity. On the farm and in my own yard, I use nitrogen fixing cover crops like hairy vetch, peas and clover, as well as other beneficial plants such as buckwheat and rye grass.