One of the challenges of living in a high desert is that our native soils are low in organic matter. Ideally soil should be composed of 5% organic matter, but local soil tests show 1-2%. 

Organic matter is any products that come from living things (like manure or grass clippings) and decaying plant or animal materials (think compost and dead insects). It’s full of building blocks necessary for plant growth—carbon, hydrogen, nitrogen, phosphorus and potassium—along with secondary nutrients, trace minerals, various acids and typically a host of microbes. 

Farmers consider their soil as a bank for lending out cash later in the form of sales. Ensuring that there’s enough organic matter in the soil now is like making a deposit that will pay off next season.

REPLENISH ORGANIC MATTER 

The beauty of a varied organic matter profile in your soil is that you’ll have all those nutrients and minerals in your crops. But the downside is that each harvest, each carrot pulled and every lawn mowed, those nutrients are removed from the soil. This means the percentage of organic matter decreases each year as it gets converted into plant food. Gardeners must actively replenish the soil bank by adding organic matter back into it.

We could have started next year’s garden last May by adding mulch to the garden, putting straw or leaves over the soil surface. The underside would already be decomposing by now, and some of it can be turned into the top couple inches of soil in the fall to further its conversion to organic matter over the winter.

One of the easiest and beneficial actions you can take this month is to cut the spent tomatoes, cucumbers, etc. at the base of the stalks and leave the roots. Ripping the plants out roots and all short-circuits the nutrient cycle. You’re instantly adding organic matter, as the roots decay deep in the soil and become nutrients for next year’s crops, right where the plant roots will be. Additionally, by laying down the cut plants on the garden soil, they too break down over winter, and you’ll already have mulch materials for the soil next season.

COVER CROPS ENRICH SOIL

Farmers also plant cover crops in their pastures and orchards to build organic matter in their soils. Alfalfa and grasses are great, as the alfalfa puts out a deeper taproot and the grasses have shallow fibrous roots. Alfalfa is a legume, so it fixes nitrogen that the grasses crave, and they both act as armor to protect the soil from erosion and outcompete weeds. You can mimic that same model, but instead of using perennial crops that come back each year, you can use annuals that are planted now and will get established before dying back or going dormant in deep frost. 

You then have the option of lightly turning the spent plants into the topsoil next spring or cutting them at the stem and planting next summer in between where their roots are decomposing. Planting cover crops in between existing plants, into any bare soil after harvested roots or along the edges of the garden works well. Being annuals, you can slip them in anywhere starting in August to replenish all the pounds of food taken out. After winter, your annuals will be spent and you can plant freely in the early spring.

Austrian peas and hairy vetch are the kings of late-season legumes. They can be planted now until about October 15 and still germinate. Triticale is a cross between rye and wheat, which are both annual grasses. It grows many small fibrous roots for the soil and acts as a windbreak to catch any rain or snow and hold it in the soil for next year. 

Arguably the best cover crop to plant now is cereal or winter rye. Local farmers have planted it before October 15, and it will continue to grow in soils down to 34 degrees! It’s not uncommon for it to finally freeze out only to burst out of dormancy in the spring and produce more biomass and eventually seeds. A home gardener could choose to incorporate the plants into the soil next season or plant them in a corner of the garden to let them go to seed, be harvested and then plant a late-season vegetable crop in its place. (Rye bread anyone? Sprouted rye berries?)

The clock is ticking, however. A couple of weeks ago we could have planted mustards, kale, chard, black oats, rapeseed or winter wheat or barley and had the same effects on our soil. Since time is short, finding a local supplier would be best for getting the seeds in the garden soon. 

The El Paso County Conservation District offers cover crop seeds, which may be ordered online at EPCCD.org and picked up from their office at 5610 Industrial Place, Suite 100 by appointment using calendly.com/epccd/visit or by calling 719-600-4706.