Building the Farm - Cover Crops

BCS walk-behind tractor with flail mower attachment to shred cover crop

Like many in Central Texas, we have heavy clay soil out here in Cedar Creek.  Pull out some weeds and grasses and you’re destined to hit what seems to be an endless stratum of dense, red clay.  Unbelievably, our soil is almost completely free of rock, the silver lining to our native soil status.   That said, our soil test demonstrates that there’s a good amount of nutrients in the soil, the challenge being for tiny plant roots to access said nutrients and minerals to thrive.  The dense soil structure doesn’t allow for much space for air, water, and microbiology to infiltrate.  

One common solution to clay soil that’s been popular in decades past is deep tillage, which amounts to breaking up the soil with (typically) large machinery.  Tilling creates a beautifully soft tilth into which planting seeds and transplants is very simple.  Unfortunately, tilling also disturbs and destroys lots of microbiology in the soil, and the large machinery leads to even worse compaction in the future.  Dead soil that has been tilled repeatedly and consistently actually ends up worse off than a native clay soil over time, and it requires lots of inputs, often fertilizers that end up in groundwater.  

Nice-sized daikon radish breaks up the clay soil.

Thankfully, there is an alternative!  At Quelite Farms, we have opted for cover crops as a regenerative solution to many of the problems tilling and dense, anaerobic clay soils can present.  We use cover crops!

Cover crops, or green manure, have been a massive boon to us.  In essence, cover crops are crops that one plants in a space to increase organic matter, aerate soil, and input nutrients into the soil.  Over time, they will build a compost-like layer of material on top of the hardpan clay layer, giving roots the time and health to break down into the clay, accessing its contents while creating small spaces for water, air and little life to enter.  

Little white nodes of nitrogen fixed with help from bacteria on clover roots.

Here’s how it went on our ¼ acre plot.  We removed the 35 or so mesquite bushes, each of which had probably 5 feet of taproot encased in dense clay.  This was a sight to behold, requiring the truck, some chain, and lots of water to loosen things up.  We mowed and covered the soil with thick black tarps, called silage tarps, to kill as much as possible underneath.  After a few months, we pulled the tarps and sowed our first round of cover crop.  For the fall, we went for winter field peas, daikon radish, crimson clover, and buckwheat.  

Field peas and crimson clover fix nitrogen, which eventually creates little nodes of visible nitrogen on roots.  Mowing them before they use that nitrogen in their later stages means it stays in the soil.  Crimson clover - along with buckwheat - provide flowers for pollinators and clover is great for shading out weeds.  Daikon radish, my favorite, sends thick taproots up to 2 feet deep into the clay, breaking it up and providing space for air, worms, and water to enter.  By leaving the radish in the field, you gain the added benefit of organic matter attractive to worms and other insects who consume the radish, leaving behind what is basically compost behind.  Of course, we harvested a daikon here and there.  

Daikon radishes split clay soil and are left to decompose in place.

At the end of the season, cover crops are flattened or - in our case - shredded and left in place.  After a good freeze killed most of the foliage, we shredded and covered the field to rest, leaving a warm layer of decomposing material on the top of the soil surface.

For our first spring, we followed up with four more cover crops - sunflower, sunn hemp, cowpeas, and sorghum Sudan grass.  Sunflower and sunn hemp both provide flowers for pollinators, and sunn hemp fixes nitrogen.  Cowpeas are great for nitrogen. Sudan grass is a huge plant that - along with the other three - provides a massive amount of biological matter, all of which - when shredded and left in place - gives microorganisms and worms a ton to munch on.  

Shredded cover crops break down more easily into the soil.

After shredding, covering, and letting the land rest, we uncovered, applied about 30 truckloads of compost, and we were ready to plant our first rows of harvestable crops, which we did in the fall of 2022.  This was technically our first season of growing, but the year of cover crop had already added a good bit of fertility to the soil.  It is no surprise, then, that we saw pretty good results without having added a single grain of fertilizer or other amendment to the soil.  Cover crop and compost, and a little time - a perfect combination!

Summer cover crop in flower, ready to be mowed.