Cover Crops: An Ecological Imperative For Walden Cannabis

August 3, 2021
Andrea Larson

There are numerous and varied reasons why a farm may opt to introduce cover crops into its regular rotation. From both an economic and ecological perspective, cover crops or “green manure” as they’re sometimes referred to are a great way to reduce the need for fertilizers, herbicides and pesticides. In addition, cover crops enhance the health of your soil, reduce and prevent erosion, conserve soil moisture, protect water quality and sequester carbon. 

At Walden Cannabis we strive to make decisions that put the planet and our customers first. Cover cropping is one of the initiatives that we’ve taken that goes above and beyond Clean Green Certification requirements. We’re breaking down the benefits of cover cropping in this week’s blog and you may be surprised to learn how critical cover cropping is in putting the health and wellness of our farm at the forefront of everything we do. 

Reduce The Need For Fertilizers, Herbicides and Pesticides

As natural weed suppressors, cover crops also mitigate damage that can be caused by certain plant diseases and pests. Certain cover crops are referred to as smother crops. They smother unwanted weeds in your garden by outcompeting them for soil, nutrients, and water. While smother crops are best at minimizing the virility of perennial weeds, they may also inhibit the growth of annual weeds when sown over multiple seasons. 

Here at Walden we plant hairy vetch during late summer and early fall, after our autoflower harvest. It remains hardy over the cold winter months and as soon as the weather shifts in the warmer months, the hairy vetch takes off ahead of the weeds. Hairy vetch is also helpful for restoring nitrogen to the soil after our nitrogen-hungry cannabis saps it of its stores. When allowed to grow long, hairy vetch scavenges nitrogen from the air, which when cut down gets reincorporated into our soil biome. This process is known as nutrient cycling. In this way, hairy vetch replenishes hundreds of pounds of nitrogen in our soil, without us having to expend fossil fuels to transport it there. 

But wait, there’s more! For cannabis production in particular, vetch is particularly great when paired with barley or oats. Both barley and oats establish themselves quickly, which prevents soil erosion and reduces dust that could damage our full term plants once they flip into flower. Barley and oats also are excellent scavengers of nitrogen from the soil. 

What does this mean? 

Just as our full term plants (which we also plant after our autoflower harvest), have transitioned from wanting to eat nitrogen (vegging nutrient), to wanting to eat phosphorous (flowering nutrient), our barley and oats are scavenging nitrogen from deep within the soil. This reduces nitrogen runoff, and restores nitrogen just like vetch does when these plants are finally cut down. It also allows our cannabis plants to get the balanced diet that they need to grow big beautiful flowers that ripen appropriately and taste smooth.

Barley roots also reach around six feet deep into the soil, which improves soil structure, sequesters carbon, and reduces erosion; and the depth of these roots is why barley is so effective at scavenging nitrogen. It also attracts beneficial insects in the spring. For all these reasons, barley is one heck of a great companion to cannabis!

Improve Soil Health Naturally

According to the experts at SARE (Sustainable Agriculture Research and Education), cover crops are highly sought after for their ability to naturally improve the health of soil and nutrient cycling. One of the most prolific cover crops for building soil naturally is rye and that’s what we use at our farm in Brewster, Washington. Cover crops can also be used to break up compacted soil. If you’re looking for a cover crop that can naturally till your soil, look no further than sorghum-sudangrass, it’s deep penetrating roots make great natural soil tillers. 

There are five ways that cover crops improve soil health:

  1. They speed up the infiltration of excess surface water
  2. Cover crops relieve compacted soil and improve soil structure
  3. Natural organic matter from cover crops encourages the good kind of microbial life
  4. They enhance nutrient cycling and limit nutrient loss 
  5. They reduce pest pressure by increasing biodiversity

Enhancing nutrient cycling and limiting nutrient loss are two of the most researched aspects of agricultural cover crops. Put simply, “nutrient cycling is the way that soil nutrients move through the Earth system,” especially as this relates to our food production systems. You can compare nutrient cycling in soil to the way that water cycles (water evaporates from bodies of water, condenses into clouds, and then is returned as rain to drain again into groundwater, lakes, and oceans.) In much the same way that water cycles, nutrients on the Earth’s surface cycle underground from one place to another. Nutrients within the soil are only available to plants when they’re in certain “pools” making nutrient cycling imperative to plant and soil health. 

Reduce and Prevent Soil Erosion

If wind and rain have begun to erode your farm’s soil, cover cropping is an eco-friendly solution for reducing and preventing any further erosion. The foliage of cover crops prevents rain drops from eroding the surface of the soil while the root systems of cover crops reduce runoff that overtime can take your soil with it. Here at Walden we’ve opted to plant Sunn Hemp (not to be confused with hemp) which is known as a “soil building superhero.” Sunn Hemp is used widely by vegetable and row crop farmers, while barley an exceptional erosion control crop is regularly used as well. 

A few fun facts about Sunn Hemp:

  1. Sunn Hemp can suppress weeds by up to 90%
  2. Its high rate of biomass production make it a soil-building goddess
  3. It can produce 120 pounds of nitrogen per acre in as little as 60 days
Farm Sunn Hemp flowers, Indian hemp flower field, Madras hemp or Crotalaria juncea is a tropical Asian plant used for green manure forage, organic soil building and cover crop applications.

Conserve Your Soil’s Moisture 

While you may initially think that cover cropping during a drought would increase your water needs and hog precious resources, the contrary is actually true. The residue from spent cover crops increases water infiltration and reduces the evaporation of moisture in the soil. A lighter planting of cover crops in certain areas is apt to trap surface water and increase infiltration to the root zone via the introduction of organic matter. Rye, which is what we plant at our farm, is particularly effective at conserving soil moisture and considered a “grass type” of cover crop. 

Protect Water Quality 

Our farm sits adjacent to the Okanogan River, which is why it’s important that we implement cover crops that will prevent erosion and nutrient runoff. While we opt to be a pesticide-free farm, even organic nutrient runoff can be damaging to a river ecosystem. Excessive nutrients in a river can create overly-dense patches of plant life. An increase in algal blooms can result in tainted drinking water and can reduce oxygen in bodies of water, suffocating fish through aquatic hypoxia. Our cover crops protect our aquatic ecosystem neighbors from the harmful effects of nutrient runoff. And like any good neighbor would, we think it’s important to take precautions not to kill them. 

Put Health & Safety First 

The implementation of seasonal cover crops allows our farm team to grow cannabis that’s free from pesticides and other harmful chemicals. Not only do we protect our team from being exposed to unnecessary chemicals, we also protect our customers who deserve clean medicine, and our non-human community members.

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