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lemons in the greenhouse

March 2022 - So Many Reasons to Use Ground Cover!

Figure 1. A diverse ground cover including clover, herbs and veggies.

There are good reasons why so many orchardists are adopting the use of low growing perennial ground cover. The list of benefits is long and impressive. It insulates the soil during high temperatures and provides an armour for the soil during heavy rains, reducing erosion and increasing water infiltration. It also helps to build soil aggregates and enhances nutrient cycling. It provides a haven for beneficial insects, enhances pollinators and plays a role in building organic matter as well. The more extreme and erratic the weather, the more benefits cover crops can provide.

Figure 2. Grass plant with healthy rhizophagy. Note the aggregates and complex root system. A worm wriggled out of it.

Eight years ago, when I first planted the greenhouse orchard, I didn’t realize the benefit of a permanent ground cover. The only plant/weed popping up everywhere was Black Medic. I knew it was an indicator of poor, compacted soil, but instead of allowing it to grow and carry out all the benefits I just listed, I vainly pulled it out and used it as mulch under the avocados.

Figure 3. A surviving Black Medic with micro clover and yarrow.

When I learned that the active roots of a living ground cover are more effective than mulch in providing a constant food source for soil microbes, I changed my tactic. Unfortunately, by that time the Black Medic had almost disappeared!

I planted seeds and bedding plants throughout the greenhouse, but nothing seemed to be growing. I discovered the problem when I shone a flashlight in the greenhouse at night. Every seedling was covered with the nocturnal sow bugs and slugs. I persisted by planting wave after wave of seedlings. It took a year, and now the soil is increasingly covered with a diverse selection of plants including a continuous supply of veggies for the kitchen.

Figure 4. Perennial arugula provides fresh greens throughout the year.

I’m on the hunt for hardy plants that share a common mycorrhizal network with citrus or avocados. My latest additions include Marais-des-Bois strawberries and Bunchberry (Cornus spp.).

Two founding principles of regenerative agriculture are to keep living roots in the soil as much as possible and to grow a diverse variety of plants. Both practices increase microbial biomass and microbial diversity. This in turn improves carbon, nitrogen and phosphorus cycling, thus increasing the plants’ resilience when dealing with challenging climate extremes. A diverse ground cover with its diverse soil community results in what has been termed ‘disease suppressive soils’.

One of the longest-running biodiversity experiments in grassland ecosystems (since 2002) is the Jena Experiment in Germany. The central aim of the Research Unit is to uncover the mechanisms that determine biodiversity-ecosystem functioning (BEF) relationships in the short- and long-term. Here’s a link to a video explaining their projects: Jena Project

This project is supported by the Canadian Agricultural Partnership, a federal-provincial-territorial initiative. The program is delivered by the Investment Agriculture Foundation of BC.

Opinions expressed in this document are those of the author and not necessarily those of the Governments of Canada and British Columbia or the Investment Agriculture Foundation of BC. The Governments of Canada and British Columbia, and the Investment Agriculture Foundation of BC, and their directors, agents, employees, or contractors will not be liable for any claims, damages, or losses of any kind whatsoever arising out of the use of, or reliance upon, this information.


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