Maximize Biodiversity

We often hear regenerative thought leaders say that biodiversity is one of the most important components for improving our farms, but why is this? The importance of diversity comes down to two reasons: increasing soil functions and the filling of biological niches. Both of these factors result in a synergistic effect between all components so that the overall system is greater than the individual parts.

Each plant, microbe, and animal within a farming operation uniquely contributes to the overall system. So when we increase the diversity of plants, microbes, and animals, we see a corresponding increase in the overall functional diversity which makes the system more resilient to changes such as a drought, flood, pest or disease.

For example, plants vary in root exudate amounts and profiles, microbial interactions, root architecture, and photosynthetic ability. Microbes range in their functions too, where some microbes associate with plants to increase growth such as plant growth-promoting bacteria (PGPB) and mycorrhizal fungi, while others produce plant autoinducers, hormones, and antibiotics, and others decompose minerals and organic matter to increase available nutrients to plants. Each has a specific and crucial role to play.

The filling of biological niches is the other reason why diversity is important. The competition for resources between different species is less than the competition between plants of the same species because different species target different aspects of resources. For example, a sunflower (deep taproot) is far less competitive with a flax plant (shallow fibrous root) than it would be against another sunflower.

When diversity is increased, more niches are filled, resulting in a synergistic effect. For example, in several studies¹, multispecies cover crops produced more root exudates, more biomass, more root mass, increased aggregation, and increased microbial activity and diversity while using less water and nutrition. One study² found the multispecies cover crop produced 3.5 t/ha (3123 lb/acre) while the average of all the individual cover crops produced 2-3.2 t/ha (1785-2856 lb/acre); moreover, the study found that the multispecies cover crops were more stable and were able to grow with less risk of failure.

Another important benefit gained from increasing plant diversity is its effect on microbial activity through quorum sensing. Quorum sensing is the population-dependent ability for microbes to communicate through chemical signals. When these chemical signals exceed a base threshold, a change of gene expression and metabolism occurs in the microbial population. This will regulate cellular processes such as reproduction, metabolism, enzyme production, and hormone synthesis. This positive regulation of genes from microbes that have reached a quorum benefit the surrounding plants through better microbial root colonization, increased plant growth-promoting bacteria, control of plant pathogens, improved systemic resilience, and improved insect resistance.

There are four main opportunities for improving biodiversity within our farms:

• Diversity in Crop Rotation: A diverse crop rotation has many benefits ranging from disease suppression, weed suppression, nutrient use efficiency, and water use efficiency. Diversity in crop rotation is not just important for soil health but also business health, where growing multiple crops reduces reliance on a single commodity market. For example, a poor year for wheat might be offset by being a better year for sorghum, therefore stabilizing year-to-year cash flows. For best crop rotation, a range of functional plant groups should be used, such as cereals, legumes, brassicas, and broadleaves.
• Diversity in Cover Crops: Cover crops give the biggest opportunity to introduce a significant amount of diversity in one season. Multispecies cover crops can include as many species and families as practically possible, resulting in a significant increase in functional diversity and the filling of many niches.
• Diversity Through Inter-row Cropping: Inter-row cropping is the addition of crops in the spaces between rows of a cash crop. This can increase the total species grown during the season by seeding plants like clovers and radishes, resulting in increased functions such as nitrogen fixation, capturing more light, and producing more biomass for post-harvest grazing. To optimize the benefit gained from diversity, we should seek to maximize plant family diversity. This means including grasses (Poaceae), legumes (Fabaceae), the Daisy family (Asteraceae), Brassicas (Brassicaseae), the Buckwheat family (Polygonaceae), and more into our rotations, cover crops, and inter-row crops.
• Livestock Integration: There are also opportunities to increase the economic and biological diversity of a farm by adding or increasing the diversity of livestock that are integrated into the system. Animal manure and saliva contributes to plant and microbial growth and diversity, which ultimately adds more functionally to the farm. New income streams can also come from the addition or expansion of livestock enterprises.

References

1. Florence, A. M., Higley, L. G., Drijber, R. A., Francis, C. A., & Lindquist, J. L. (2019). Cover crop mixture diversity, biomass productivity, weed suppression, and stability. PLoS One, 14(3), e0206195; Lange, M., Eisenhauer, N., Sierra, C. A., Bessler, H., Engels, C., Griffiths, R. I., ... & Gleixner, G. (2015). Plant diversity increases soil microbial activity and soil carbon storage. Nature Communications, 6(1), 6707; Chu, M., Jagadamma, S., Walker, F. R., Eash, N. S., Buschermohle, M. J., & Duncan, L. A. (2017). Effect of multispecies cover crop mixture on soil properties and crop yield. Agricultural & Environmental Letters, 2(1), 170030; Saleem, M., Pervaiz, Z. H., Contreras, J., Lindenberger, J. H., Hupp, B. M., Chen, D., & Twigg, P. (2020). Cover crop diversity improves multiple soil properties via altering root architectural traits. Rhizosphere, 16, 100248.
2. Wendling, M., Charles, R., Herrera, J., Amossé, C., Jeangros, B., Walter, A., & Büchi, L. (2019). Effect of species identity and diversity on biomass production and its stability in cover crop mixtures. Agriculture, Ecosystems & Environment, 281, 81-91.