Rooted in Sustainability: Harnessing the Power of Cover Crops

Agricultural sustainability means meeting the current needs of society without jeopardizing the needs of future generations [1]. Today, this requires an agroecosystems and food systems perspective that supports ecosystem services [2] and prioritizes resilience and adaptability [1].  A sustainable agroecosystem aims to use natural resources to regenerate productivity while mitigating adverse effects on ecosystems within and beyond the confines of the farm [3]. Farmers pursue these objectives by utilising existing natural processes and integrating the functions of natural ecosystems into their farming systems.

Cover crops serve as a crucial tool in achieving agricultural sustainability. These crops, integrated into cash crop rotations, are strategically planted alongside or between cash crops to maintain continuous soil cover [4]. They can serve as either living or dead mulch on the soil surface, or they can be incorporated into the soil as green manure [2, 4]. The selection of cover crop species and timing of cover crop planting depends on the specific objectives of the production system [2]. For instance, if the goal is winter grazing, temperate species might be chosen to thrive post-cash crop harvest. Alternatively, for weed or pest suppression, species that grow concurrently with cash crops may be preferred. Cover crop selection is diverse, tailored to fit into crop rotations at various stages, rather than relying on a single option for each operation.

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Choosing suitable cover crops requires careful consideration of one’s specific operating system, taking into account factors such as climatic and soil conditions  and operational objectives [2]. For drought-prone regions, selecting drought-resistant cover crops is essential to avoid competition with cash crops for water. Irrigated areas typically offer a broader range of cover crop options compared to dry-land systems. Integrated crop and livestock operations benefit from nutrient-rich cover crops that thrive during dry or unproductive seasons to support livestock feed. Some orchard cover crops might be chosen based on their tolerance to shade.

Typically, cover crops are planted before or after the cash crop. Machinery commonly used for planting cover crops includes grain drills, conventional maize planters (offering precise control over seeding rates and placement), and broadcast planters. Precision planters enable farmers to minimize seeding rates, leading to cost savings on seeds. Multiple studies have indicated that cover crops used in combination with a conservation tillage system has a greater effect on improving soil quality and increasing crop yields [5-7]. Conservation Tillage is characterized by a tillage method or a combination of tillage and planting that maintains a crop residue cover of 30% or more on the soil surface. [8].

As climate change alters weather patterns, such as increased rainfall leading to soil erosion and nutrient runoff, or drought emphasizing water conservation, cover crops become crucial. Some of the benefits of cover crops include [2, 9-11]:

  • Their roots undergo turnover, increasing soil organic matter and enhancing soil texture by forming stable aggregates. This reduces runoff while improving water-holding capacity and resisting soil erosion. Additionally, cover crop roots aid soil aeration, reducing compaction and waterlogging.
  • Cover crops reduce the kinetic energy of the raindrops on the ground.
  • Leguminous cover crops like clover and vetch can fix atmospheric nitrogen (N), and retain excess soil N for the following growing season, reducing the need for synthetic agrochemicals and decreasing pollution from the eutrophication of local water sources.
  • Cover crops provide shading at the soil level, which cools the soil surface, maintaining a stable microclimate and preventing excess evaporation of soil moisture.
  • Some cover crops can be harvested for additional income or used as forage for livestock post-cash crop harvest, enhancing nutrient cycling from livestock dung and urine, reducing reliance on synthetic agrochemical inputs, and aiding livestock weight maintenance during unproductive seasons.
  • Integrating cover crops into crop rotation systems can break pest and disease cycles, attract pollinators and control pests by providing a habitat for beneficial predators.
  • They suppress weeds by outcompeting them for resources like space, sunlight, nutrients, and moisture or through the release of allelopathic exudates.

These benefits ultimately contribute to increased cash crop yields.

Selecting the appropriate cover crop for your operation and climate is crucial, as choosing the wrong one can result in adverse effects. The degree and duration of benefits from cover crops are influenced by factors such as climate, management practices, and genetics. Cover crops may immobilize N or deplete soil moisture, leading to yield losses in subsequent crops. Improperly managed cover crops may prove challenging to terminate, produce seeds, and potentially evolve into weeds. Additionally, short-term economic costs, such as seed, fuel, and planting expenses, which may not immediately offset the benefits of cover crops, but long-term advantages are often realized [12].

To ensure you select the appropriate cover crops for your operation system and climate, consider consulting local agricultural extension services, regional agricultural universities, experienced farmers in your area, and online resources from reputable agricultural organizations. Additionally, agricultural publications, government agricultural departments, and online databases specific to your region can provide valuable information on cover crop selection based on local conditions and climate.

In conclusion, agricultural sustainability requires a holistic approach that integrates agroecosystems and food systems, prioritizing resilience, adaptability, and the preservation of ecosystem services. Cover crops emerge as a vital tool in achieving these goals, offering multifaceted benefits such as soil conservation, nutrient management, weed suppression, and climate resilience. However, the successful integration of cover crops relies upon careful selection tailored to specific operational needs, climate conditions, and management objectives. While challenges such as potential yield losses and management complexities exist, the long-term advantages of cover crops outweigh these concerns. To navigate the complexities of cover crop selection effectively, accessing a diverse array of resources and seeking expert guidance is paramount. By embracing cover crops as an integral component of sustainable agricultural practices, farmers can cultivate resilient and productive farming systems that meet the needs of both present and future generations.

 

References

  1. Brodt, S., Six, J., Feenstra, G., Ingels, C. & Campbell, D. . Sustainable Agriculture. Nature Education Knowledge 2011; 3(10):1:[Available from: https://www.nature.com/scitable/knowledge/library/sustainable-agriculture-23562787/.
  2. Adetunji, A.T., et al., Management impact and benefit of cover crops on soil quality: A review. Soil and Tillage Research, 2020. 204: p. 104717.
  3. Hawes, C., P.P. Iannetta, and G.R. Squire, Agroecological practices for whole-system sustainability. CABI Reviews, 2021(2021).
  4. Benedict, C., C.G. Cogger, and N.N. Andrews, Methods for successful cover crop management in your home garden. 2014.
  5. Blanco‐Canqui, H., M. Claassen, and D. Presley, Summer cover crops fix nitrogen, increase crop yield, and improve soil–crop relationships. Agronomy journal, 2012. 104(1): p. 137-147.
  6. Sainju, U.M. and B.P. Singh, Winter cover crops for sustainable agricultural systems: influence on soil properties, water quality, and crop yields. HortScience, 1997. 32(1): p. 21-28.
  7. dos Santos Cordeiro, C.F., F.R. Echer, and F.F. Araujo, Cover crops impact crops yields by improving microbiological activity and fertility in sandy soil. Journal of Soil Science and Plant Nutrition, 2021. 21(3): p. 1968-1977.
  8. Derpsch, R., Conservation tillage, no-tillage and related technologies, in Conservation agriculture: environment, farmers experiences, innovations, socio-economy, policy. 2003, Springer. p. 181-190.
  9. Bjorkman, T., Cavigelli, M., Dostie, D., Faulkner, J., Knight, L.G., Mirsky, S., Smith, B. Cover Cropping to Improve Climate Resilience. Northeast Climate Hub 2019; Available from: https://www.climatehubs.usda.gov/sites/default/files/CoverCropsFactsheet_Feb2019_web508.pdf.
  10. Cordeau, S., et al., Weed species differ in their ability to emerge in notill systems that include cover crops. Annals of Applied Biology, 2015. 166(3): p. 444-455.
  11. Masilionyte, L., et al., Effect of cover crops in smothering weeds and volunteer plants in alternative farming systems. Crop Protection, 2017. 91: p. 74-81.
  12. Clark, C. Cover Crops for Sustainable Crop Rotations. 2015; Available from: https://www.sare.org/resources/cover-crops/.