Improving Soil Structure with Deep Rooting Crop Species

What

Deep rooted crops can alleviate the effects of soil compaction by penetrating the compacted layer, creating pore space that allows air, water, and crop roots to penetrate deeper in the soil profile. In compacted or clay soils, spreading roots break up soil and create pathways through which water can seep deep within the subsoil. Decomposing root masses provide organic material that soaks up water like a sponge. In dry, sandy or rocky soils, organic material helps hold soil together and increases water retention. However, it is important to choose crops carefully in areas with subsurface drainage. Even some crops that are not quite as deep rooted can have a good effect on soil structure (e.g., red clover).

Why

Deep rooted cover crops can help break up soil compaction as well as catch nutrients which may have moved beneath the root zone of shallow rooted plants. These deep roots cycle nutrients through the system and prevent them from being lost through leaching. Introducing pasture plants with deep or fibrous roots will help to increase porosity and adding organic material will help to bind soil particles together. Lucerne and Chicory have deep rooting systems and Tall Fescue and Cocksfoot are examples of pasture grasses which also source nutrients and water through deep roots.

Collage of deep rooting crops.
Lucerne, chicory, and tall fescue.
Image Source: DairyNZ

References

Hamza, M. A., & Anderson, W. K. (2005). Soil compaction in cropping systems: A review of the nature, causes and possible solutions.  Soil and tillage research, 82(2), 121-145.

Uteau, D., Pagenkemper, S. K., Peth, S., & Horn, R. (2013). Root and time dependent soil structure formation and its influence on gas transport in the subsoil. Soil and Tillage Research, 132, 69-76.