Perennial groundcovers: an emerging technology for soil conservation and the sustainable intensification of agriculture

Abstract

Integrating perennial groundcovers (PGC) — sometimes referred to as living mulches or perennial cover crops — into annual cash-crop systems could address root causes of bare-soil practices that lead to negative impacts on soil and water quality. Perennial groundcovers bring otherwise absent functional traits — namely perenniality — into cash-crop systems to preserve soil and regenerate water, carbon, and nutrient cycles. However, if not optimized, they can also cause competitive interactions and yield loss. When designing PGC systems, the goal is to maximize complementarity — spatial and temporal separation of growth and resource acquisition — between PGC and cash crops through both breeding and management. Traits of interest include complementary root and shoot systems, reduced shade avoidance response in the cash-crop, and PGC summer dormancy. Successful deployment of PGC systems could increase both productivity and profitability by improving water- and nutrient-use-efficiency, improving weed and pest control, and creating additional value-added opportunities like stover harvest. Many scientific questions about the inherent interactions at the cell, plant, and ecosystem levels in PGC systems are waiting to be explored. Their answers could enable innovation and refinement of PGC system design for multiple geographies, crops, and food systems, creating a practical and scalable pathway towards resiliency, crop diversification, and sustainable intensification in agriculture.

Ecological Intensification of Food Production by Integrating Forages

“…To be successful, perennial forages utilized as living mulch should have good persistence during long-term intercropping and possess growth characteristics and be managed in a manner that minimizes direct competition with the primary annual crop. Depending on seedling vigor, perennial forages are usually sown several months or up to a year prior to intercropping to ensure good establishment and their long-term persistence as living mulches [148]. Once established, perennial forages are typically severely suppressed in early spring with herbicides and then narrow strips are killed preferably with tillage to lessen their direct competitive effects of the living mulch and create a seed bed for planting the annual crop [149].…”

“…The long-term persistence of the living mulch by planting maize in wider rows and using narrower strips of killed mulch [145], and likely by alternating intercropping with periods of perennial forage production to restore stand vigor. Persistence is also enhanced if the perennial much has the ability to spread vegetatively via rhizomes or stolons or reseeding [148]. Living mulch systems usually reduce maize yields relative to monocropped maize, especially if precipitation is limited [96,140,[142][143][144][145][146][147], but yield reductions can be partially alleviated through use of drought-tolerant hybrids [152].…”

“…Full realization of these benefits will, however, require reliable and cost-effective establishment of forage legumes while maintaining relatively high yields of the maize companion crop. Due to lower maize yields, living mulch systems appear to be less profitable than monocropped maize, but the economic outcome can be improved if the living mulch can also be used as a forage source, permit greater harvest and utilization of maize stover, or provide longer-term benefits that increase cropland productivity [148,150].…”

Plant Breeding for Intercropping in Temperate Field Crop Systems: A Review

“…Temporal dynamics play a role in both cropping system design and breeding. For example, understanding key growth periods during which competition will be more detrimental (e.g., through modeling yield loss due to competition) may help to select appropriate crop pairings and determine breeding objectives (e.g., early maturity; Gaudio et al, 2019 ; Cheriere et al, 2020 ; Bourke et al, 2021 ; Schlautman et al, 2021 ).…”

Introduction to emerging technologies in plant science

“…Efforts to meet the challenge of feeding a growing population also sparks efforts to bring new crops to farmers through technology-enabled rapid domestication, as reported by Marks et al [16], who use pennycress, a new oilseed cash cover crop as an example. Schlautman et al [17] focus on perennial groundcovers that can increase both the production and regenerative potential of agricultural systems if key multiscale interactions can be better understood.…”