The Potential of Multi-Species Mixtures to Diversify Cover Crop Benefits

Abstract

Cover crops provide a range of well-documented benefits to growers and the environment. However, no single species can deliver all of these benefits, and hence planting mixtures is gaining increasing attention. To the best of our knowledge, there is no comprehensive review on different multi-mix strategies. This article reviews available studies on multi-mixes, focusing on temperate North America, and discusses objective criteria for selecting components of a multi-mix and what future research is needed. Very few peer-reviewed studies on multi-mixes are currently available; a diversity of species compositions is being tested with a wide range of potential benefits but also with various limitations. Selection of species in multi-mixes is based on different criteria that help improve multiple ecosystem services. An emerging concept is the importance of selecting cover crop species with functional complementarity rather than simply increasing the number of species. Based on this concept, objective criteria have been developed to select the species for a multi-mix: grower objectives/primary purpose of planting the cover crop, crop rotation and cropping system compatibility, above and belowground compatibility, complementarity of different ecosystem functions, compatibility with the growing environment, duration for cover crop growth, termination option(s) available, input/labour costs, planting equipment required, persistence/weediness, and potential net economic returns. We propose a step-wise procedure to develop effective multi-species mixtures. The number of species and their ratio in the mixtures will depend on objective criteria, and hence long-term research is required to assess different species compositions and their impacts.Sustainability 2020, 12, 2058 2 of 16 and wheat (Triticum aestivum L.) in a 3 year rotation system (e.g., CSW rotation). Unfortunately, from August to April, depending on the cash crop, the ground is often bare. This creates potential for using cover crops to produce ecosystem services or to mitigate ecosystem dis-services associated with existing cropping system(s) [20]. Some examples of cover crops used in the region are: 1) red clover (Trifolium pratense L.), frost-seeded into winter wheat [18,19,21], which can be terminated in late fall (or can be over-wintered under no-till condition), with corn planted in the following spring, and 2) oats (Avena sativa L.), seeded after winter wheat or cereal rye (Secale cereale L.) sown after corn or soybean, which are terminated in late-fall (i.e., November) or the following spring (i.e., April-May) prior to planting another main crop, usually corn or soybean [22,23].Planting a single species of the cover crop has both benefits and disadvantages. Cover crop species such as oats and cereal rye produce excellent amounts of aboveground biomass, and they appear to be economic (e.g., low seed cost and high availability). However, they also come with certain drawbacks, e.g., they are not nitrogen-fixing; the biomass contains a higher C:N ratio compared...

Using fall‐seeded cover crop mixtures to enhance agroecosystem services: A review

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