Achieving Diverse Cover Crop Mixtures: Effects of Planting Date and Seeding Rate

Abstract

Cover crop mixtures retain higher diversity when allowed sufficient growth in fall. Cereal rye dominates mixtures in spring, particularly when fall planting is delayed. Grasses overperform in cover crop mixtures compared to their growth in monoculture. Brassicas underperform in cover crop mixtures compared to their growth in monoculture. Legumes’ growth in cover crop mixtures varies depending on species and planting time. Cover crop mixtures may provide greater diversity of benefits than monocultures. To develop management principles to establish diverse cover crop mixtures, we conducted a 3‐yr study in which monocultures and mixtures of six cover crop species (cereal rye [Secale cereale L.], oat [Avena sativa L.], common medium red clover [Trifolium pratense L.], Austrian winter pea [Pisum sativum L.], forage radish [Raphanus sativus L.], and winter canola [Brassica napus L.]) were planted in a wheat (Triticum aestivum L.)–maize (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation after wheat (AW) and after maize (AM). Post‐emergence stand counts and aboveground biomass in fall and spring were measured by species for all cover crop treatments. All species planted manifested in monocultures and mixtures in fall, though oat dominated and red clover, canola, and radish underperformed in mixtures. Cereal rye had the highest spring biomass in all mixtures, especially AM. Pea spring biomass was disproportionally greater in relation to seeding rate in the six‐species mixture (6 Spp.) than in monoculture when planted AW. A four‐species mixture (4 Spp.) planted AW retained the highest diversity after overwintering in two of the three planting years. Our study demonstrated that (i) cover crop mixtures retain higher diversity when allowed sufficient growth in fall; (ii) cereal rye dominates mixtures in spring, particularly when fall planting is delayed; (iii) grasses overperform in mixtures compared to their growth in monocultures; (iv) brassicas underperform in mixtures vs. monocultures; and (v) legume growth in mixtures depends on species and planting time.

Ecosystem Services and Disservices Are Bundled in Simple and Diverse Cover Cropping Systems

“…Notably, more functionally diverse mixtures increased multifunctionality by ameliorating disservices associated with component species, not by enhancing services. In this study, cereal rye was included in all mixtures and comprised 20 to 40% of fall and 70 to 90% of spring aboveground biomass (Murrell et al, 2017). Rye was exceptional in providing services in the biomass bundle, but it had high disservice scores for the nutrient bundle.…”

“…From 2012 to 2015 on land transitioning to organic certification in Rock Springs, PA (40°43ʹ N, 77°55ʹ W), 10 cover crop treatments (Table 1) and a no‐cover crop control (hereafter, “control”) were planted after wheat ( Triticum aestivum L.) and terminated prior to planting maize ( Zea mays L.; Murrell et al, 2017). We quantified eight ecosystem services provided by cover crops for three consecutive years.…”

“…We quantified eight ecosystem services provided by cover crops for three consecutive years. The cover crop biomass (hereafter, “biomass”) production service was the fall plus spring aboveground biomass (kg ha −1 ) sampled as in Murrell et al (2017). The weed suppression service was the fall plus spring weed biomass minus weed biomass in the control (Baraibar et al, 2017).…”

Effects of cover crops sown in autumn on N and P leaching

“…Murrell et al. () found that fodder radish performed better in monoculture than in mixture. Oilseed radish has high weed suppressive ability (Sturm, Kunz, Peteinatos, & Gerhards, ), but a negative aspect of oilseed radish is its ability to host the pathogen Plasmodiophora brassicae , which causes the disease clubroot in some Brassicaceae species, for example oilseed rape ( Brassica napus ) (Wallenhammar, Almquist, Söderström, & Jonsson, ).…”

“…Danish field experiments have found that fodder radish has greater above-ground biomass production and N uptake than other commonly used cover crops as perennial ryegrass, chicory (Cichorium intybus), dyer′s woad (Isatis tinctoria) (Munkholm & Hansen, 2012;Sapkota et al, 2012) and winter rye (Secale cereale) (Thorup-Kristensen, 1994). Murrell et al (2017) found that fodder radish performed better in monoculture than in mixture. Oilseed radish has high weed suppressive ability (Sturm, Kunz, Peteinatos, & Gerhards, 2017), but a negative aspect of oilseed radish is its ability to host the pathogen Plasmodiophora brassicae, which causes the disease clubroot in some Brassicaceae species, for example oilseed rape (Brassica napus) (Wallenhammar, Almquist, Söderström, & Jonsson, 2012).…”