Weed Control Ability of Single Sown Cover Crops Compared to Species Mixtures

Abstract

To achieve efficient weed control through cover cropping, the plant species chosen needs particular consideration. Combing different cover crop (CC) species in mixtures may increase the number of provided ecosystem services, including reliable suppression of weeds. We tested the weed suppression ability of single CC species and CC mixtures in a field trial during the autumn-to-winter growing season of 2016 and 2017. Anethum graveolens L. (dill), Raphanus sativus var. oleiformis Pers. (oilseed radish), Avena strigosa Schreb. (black oat), Carthamus tinctorius L. (safflower), Vicia sativa L. (vetch) and Phacelia tanacetifolia Benth. (phacelia) were sown in monocultures, as well as in mixtures with three or six species. Treatments with favorable establishment and above-average biomass yields tended to suppress weeds by showing lower weed dry matter and weed numbers. The highest weed control efficacy within the monocultures was reached in 2017 by black oat and oilseed radish with 72% and 83%, respectively. The mixture treatments reached a generally lower soil cover, aboveground dry matter and weed control efficacy (with an average of 57% in 2017). Even though mixtures were not as effective as the best performing single sown CCs, species combinations increased resilience against adverse weather conditions, an advantage to achieving efficient weed control over a long-term period. Therefore, species composition within mixtures is more relevant than the number of species included.Agronomy 2019, 9, 294 2 of 12 are left on the soil surface, they additionally act as a physical layer that small weed seedlings need to penetrate [13,14]. This slows down the development of the weed populations in spring after the main crop has already been sown [15]. Therefore, CCs are able to affect weed populations from their sowing date until a certain time after the subsequent main crop is established [16]. Naturally, the weed suppressive ability of a CC depends on several environmental influences that determine, e.g., the level and activity of allelochemicals [17], the speed of CC development and the build-up of biomass [18]. Under unfavorable conditions, a single sown CC might not be able to provide a sufficient level of weed suppression.Crop stands of single CC species are not able to buffer rapidly changing environmental conditions. Therefore, many studies have investigated the adaptability of mixtures [19][20][21]. Higher species diversity increases the likelihood that some of the species in a mixture are more productive, because they are better adapted to a certain set of environmental conditions (sampling effect) [22,23]. The CC species Vicia sativa L. and Phacelia tanacetifolia Benth. were not germinating well under high temperatures, whereas Guizotia abyssinica (L.f.) Cass. performed well [24]. Combinations of contrasting species in regard to environmental conditions, therefore, might provide resilience to weather conditions and provide stability in their service provision. The conditions that drive CC species performance are also d...

Are cover crop mixtures better at suppressing weeds than cover crop monocultures?

“…These results are congruent with recent research showing cover crop mixtures are rarely if ever more productive or weed suppressive than the best-performing monoculture (Baraibar et al 2018;Blesh et al 2019;Creamer et al 1996;Finney et al 2016;Florence et al 2019;MacLaren et al 2019;Nelson et al 2011;Osipitan et al 2018;Schappert et al 2019;Smith et al 2014;Wortman et al 2012). The majority of these studies examined mixture performance for a single temporal cover-cropping niche.…”

Crop Diversification for Improved Weed Management: A Review

“…Mixture species with different characteristics create a single crop to perform various functions [132]. However, weed management studies have shown that mixture performs better when composed of highly competitive species since biomass is a major predictor of weed suppression [133][134][135][136]. Furthermore, Florence and McGuire [137] performed a meta-analysis on 27 studies and found that mixture and monoculture cover crops perform comparably equal in seven metrics (biomass, N, weed, water, biology, yield, and stability).…”

A trait-based analysis to assess the ability of cover crops to control weeds in a tropical island

“…High biomass production can increase the effect of competition (den Hollander et al, 2007;Tobin et al, 2012) and many studies have highlighted the relation between cover crop biomass and weed control (e.g. Bhaskar et al, 2018;Florence et al, 2019;Osipitan et al, 2019;Schappert et al, 2019). Nevertheless, cover crop biomass is not always a good predictor of weed control (Baraibar et al, 2018;Kunz et al, 2016) and some authors like Dorn et al (2015) suggest that rapid plant development after sowing is more important than the final biomass.…”

“…Some authors suggest that increased cover crop diversity results in greater weed suppression (Akemo et al 2000;Brennan and Smith 2005;Lawson et al 2015), while others are more nuanced (Baraibar et al, 2018;Finney et al, 2016;Florence and McGuire, 2020;Schappert et al, 2019;Smith et al, 2014). In our study, average weed control efficiency by pure and mixed cover crop species was similar.…”