Cereal species mixtures: an ancient practice with potential for climate resilience. A review

Abstract

Food security depends on the ability of staple crops to tolerate new abiotic and biotic pressures. Wheat, barley, and other small grains face substantial yield losses under all climate change scenarios. Intra-plot diversification is an important strategy for smallholder farmers to mitigate losses due to variable environmental conditions. While this commonly involves sowing polycultures of distinct species from different botanical families in the same field or multiple varieties of the same species (varietal mixtures), mixed plantings of multiple species from the same family are less well known. However, the sowing of maslins, or cereal species mixtures, was formerly widespread in Eurasia and Northern Africa and continues to be employed by smallholder farmers in the Caucasus, Greek Islands, and the Horn of Africa, where they may represent a risk management strategy for climate variability. Here, we review ethnohistorical, agronomic, and ecological literature on maslins with a focus on climate change adaptation, including two case studies from Ethiopian smallholder farmers. The major points are the following: (1) farmers in Ethiopia, Eritrea, and Georgia report that mixtures are a strategy for ensuring some yield under unpredictable precipitation and on marginal soils; (2) experimental trials support these observations, demonstrating increased yield advantage and stability under certain conditions, making maslins a potentially adaptive practice when crops are impacted by new biotic and abiotic conditions due to climate change; (3) maslins may balance trade-offs between interfamilial species plantings and varietal mixtures, and expand the total portfolio of traits available for formulating mixtures from varietal mixtures alone; and (4) they may buffer against the impacts of climate trends through passive shifts in species composition in response to environmental pressures. We demonstrate the potential benefits of maslins as an agroecological intensification and climate adaptation strategy and lay out the next steps and outstanding questions regarding the applicability of these cropping systems.

Mixing things up! Identifying early diversity benefits and facilitating the development of improved variety mixtures with high throughput field phenotyping

“…Meta‐analyses of the benefits of variety mixtures have indeed shown that (i) variety mixtures often have higher yields than their respective pure stands (overyielding), albeit average benefits are relatively minor, for example, approximately 2% –4% in wheat; (ii) mixtures are effective in suppressing disease epidemics, and overyielding strongly increases under high disease pressure, and (iii) yield stability is often slightly higher in variety mixtures (Borg et al., 2018; Kristoffersen et al., 2020; Kiær et al., 2009; Reiss & Drinkwater, 2018; Smithson & Lenné, 1996). Furthermore, mixtures may buffer effects from environmental influences and tend to show a higher resilience (McAlvay et al., 2022). Importantly, these identified benefits can be expected to occur on average in any random mixture, and even without prior knowledge of the potential drivers of positive mixture effects.…”

Contrasted reaction norms of wheat yield in pure vs mixed stands explained by tillering plasticities and shade avoidance

“…Such a design can also be of interest to study intercropping, as long as the plants are easily separable to be phenotyped individually. This should be the case of mixtures of cereals (McAlvay et al, 2022), but not of some cereal-legume mixtures such as those with vining cultivars of field pea whose tendrils coil around neighboring plants, allowing them to climb and use them as support (Podgórska-Lesiak and Sobkowicz, 2013).…”

Decent work, sustainable livelihoods and climate action: Time for a clean slate?

“…Sustainable Livelihoods is a newish term but probably an ancient idea, which draws from; resonates with ancient practices in the occupation of farming for a livelihood. This included practices such as multi-cropping, for instance, cereal-mixing, in which multiple seeds planted at the same time also provided protection when one of them was attached by a bug, or a drought, or a flood (McAlvay et al, 2022). The job is a form of monocropping, which works well only until the first bug comes along, and then all is all too readily lost.…”