Abstract
The perennial forage grass Thinopyrum intermedium (Host) Barkworth & Dewey, commonly known as intermediate wheatgrass (IWG) or by the commercial name Kernza™, is being developed as a perennial grain crop, i.e. being bred for its improved agronomic performance and food qualities. Intercropping legumes and grasses is a strategy for improving resource use and sustainability in cropping systems. Here, we show for the first time the agronomic performance of IWG as a perennial cereal grown as a monocrop and as an intercrop (alternate row, 0.5:0.5) with Medicago sativa L. (alfalfa/lucerne) in southern Sweden. The seeds of cycle 3 IWG were accessed from The Land Institute (TLI) of Salinas, Kansas, USA, and used to establish a local seed production plot (in 2014) for the establishment of the perennial systems (in 2016) utilised in this study. Both the monocrop and intercrop were sown with 25 cm row spacing with alternate rows of IWG and alfalfa in the intercrop (i.e. replacement design) with unknown sowing density. Intercropping provided sustained IWG grain production under the dry conditions of 2018, but also in the following year. This was evidently associated with a higher nitrogen accumulation in intercropped practice. Thus, intercropping seems to have stabilised the IWG grain production in the dry conditions of 2018, when the grain production in the intercrop was similar to that of the monocrop in the same year. This result was further supported by the lower discrimination against 13C (as an indicator of water use efficiency) in the intercrop components compared to the sole crop in 2018. The lower discrimination indicates high water use efficiency in the intercropped IWG in comparison to the IWG in monoculture, and we conclude that intercropping perennial cereal grain crops with legumes provides better growing conditions in terms of nitrogen acquisition, and water status, to cope with more extreme drought spells expected from climate change.
Highlights
Perennial crops represent a paradigm shift in agriculture and have the potential to contribute to increased sustainability of production systems (Crews et al 2018; FAO 2013)
In the intermediate wheatgrass (IWG) monocrop, the IWG straw dry matter yield was significantly lower in the dry year 2018 and in 2017 and 2019, while in the intercrop, IWG straw biomass was similar over all three experimental years
The harvest index (HI) of IWG was highest in both crops in 2017, with declining values over the 3 experimental years (Table 2)
Summary
Perennial crops represent a paradigm shift in agriculture and have the potential to contribute to increased sustainability of production systems (Crews et al 2018; FAO 2013). In the pursuit for suitable candidates for the development of perennial grain cereal crops, the perennial forage grass Thinopyrum intermedium (Host) Barkworth & D.R. Dewey, commonly known as intermediate wheatgrass (henceforward referred to as IWG), was selected for domestication in 1983 (Wagoner and Schauer 1990) and included in a breeding programme for perennial cereal grain production in 2002 (DeHaan et al 2013) and trademarked under the name KernzaTM (Fig. 1). While plant breeding improves grain yields, it has been suggested to focus on the crop multifunctionality, which perennial cereal may provide besides grain production (Duchene et al 2019). Potential multiple functions from perennial cereals include feed and forage production, protection and regeneration of soil quality, reduced nutrient losses, reduced requirements for agrochemicals, climate change adaptation and mitigation, conservation of biodiversity and
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