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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.

The global interest in growing perennial grain crops such as intermediate wheatgrass (Thinopyrum intermedium) (Kernza) for production of food and feed is increasing. Intercropping Kernza with legum...

Intercropping is a globally accepted method of forage production and its effect on silage quality depends not only on forage combination but also fertilization strategy. In the present study, field intercropping of orchardgrass (Dactylis glomerata) and alfalfa (Medicago sativa) at five seed ratios (100:0, 75:25: 50:50, 25:75, 0:100 in %, based on seed weight) was applied under three N fertilizing levels (0, 50, and 100 kg/ha), and harvested for silage making and in vitro rumen degradation. As a result of intercropping, the actual proportions (based on dry matter) of alfalfa in mixtures were much closer to seed proportion of alfalfa in field, except 75:25 orchardgrass-alfalfa intercrops with no fertilization. The actual proportions of alfalfa in mixtures decreased by 3%&ndash, 13% with the increase of N level. Increases of alfalfa proportion in mixtures increased silage quality, nutrients degradability and CH4 emissions. Increasing N levels increased silage pH, concentration of butyric acid, and fiber fractions. In summary, inclusion of alfalfa at around 50% in orchardgrass-alfalfa silage mixtures were selected for favorable ensiling and higher forage use efficiency while also limiting CH4 emissions, compared to monocultures. The silage quality and feeding values of mixtures were influenced more by forage ratios than by N levels.

CONTEXT The sustainability of winter wheat (Triticum aestivum L.) − summer maize (Zea mays L.) rotation (W − M), which is commonly practiced in the North China Plain (NCP), is threatened by severe groundwater deficits and environmental pollution due to excessive nitrogen (N) applications. OBJECTIVE Considering the need for protein-rich forages by local livestock operations and the environmental benefits of growing perennial legumes, we propose that an alfalfa (Medicago sativa L.)-based system is worth introducing for field practice in the NCP. METHODS An integrated evaluation was used in this four-year study to compare the agronomic, economic, and environmental performances of the following four cropping patterns: alfalfa monoculture (AA), alfalfa and silage maize intercropping with or without N input which is designed for local climate condition, maize monoculture with or without N input which is much-discussed as a resources-saving substitution and commonly practiced W − M. RESULTS AND CONCLUSIONS W − M obtained the highest aboveground dry matter (DM) productivity (P SIGNIFICANCE Alfalfa and silage maize intercropping with an appropriate N input, which acquired comprehensive performances in terms of productivity, environmental impacts as well as economic profits, would be an optimal alternative system in the NCP.

Although intercropping is a common technique that has been widely applied, the effect of phosphorus (P) fertilization on productivity of a fully-mixed perennial intercropping system composed of four species, including two legumes and two grasses, has rarely been studied. The objective of this study was to determine the effect of interspecific interactions on forage yield and the influence of P application on interspecific competitiveness and yield in a fully-mixed intercropping system of alfalfa (Medicago sativa L.), sainfoin (Onobrychis viciifolia Scop.), orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.). A three-year (2016–2018) field experiment was conducted in central China with an annual rainfall and temperature of 456 mm and 9.5 ℃, respectively. Five legume and grass seeding ratios (L: G) of 5:5, 4:6, 3:7, 6:4, and 7:3 were included, with four monocultures used as the control. The total forage yield was measured when 20% of the alfalfa flowers had opened (BBCH 62). Competitiveness indices, including the land equivalent ratio (LER), aggressivity (A), relative crowding coefficient (K values), competitive ratio (CR), and actual yield loss (AYL), were assessed. The total forage yield increased under fully-mixed intercropping in 2017–2018 when a transgressive overyielding advantage was attained, which was contributed by the interspecific interactions and P application. Moreover, the maximum yield and highest intercropping advantage appeared in L: G 3:7 and L: G 5:5 under 80 kg ha−1 P application in 2017–2018. Additionally, adequate P (80 kg ha−1) contributed to higher A values, K values, CR, and AYL of alfalfa and orchardgrass than in sainfoin and tall fescue, which suggested greater interspecific benefits and land-use efficiency. The fully-mixed intercropping system of alfalfa, sainfoin, orchardgrass, and tall fescue realized these potential advantages by coordinating interspecific interactions and environmental resources, which were manipulated by P application.