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.
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1 Introduction
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). Perennial cereal grain crops are more robust and multifunctional than annual crops (Ryan et al. 2018). 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 Kernza™ (Fig. 1). The selection was based on flavour, ease of threshing, large seed size, resistance to shattering, lodging resistance, ease of harvest and perennial growth, and was identified as the most promising species among 100 other perennial grasses (Wagoner and Schauer 1990). While plant breeding improves grain yields, it has been suggested also 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 improved agroecosystem resilience (Ryan et al. 2018). Taking the landscape perspective into account, multifunctionality is vital and the inclusion of elements of perennial crops in the production landscape may provide a higher delivery of several ecosystem services beyond the provisioning service of crop yields (Asbjornsen et al. 2014; Landis 2017) (Fig. 2).
The inclusion of legumes in the cropping system provides a wider range of ecosystem services like the increase in the N use efficiency (NUE) (Jensen et al. 2020), leading to a more sustainable agricultural production. Moreover, biological N2 fixation reduces the need for synthetic N fertilisers (Jensen et al. 2020) and reduces environmental costs related to fertiliser production, transportation and use, not the least in terms of climate change (Jensen et al. 2012). Intercropping IWG with perennial legumes makes atmospheric N2 available to the production system via symbiotic N2 fixation. With time, fixed N in legume residues and exudates are mineralised and made available to the perennial cereal (Crews et al. 2016), while N also may be transferred from legumes via mycorrhizal networks (Johansen and Jensen 1996; Thilakarathna et al. 2016). Niche complementarity is a well-known mechanism driving coexistence resulting in potential over-yielding (Gross et al. 2007). This mechanism often erases or supplements the mutual competition pressure between the legume and cereal crops. It is well-known that intercropping cereals and grain legumes result in higher and more stable grain yields, and a higher cereal protein concentration compared to the sole crop cereals (Bedoussac et al. 2015). However, for the novel production systems including IWG, studies on intercropping in Kernza production are sparse and results contradictory. While Dick et al. (2018) did not find and effect of intercropping with alfalfa (Medicago sativa), sweet clover (Melilotus officinalis) and white clover (Trifolium repens) on Kernza grain production, Tautges et al. (2018) found that the yield loss with stand age was reduced when IWG was intercropped with alfalfa (Medicago sativa). Furthermore, IWG has been found to provide suitable forage for beef and dairy cows, as well as for growing heifers, and that intercropping IWG with red clover (Trifolium pratense) increased the forage nutritive value in the fall (Favre et al. 2019).
Intermediate wheatgrass has been shown to tolerate partial-season irrigation deficits better than other perennial grasses (Orloff et al. 2016) and to maintain a relatively high water use efficiency during the growing season (Culman et al. 2013; Oliveira et al. 2019). This is an important feature in the current climatic conditions, where drought events are expected to increase in frequency and severity in southern Europe (Roudier et al. 2016), but also for northern Europe (SMHI 2019). The performance of perennial grasses can be related to the capability of sustained aboveground biomass production under dry conditions through enhanced water use efficiency (WUE), which has been proven to occur in C3 grasses (Kørup et al. 2018), often resulting from the response mechanism of reducing discrimination against 13C in photosynthesis (Mårtensson et al. 2017). In addition, the larger root system of IWG allows access to water in deeper soil layers, while the annual crops do not have access to these resources (Vico and Brunsell 2018). Dry growing conditions make the soil nutrients, especially N, immobile, resulting in reduced NUE. Indeed, the relationship between crop water use, WUE and grain NUE has been confirmed (Dalal et al. 2013).
To our knowledge, research on agronomy and nitrogen nutrition in IWG and Kernza grain production has not yet been carried out in Scandinavia to any large extent, neither in sole cropping nor in intercropping with perennial legumes. This study is the first one to determine the agronomic performance and nitrogen acquisition of IWG when grown under the temperate climate of southern Sweden with and without a perennial legume companion/service crop during the initial three years. The study also demonstrate the capability of sustained aboveground biomass production under dry conditions through enhanced water use efficiency as indicated by the downregulation of 13C discrimination. To elucidate the effect of intercropping on IWG, we pose the following hypothesis:
Intercropping IWG with alfalfa will increase IWG grain and straw biomass yields, N concentrations and N accumulated in the IWG biomass, as well as reduce the discrimination against 13C in IWG under dry conditions.
2 Methods and materials
2.1 Experimental design
The SITES (Swedish Infrastructure for Ecosystem Science) Agroecological Field Experiment (SAFE), is a long-term south Swedish cropping system large-scale experimental facility, was established in 2016 on previously conventionally managed land. The SAFE is located at the SITES Lönnstorp Research Station, SLU, in Alnarp (55.65° N, 13.06° E) in a region with a humid continental climate (Fig. 3). The soil type is a sandy loam soil (67% sand, 18% clay), with a soil pHH2O (0–30 cm) of 7.3, and 0.9% soil organic matter content. Soil nutrient conditions for the site correspond to 51 mg kg−1 of aluminium lactate extractable P, 0.36 g kg−1 total P, 65 mg kg−1 aluminium lactate extractable K, 1.4 g kg−1 total K and a total N content of 0.2 %. The SAFE has a block design with spatially contained blocks where the geographical layout was guided by initial measurements on soil variables (pH, moisture, nitrogen levels, etc.) to ensure similar conditions within the blocks. The SAFE includes a perennial cereal grain system, representing a model for future potential perennial cereal grain production under low input organic management. The perennial cereal grain system in SAFE holds a monocrop with IWG and an intercrop with IWG and alfalfa (Medicago sativa cv. Power 4.2; Fig. 2) in large plots (48 × 50 m). Seeds of intermediate wheatgrass were accessed from the cycle 3 (2014) germplasm of the perennial grain breeding program of The Land Institute (TLI) of Salinas, Kansas, USA (Zhang et al. 2016). The seeds were used to establish a local seed production plot (5 kg sown on 3000 m2 in September 2014) for the establishment of the perennial systems in SAFE.
The IWG sole crop and IWG-alfalfa intercrop was sown in May 2016 with complementary sowing in September 2016 (Table 1). Both the sole crop and the intercrop were sown with 25 cm row spacing with alternate rows of IWG and alfalfa in the intercrop (i.e. replacement design). The IWG sowing density was not possible to record, due to faults in the sowing equipment, which also led to the complementary sowing September 2016. The density was estimated to be approximately 17 kg ha−1. The sowing density of alfalfa inoculated with Sinorhizobium meliloti was 8 kg ha−1. In 2017, the IWG and IWG-alfalfa intercrop was fertilised using 444 kg Biofer® ha−1 year−1 (Gyllebo gödning AB, Malmö, Sweden; Biofer is certified for organic farming) (444 kg Biofer correspond to 40 kg N, 12 kg P and 4 kg K ha−1 year−1). In 2017, row crop cultivator was used for mechanical weeding in the IWG sole crop. The alfalfa in the IWG-alfalfa intercrop was cut in May 2017 to restrict alfalfa from overgrowing the IWG and the alfalfa residues were left to decompose in the rows as a green manure. In 2018 and 2019, 17 tonnes of biogas digestate per hectare−1, corresponding to 35-40 kg N ha−1, were applied as fertiliser to the IWG sole crop and intercrop. No weed management substance was applied in 2018 and 2019.
2.2 Sampling and analyses
Aboveground plant material was sampled in four 0.25 m2 subplots in each experimental plot before harvest in 2017, 2018 and 2019. The grain and biomass yield of IWG, the biomass yield of alfalfa and the biomass of weeds were determined after threshing and drying (65 °C, 48 h). The dry matter harvest index of IWG was calculated as the percentage grain yield of total dry matter, and the nitrogen harvest index was calculated as the percentage grain N accumulation of total N accumulation. The proportion of C and N, and the isotopic composition of 13C and 15N, was analysed on dried (65 °C, 48 h), milled (<1 mm) plant material using Dumas combustion on an elemental analyser (CE 1110, Thermo Electron, Milan, Italy) coupled in continuous flow mode to a Finnigan MAT Delta PLUS isotope ratio mass spectrometer (Thermo Scientific, Bremen, Germany). The isotopic analysis was done at the Department of Geosciences and Natural Resource Management at the University of Copenhagen.
2.3 Land equivalent ratio
The Land Equivalent Ratio, LER (Willey and Osiru 1972), is the area of legume and cereal monocrops required to produce the same amount of grain as one unit area of the cereal–legume intercrop. Since no monocrop of alfalfa was available, the partial Land Equivalent Ratio of IWG, pLERIWG, was calculated as the ratio between IWG grain dry matter yield in the monocrop and the intercrop (Eq. 1).
2.4 Nitrogen fixation and soil N acquisition in alfalfa
The 15N abundance in legume and non-legume samples, expressed as δ15N (‰ deviation from the 15N abundance in atmospheric N2; Unkovich et al. 2008), was used to calculate the proportion (%Ndfa; Eq. 2) and the amount (NFIX; Eq. 3) of N in the aboveground legume biomass that was derived from biological N2 fixation.
The mean δ15N value of the IWG and weed samples from each experimental plot was used as δ15Nreference to calculate %Ndfa in the legumes present in the same plot. The B value for alfalfa, i.e. the δ15N in the legume when relying on N2 fixation as its only N source, was −0.677 (Unkovich et al. 2008), and is included in the equation to account for discrimination against 15N during N2 fixation and N translocation within the legume plant (Högberg 1997). The values of legume N accumulation (N concentration multiplied by biomass dry weight) and %Ndfa were used to calculate the amount of legume N derived from N2 fixation (Eq. 3). The amount of N derived from the soil and fertiliser (NSOIL) constitutes the remaining proportion N acquired (Eq. 4).
2.5 Discrimination against 13C
Natural abundance of 13C was used to calculate the discrimination against 13C (Δ13C), which is positively related with water use efficiency (Farquhar et al. 1982; Farquhar et al. 1989; Farquhar and Richards 1984; O’Leary 1981). The 13C composition (δ13C) is given by the measured ratio of 13C/12C and the Vienna Pee Dee Belemnite reference material, where RPDB = 0.01117960 (Coplen 2011) (Eq. 5) (Farquhar et al. 1982; O’Leary 1981; O'Leary 1988; Park and Epstein 1960). The discrimination against 13C was calculated (Eq. 6), using δatmos and δplant which refer to the carbon isotope composition of the atmospheric CO2 and plant material, respectively. The carbon isotope composition of the atmospheric CO2, δatmos, is approximately −8.0‰ (Farquhar et al. 1989; O'Leary 1988).
2.6 Statistics
The effects of intercropping on the grain and straw yields, the N concentrations in dry matter, the N accumulated in the aboveground biomass and the discrimination against 13C were statistically analysed using a factorial design with repeated measures. In the model, block was a random factor and the ‘crop’, ‘year’ and the interaction between ‘crop’ and ‘year’ were fixed factors with the correlation structure AR(1) for observations from the same block and ‘crop’. The analysis was done using proc MIXED in SAS (SAS 9.4) with Kenward-Rogers method for denominator degrees of freedom. Tukey’s post hoc test at the p < 0.05 level of significance was used for pairwise differences between treatment levels. The interaction ‘crop*year’ was significant in all analyses except for intermediate wheatgrass straw yield, harvest index and nitrogen concentration in intermediate wheatgrass grain. The amount of N2 fixation in legumes was analysed with only ‘year’ as fixed factor. Bivariate parametric Pearson correlation tests, with p < 0.05 as the level of significance, were run to explore the relationships between discrimination against 13C, yield, N concentrations and N accumulation. The correlations were run on data separated by year (2017, 2018 and 2019), cropping system (monocrop and intercrop) and yield fractions (grain and straw). The correlations were performed with IBM Statistics SPSS software.
3 Results and discussion
3.1 Dry matter production
The IWG grain dry matter yield varied between 0.26 and 0.88 t ha−1 in the monocrop and between 0.28 and 0.55 t ha−1 in the intercrop (Fig. 4). The IWG grain dry matter yield was significantly higher in the monocrop than the intercrop in 2017, and significantly greater in 2017 than during the subsequent 2 years in both the monocrop and the intercrop (Fig. 4). The IWG straw biomass did not follow the same pattern as the IWG grain, but was rather stable throughout the 3 years. The IWG straw dry matter yield varied between 5.4 and 8.2 t ha−1 in the sole crop and between 4.6 and 5.3 ha−1 in the intercrop (Fig. 4). In the IWG monocrop, the IWG straw dry matter yield was significantly lower in the dry year 2018 and then in 2017 and 2019, while in the intercrop, IWG straw biomass was similar over all three experimental years. The alfalfa biomass yield varied between 3.8 and 4.5 t ha−1 and did not differ significantly between the experimental years. The IWG grain partial land equivalent ratio in the intercrop was higher in 2018 and 2019 than in 2017 (Table 2). The harvest index (HI) of IWG was highest in both crops in 2017, with declining values over the 3 experimental years (Table 2).
The levels and pattern of the IWG grain yields are in coherence with what other reports (Hunter et al. 2020; Jungers et al. 2019; Tautges et al. 2018), despite the comparably low amount of fertiliser used in our low-input management design. The reported IWG grain dry matter production levels are mainly stemming from the IWG germplasm coming from the TLI third cycle of IWG, which is quite an early line in the IWG breeding programme. The programme is constantly making progress towards higher seed yield (DeHaan et al. 2013) together with other important agronomic features (Wagoner and Schauer 1990). In parallel to a higher grain yield, the longevity of IWG grain production is also questioned. The decline in grain yield over years may be reduced under high fertilisation rates (120–160 kg N ha−1) (Culman et al. 2013; Jungers et al. 2019), but may be simultaneously associated with stronger environmental impacts through leaching and N2O emissions. However, the large and deep root system of IWG (Sprunger et al. 2019) and the high capability of IWG to exploit the soil volume (Duchene et al. 2020), compared to annual crops, may reduce the leaching risk to a minimum (Culman et al. 2013; Jungers et al. 2019).
The higher IWG grain partial land equivalent ratio in the intercrop in 2018 and 2019, than in 2017, indicates the better growing conditions for IWG when intercropped with alfalfa. The increasing amount of N becoming available from the alfalfa over time, together with a lower density, and thus lower intraspecific competition, of IWG in the intercrop may also positively influence the performance of IWG in the intercrop compared to in the monocrop. The HI follows the pattern of declining grain yield over years, which is in line with the findings from Hunter et al. (2020) who reported that yield of IWG declined, due to low grain number, few highly productive spikes, increased intra-stand competition and declined resource allocation to reproduction over time, motivating future studies focused on maintaining seed set, and thus productivity from a management perspective. The decline in the harvest index was less pronounced in the intercrop as compared to the sole crop, which may be attributed to the expected improved nitrogen supplies provided by the alfalfa root and shoot turnover resulting in a green manure (Bedoussac et al. 2015; Jensen et al. 2020). The growing season of 2018 was unusually dry and warm, resulting in severe drought effects. The hampered growth is not only attributed to physiological constraints, but also to restricted ability of the plant to make use of nutrients, due to lack of precipitation and resulting low soil moisture level. In fact, the digestate applied that year was crusting on the soil surface, seemingly inaccessible to the crops during peak of growth, but later in the season, the nutrients may have become accessible. However, alfalfa did sustain its growth also under the dry conditions in 2018, probably due to its ability to biologically to fix N2.
3.2 Nitrogen concentration in dry matter and N accumulation
The grain N concentration of IWG varied between 2.7 and 3.5% N. Several intercrop studies of annual cereals and grain legumes have shown that intercropping increases the nitrogen/protein concentration of the intercropped cereal grain and potentially also the baking quality (Gooding et al. 2007; Hauggaard-Nielsen et al. 2008). In 2018, the N concentration of IWG grain is higher when intercropped than when grown as monocrop, while the N concentration in the IWG straw was higher in the intercrop compared to the monocrop in each individual year (Table 3). In the intercrop, the N concentration in IWG straw was higher in 2017 as compared to in 2018 and 2019, while there was no difference between years in the monocrop. The N concentration of the alfalfa biomass was stable at approximately 2.6% N throughout the 3 years (Table 3).
Higher N concentration of the harvested IWG material from intercropped conditions may have positive implications for the use of the IWG straw as forage in animal production as well as the use of the IWG grain in the food industry. Surprisingly, the N concentration in the grain and straw of IWG tends to decline with time both in the sole and the intercrop. Even though just evident as a weak tendency, it can be seen in both the monocrop and the intercrop as well as for both grain and straw components of IWG. This decline may be a result of the low-input management strategy applied to the two crops in this particular experiment. The land of the experimental site was previously used for conventional cropping with a crop rotation based on only annual crops supplied with generous nutrient additions. Thus, the first experimental year is highly influenced by carry-over effects from previous management, while the subsequent years better represent the targeted low-input system with limited nutrient resources. In the light of the multipurpose use of IWG, i.e. both as a grain and feed crop, intercropping is known to improve the nutrient concentration of the biomass and thus its suitability as animal feed (Favre et al. 2019) or biogas digestate usage of the straw fraction. In the context of a changing climate, in terms of the more frequent drought spells, the higher N concentration in IWG grain in the dry year of 2018 may indicate a suitable crop for climate adaptation.
The N accumulation (Fig. 5) of IWG grains was higher in 2017 than in 2018 and 2019 in the monocrop. The N accumulated in IWG grains in the intercrop was higher in 2018 than in 2019, while neither differed from 2017. Furthermore, the N accumulated in IWG grains was higher in the monocrop in 2017 than in the intercrop in 2017, while there was no difference between the cropping systems on 2018 and 2019. In the monocrop, the N accumulation of the IWG straw (Fig. 5) was higher in 2017 compared to in 2019. In the intercrop, the N accumulated in IWG straw was higher in 2017 compared to in 2018 and 2019. No differences were found between the two cropping systems within each year. The amount of N accumulated in alfalfa did not differ between years. Neither did the amount of N accumulated from the soil and fertiliser, but the amount of N derived from the atmosphere was higher in 2017 than in the 2 subsequent years (Fig. 5). Our study shows that high amounts of N in lucerne (63 ± 27, 89 ± 2.8 and 87 ± 4.3%; Fig. 5) are derived from the atmosphere and smaller amounts of N (11 to 37%) are derived from soil. The proportion of N2 fixed from the atmosphere showed a tendency to be higher in 2018 and 2019 compared to in 2017 (F = 4.69 (df = 2) p < 0.1).
The amount of accumulated N in the studied systems is clearly connected to the amount of biomass produced, further supporting the argument above that growing conditions and production are related to the availability of resources (Hawkesford 2011), in this case nitrogen. The patterns of the N accumulation of IWG grains most probably arise from a depletion of time in the cropping systems, with the pattern more pronounced in the monocrop than in the intercrop (where the depletion is less pronounced) since legumes improve the availability of soil N (Jensen et al. 2020). Interestingly, the rather high level of accumulated N in IWG grain in the intercrop in 2018 potentially demonstrates intercropping as a management tool for production security under unexpected or deviating climate events, such as drought. The lowest values of accumulated N in IWG grains were found in the monocrop in 2019, which may indicate that the IWG crop received a suboptimal supply of N with the low-input management. However, the legume companion is expected to supplement some of the nutrient requirements with time and the tendency of increased fixation of nitrogen from the atmosphere somewhat meets this expectation. This tendency reflects the interspecies interaction in intercrops of cereals and legumes, where the cereal most often acquires a larger proportion of the soil N in comparison to its proportional abundance, which leads to increased N2 fixation in the grain legume crop (Rodriguez et al. 2021). On the other hand, Li et al. (2019) identified a need for fertilisation to support the development of IWG in the establishment phase when intercropped with alfalfa, possibly indicating that alfalfa is too aggressive for intercropping with IWG, at least when established at the same time point. The study of Li et al. (2019) needs validation in the field, but gives clear indications that we need more knowledge on appropriate intercropping companion and establishment practices for IWG production. Surprisingly, the aboveground N accumulation in IWG straw did not differ between the monocrop and the intercrop in either of the 3 years, despite the IWG straw biomass was generally lower in the intercrop than in the sole crop. Under intercropped conditions as those in this experimental setup, the cereal is established on half of the area compared to that in the monocrop. Thus, our results clearly demonstrate the benefits of intercropping in terms of nutritional value (Favre et al. 2019; Bedoussac et al. 2015), irrespective of the end-usage of the crop.
3.3 Discrimination against 13C as an indicator of water use efficiency
In the dry year of 2018 (Fig. 3), the discrimination against 13C in the IWG aboveground biomass was lower in both the sole cropped and the intercropped system compared to the other years, i.e. 2017 and 2019 (Table 3). This was probably a response to drought, which has been observed in other C3 forage grasses (Mårtensson et al. 2017), where improved water use efficiency is gained through stomatal closure (Farquhar et al. 1982; Farquhar et al. 1989). Water limitation is often closely connected to lowered availability of nutrients (Kreuzwieser and Gessler 2010) partly through the limitation of microbial activity (Borken and Matzner 2009) and hence nutrient mineralisation, but also through the restricted transport and uptake of soil water and the associated mass flow uptake of nutrients. Water limitation seems to be better met when intercropping with legumes, where IWG showed even lower discrimination against 13C when intercropped with alfalfa. Some varieties of alfalfa have been described as drought resistant (Guo et al. 2005), due to their extensive and deep root system (Dolling et al. 2003; Julier et al. 2017). Indeed, the reduced discrimination under drought also occurred in alfalfa shoots, where the discrimination against 13C was lower in 2018 compared to in 2017 and 2019 but this legume exhibits low stomatal closure in the early stages of drought (Durand 2007). Furthermore, it can be hypothesised that alfalfa potentially provides a shading effect on the soil surface, thus reducing the evaporation and improving the soil water status.
Under intercropped management, discrimination against 13C in IWG grains was well correlated to IWG grain yield (ρ = 0.971, p < 0.05; data not shown) and IWG grain N accumulation (ρ = 0.987, p < 0.05; data not shown) in 2018. In 2019, positive correlations were found between discrimination against 13C in IWG straw and both IWG straw yield (ρ = 0.982, p < 0.05; data not shown) and IWG straw N yield (ρ = 0.961, p < 0.05; data not shown) in intercrops. These results clearly demonstrate the ability of IWG to improve water use efficiency, which may lead to downregulation of the discrimination against 13C to sustain photosynthesis under the dry summer of 2018 and the possibly still dry soils in 2019. These results are supported by other studies which have proven that IWG maintains relatively high water-use efficiency during the growing season (Culman et al. 2013; de Oliveira et al. 2020), which helps to mitigate water stress.
4 Conclusions
Here, we show for the first time potential benefits of the intercropping of perennial cereal crop, IWG, with alfalfa in terms of grain yield and biomass production in Scandinavia, also under a drought spell. In particular, the ability to acquire N2 from the atmosphere to the production system under intercropped conditions over the experimental period (2017–2019) illustrates the important function of acquiring additional nitrogen from the atmosphere into this production system, especially under dry conditions to sustain photosynthesis and, thus, growth. We suggest that perennial cereal crops intercropped with legume companions could be a suitable addition to cropping systems under the expected increased frequency of drought events.
Data availability
The data generated and analysed during this study are available from the corresponding author upon reasonable request.
Code availability
Not applicable.
References
Asbjornsen H, Hernandez-Santana V, Liebman M, Bayala J, Chen J, Helmers M, Ong CK, Schulte LA (2014) Targeting perennial vegetation in agricultural landscapes for enhancing ecosystem services. Renew Agric Food Syst 29:101–125. https://doi.org/10.1017/S1742170512000385
Bedoussac L, Journet EP, Hauggaard-Nielsen H, Naudin C, Corre-Hellou G, Jensen ES, Prieur L, Justes E (2015) Ecological principles underlying the increase of productivity achieved by cereal-grain legume intercrops in organic farming. A review. Agron Sustain Dev 35:911–935. https://doi.org/10.1007/s13593-014-0277-7
Borken W, Matzner E (2009) Reappraisal of drying and wetting effects on C and N mineralization and fluxes in soils. Glob Chang Biol 15:808–824. https://doi.org/10.1111/j.1365-2486.2008.01681.x
Coplen TB (2011) Guidelines and recommended terms for expression of stable isotope-ratio and gas-ratio measurement results. Rapid Commun Mass Spectrom 25:2538–2560. https://doi.org/10.1002/rcm.5129
Crews T, Blesh J, Culman SW, Hayes RC, Jensen ES, Mack MC, Peoples MB, Schipanski ME (2016) Going where no grains have gone before: From early to mid-succession. Agric Ecosyst Environ 223:223–238. https://doi.org/10.1016/j.agee.2016.03.012
Crews TE, Carton W, Olsson L (2018) Is the future of agriculture perennial? Imperatives and opportunities to reinvent agriculture by shifting from annual monocultures to perennial polycultures. Glob Sustain 1:1–18. https://doi.org/10.1017/sus.2018.11
Culman S, Snapp SS, Ollenburger M, Basso B, Dehaan L (2013) Soil and water quality rapidly responds to the perennial grain Kernza wheatgrass. Agron J 105:735–744. https://doi.org/10.2134/agronj2012.0273
Dalal RC, Strong WM, Cooper JE, King AJ (2013) Relationship between water use and nitrogen use efficiency discerned by 13C discrimination and 15 N isotope ratio in bread wheat grown under no-till. Soil Tillage Res 128:110–118. https://doi.org/10.1016/j.still.2012.07.019
de Oliveira G, Brunsell N, Crews TE, DeHaan L, Vico G (2020) Carbon and water relations in perennial Kernza (Thinopyrum intermedium): an overview. Plant Sci 295:735–744. https://doi.org/10.2134/agronj2012.0273
de Oliveira G, Brunsell NA, Crews TE, DeHaan LR, Vico G (2019) Carbon and water relations in perennial Kernza (Thinopyrum intermedium): An overview. Plant Science 295:110279. https://doi.org/10.1016/j.plantsci.2019.110279
DeHaan L, Wang S, Larson SR, Kantarski T, Zhang X, Cattani D, Viinanen TR (2013) Current efforts to develop perennial wheat and domesticate Thinopyrum intermedium as a perennial grain. Perennial Crops for Food Security, Proceedings of the FAO Expert Workshop, Genetics and breeding: State of the Art, Gaps and Opportunities. Corpus ID: 91322649. https://landinstitute.org/wp-content/uploads/2014/11/PF_FAO14_ch06.pdf
Dick C, Cattani D, Entz MH (2018) Kernza intermediate wheatgrass (Thinopyrum intermedium) grain production as influenced by legume intercropping and residue management. Can J Plant Sci 98:1376–1379. https://doi.org/10.1139/cjps-2018-0146
Dolling PJ, Ward PR, Latta RA, Ryder A, Asseng S, Robertson MJ, Cocks PS, Ewing MA (2003) Rate of root growth in lucerne varies with soil type in Western Australia. Australian Society of Agronomy. "Solutions for a better environment". Proceedings of the 11th Australian Agronomy Conference, 2-6 Feb. 2003, Geelong, Victoria. ISBN 0-9750313-0-9
Duchene O, Celette F, Ryan MR, Dehaan LR, Crews TE, David C (2019) Integrating multipurpose perennial grains crops in Western European farming systems. Agric Ecosyst Environ 284:106591. https://doi.org/10.1016/j.agee.2019.106591
Duchene O, Celette F, Barreiro A, Dimitrova Mårtensson LM, Freschet GT, David C (2020) Introducing perennial grain in grain crops rotation: the role of rooting pattern in soil quality management. Agron 10:1–17. https://doi.org/10.3390/agronomy10091254
Durand JL (2007) Effects of water shortage on forage plants. Fourrages 190:181–196
FAO (2013) Perennial Crops for Food Security. Proceedings of the FAO Expert Workshop 28-30 August, 2013, Rome, Italy. ISBN 978-92-5-107998-0
Farquhar GD, Richards RA (1984) Isotopic composition of plant carbon correlates with water-use efficiency of wheat genotypes. Aust J Plant Physiol 11:539–552. https://doi.org/10.1071/PP9840539
Farquhar GD, Oleary MH, Berry JA (1982) On the relationship between carbon isotope discrimination and the inter-cellular carbon-dioxide concentration in leaves. Aust J Plant Physiol 9:121–137. https://doi.org/10.1071/PP9820121
Farquhar GD, Ehleringer JR, Hubick KT (1989) Carbon isotope discrimination and photosynthesis. Annu Rev Plant Physiol Plant Mol Biol 40:503–537. https://doi.org/10.1146/annurev.pp.40.060189.002443
Favre JR, Munoz Castiblanco T, Combs DK, Wattiaux MA, Picasso VD (2019) Forage nutritive value and predicted fiber digestibility of Kernza intermediate wheatgrass in monoculture and in mixture with red clover during the first production year. Anim Feed Sci Technol:258. https://doi.org/10.1016/j.anifeedsci.2019.114298
Gooding MJ, Kasyanova E, Ruske R, Hauggaard-Nielsen H, Jensen ES, Dahlmann C, von Fragstein P, Dibet A, Corre-Hellou G, Crozat Y, Pristeri A, Romeo M, Monti M, Launay M (2007) lntercropping with pulses to concentrate nitrogen and sulphur in wheat. J Agric Sci 145:469–479. https://doi.org/10.1017/S0021859607007241
Gross N, Suding K, Lavorel S, Roumet C (2007) Complementarity as a mechanism of coexistence between functional groups of grasses. J Ecol 95:1296–1305. https://doi.org/10.1111/j.1365-2745.2007.01303.x
Guo ZG, Liu HX, Wang SM, Tian FP, Cheng GD (2005) Biomass, persistence and drought resistance of nine lucerne varieties in the dry environment of west China. Aust J Exp Agric 45:59–64. https://doi.org/10.1071/ea03119
Hauggaard-Nielsen H, Jørnsgaard B, Kinane J, Jensen ES (2008) Grain legume–cereal intercropping: the practical application of diversity, competition and facilitation in arable and organic cropping systems. Renew Agric Food Syst 23:3–12. https://doi.org/10.1017/S1742170507002025
Hawkesford MJ (2011) An overview of nutrient use efficiency and strategies for crop improvement. In: The molecular and physiological basis of nutrient use efficiency in crops, pp. 5-19. https://doi.org/10.1002/9780470960707
Högberg P (1997) Tansley Review No. 95 15 N natural abundance in soil-plant systems. New Phytol 137:179–203. https://doi.org/10.1046/j.1469-8137.1997.00808.x
Hunter MC, Sheaffer CC, Culman SW, Jungers JM (2020) Effects of defoliation and row spacing on intermediate wheatgrass I: Grain production. Agron J 112:1748–1763. https://doi.org/10.1002/agj2.20128
Jensen ES, Peoples MB, Boddey RM, Gresshoff PM, Hauggaard-Nielsen H, Alves BJR, Morrison MJ (2012) Legumes for mitigation of climate change and the provision of feedstock for biofuels and biorefineries. A review. Agron Sustain Dev 32:329–364. https://doi.org/10.1007/s13593-011-0056-7
Jensen ES, Carlsson G, Hauggaard-Nielsen H (2020) Intercropping of grain legumes and cereals improves the use of soil N resources and reduces the requirement for synthetic fertilizer N: a global-scale analysis. Agron Sustain Dev 40:5. https://doi.org/10.1007/s13593-020-0607-x
Johansen A, Jensen ES (1996) Transfer of N and P from intact or decomposing roots of pea to barley interconnected by an arbuscular mycorrhizal fungus. Soil Biol Biochem 28:73–81. https://doi.org/10.1016/0038-0717(95)00117-4
Julier B, Gastal F, Louarn G, Badenhausser I, Annicchiarico P, Crocq G, Emile JC (2017) Lucerne (Alfalfa) in European Cropping Systems. In: Legumes in Cropping Systems. CABI. ISBN 9781780644981
Jungers JM, Dehaan LH, Mulla DJ, Sheaffer CC, Wyse DL (2019) Reduced nitrate leaching in a perennial grain crop compared to maize in the Upper Midwest, USA. Agric Ecosyst Environ 272:63–73. https://doi.org/10.1016/j.agee.2018.11.007
Kørup K, Lærke PE, Baadsgaard H, Andersen MN, Kristensen K, Münnich C, Didion T, Jensen ES, Mårtensson L-M, Jørgensen U (2018) Biomass production and water use efficiency in perennial grasses during and after drought stress. GCB Bioenergy 10:12–27. https://doi.org/10.1111/gcbb.12464
Kreuzwieser J, Gessler A (2010) Global climate change and tree nutrition: influence of water availability. Tree Physiol 30:1221–1234. https://doi.org/10.1093/treephys/tpq055
Landis DA (2017) Designing agricultural landscapes for biodiversity-based ecosystem services. Basic Applied Ecol 18:1–12. https://doi.org/10.1016/j.baae.2016.07.005
Li S, Barreiro A, Jensen ES, Zhang Y, Dimitrova Mårtensson LM (2019) Early interspecific dynamics, dry matter production and nitrogen use in Kernza (Thinopyrum intermedium) - alfalfa (Medicago sativa) mixed intercropping. Acta Agr Scand B-SP 70:165–175. https://doi.org/10.1080/09064710.2019.1686164
Mårtensson LM, Carlsson G, Prade T, Kørup K, Lærke PE, Jensen ES (2017) Water use efficiency and shoot biomass production under water limitation is negatively correlated to the discrimination against (13)C in the C(3) grasses Dactylis glomerata, Festuca arundinacea and Phalaris arundinacea. Plant Physiol Biochem 113:1–5. https://doi.org/10.1016/j.plaphy.2017.01.021
O’Leary MH (1981) Carbon isotope fractionation in plants. Phytochem 20:553–567. https://doi.org/10.1016/0031-9422(81)85134-5
O'Leary MH (1988) Carbon Isotopes in Photosynthesis. BioSci 38:328–336. https://doi.org/10.2307/1310735
Orloff SB, Brummer EC, Shrestha A, Putnam DH (2016) Cool-season perennial grasses differ in tolerance to partial-season irrigation deficits. Agron J 108:692–700. https://doi.org/10.2134/agronj2015.0384
Park R, Epstein S (1960) Carbon isotope fractionation during photosynthesis. Geochim Cosmochim Acta 21:110–126. https://doi.org/10.1016/S0016-7037(60)80006-3
Rodriguez C, Dimitrova Mårtensson L-M, Jensen ES, Carlsson G (2021) Combining crop diversification practices can benefit cereal production in temperate climates. Agron Sustain Dev 41:1–14. https://doi.org/10.1007/s13593-021-00703-1
Roudier P, Andersson JCM, Donnelly C, Feyen L, Greuell W, Ludwig F (2016) Projections of future floods and hydrological droughts in Europe under a + 2 °C global warming. Clim Chang 135:341–355. https://doi.org/10.1007/s10584-015-1570-4
Ryan MR, Crews TE, Culman SW, DeHaan LR, Hayes RC, Jungers JM, Bakker MG (2018) Managing for Multifunctionality in Perennial Grain Crops. BioSci 68:294–304. https://doi.org/10.1093/biosci/biy014
SMHI (2019) State of knowledge and implications for adaptation and mitigation. Swedish Meteorological and Hydrological Institute. Ed: Ralf Döscher. 10.17200/Climate_Extremes_Sweden
Sprunger CD, Culman SW, Peralta AL, DuPont ST, Lennon JT, Snapp SS (2019) Perennial grain crop roots and nitrogen management shape soil food webs and soil carbon dynamics. Soil Biol Biochem 137:107573. https://doi.org/10.1016/j.soilbio.2019.107573
Tautges NE, Jungers JM, DeHaan LR, Wyse DL, Sheaffer CC (2018) Maintaining grain yields of the perennial cereal intermediate wheatgrass in monoculture v. bi-culture with alfalfa in the Upper Midwestern USA. J Agric Sci 156:758–773. https://doi.org/10.1017/S0021859618000680
Thilakarathna MS, McElroy MS, Chapagain T, Papadopoulos YA, Raizada MN (2016) Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review. Agron Sustain Dev 36. https://doi.org/10.1007/s13593-016-0396-4
Unkovich M, Herridge D, Peoples M, Cadisch G, Boddey B, Giller K, Alves B, Chalk P (2008) Measuring plant-associated nitrogen fixation in agricultural systems. Australian Centre for International Agricultural Research (ACIAR), Canberra. ISBN 978 1 921531 26 2
Vico G, Brunsell NA (2018) Tradeoffs between water requirements and yield stability in annual vs. perennial crops. Adv Water Resour 112:189–202. https://doi.org/10.1016/j.advwatres.2017.12.014
Wagoner P, Schauer A (1990) Intermediate wheatgrass as a perennial grain crop. In: Advances in new crops - proceedings of the First National Symposium NEW CROPS, Research, Development, Economics, Indianapolis, Indiana, October 23-26, 1988. Timber Press, Portland. ISBN: 0881921661
Willey RW, Osiru DSO (1972) Studies on mixtures of maize and beans (Phaseolus vulgaris) with special reference to plant population. J Agric Sci 79:519–529. https://doi.org/10.1017/S0021859600025909
Zhang X, Sallam A, Gao L, Kantarski T, Poland J, DeHaan LR, Wyse DL, Anderson JA (2016) Establishment and optimization of genomic selection to accelerate the domestication and improvement of intermediate wheatgrass. Plant Genome 9. https://doi.org/10.3835/plantgenome2015.07.0059
Acknowledgements
Financial support for this study is gratefully acknowledged from the Crafoord Foundation. This study has also been made possible by the Swedish Infrastructure for Ecosystem Science (SITES), in this case at the Lönnstorp Research Station at Alnarp, Sweden. We would also like to thank Ryan Davidson and Karl-Erik Gustavsson for valuable assistance in experimental management, sampling and laboratory analyses. Jan-Eric Englund and Adam Flöhr are gratefully acknowledged for valuable statistical assistance.
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Open access funding provided by Swedish University of Agricultural Sciences. The Crafoord Foundation 20160622
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Jensen was responsible for the development and design of the SAFE. Li carried out sample preparation for laboratory analyses. Dimitrova Mårtensson carried out statistical analyses. Results were interpreted by Dimitrova Mårtensson, Li, Barreiro and Jensen. The manuscript was written by Dimitrova Mårtensson with input from Li, Barreiro and Jensen.
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Mårtensson, LM.D., Barreiro, A., Li, S. et al. Agronomic performance, nitrogen acquisition and water-use efficiency of the perennial grain crop Thinopyrum intermedium in a monoculture and intercropped with alfalfa in Scandinavia. Agron. Sustain. Dev. 42, 21 (2022). https://doi.org/10.1007/s13593-022-00752-0
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DOI: https://doi.org/10.1007/s13593-022-00752-0