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Winter cereals play a crucial role in human diets. The initial impacts of climate change on these strategic crops include yield stagnation and increased yield variability (Olesen et al., 2011). Projections indicate that for every additional degree Celsius of temperature increase, global wheat production could decrease by 6% (Asseng et al., 2015). Climate change impacts and adaptation strategies vary regionally due to interactions with soil, existing climate conditions, and agricultural practices (Olesen et al., 2011). Effective management practices can compensate the effects of climate variability, emphasizing the need for region-specific studies to identify suitable adaptation strategies. In irrigated areas, compensating for reduced precipitation risk can be feasible, but addressing temperature rise presents significant challenges. This study aims to empirically evaluate the effectiveness of different N fertilisation strategies to adapt to warming on winter cereals in Mediterranean irrigated conditions.
An on-farm field experiment was established in the Ebro valley (Sucs, Lleida, Spain; 41°41'50.0"N 0°26'51.1"E) in a surface irrigated area, for 2 winter cropping seasons (2022-2023, 2023-2024) in the framework of the ECO-TRACE project. Winter hybrid wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) were cropped on the first and second cropping seasons, respectively, under two climate scenarios: current climate and warming. Passive open-top chambers (OTC) were used to simulate warming, adapted from the design of Welshofer et al., (2018). Six N fertilisation scenarios were also assessed: control (0N); business as usual (BAU), consisting of a pre-sowing fertilisation with pig slurry (220 kg N ha-1 yr-1) and top-dressed synthetic fertiliser (70 kg N ha-1 yr-1); full slurry (the sole application of pig slurry before sowing at same rate than BAU); full synthetic, including pre-sowing and top-dressing synthetic fertilisation (50 and 120 kg N ha-1 yr-1, respectively); and two treatments including a mixture of legumes (Medicago sativa L. and Trifolium repens), undersown in one treatment as living mulch and in the other as non-living mulch. Treatments were assessed using a split-plot design with 3 replications. Grain yield, its components, above-ground biomass, and their N concentration were measured at physiological maturity. Air (at 12.5 cm), soil (at 10 cm depth), and soil surface temperature were continuously monitored with sensors, along with soil volumetric moisture.
The 2022-2023 cropping season was dry from October until May (110 mm, 39% of the average), offset by 3 irrigation events of 100 mm each. During the reproductive phase, in April and May, mean temperatures exceeded the average by 5ºC, reaching above 28ºC for 7 days. Legumes couldn’t get satisfactorily established. Warming led to an increase of monthly air, soil surface and soil temperature of 1.5 and 2 and 2.4ºC compared to the current climate, respectively, and a decrease of soil volumetric moisture of 12%. Warming reduced grain yield and above-ground biomass production by 20% (6.2 vs. 7.6 t ha-1, 14% Hº, p=0.01) and 11%, respectively, compared to the current climate. This was related to yields components with i) less grains per spike (34.9 vs. 41.9, p<0.01), and ii) a lower TGW (39.7 vs. 43.9, p<0.01) under warming. TGW was also affected by the fertilisation scenarios, with lower values in BAU (35.5 g) compared to full synthetic (41.5 g) and 0N (43.9 g) (p<0.01). Warming increased grain and biomass N concentration due to dilution effect (2.21 vs. 1.96% for grain, and 1.37 vs. 1.14% for biomass, respectively) (p<0.01). As result, crops under warming climate, in both BAU and full synthetic scenarios, exhibit reduced uptake of grain N compared to current climate (p<0.01).
Fertilisation strategies failed to counteract the significant impacts of warming; instead, some resulted in reduced grain N uptake, indicating lower resilience. Further validation of these preliminary findings will be presented based on the results of the on-going 2023-2024 cropping season.
References
Asseng, S., F. Ewert, P. Martre, R.P. Rötter, D.B. Lobell, et al. 2015. Rising temperatures reduce global wheat production. Nat. Clim. Chang. 5(2): 143–147. doi: 10.1038/nclimate2470.
Olesen, J.E., M. Trnka, K.C. Kersebaum, A.O. Skjelvåg, B. Seguin, et al. 2011. Impacts and adaptation of European crop production systems to climate change. Eur. J. Agron. 34(2): 96–112. doi: 10.1016/j.eja.2010.11.003.
Welshofer, K.B., P.L. Zarnetske, N.K. Lany, and L.A.E. Thompson. 2018. Open-top chambers for temperature manipulation in taller-stature plant communities. Methods Ecol. Evol. 9(2): 254–259. doi: 10.1111/2041-210X.12863.
| Keywords | adaptation, climate change, open top chamber, field work. |
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