Giorgio Testa

Agriculture is facing several challenges related to its sustainability. In this regard, the need to reduce its environmental impact related to the use of synthetic inputs and its potential role in mitigating global warming and climate change call for a review of crop management. In this context, and in the framework of achieving sustainable development goals, the use of organic fertilizers and bio-waste represents a valuable contribution to the agricultural transition towards a bioeconomy model by reducing the negative impacts of waste disposal. Farmyard manure, composts, digestate from agrifood processes, and biochar are, among organic fertilizers, commonly used to manage soils and support crop growth. These fertilizers can provide essential nutrients, improve structure, and enhance microbial activity, thus increasing soil fertility and agriculture sustainability. While organic fertilizers offer the benefits of soil fertility and plant nutrition, their impact on greenhouse gas (GHG) emissions is complex and varies depending on factors such as fertilizer type, soil conditions, and management practices. Although organic fertilizers may initially increase GHG emissions, they often lead to carbon sequestration in soils highlighting a negative C balance. Additionally, organic fertilizers promote a reduction in fossil fuel consumption used for synthetic fertilizer production, further contributing to GHG emissions’ reduction. Therefore, while organic fertilizers pose challenges in managing GHG emissions, their various benefits warrant careful consideration and strategic implementation in agricultural systems.

The persistence of perennial herbaceous species is threatened by increasing aridity. However, summer dormancy is a strategy conferring superior survival to grasses adapted to hot and dry summers. The role of temperature on the induction of summer dormancy was investigated in the perennial grass Dactylis glomerata to analyse the potential expression of this strategy under warmer climates. We tested seven populations of D. glomerata originating from Morocco to Norway across the same latitudinal gradient in a five‐site experiment. One population of the highly summer‐dormant grass Poa bulbosa was used as a reference. Plants were grown from autumn in pots under full irrigation for 1 year mostly under open‐air shelters. Heading date (ear emergence preceding flowering) was recorded and foliage senescence was assessed from end of spring until autumn. The maximum plant senescence under summer irrigation indicated the level of dormancy expression. Summer dormancy onset, release, expression and duration were modelled as a function of climatic variables. From north to south, the duration of summer dormancy of the Mediterranean populations of D. glomerata and P. bulbosa ranged from 0 to 122 days, and 79 to 200 days, respectively. P. bulbosa was always completely dormant, while dormancy expression of D. glomerata was positively correlated with the sum of temperatures from winter onset ( R 2 = 0.57) and with the mean of minimum temperatures in summer ( R 2 = 0.73). Dormancy onset, release and duration were also positively correlated with thermal time from winter onset, while the duration of summer dormancy was longer as maximum temperatures increased. Mapping the European regions with climates allowing the expression of summer dormancy in D. glomerata showed that the potentially inductive areas for this strategy may expand in parallel with increasing summer aridity under a future climate warming scenario. Synthesis . The large phenotypic variability of the expression of summer dormancy in D. glomerata was driven by temperature, suggesting that this strategy may have a greater role in higher latitudes to increase plant survival over the predicted hotter and drier summers. Leveraging this strategy for the choice and selection of suitable populations could enhance future adaptation of major perennial grasses to climate change.