The use of cover crops in climate change scenarios

Cover crops (CC) are emerging as key tools in agrosystems, providing essential ecosystem services for climate change adaptation and mitigation. The great diversity of possible cover crops and climate scenarios makes it necessary to investigate how combinations of these two factors (cover crop type and climate scenario) affect agrosystems.

The experiment was carried out with mesocosms with soil of a Typic Calcixerept, inside a growth chamber with continuous control and programming of temperature, humidity, luminosity and ventilation. The climatic scenarios studied correspond to an average temperature increase of +3 ^oC and three levels of rainfall or water availability of: +10%, -5% and -20% with respect to the records of the reference area in the center of the Iberian Peninsula in the period 1950-2015.

In this work, the effect of five CC was evaluated: i.e. 1) without CC. 2) With CC composed by a Brassica (Camelina sativa L.). 3) with CC composed of a grass (Hordeum vulgare L.). 4) with CC composed of a legume (Vicia sativa L.) and 5) with CC composed of a mixture of the three species mentioned above. After the simulation from October 15 to January 1, the total population of Fungi (ITS), Archaea (16SA), Bacteria (16SB), electrical conductivity, macro and micro nutrients in the rhizospheric soil were evaluated. In addition, the biomass production and their macro and micronutrient concentrations were quantified.

The results obtained were modulated by water availability and microbial activity in the soil. In this sense, an increase in the population of ITS and 16SB was observed as the available water increased, especially at the +10% level. These results allow us to establish that the increase in moisture favored microbial activity in the study conditions, which is related to greater mineralization of organic matter. The CC composed of grasses and +10% rainfall stood out with a greater contribution of plant biomass, revealing the importance of soil moisture and the presence of grasses to increase the contribution of organic matter to the soil. On the contrary, the lower water availability (-20%) and the soil without cover produced an increase in electrical conductivity with respect to other treatments, and adversely affected numerous variables.

Among the cover crops, the legume and the mixture proved to be less affected by changes in the amount of available water. In addition, the mixture exhibited a mechanism that enabled it to achieve the highest Mg concentration in the plant. Possibly because the acquisition traits of the different species showed some complementarity.

For future research, the study of these CC will be carried out under other climatic scenarios, in order to elaborate a digital twin of each CC that will provide a more accurate information on their effects on the agrosystem according to the expected temperatures and water availability. This could help to choose the best cover crop for each scenario and objective.