Wheat-Persian clover temporary intercropping for wheat quality and weed management. A Participatory Learning and Action Research project

This thesis is embedded within the paradigm of Agroecology, the science, practice and movement of agri-food systems. In particular, this PhD thesis deals with common wheat-Persian clover temporary intercropping, where two crops are simultaneously cultivated in the same space for a significant part of their life time. In temporary intercropping, adding one extra crop (i.e. planned biodiversity) is done to obtain specific agro-ecosystem services. In our experiments, the Persian clover is incorporated into the soil at the wheat stem elongation phase, with the scope of providing an organic fertilization for the wheat crop and in turn improving grain quantity and quality, as well as controlling weeds. Temporary intercropping has proven to provide benefits in terms of increased productivity, resilience to disturbance, stability of outputs, weed smothering capacity, soil chemical, physical and biological improvements, climate change mitigation. Yet farmers in the area of study do not adopt this practice, and also hardly convert to other forms of ecological intensification (e.g. organic agriculture). This thesis then tackles the subject both from an agronomic and a socio-ecological perspective, employing natural science as well as social science methods. The research is interested in understanding: i) the socio-ecological system where arable farms operate and the barriers and drivers of adoption of agricultural innovations; ii) the effect of temporary intercropping on wheat, clover and weed biomass, plant nitrogen uptake, and wheat grain quality; iii) the effect of temporary intercropping on weed abundance, weed community diversity and composition; iv) the role of systems thinking and Participatory Learning and Action Research methodologies (PLAR) in the knowledge production of agricultural innovations, as well as on the researcher’s own learning process. We set up two farm experiments in the growing season 2015/2016 and 2016/2017, both embedded in the cropping systems of two arable farms in the surrounding of Pisa, central-western part of Italy. We tested common wheat-Persian clover temporary intercropping against a farming control treatment (fertilized wheat as a sole crop, customarily sown in single rows) and an ecological control treatment (CONTROLSTRIP, unfertilized wheat as a sole crop, sown in paired rows). We used the field trials to perform biomass, weed, SPAD, height samplings, and consequent laboratory analysis; we also organized focus groups and field days on the farm sites to engage stakeholders during the PLAR process. We found that farmers are forced to think about the short-term financial return of their activity, while they face serious environmental issues. This may push them to adopt alternative practices in the future, helpful for the long-term sustainability of their agro-ecosystems. Factors other than financial are related to the farmer’s decision to adopt or reject an innovative. Intercropping, for example, is largely opposed cause it presents management and logistic problems. We found that Persian clover at early growth stages competes with wheat in terms of aboveground biomass, but facilitates N uptake. At harvest, wheat protein content and wheat nitrogen concentration are 13% higher in the intercropped wheat than in both control treatments. Moreover, we showed that the co-existence of the two species in the temporary intercropping system significantly decreases weed density at early stages compared to both control treatments. We also found that weed diversity, especially of dominant species, decreases in the intercropping system compared to the control treatments. Lastly, we witnessed the occurrence of learning in the various phases of the PLAR process: participants produced and acquired knowledge on technical issues related to intercropping, to wheat production, and to the political dimension of their activity. We conclude that farmers may take into consideration temporary intercropping as one of the alternative measures for improving wheat quality and managing weeds in organic and low-input arable farming systems. Research and extension institutions should consider systems thinking and the Participatory Learning and Action Research approach as useful tools to develop and assess appropriate farming innovations.