MITIORG Long-term Experiment Climatic change adaptation in organic farming: synergistic combination of hydraulic arrangement, crop rotations, agro-ecological service crops and agronomic techniques

Summary

As a result of the extreme rainfall events, temporary flooding of the soil, determining poor soil aeration, affects plant growth and survival. These frequent high intensity rainfalls, which usually occur after a very dry summer, and the climatic fluctuation in short- and long-term (especially in rainfall quantity), have been pointed out as the main climatic characteristics affecting the vulnerability of the Mediterranean basin to soil erosion. The inclusion in vegetable rotations (and best management) of cover crops provides soil cover and helps regulating microclimate and local hydrological processes, thus preventing soil erosion by wind and rainwater strength during extreme rainfall events, which reduces soil organic matter (SOM) content in the long run. Therefore, the innovation we propose is an experimental device combining a suite of functionally integrated techniques conceptually identified as ”layers”. The ultimate goal is to ensure the adaptation of horticultural systems to the extreme rainfall events, particularly in the Mediterranean area. The base layer is the soil hydraulic arrangement by means of soil surface shaping as a kind of ridge system, in which vegetable crops are cultivated both above the raised bed (ridges 2.5 m wide) and in the 2.5 m flat areas (or strips) between them. Rotation (the second conceptual layer) is designed avoiding cash crops cultivation during the winter-rainy period of the year in the flat strips, which can be waterlogged in the case of heavy rain and/or temporary flooding, as frequently have occurred in the study area over the last 10 years. In order to protect the soil from erosion and provide N to the system via biological fixation, a next conceptual layer based on tailored introduction of agro-ecological service crops (ASC) is implemented. These (cover) crops can promote in-field biodiversity, contribute to weed, pest and diseases management, NO3– leaching reduction, SOM improvement, etc. On the top of the ridges, a leguminous ASC is living mulched in the winter vegetable crop and maintained as a living ground cover throughout its cycle (controlling the growth by mowing). In the flat soil strips, the cash crops in rotation are always summer crops (e.g., tomato and lettuce), and pure ASC or mixtures of different proportions of legume and non-legume crops are cultivated (being potentially unaffected by temporary water excess) in the winter-rainy period as break crops. These break ASCs are terminated by the no-till roller crimper technique or they are green manured before the transplant of cash crops. The last layer consists of an organic fertilization strategy, by using commercial and/or on-farm fertilizers and amendments (e.g., anaerobic digestates and composted municipal solid organic wastes), to maintain or increase long-term SOM and fertility