The objectives, obstacles and methodological strategy of axis 2 remain similar to those defined for NAILA 1. The objective is the study of biophysical and social functioning. On the one hand, it is a question of understanding the choices of the stakeholders and the resulting spatio-temporal arrangements (e.g., hydro-agricultural developments, land use, crop successions, technical itineraries) and on the other hand of characterizing the consequences on the biophysical processes linked to (1) green water (e.g., irrigation, evapotranspiration), (2) blue water (e.g., runoff, sediment transport, infiltration, aquifer recharge) and (3) contaminated water (e.g., transfers and reactivities of pesticides and emerging pollutants).
During NAÏLA1, cognitive and methodological advances made it possible to partially characterize the dynamics of agro systems, the dynamics of crop water consumption, the diffuse and concentrated contributions in erosive transport, while the study of agricultural contamination is an emerging theme in Tunisia. . The work has focused on individual processes and integrated functioning, on panels of large spatial and temporal scales, and the advances have made it possible to propose innovative tools for the analysis of trajectories (axis 3). During NAÏLA 2 we propose to deepen certain themes around these four guidelines, while developing new approaches and new tools.
“Surface hydrodynamic properties” sub-axis
Following on from NAÏLA 1, this sub-axis studies crop rotation logics in their spatio-temporal dimension, including neighborhood distributions and influences. The aim is to deepen the understanding of the logics observed during NAÏLA 1, and to formalize these logics with decision-making modeling tools.
We will deepen our understanding of combination logics for associated cultures, including the impact of sociotechnical knowledge, but also the constraints / opportunities that drive the implementation of these associations.
“Hydro-sedimentary flows” sub-axis
Crop water consumption is approached from several complementary angles dedicated to understanding water flows in the soil-plant-atmosphere continuum: interactions between the root system and the soil in connection with water availability, functioning of carrier associations. Grafting/variety in situations of deficit irrigation, functioning of associated crops in a context of bio-diversification, and quantification of water stress. The main objects of study are arboreal covers (e.g., olive trees), sometimes in associations, which present strong surface and subsurface heterogeneity and which result in significant lateral flows.
The joint use of measurements and models will be used to design drought indicators based on time series.
“Hydro-sedimentary flows” sub-axis
We study within this sub-axis several entities of the hydrological cycle and associated material flows, including (1) runoff for heterogeneous agricultural soils in hilly environments, (2) exchanges between surface and superficial aquifer in fractured porous environments, as well as that(3) the spatial redistribution and fate of organic matter under the influence of water erosion.
“Contamination of agrosystems” sub-theme
The problem of contamination of agricultural origin is studied according to three aspects: (1) identifying the types and doses of pesticides and emerging contaminants used, (2) characterizing the transport processes linked to adsorption / desorption mechanisms, and (3) consider biochar amendment-type mitigation solutions for pesticide immobilization
The interaction processes between contaminants and substrate (i.e., soil with/without biochar) will be characterized in batch thanks to adsorption / desorption tests, while studying the degradation of contaminants according to salinity and support. The interactions will be measured during percolation experiments on soil columns and in the field (plot) under controlled conditions, for different herbicide contents. The modeling of water and pollutant transport, based on Richard’s equation, will require calibration phases to determine the transport parameters, both in soil columns and in the field.