International Symposium on
Drylands Ecology and Human Security
Integrating Soil Hydrostructural Characterization and Mapping, Cropping Systems Modeling and GIS for a Regional Agricultural Management in Tunisia:
Hatem Belhouchette1, Erik Braudeau2, Rabi H. Mohtar3,
1 Presenting Author: INRA-Agro M. UMR SYSTEM, Montpellier, France
Analysis of sustainable cropping systems from a biophysical perspective requires the quantification of the impact of agricultural management on crop growth, short and long term water and nutrient soil dynamics. A cropping system simulation model linked to a spatial analysis tool (GIS) is typically used for the purpose. However, when used at the regional level, such tools lack the spatial repartition of the soil characteristics required for the field scale simulation. The soil characterization used in these models is generally empirical and characteristic parameters are generally estimated from texture data without any reference to the internal hydrostructural organization and functionality of the soil unit (pedon). The objective of this paper is to show an application of the new methodology that we used for integrating a soil map and soil characterization with agronomic models for soil and water management purposes in Northern Tunisia. The system approach was taken as the basis of the soil mapping and characterization methodology, allowing using efficiently the CropSyst model and the GIS of the zone for cropping systems simulations at larger scales. A new map of hierarchical soil units in the irrigation area of Cebalat was established using an old pedological map and additional soil hydrostructural measurements in laboratory in order to build a geo- referenced soil information system for the study area according to the system approach. Additional information from the GIS was overlaid to produce “agronomic soil units” which define the spatial superposition of the soil information system and the farm boundary and patterns. The inputs for the model were different sets of each agronomic unit. Simulations were conducted at the field scale for testing the ability to simulate yield, soil water dynamics, soil salinity and nitrogen leached, and at the regional level for regional yields. At the field scale, the model accurately simulates and without calibration the soil water content, salinity and nitrogen leaching. At regional scale, the model offered an overall good integrated performance in simulating yield in the area under evaluation.
Keywords: soil characterization, systems approach, agronomic unit, soil mapping unit, cropping system, CropSyst, GIS, Tunisia, regional agricultural management