Effects of land use intensification and soil management practices on field water cycles and water use efficiency

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In the rural-urban interface of Bangalore water is an increasingly limited factor in crop production. Intensification of land use, transitions in soil management practices and the urbanization driven increase in water use are expected to exert additional pressure on the already scarce water resources. Water saving strategies by implementing efficient irrigation systems for water demanding crops (e.g. vegetables, grapes) or optimizing soil moisture conserving management approaches (e.g. mulching, humus management, increase in water use efficiency) will be crucial factors for sustaining future crop production in this region. This project aims at investigating the effects of agricultural transformation in the course of urbanization on the field water cycle. We will analyze changes in hydraulic and physical soil functions with land use intensification along a transect representing the transition from rural to urban areas (short rural-urban interface, RUI). Physical soil properties will be determined both by lab methods using representative undisturbed soil samples and in the field (e.g. infiltrability, soil moisture dynamics, shear strength and penetrometer resistance). Investigations will be carried out (i) on-station under researcher managed conditions (with factors irrigation, N-level and crop rotation) at the experimental station at UAS/Bangalore and (ii) on-farm managed by farmers with two levels of water management (rainfed vs. irrigated) combined with two levels of crop diversity (monoculture vs. polyculture) at selected farms along the urban-rural gradient. On-farm field analysis will be done in nested grids at several times of the year in order to derive farm scale spatial and temporal distribution of soil properties using geostatistical approaches. To calculate field water balances, water and rain use efficiencies for the various treatments (e.g. N application, irrigation, crop diversity) we will parameterize a deterministic transport model (HYDRUS) combining the soil physical measurements from the lab and the field. The model will be calibrated and validated based on in situ data of soil moisture and temperature which are obtained by monitoring profiles installed at the on-station experimental sites of the UAS. The validated model provides a physically based tool to predict soil water availability and fluxes in the SPAC and can potentially be coupled with crop simulation models to assess crop performance under varying management and climate scenarios.