Plant growth, water quality, carbon, and nutrient flows in rural-urban cropping systems at different spatial scales

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Scarcity of land, water, and labour are the main constraints to agricultural production along the rural-urban interface of Bangalore. This has led to the widespread replacement of diverse dryland farming systems by intensive irrigated vegetable production on open lands at the city fringe and in scattered city areas. The consequences of such changes in traditional Indian farming systems on the nutrient dynamics and soil fertility are largely unknown. This project therefore addresses transformation-related changes in the intensity of agricultural production systems at the micro(plot)- and meso-scale (field and household) by analysing horizontal and vertical flows of nutrients and carbon in field and laboratory experiments, turnover of soil organic carbon and soil nitrogen in different pools, and their effects on nutrient and water use efficiency under rainfed and irrigated conditions on-station and on 72 selected farmer fields. It combines expertise in agronomy, plant nutrition and non-destructive measurements of soil physical properties and plant growth (Bürkert) with modelling of water dynamics, crop growth, and carbon (C) and nutrient fluxes (Ludwig). The project will contribute to the overall goals of FOR2432 by providing spatially explicit data on the effects of intensification-related land use changes on nutrient and water use efficiencies for major food crops in the study region. It also aims at assessing the impact of these changes on key chemical soil parameters (pools of C and nitrogen N, phosphorus P, potassium K, and sulphur S) that govern crop output and ecosystem services. It thereby provides data for the calibration and validation of models to predict medium- and long-term changes of key soil parameters determining crop productivity and ESS. To this end we will investigate the plant uptake and turnover of C and N, P, K, and S including gaseous (N2O, NH3, CO2) and leaching losses (NO3-, dissolved organic carbon, organic P, and SO4[2-]), by photo-acoustic spectroscopy, gas chromatography, and resin cartridges /micro-lysimeters, respectively, and relate them to the soil hydrological data of A02 and the multi-spectral cropping / land use signatures of C01 and C02. Using 15N in the central experiment will allow to determine the fate of added fertilizer N. The data will also be used to parameterize the DNDC model. High resolution aerial photography and multispectral canopy scanning from hexacopters will be used to non-destructively monitor, in cooperation with C01, plant growth in the on-station experiments and the spatial variability of final biomass on-farm and to collect high resolution, low altitude multispectral crop signature data. Thereby this project will contribute to the estimation of the current productive value of agricultural lands which partly explain a decisions of farmers to intensify crop production or give up land for urban development.