Use of passive sensor technologies to determine N-status of tomato plants( Lycopersicon esculentum L.).

The advantages of precision agriculture in the vegetable growing and high value crop sector may accrue to horticulturists especially with respect to meet quality standards and to carry out selective and subsequent harvesting. However, the implementation and use of site-specific sensor technologies has never been adopted for horticultural purposes in the context of nitrogen fertilization sufficiently. Suitable sensor technologies and especially crop specific calibrations to determine crop nitrogen status and adapt fertilization strategies are still missing in this area. The aim of this study was to evaluate the use of a passive sensor technology to set up suitable calibrations to determine the N-status of tomato plants cv. Vanessa, and to adapt N-fertilization rates in the early stages of a growing period based on the sensor measurements. A greenhouse study was conducted with tomato plants during three months in 06 (April-June). Three different N fertilization rates (30 kg, 60 kg, and 100 kg) were implemented. As soon as the first inflorescence of the tomato plant was visible, sensor measurements were carried out on the first expanded leaf above the inflorescence with a digital imager (Leica S1 Pro) and repeated once a week. The results of the study indicate that the fine tuning of fertilizer operations using feedback signals from the tomato plant based on sensor measurements is clearly a promising way for optimizing nitrogen fertilizer inputs in horticulture and thus enhancing crop yield and quality.