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Giorgio Gianquinto, Paolo Sambo, Francesco Orsini, Marco Sciortino and Valente Forte

Technology provides new tools for agriculture to be able to optimize fertilization. Optical instruments are becoming valid tools for farmers in making decisions about fertilization, even though they need to be calibrated for specific crops. Chlorophyll meters and multispectral radiometers have been tested on rice, corn, and wheat and afterwards on vegetables, in timing fertilization. Today, threshold lines that are able to detect crop N status in tomato crops are available. These thresholds, obtained in experiments carried out at Padova University, were validated in three open-field experiments. The first experiment was carried out in 2004 at the University experimental farm on tomato cv. Perfect Peel. The second and third experiments were conducted in a commercial farm at Codigoro (Ferrara) in 2004–2005. Tomato cultivars used were `UGX 822' and `Precocix' in 2004, in 2005 `Jet' was also used. In all trials, a “standard fertilization” management was compared with fertigation guided using SPAD and/or Cropscan. Optical tools were used to manage fertigation adopting both “threshold method” and “reference plot method”. In general “guided fertigation” resulted in less nitrogen application (N supply reduced between 18% and 45%), especially when “threshold method” was adopted. Yields were comparable to “standard fertilization” treatments, showing a better efficiency of “guided fertigation”. In some cases, guiding fertigation by means of optical instruments allowed higher fruit fresh weight, although dry matter content and °Brix were not influenced. Guided fertigation reduced also the number of damaged fruit and the percentage of nonmarketable product.

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Giorgio Gianquinto, Francesco Orsini, Paolo Sambo and Matilde Paino D'Urzo

Dynamic fertilization management is a way of bringing nutrients to the plant when they are crucial for its development. However, destructive measurements of crop nitrogen (N) status are still too costly and time consuming to justify their use, and the implementation of methodologies based on non-destructive, quick, and easy to use tools for plant nutritional status monitoring appears as an appealing opportunity. Several optical tools for plant monitoring have been developed in recent years, and many studies have assessed their ability to discriminate plant N status. Such tools can measure at leaf level (hand-held optical instruments) or may consider the canopy of a plant or few plants (portable radiometers) or even measure areas, such as a field, a farm, or a region (aerial photography). The application of vegetation indices, which combine the readings at different wavelengths, may improve the reliability of the collected data, giving a more precise determination of the plant nutritional status. In this article, we report on the state of the art of the available optical tools for plant N status monitoring.