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RESEARCH PRODUCT

Discussion of “Laboratory and field calibration of the Diviner 2000 probe in two types of soil” by J. Haberland, PhD, R. Galvez, C. Kremer, PhD, and C. Carter.

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The authors deal with the quite interesting and actual problem of Diviner 2000 capacitance probe calibration and present some field and laboratory data obtained on two different layers (0-0.26 cm and 0.26-0.50 cm) of the same soil profile, characterized by different textural class. The importance of site-specific calibration of sensors used to monitor soil or plant water status assumes a particular relevance in semi-arid environments where the application of precision irrigation represents an appropriate management strategy aimed to achieve high values of water use efficiency (Cammalleri et al., 2013). Moreover in clay soils, physical properties are strongly influenced by soil water content (Provenzano et al., 2013), so that the correct measurement of this variable plays a key role to increasing crop yield and preserving water. However, these discussers would focus on some significant points to be corrected in the manuscript and some others that AA. should have been specified in the methodology and considered in the final discussion, as following specified, for the benefit of potential readers. The need to install adequately the access tube, aimed to ensure the contact between the tube and the surrounding soil, is not only to avoid preferential flow of water down the walls of the tube, as considered in the paper, but also to reduce air gap around the tube and to avoid rough measurements of scaled frequency, used to estimate soil water contents, whose values depend on the mutual proportion of soil, water and air in the soil volume investigated by the sensor. With reference to the second part of eq. (2) it is necessary to precise that the function w(SF) correctly results: