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Soil water status plays an important role in growth-yield and grape quality of Vitis vinifera (L.). In some cases, periods of moderate water stress have been indicated to exert a positive effect on the quality of grape production. However, prolonged water stress may have a strong negative affect grapevine photosynthesis and grape yield, especially in dry Mediterranean environments. Biochar is a co-product of a thermochemical conversion of biomass that is recognized to be a beneficial soil amendment, which when incorporated into the soil increases soil water retention. We investigated the effect of two rates of biochar application (22 and 44 ton ha−1) on plant water relations of V. vinifera in a field experiment in central Italy. Biochar obtained from the carbonization of orchard pruning waste was applied to the soil over two consecutive growing seasons. The treatments did not show a significant increase in soil hydrophobicity. Moreover, soil analysis and ecophysiological measurements indicated a substantial relative increases in available soil water content compared to control soils (from 3.2% to 45% in the 22 and 44 ton ha−1 application rates, respectively) and in leaf water potential (24–37%) during droughts.

The presence of free water on a leaf surface caused by dew is the result of the radiative balance determined by the interactions between the canopy and the atmosphere. Leaf wetness duration (LWD) depends on leaf and canopy characteristics (exposure, position on the plant, etc.). To study the LWD in a horizontal canopy, a set of sensors were placed inside a sunflower (Helianthus annuus) experimental field and the records were compared with visual observations. An agrometeorological station was installed outside the crop to collect the variables necessary to feed a LWD model. The simulations were compared both to sensor measurements and to visual observations. The main aims were the verification of the sensor performances in the detection of dew and the analysis of LWD spatial variability inside the crop canopy. The potential of simulation models as an alternative to field instruments was also investigated. Our results showed that in sunflower canopy, organised in different layers, the LWD increases with height in the canopy but the sensors are not always able to reproduce the observed variability. The use of models can be considered as an operational procedure but attention should be paid to their calibration.