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Management scenarios aimed at optimizing irrigation in a Sicilian vineyard characterized by a cracking clay soil irrigated with saline water were explored for seven soil profiles (Baglio 1-Baglio 7), by using the simulation model soil-water-atmosphere-plant environment (SWAP), which accounts for shrinkage and cracking. Accurate prediction of water content, 0, was obtained for the seven profiles by expressing the soil hydraulic properties according to the Brutsaert retention equation coupled with the hydraulic conductivity model proposed by Gardner (B-G model). A satisfactory prediction of the electrical conductivity of saturated extract (EC sat ) was obtained using for the dispersivity (L dis ), a calibration value of 20 cm. Different irrigation schedulings and alternating waters of different quality were then explored as viable management options. The results showed that bypass flow determined a favorable water distribution, and that the best irrigation strategy was to make a minimum number of irrigations, by maximizing at the same time the amount of water supplied at each irrigation. Water storage in cracks was found to promote salt-leaching; neglecting cracks and bypass flow was shown to overestimate salinization. Alternating two different irrigation waters proved to be the best strategy, which could be adopted to reduce soil salinization and enhance crop transpiration. Findings concerning the role of cracks in the process of salt-leaching suggested that, under field conditions, application of a leaching solution was more efficient if the soil presented a considerable degree of cracking.

In Sicily, the increasing scarcity of good-quality waters is spreading irrigation with saline–sodic waters, thus enhancing the risk of soil secondary salinization and sodication. Sustainable management strategies are urgently needed in Sicily to prevent extent of salinization and sodication, thus preserving soil quality. Since irrigation is performed in cracking soils using irrigation systems involving high application rates, bypass flow of water and solutes occurs during irrigation. The objectives of this paper were (i) to investigate the process of Na–Ca exchange and subsequent salinization/sodication during bypass flow and (ii) to explore possibilities of using cyclic strategies, based on alternating good-quality waters to saline solutions, to prevent salinization. Six NaCl–CaCl 2 solutions (named 1–6) with the following values of sodium adsorption ratio (SAR, [mmol c /l] 0.5 ) and of cationic concentration ( C , mmol c /l)—(1) SAR=5, C =20; (2) SAR=5, C =1; (3) SAR=15, C =25; (4) SAR=15, C =2; (5) SAR=30, C =30; and (6) SAR=30, C =5—were prepared in laboratory. Two undisturbed soil columns were sampled in a Sicilian irrigated area where a risk of secondary salinization and sodication was indicated by previous investigations. Bypass flow experiments were performed by supplying the six solutions to each soil column in the order from 1 to 6 at an almost constant initial value of the cracking volume, using an application intensity determining occurrence of bypass flow. Results of experiments showed that in concomitance with bypass flow, (1) a process of Na–Ca exchange occurred, with Na adsorption and accumulation in the soil. In both the two columns, the exchangeable sodium percentage (ESP) was found to increase by about 100% at the end of the six bypass flow experiments. Being the volume of the supplied saline/sodic solutions much smaller than the pore volume, this result indicates that a considerable risk of sodication may occur under bypass flow conditions; (2) cyclic strategies are useful for preventing accumulation of solutes when solutions with SAR close to the soil ESP are used. Instead, when solutions with SAR higher than the initial ESP are supplied to the same soil, due to the Na–Ca exchange and subsequent sodication, alternating waters having not only lower C but also lower SAR could be necessary to prevent salinization and sodication.

The relevance of bypass flow on water flow, solute or pesticide transport is becoming increasingly recognized. Recent investigations proved that soil salinization may be influenced by bypass flow, i.e. the rapid transport of water and solutes via macropores and/or shrinkage cracks to subsoil and groundwater. This paper explores the role of bypass flow in the process of accumulation and leaching of solutes, as well as of sodium, in a Mediterranean cracking soil irrigated with saline/sodic waters. The results of bypass flow experiments performed on undisturbed soil cores showed that leaching of solutes occurred in concomitance with bypass fluxes when a low salinity solution was alternated with a high salinity solution. Exchange of solutes between the incoming solution and the soil matrix occurred during the bypass flow events at the contact surfaces (cracks walls) between the solution and the soil matrix and where cracks terminated in the soil samples. Concomitant exchanges of sodium were indicated by measurements performed in the effluent solution during the bypass flow measurements. The amount of Sodium released from the soil during the bypass flow events, as well as that of the soluble salts leached from the soil, were found to depend on the degree of soil cracking. These results indicated that: 1 in management of irrigation in cracking soils, under the occurrence of bypass fluxes, alternating a low salinity/sodicity water with a high salinity/sodicity solution can be effective for preventing salinization and sodification: 2 greater efficiency of removal of sodium/soluble salts can be obtained if application of the leaching solution is performed when the soil is at a considerable degree of cracking.

This chapter presents results of a 3-year field investigation in a vineyard located in Sicily (Mazara del Vallo, Trapani) within the framework of the Project “Evolution of cropping systems as affected by climate change” (CLIMESCO). Soil-plant responses to two saline irrigation waters were determined by measuring soil hydrological characteristics, soil salinity, crop transpiration and stomatal conductance in field plots of a Sicilian vineyard. The results proved that crop transpiration (T r) and stomatal conductance (G s) were significantly affected by soil salinity conditions, expressed by electrical conductivity of soil saturation extract (ECe). Significant reductions in T r and G s were found in plants irrigated with water of ECw = 1.6 dS m−1 (L) compared to T r and G s values in plots irrigated with water ECw = 0.6 dS m−1 (R). Significantly higher crop water stress index (CWSI) values, indicating stronger stress conditions, were measured in the L treatment, relative to the R treatment. Validity of the linear relationship between relative yield and relative transpiration was confirmed. A value of 0.7 for the yield response factor (Ky) provided accurate prediction of yield reduction in years 2008 and 2009. Reductions due to soil salinity, calculated according to Maas and Hoffman equation, showed that under conditions of water and salinity stress, yield reduction due to salinity represented a percentage of the total yield reduction of up to 11% in the L plots and up to 3.5% in the R plots. The investigation also indicated that ECe (1.5 dS m−1) discriminated a different plant response to salinity, indirectly confirming the Maas threshold value for grapes. Under the irrigation conditions in the Sicilian vineyard, it is suggested to implement management strategies aimed at keeping soil salinity below this threshold value. This can be realized by using low-salinity irrigation water only or by alternating the two irrigation sources.

In Sicily, the increasing scarcity of quality water is leading to irrigation with saline water in soils having a considerable susceptibility to salinization and degradation. In this paper, water flow and solute transport in a Sicilian irrigated soil was simulated by using the SWAP model, and the simulated results compared to measured values of soil moisture and salinity. The investigation was carried out in a vineyard located in Sicily (Mazara del Vallo, Trapani Province) within the framework of the Project: Evolution of cropping systems as affected by climate change (CLIMESCO). The soil hydraulic parameters were obtained by inverse method based on multi-step outflow experiments. The results obtained using field measurements from two soil profiles showed that SWAP provided reliable predictions of water content, θ, and of electrical conductivity of saturated extract, ECsat. The effect of climate change on soil water balance was predicted by application of SWAP under the soil-crop and irrigation management conditions currently practiced in the vineyard. Simulations were carried out with climatic data generated by the statistical downscaling process based on the global CGM HADCM3 for two IPCC scenarios (A2 and B1) and for the 2070-2100 time interval. The two mentioned IPCC scenarios (A2 and B1) were then compared to a third reference scenario (BASELINE) obtained by using the climatic data recorded from 1951 to 2004. The results indicated that the only significant effect of climate change was to shorten and to advance the crop cycle length, which decreased of 16 and 27 days respectively in B1 and A2 compared to values obtained for the BASELINE scenario. Further application of SWAP carried out simulating an advance in the irrigation starting time according to the advance in the crop cycle indicated that this could be considered a kind of adaptation strategy to be applied in the future in the vineyard to counterbalance the impact of climate change. This means that in the future farmers might be likely to anticipate the irrigation season in order to avoid any significant reduction in the crop productivity.

Water demand is increasing worldwide. In regions affected by water scarcity such as those located in the Mediterranean basin, water supplies are already degraded, or subjected to degradation processes, which worsen the water shortage. In Sicily, the increasing scarcity of good quality water is expanding irrigation with saline-sodic waters, thus enhancing the risk of secondary salinization and sodification. Adequate management practices are urgently needed for sustainable use of saline/sodic waters. This chapter illustrates how the Geonics EM-38 probe was used for monitoring salinization in a Sicilian area where irrigation with saline water is increasingly practiced, and the risk of salinisation and desertification is envisaged. Electrical conductivity of bulk soil (ECa) measurement grids were taken with the EM-38 in a Sicilian vineyard at several dates, both prior to, and following irrigations, with two distinct irrigation treatments of different salinities (0.6 and 1.6 dS m–1 respectively). Though both water sources contributed to field salinity, high salinity source had a more adverse effect. This investigation proved the usefulness of EM-38 for efficient, rapid monitoring of the progressive effects of different irrigation strategies on soil salinization.

Water demand is increasing worldwide. In regions affected by water scarcity such as those located in the Mediterranean basin, water supplies are already degraded, or subjected to degradation processes, which worsen the shortage of water. In such regions, competition for scarce water resources among users will inevitably reduce the supplies of freshwater available for crop irrigation. Detailed studies and experimental projects are needed to develop management scenarios aimed at preventing desertification and conflicts for use of the increasingly limited water resources and cultivable land. This paper illustrates soil-plant responses to irrigation with saline water in a Sicilian vineyard located in a wine production area (Mazara del Vallo, Trapani, TP). Two irrigation treatments of different salinities, R and L, having electrical conductivities of 0.6 and 1.6 dS m, respectively, were applied at several dates, using a drip system, in a silty-clay soil. Soil measurements were taken to monitor water content (θ) and EC of saturated extract (ECsat). Plant responses to water and salinity conditions were explored by measuring crop transpiration (T) and stomatal conductance (Gs) at several dates during the irrigated season. Results showed that significantly lower T and Gs values were measured in field sites with lowest and highest ECsat.

In Sicily, the increasing scarcity of quality water is leading to irriga- from salinization (Crescimanno et al., 2004). tion with saline water in soils having a considerable susceptibility to In Sicily, the increasing scarcity of good quality water cracking. Irrigation systems involving high application rates are used coupled with intensive use of soil under semiarid to arid in these irrigated areas, and bypass flow during irrigation is thus climatic conditions, is leading to irrigation with saline prevalent. Adoption of management practices accounting for cracking water on soils having a high shrink-swell potential and is therefore necessary to prevent salinization and land degradation. susceptibility to cracking (Crescimanno and Provenzano, In this paper, water flow and solute transport in a Sicilian cracking 1999). These soils are irrigated in the summer season, soil irrigated with saline water was simulated by using the soil-water- when the cracks open up, by sprinkler systems, which inatmosphere- plant environment (SWAP) model, and the simulated volve high application rates. Because of these high apresults compared with measured values of soil moisture and salinity. plication rates, bypass flow, that is, the rapid transport The soil hydraulic parameters were obtained by inverse method based of water and solutes via macropores or cracks to subsoil on multi-step outflow experiments, adopting two different sets of hy- or to groundwater (Bouma, 1991; Crescimanno, 2001), draulic parameters/functions, that is, (i) the van Genuchten-Mualem, (VGM model) and (ii) the Brutsaert retention equation coupled with is prevalent during irrigation. the hydraulic conductivity model proposed by Gardner (B-G model). Laboratory investigations performed on undisturbed The results obtained using field measurements from four soil profiles soil columns sampled from these areas showed that saliof a cracking clay soil showed that SWAP provided accurate predic- nization or leaching occurred during bypass flow dependtions of water content, , when the soil hydraulic properties were ing on the concentration of the applied solution compared expressed according to the B-G model. Using the B-G hydraulic pa- with the concentration of the pore solution (Crescimanno rameters/functions, the model was calibrated with reference to the and De Santis, 2004); the efficiency of salt-leaching was dispersivity (Ldis).Acalibration value of about 20 cm was found for the found to depend on crack volume (Crescimanno et al., four different profiles. In the conditions occurring in the Sicilian area 2002). The low values of the sodium adsorption ratio where we are focusing our attention, the predictive errors associated (SAR) of irrigation water, and the low values of the exwith the simulated ECsat, can be considered acceptable if the purpose changeable sodium percentage (ESP) measured in these of application is to predict the influence of salinity on crop yield.