Application and evaluation of the SWAP model for simulating water and solute transport in a cracking clay soil

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

Plant response to irrigation with saline water in a Sicilian vineyard: results of a three-year field investigation

This paper reports the results of a three-year field investigation carried out 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). Research investigated soil-plant response to irrigation performed with water having two different salinity levels; soil hydrological characteristics, soil salinity, crop transpiration and stomatal conductance were measured in field plots. The results proved that crop transpiration and stomatal conductance were significantly affected by soil salinity conditions (expressed as electrical conductivity of the soil saturated water extract). A significant reduction in both the physiological parameters was observed in the treatment irrigated with water having higher salinity (electrical conductivity equal to 1.6 dS m–1) as compared to the treatment irrigated with water of lower salinity (electrical conductivity equal to 0.6 dS m–1)

Soil structure and bypass flwo processes in a Vertsol under sprinkler and drip irrigation.

In this paper morphological and physical characteristics, as well as flow behaviour of a Mediterranean Vertisol under the influence of two different irrigation systems currently used for irrigation, i.e. drip and sprinkler systems, were compared. No differences in soil texture, compaction and in potential cracking were found on cores from the two fields. However, field application of methylene blue showed the presence of continuous macropores, penetrating up to depths of 20-25 cm from the soil surface, in the field where the drip system was in use (field 1). This was considered to be the pre-existing soil structure. Instead, macropores terminating at a depth ranging between 5 and 10 cm from the soil surface were observed in the sprinkler irrigated field (field 2). The same difference in terms of macropores' continuity was also observed on soil cores sampled from the two irrigated fields. The higher raindrop impact and the non-point water application involved in the sprinkler irrigation system were assumed to have determined, during several years, the different depth of penetration of the macropores in the two fields. A different hydraulic behaviour was evidenced by laboratory measurement of bypass flow on soil cores taken from the two fields. Specifically, higher values of the saturated hydraulic conductivity were found in the cores from the drip irrigated field compared to those sampled in the sprinkler field. In addition no bypass flow was measured in the columns under the sprinkler field, while high rates and amounts of bypass flow were obtained in the cores taken from the drip irrigated field. The different hydraulic behaviour observed in the cores taken from the drip and from the sprinkler irrigated field was in agreement with the difference in terms of macropores' continuity between the two fields. Being bypass flow a mechanism inducing leaching of solutes, results of this investigation suggest that irrigation systems affecting soil structure, and altering macropores' continuity, should be avoided in clay soils. (c) 2006 Published by Elsevier B.

Structure alteration of a sandy-clay soil by biochar amendments

The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f (bc) ). All the f (bc) samples were analyzed by high energy moisture characteristic (HEMC) technique and H-1 nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. H-1 NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased as the amount of biochar was raised up. The H-1 NMR relaxometry revealed a unimodal T (1) distribution for both the sole sandy-clay soil and the biochar. Conversely, a bimodal T (1) distribution was acquired for all the different f (bc) samples. Improvement in aggregate stability was obtained as biochar was progressively added to the sandy-clay soil. A dual mechanism of water retention has been hypothesized. In particular, intra-aggregate porosity was indicated as the main responsible for molecular water diffusion when f (bc) comprised between 0 and 0.33. Conversely, inter-aggregate porosity resulted predominant, through swelling processes, when f (bc) overcame 0.33

Lack of Dystrophin Affects Bronchial Epithelium in mdx Mice

Mild exercise training may positively affect the course of Duchenne Muscular Dystrophy (DMD). Training causes mild bronchial epithelial injury in both humans and mice, but no study assessed the effects of exercise in mdx mice, a well known model of DMD. The airway epithelium was examined in mdx (C57BL/10ScSn-Dmdmdx) mice, and in wild type (WT, C57BL/10ScSc) mice either under sedentary conditions (mdx-SD, WT-SD) or during mild exercise training (mdx-EX, WT-EX). At baseline, and after 30 and 45 days of training (5 d/wk for 6 weeks), epithelial morphology and markers of regeneration, apoptosis, and cellular stress were assessed. The number of goblet cells in bronchial epithelium was much lower in mdx than in WT mice under all conditions. At 30 days, epithelial regeneration (PCNA positive cells) was higher in EX than SD animals in both groups; however, at 45 days, epithelial regeneration decreased in mdx mice irrespective of training, and the percentage of apoptotic (TUNEL positive) cells was higher in mdx-EX than in WT-EX mice. Epithelial expression of HSP60 (marker of stress) progressively decreased, and inversely correlated with epithelial apoptosis (r=-0.66, P=0.01) only in mdx mice. Lack of dystrophin in mdx mice appears associated with defective epithelial differentiation, and transient epithelial regeneration during mild exercise training. Hence, lack of dystrophin might impair repair in bronchial epithelium, with potential clinical consequences in DMD patients