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Pags.- 4 Tabls.- 7 Figs. The definitive version is available at: http://link.springer.com/journal/10457, Unproductive saline and waterlogged (WT) wastelands could be beneficially transformed into agroforestry systems using trees tolerant to these stresses. We studied the salinity and waterlogging tolerance of five Australian tree species (Acacia salicina, Casuarina glauca, Casuarina obesa, Eucalyptus camaldulensis and Eucalyptus occidentalis) during seedling stage and their relationships with root and leaf ion concentrations. 8-month old plants were exposed for 5 months to five irrigation water salinity treatments (EC values between 2 and 22 dS m−1) and two waterlogging treatments (drained or WT). The salinity tolerance of the five species was high, although decreased in WT conditions. Irrespective of salinity, the two Casuarina species were more tolerant and the other three species were less tolerant to WT than drained conditions. In all species, salinity and waterlogging increased leaf Cl− and Na+ and decreased leaf Ca2+, but not leaf K+. Root Cl− and Na+ increased with salinity but not with waterlogging. Salinity tolerance was negatively correlated with Cl− and Na+ leaf accumulation rates per unit increase in salinity. Waterlogging reduced the ability of the seedlings to exclude Cl− and Na+ from the leaves. The two most salt tolerant Casuarina species under both drained and WT conditions showed the highest leaf Cl− and Na+ exclusion and the highest root Cl− and Na+ accumulation, suggesting that sequestration of these toxic ions in their roots was a significant salt-tolerant mechanism. Revegetation of saline and WT wastelands with these tolerant Casuarina species could be profitably used for biomass, biofuel and renewable energy production., The study was funded by the European Community (Contract No. INCO-CT-2007-032502, BIOSAFOR) and the International Centre for Advanced Mediterranean Studies (CIHEAM) in Zaragoza (Spain).

30 Pags., 3 Tabls., 9 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809, Irrigation district salt balances identify the main sources and sinks of salts and quantify salt loads in irrigation return flows. Salt balances were performed in La Violada Irrigation District during the 80s (1982–1984), 90s (1995–1998) and 00s (2006–2008) decades. Total Dissolved Solids (TDS) and loads in irrigation return flows were related with changes in irrigation performance and infrastructures during these decades. TDS increased linearly to increases in Irrigation Consumptive Use Coefficient (ICUC) (P < 0.01), and decreased with increases in Drainage Fraction (DRF) (P < 0.001). The salt balances revealed that 82% of the exported salts originated from soil gypsum dissolution. Annual salt yields in return flows were high and similar in the 80s and 90s (about 19.3 Mg/ha year), and halved in the 00s (9.9 Mg/ha year) due to comparable reductions in irrigation and drainage volumes derived from a better irrigation performance. Irrigation season salt yields were high and steady around 14.1 Mg/ha for ICUC < 51% and DRF > 66%, and decreased exponentially for values above and below these thresholds, respectively. Therefore, the key management strategy to reduce salt discharge to downstream areas is to decrease drainage volumes by improving irrigation management., This work was sponsored by the Spanish Ministry of Science and Education project AGL2006-11860/AGR, the European Regional Development Fund (FEDER) and the European Union project INCO CT-2005-015031.

This study was partially supported by the European Commission (Qualiwater project INCO-CT-2005-015031) and by an INIA (Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, Spain) doctoral fellowship given to V. Urdanoz. We kindly acknowledge the technical assistance of N. Claveri´a, M. Izquierdo, J. Gaudo´ and D. Naval

32 Pag., 2 Tabl. 5 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, The analysis of long-term irrigation performance series is a valuable tool to improve irrigation management and efficiency. This work focuses in the assessment of irrigation performance indices along years 1995–2008, and the cause–effect relationships with irrigation modernization works taking place in the 4000 ha surface-irrigated La Violada Irrigation District (VID). Irrigation management was poor, as shown by the low mean seasonal irrigation consumptive use coefficient (ICUC = 51%) and the high relative water deficit (RWD = 20%) and drainage fraction (DRF = 54%). April had the poorest irrigation performance because corn (with low water demand in this month) was irrigated to promote its emergence, whereas winter grains (with high water demands in this month) were not fully irrigated in water-scarce years. Corn, highly sensitive to water stress, was the crop with best irrigation performance because it was preferentially irrigated to minimize yield losses. The construction of a new elevated canal that decreased seepage and drainage fractions, the entrance in operation of six internal reservoirs that would increase irrigation scheduling flexibility, and the on-going transformation from surface to sprinkler irrigation systems are critical changes in VID that should lead to improved ICUC, lower RWD and lower DRF. The implications of these modernization works on the conservation of water quantity and quality within and outside VID is further discussed., This work was sponsored by the Spanish Ministry of Science and Education project AGL2006-11860/AGR, the European Regional Development Fund (FEDER) and the European Union project Qualiwater (INCO CT-2005-015031).

9 Pag., 5 Tabl., 6 Fig., Irrigated agriculture may impair negative “on-site” (i.e., soil salinization) and “off-site” (i.e., salts exported in irrigation return flows) effects. The aim of this study was to assess these effects, and the relationships between soil- and drainage-water salinity in a basin before and after the development of irrigation. Soil salinity (ECe) was estimated through electromagnetic induction (EMI) techniques (ECa) and the corresponding calibration equations, and drainage water salinity (ECdw) was measured in the outlets of 22 watersheds delineated within a 505-ha study area before (Year 2006) and after (Year 2008) irrigation development. Apparent soil EC was about 50% higher in 2008 than in 2006 due to increasing soil water contents, but estimated ECe was about 15% lower in 2008 than in 2006 due to salt leaching induced by irrigation. Drainage water EC increased by one order of magnitude from the upper (ECdw = 0.4 dS m−1) to the lower (ECdw = 4.5 dS m−1) reaches of the drainage network. The mean ECdw of the 22 watershed drainage outlets increased from pre-irrigation 2006 (2.4 dS m−1) to post-irrigation 2007 (3.1 dS m−1) and 2008 (2.7 dS m−1) years. Drainage water EC significantly depended (P < 0.001) on surface-weighted EC (ECe*) of each watershed, but the linear regressions were different in 2006 and 2008. The transformation from dryland to irrigation led to the leaching of salts and its export in the irrigation return flows. A compromise needs to be attained in the study area to achieve the beneficial “on-site” leaching of salts while minimizing the detrimental “off-site” export of salts., This study was partially supported by the European Commission (INCO-CT-2005-015031) and by an INIA (Instituto Nacional de Investigación y Tecnologia Agraria y Alimentaria, Spain) doctoral fellowship given to V. Urdanoz.

44 Pag., 3 Tabl., 3 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, This study analyzes the effects of irrigation modernization on water conservation, using the Riegos del Alto Aragón (RAA) irrigation project (NE Spain, 123354 ha) as a case study. A conceptual approach, based on water accounting and water productivity, has been used. Traditional surface irrigation systems and modern sprinkler systems currently occupy 73% and 27% of the irrigated area, respectively. Virtually all the irrigated area is devoted to field crops. Nowadays, farmers are investing on irrigation modernization by switching from surface to sprinkler irrigation because of the lack of labour and the reduction of net incomes as a consequence of reduction in European subsidies, among other factors. At the RAA project, modern sprinkler systems present higher crop yields and more intense cropping patterns than traditional surface irrigation systems. Crop evapotranspiration and non-beneficial evapotranspiration (mainly wind drift and evaporation loses, WDEL) per unit area are higher in sprinkler irrigated than in surface irrigated areas. Our results indicate that irrigation modernization will increase water depletion and water use. Farmers will achieve higher productivity and better working conditions. Likewise, the expected decreases in RAA irrigation return flows will lead to improvements in the quality of the receiving water bodies. However, water productivity computed over water depletion will not vary with irrigation modernization due to the typical linear relationship between yield and evapotranspiration and to the effect of WDEL on the regional water balance. Future variations in crop and energy prices might change the conclusions on economic productivity.

26 Pag., 6 Tabl., 6 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03784290, The increasing competition for good-quality waters is forcing to use saline waters for irrigation in many areas around the world. Maize (Zea mays L.) is considered a moderately sensitive crop to soil salinity, but its response to saline sprinkling irrigations and the potential benefits of irrigating at night to minimize leaf Na+ and Cl- uptake are not established. Our objective was to appraise plant ion concentrations and yields of maize subject to diurnal and nocturnal saline sprinkling irrigations. The work was performed in the Middle Ebro River Basin (NE Spain) during three years using a triple line source sprinkler system that diverts waters with an electrical conductivity gradient in-between 0.5 and 5 dS m-1. Na+ and Cl- concentrations in different plant tissues increased linearly with applied water ECaw. Plant Cl- was much higher than plant Na+ at low ECaw, but leaf ion uptake with increasing ECaw was higher for Na+ than for Cl-, and yields were more sensitive to plant Na+ than to plant Cl- accumulation. Grain yields were slightly affected by saline sprinkling irrigations in the first year, when soil salinity (ECe < 3 dS m-1) and irrigation water Na+ (12 meq l-1) and Cl- (26 meq l-1) concentrations were relatively low. Yields decreased drastically in the third year, due to increasing soil salinity (maximum ECe about 4.5 dS m-1) and irrigation water Na+ and Cl- concentrations (about 34 meq l-1). Yields in the diurnal and nocturnal sprinkler irrigations were similar, except in the second year where yield decline was somewhat lower in the nocturnal treatment. Plant Cl- was similar and plant Na+ was higher in diurnal than in nocturnal saline sprinkler irrigations, but no significant differences (P > 0.05) were found in general among the two irrigation treatments. Even though water evaporation rate was about ten times lower at night than at daytime, irrigating at night was not beneficial in maize in terms of reduced leaf Na+ and Cl- accumulation and increased yield., This study was supported by the Ministry of Education and Science of the Spanish Government (Project AGL2003-01942).

Little information is available on the quantitative effects on crops of saline sprinkler irrigations and the presumable beneficial effects of nocturnal versus diurnal irrigations. We measured crude protein content, carbon isotope discrimination and total dry matter (TDM) of alfalfa (Medicago sativa L.) subject to diurnal and nocturnal saline sprinkler irrigations. The work was carried out in Zaragoza (Spain) during the 2004–2006 growing seasons with a triple line source sprinkler system using synthetic saline waters dominated by NaCl with an irrigation water EC ranging from 0.5 to 5.6 dS m−1. The quality of alfalfa hay assessed through its crude protein concentration was not significantly affected by salinity. Carbon isotope discrimination, an indicator of the effect of osmotic stress on plant water status, tended to decrease with increases in salinity. Based on a piecewise linear response model, alfalfa grown under saline sprinkler irrigation was shown to be more tolerant (threshold soil salinity, ECe = 3.5 dS m−1) than in previous experiments under surface irrigation (threshold ECe = 2.0 dS m−1) at relatively low salinity values, but became more sensitive at higher salinity values as shown by the higher absolute slope (13.4%) for sprinkler as compared to surface irrigation (7.3%). No significant differences in TDM were found between diurnal and nocturnal saline sprinkler irrigations. The recommended practice of irrigating at night for sprinkler irrigation using saline water is therefore not supported by our results in alfalfa grown under semiarid conditions.

17 Pag., 2 Tabl., 4 Fig. The definitive version is available at: http://www.springerlink.com/content/0342-7188/, When using saline waters, sprinkling irrigation at night is a recommended practice to reduce evaporation, salt absorption by the wetted leaves and its negative effects on crops. We measured shoot ion concentrations (Cl−, Na+ and K+) and total dry matter (TDM) in alfalfa subject to diurnal and nocturnal saline sprinkler irrigations and established potential relationships among them. The work was carried out along the 2004–2006 growing seasons using EC waters from 0.5 to 5.6 dS m−1. Saline sprinkling irrigations linearly increased shoot Cl− and Na+ and decreased shoot K+. Even though daytime evaporation was much higher than nigh-time, shoot ion accumulation and TDM were similar in the diurnal and nocturnal irrigations. The salinity tolerance of alfalfa decreased in year 2006 due to increases in shoot Cl− and, particularly, shoot Na+. The lower threshold for shoot Na+ (276 meq kg−1) than for shoot Cl− (726 meq kg−1) shows that alfalfa is more sensitive to Na+ than to Cl−, and that Na+ accumulation is the preponderant cause of alfalfa yield decline after 3 years of sprinkling with saline waters., This study was supported by the Ministry of Education and Science of Spanish Government (Project AGL2003-01942).

24 Pag., 6 Tabl., 3 Fig. The definitive version is available at: http://www.springerlink.com/content/0032-079x/, We evaluated the salinity tolerance of young Tempranillo grapevines over a three year’s period, and the related effects on growth to leaf Na and Cl concentrations. Soil salinity, rootstock growth and leaf Na and Cl concentrations were measured in a drip-irrigated saline field. Salinity tolerance was determined using the slope (percent growth decline per unit increase in soil salinity) of the upper-boundary line fitted to the maximum growth-salinity observations. Based on a slope of 17.1% for the 3 years, Tempranillo was shown to be more sensitive to salinity than other reported varieties (slopes between 9.3% and 13.2%). The salinity tolerance of Tempranillo decreased along the study period. Tempranillo excluded Cl and, in particular, Na from the leaves more efficiently than other grape rootstock-scion combinations. Tempranillo was classified as moderately sensitive to salinity, and decreases in growth with increases in salinity were attributed to the osmotic effect rather than to specific ion toxicities., This study was partially supported by the European Commission (INCO-CT-2005-015031) and by an INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Spain) doctoral fellowship given to V. Urdanoz.

5 Pag., 1 Tabl. 2 Fig., As the pressure to use marginal or low-quality lands for crop production increases, it becomes increasingly necessary to determine the influence of stress factors such as salinity or waterlogging on crop growth and yield. This paper models the survival of olive trees (Olea europaea L. cv. Arbequina) under salinity and waterlogging field conditions. The effects of soil salinity [electrical conductivity of the saturation extract (ECe)] and waterlogging [relative ground elevation (RGE) and water table depth (WTD)] on the survival of 338 young olive trees were analyzed by logistic regression. The logit and probit models based on ECe, RGE, and WTD and their interactions were fitted to the data. Also, a nonlinear regression with 100% probability of olive survival (P) below a first ECe limit, 0% P above a second ECe limit, and a linear decrease in between (threshold-slope regression model) was fitted to the ECe data. The ECe and RGE were the two factors significantly affecting olive survival. The ECe was 7.7 dS m−1 for P = 50% (estimated median lethal ECe) and 3.7 dS m−1 for P = 95%. The threshold-slope model ECe estimates were 5.0 dS m−1 (upper threshold for unrestricted survival or P = 100%) and 10.3 dS m−1 (lower limit for the nonsurvival or P = 0%). Young olive trees were moderately tolerant to soil salinity, and their P under saline conditions was satisfactorily explained by both the logistic and the threshold-slope regression models., This study was partially supported by INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Spain). A Fulbright Grant and the financial sponsorship of the Spanish Ministry of Education supported Daniel Isidoro.

Sulfuric acid and gypsum-like by-products are potentially effective amendments in preventing soil crusting and reclaiming calcareous sodic soils. However, their relative efficiencies at chemically equivalent rates are not well documented. We evaluated the efficiency of four amendments (sulfuric add, mined-gypsum, and the by-products coal-gypsum and lacto-gypsum) in crusting prevention of two calcareous nonsodic and sodic soils and in sodic soil reclamation. Treatments for crust prevention consisted of surface-applied amendments at equivalent rates of 5 Mg pure-gypsum ha -1 . Treatments for sodic soil reclamation consisted of surface-applied add and soil-incorporated gypsums at rates of 1 pure-gypsum requirement. The efficiency of these amendments was evaluated by comparing the final infiltration rates (FIR) of the amended vs. the nonamended soils measured in disturbed-soil columns pounded with low-salinity irrigation water. Electrical conductivity (EC) and Na in the leachates of the sodic soil were measured. In the crusting prevention experiment, FIRs (mm h -1 ) of the nonsodic soil were 21 (nonamended), 33 to 35 (gypsum materials), and 53 (sulfuric acid), whereas those for the sodic soil were 0 (nonamended), 9 (lacto-gypsum), 15 to 17 (coal- and minedgypsum), and 21 (sulfuric acid). In the sodic-soil reclamation experiment, FIRs were 0 (nonamended), 8 to 9 (gypsum-materials), and 17 (sulfuric add) mm h -1 . All amendments were effective in crusting prevention and soil reclamation, but sulfuric acid was the most efficient due to the fastest EC and Na reductions in the leachates. The three gypsum-materials were equally effective in the reclamation process and in the nonsodic soil crusting-prevention, whereas lacto-gypsum was less efficient in the sodic-soil crusting-prevention.

Irrigation return flows may induce salt and nitrate pollution of receiving water bodies. The objectives of this study were to perform a salt and nitrogen mass balance at the hydrological basin level and to quantify the salt and nitrate loads exported in the drainage waters of three basins located in a 15,500 ha irrigation district of the Ebro River Basin (Spain). The main salt and nitrogen inputs and outputs were measured or estimated in these basins along the 2001 hydrological year. Groundwater inflows in the three basins and groundwater outflow in one basin were significant components of the measured mass balances. Thus, the off-site impact ascribed solely to irrigation in these basins was estimated in the soil drainage water. Salt concentrations in soil drainage were low (TDS of around 400–700 mg/l, depending on basins) due to the low TDS of irrigation water and the low presence of salts in the geologic materials, and were inversely related to the drainage fractions (DF = 37–57%). However, due to these high DF, salt loads in soil drainage were relatively high (between 3.4 and 4.7 Mg/ha), although moderate compared to other areas with more saline geological materials. Nitrate concentrations and nitrogen loads in soil drainage were highest (77 mg NO 3 − /l and 195 kg N/ha) in basin III, heavily fertilized (357 kg N/ha), with the highest percentage of corn and with shallow, low water retention flood-irrigated soils. In contrast, the lowest nitrate concentrations and nitrogen loads (21 mg NO 3 − /l and 23 kg N/ha) were found in basin II, fertilized with 203 kg N/ha and preponderant in deep, alluvial valley soils, crops with low N requirements (alfalfa and pasture), the highest non-cropped area (26% of total) and with fertigation practices in the sprinkler-irrigated fields (36% of the irrigated area). Thus, 56% of the N applied by fertilization was lost in soil drainage in basin III, as compared to only 16% in basin II. In summary, a low irrigation efficiency coupled to an inadequate management of nitrogen fertilization are responsible for the low-salt, high-nitrate concentrations in soil and surface drainage outflows from the studied basins. In consequence, higher irrigation efficiencies, optimized nitrogen fertilization and the reuse for irrigation of the low-salt, high-nitrate drainage waters are key management strategies for a better control of the off-site pollution from the studied irrigation district.

14 Pags.- 9 Figs., The return flows from irrigated agriculture may increase the salt and nitrate concentrations of the receiving water bodies, limiting their agricultural, industrial, urban and ecological uses. The objectives of this study are (i) to analyze the sources and levels of salt and nitrate concentrations in the surface waters of the irrigation district n° V of Bardenas I (CR-V), and (ii) to prescribe management practices aimed at protecting the quality of water resources. The electrical conductivity (EC) and nitrate concentration ([NO3−]) were measured in water samples collected in 28 drainage ditches of CR-V and in eight points along the Riguel River (the main drainage outlet for CR-V) in 14 dates of the 1999–2000 hydrological year. Drainage waters were moderate in salts (year-average EC=0.87 dS/m) and high in nitrates (year-average [NO3−]=55 mg/l), and both of them increased during the non-irrigation season. The lowest EC and [NO3−] in the Riguel River were measured at the entrance of CR-V and during the April–September irrigation season (season-average=0.45 dS/m and 2 mg/l, respectively), and attained the highest values at the river outlet (end of CR-V) and during the October–March non-irrigation season (season-average=1.55 dS/m and 50 mg/l, respectively). Salt loadings at the river outlet were correlated with river flows (P0.05) due to the higher nitrate variability in drainage waters. The unitary annual upper limit load emissions from CR-V were 7.2 t total dissolved salts/ha and 59 kg NO3−-N/ha. The optimization of nitrogen fertilization, the improvement of irrigation efficiency and the internal reuse for irrigation of the low EC-high NO3− drainage waters are the key management strategies for decreasing salt and nitrogen load emissions from CR-V and protecting the quality of the receiving water bodies., This work has been financed by the Plan Nacional I+D and FEDER funds through Project 2FD 1997-0547, with the invaluable collaboration of the CR-V irrigation district.

This work diagnoses the present salinity of the Riguel and Arba Rivers (Spain) and predicts its expected evolution using geochemical models applied to the modernization of the actual Bardenas I and the completion of irrigation in the Bardenas II irrigation districts. The results show a progressive increase in salinity (from 0.39 to 2.21 dS/m electrical conductivity) in the Riguel-Arba system, due to the cumulative collection of irrigation return flows and its progression towards more saline facies. The Bardenas I modernization, involving an increase in irrigation efficiency from 50 to 90%, will decrease the volume and salinity of the Riguel River by 30%. In contrast, irrigation of the new 24,000 ha Bardenas II land will increase the flow (12%) and salinity (21%) of the Arba River. Geochemical models may help in providing sensible estimates on the impact of irrigation on the salinity of the receiving water bodies.

Diagnosis of water management at the irrigation district level is required for the rational modernisation of the irrigation schemes and the subsequent increase in the efficiency of water allocation and application. Our objectives were to: (i) evaluate the global irrigation performance in the 5282 ha La Violada surface-irrigated district (Ebro River Basin, northeast Spain), and (ii) estimate the water that could potentially be conserved under two scenarios of modernisation and three increased irrigation efficiencies. The main district’s water inputs and outputs were measured (irrigation, precipitation, and outflow surface drainage) or estimated (canal releases, lateral surface runoff, municipal wastewaters, and actual evapotranspiration of crops) during the 1995–1998 hydrological years. The annual average water outputs were 23% higher than the corresponding water inputs, presumably due to canal seepage and lateral groundwater inflows from the 14 355 ha dry-land watershed. The district-level irrigation performance was poor (mean 1995–1998 seasonal irrigation consumptive use coefficient (ICUC)=48%), due to the low distribution (DE) and on-farm (ICUCf) efficiencies (i.e., mean estimates of 83% (DE) and 61% (ICUCf) for the 1995–1996 irrigation seasons). Thus, despite the high volume of applied irrigation water, the actual district ET was 16% lower than the maximum achievable ET, indicating that the water-stressed crops yielded below their maximums. Potential reductions in water allocation were estimated for three ICUC values (65, 75 and 85%) and two scenarios of modernisation (I and II). In scenario I, where the aim was to achieve maximum ET and crop yields, water allocation could be reduced from 8 to 30% of the current allocation. In scenario II, where the aim was to achieve the maximum conservation of water under the actual ET and crop yields, reductions in water allocation would be much higher (from 26 to 43% of current allocation). Thus, significant volumes of water could be conserved in the rehabilitation of this 50-year-old district by increasing the distribution efficiency and, in particular, the on-farm irrigation efficiency.

20 Pag., 3 Tabl., 6 Fig. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1475-2743/, Diagnosis of soil salinity and its spatial variability is required to establish control measures in irrigated agriculture. This article shows the usefulness of electromagnetic (EM) and soil sampling techniques to map salinity. We analysed the salinity of a 1-ha plot of surface-irrigated olive plantation in Aragon, NE Spain, by measuring the electrical conductivity of the saturation extract (ECe) of soil samples taken at 22 points, and by reading the Geonics EM38 sensor at 141 points in the horizontal (EMH) and vertical (EMV) dipole positions. EMH and EMV values had asymmetrical bimodal distributions, with most readings in the non-saline range and a sharp transition to relatively high readings. Most salinity profiles were uniform (i.e. EMH=EMV), except in areas with high salinity and concurrent shallow water tables, where the profiles were inverted as shown by EMH > EMV, and by ECe being greater in shallow than in deeper layers. The regressions of ECe on EM readings predicted ECe with R2 > 84% for the 0–100 to 0–150 cm soil depths. We then produced salinity contour maps from the 141 ECe values estimated from the electromagnetic readings and the 22 measured values of ECe. Owing to the high soil sampling density, the maps were similar (i.e. mean surface-weighted ECe values between 3.9 dS m−1 and 4.2 dS m−1), although the electromagnetically estimated ECe improved the mapping of details. Whereas soil sampling is preferred for analysing the vertical distribution of soil salinity, the electromagnetic sensor is ideal for mapping the lateral variability of soil salinity., This article is a result of the project RTA01-001, funded by INIA (Ministry of Science and Technology of Spain). The second author was granted by Fundación Cándido Iturriaga - María Dañobeitia.

Appropriate estimates of salt and nitrate loads exported by irrigated agriculture are needed to ascertain the potential negative impacts on the quality of the receiving water bodies. The irrigation return flows of the La Violada irrigation district (NE Spain), collected by La Violada Gully, were monitored for 4 years (1995–1998) in order to estimate salt and nitrate loads. The existence of a daily cycle in the Gully flow during the April to September 1995 irrigation season, associated with a cycle in the electrical conductivity, made it necessary to analyse the influence of the sampling hour on the daily estimates of salt and nitrate loads. Interpolation and regression methods were evaluated using nine 2-days surveys with samples taken at all even hours. The interpolation approach proved to be reliable for daily load estimations, whereas the regression approach was unacceptable due to the poor salinity-flow and nitrate concentration-flow relationships. The sampling time was important for the determination of salt load by the interpolation method, but resulted almost irrelevant for the estimation of nitrate load. Although the biases represent a small percentage of the mean (

The analysis of irrigation and drainage management and their effects on the loading of salts is important for the control of on-site and off-site salinity effects of irrigated agriculture in semi-arid areas. We evaluated the irrigation management and performed the hydrosalinity balance in the D-XI hydrological basin of the Monegros Il system(Aragòn, Spain)by measuring or estimating the volume, salt concentration and salt mass in the water inputs(irrigation, precipitation and Canal scepage) and outputs(evapotranspiration and drainage)during the period June 1997—September 1998. This area is irrigated by solid-set sprinklers and center pivots, and corn and alfalfa account for 90% of the 470 ha irrigated land. The soils are low in salts(only 10% of the irrigated land is salt affected),but shallow (

Evaluation of the salt tolerance of crop cultivars under field conditions is greatly complicated by the typical temporal and spatial variability of soil salinity. We obtained the grain yield – salinity response functions of 124 barley genotypes by growing them in ten salinity treatments imposed by a Triple Line Source Sprinkler (TLS) system during five consecutive years. Additional objectives were to ascertain the consistency and reproducibility over years of these functions, to quantify the deleterious effects of saline sprinkling irrigations, and to assess correlations between salinity tolerance and leaf sap salt concentration. The consistency and reproducibility of the response functions within and between years were adequate (only 8% of the response functions were discarded for statistical reasons). The Ym (grain yield without salinity) and the EC50 (the ECe that reduces yield by 50%) estimates were not correlated (P > 0.05) suggesting that the most productive genotypes were not necessarily less salinity tolerant. Ym was positively and significantly (P < 0.01) correlated with Y6 and Y12 (fitted grain yields at ECevalues of 6 dS m-1, and 12 dS m-1, respectively), indicating that it is a useful statistic in the selection of barley genotypes most productive under medium and high salinities. Foliar salt uptake due to saline sprinkling irrigations decreased the EC50 by around 50% as compared with the salinity tolerance obtained with surface irrigation systems. No consistent relationships were found between either Ym or EC50 and the leaf sap osmotic potential, Cl, Ca, Na and K concentrations. They could not therefore be used in screening for salinity tolerance of barley. On the basis of the evidence from the present study, Ym is the best statistic for predicting the most productive barley genotypes in salt-affected soils.

11 Pags.- 4 Tabls.- 5 Figs., Limited knowledge of the physiological basis of the detrimental effects of soil salinity on growth and yield of barley and the consequent lack of suitable screening traits are two reasons for the limited success of plant breeding in saline environments. We assessed the relationships between grain yield, carbon isotope discrimination (Δ), canopy temperature, stomatal conductance, and grain ash content in a set of barley cultivars grown in a soil salinity gradient imposed by a triple-line-source sprinkler system. A linear increase in soil salinity produced significant (P0.05). A multiple linear regression of Δ, stomatal conductance and grain ash content on grain yield was highly significant (R2=0.77, P, This research was supported by a CICYT (Ministry of education, Spain) research project founds and a CONAI (Government of Aragón, Spain) fellowship to R. Isla.

8 Pags.- 3 Figs.- 1 Tabl., Soil mulching is a sensible strategy to reduce evaporation, accelerate crop development, reduce erosion and assist in weed control, but its efficiency for soil salinity control is not as well documented. The benefits of inorganic (plastic) and organic (grapevine pruning residues) mulching for soil salinity and sodicity control were quantified in a grapevine orchard (cultivars ‘Autumn’ Royal and ‘Crimson’) drip-irrigated with moderately saline waters. Soil samples were taken at the beginning and end of the 2008 and 2009 irrigation seasons in six vines of each cultivar and mulching treatment. Soil saturation extract electrical conductivity (ECe), chloride (Cle) and sodium adsorption ratio (SARe) values increased in all treatments of both grapevines along the irrigation seasons, but the increases were much lower in the mulched than in the bare soils due to reduced evaporation losses and concomitant decreases in salt evapo-concentration. The absolute salinity and sodicity daily increases in ‘Autumn’ and ‘Crimson’ 2008 and in ‘Crimson’ 2009 were on the average 44% lower in the plastic and 76% lower in the organic mulched soils than in the bare soil. The greater efficiency of the organic than the plastic mulch in ‘Crimson’ 2009 was attributed to the leaching of salts by a precipitation of 104 mm that infiltrated the organic mulch but was intercepted by the plastic mulch. Although further work is needed to substantiate these results, the conclusion is that the plastic mulch and, particularly, the organic mulch were more efficient than the bare soil for soil salinity and sodicity control., This work was financed by the CSD2006-00067project (CONSOLIDER-INGENIO 2010).

28 Pags., 4 Tabls., 6 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Deficit irrigation strategies save water, but may enhance soil salinization and sodification when irrigated with low-quality waters. The objectives of this five-year study performed in the middle Ebro Basin (Spain) were to quantify these processes and assess their potential deleterious impact on the response of peach trees subjected to full irrigation (FULL), sustained deficit irrigation (SDI, irrigated at 62.5% of FULL) and regulated deficit irrigation (RDI, irrigated at 50% of FULL in Stage II of fruit development). In relation to FULL, water savings were 40% in SDI and 9% in RDI. Soil salinity (ECe), chloride concentration (Cle) and sodicity (SARe) measured in the saturation extract of 480 soil samples generally increased in the irrigation seasons, particularly in the more severe deficit irrigation strategy (SDI). These increases were counteracted by the leaching of salts induced by high leaching fractions (LF) and low water deficits (WD) attained during the non irrigation seasons. The changes in ECe, Cle and SARe measured between sampling dates were significantly correlated (p < 0.01) with WD and LF calculated for the periods between sampling dates. These parameters were therefore suitable to estimate the required irrigation depths for soil salinity and sodicity control. Peach trees were unaffected by the irrigation treatments, but yield productivity tended to decline above a threshold ECe of 4 dS m−1. Under the irrigation salinity (mean EC = 1.1 dS m−1) and the semiarid climatic characteristics of the study area, the three examined irrigation strategies proved to be sustainable in the five studied years., This work was financed by the CSD2006-00067 project (CONSOLIDER-INGENIO 2010).

19 Pags.- 4 Tabls.- 3 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987, Soil evaporation is an important component of the water balance in irrigated agriculture. Mulching can be an effective technique to reduce soil evaporation but its efficiency depends on meteorological conditions and the characteristics of the different mulching materials. The objective of this work was to assess the effectiveness of inorganic (plastic) and organic (pine bark, vine pruning residues, geotextile, and wheat straw) mulching materials for soil evaporation control during the energy-limited and falling-rate evaporation stages. Soil evaporation rates (ER) were quantified through consecutive weighings of initially wet soils placed in trays in the laboratory and in microlysimeters in the field. ER depended on meteorological and experimental conditions, stage of evaporation and type of mulching material. In the falling-rate stage, ERs decreased linearly (p < 0.001) with decreases in GWC, and for long drying periods the ERs were low and similar among treatments, implying that soil mulching will be ineffective for soil evaporation control in low-frequency irrigation systems. In the energy-limited stage, all mulching materials decreased the ERs in relation to the bare soil, but the plastic, vine residues and pine bark materials had lower ERs than the rest of mulching materials. These materials will be therefore recommended for soil evaporation control in high-frequency irrigation systems where the soil surface remains wet most of the time., This work was financed by the CSD2006-00067 project (CONSOLIDER-INGENIO 2010).

The establishment of proper agronomical practices and plant breeding programs for saline environments is limited by the lack of adequate field screening methods. We assessed the relationships between leaf ion concentration and grain yield in a set of barley cultivars and compared their ranking for salinity tolerance established with a triple-line-source (TLS) sprinkler system, where the absorption of salts is through the leaves and the roots, with that obtained with a drip-irrigation (DI) system, where the absorption of salts is only through the roots. The saline solution in both systems was made up of sodium and hydrated calcium chloride (1:1 w/w). Except for the highest saline treatments, direct leaf absorption of toxic Na+ and Cl- was minor or negligible, but it was substantial for Ca2+. Irrespective of barley cultivar and leaf age, the accumulation of Cl- in the TLS was 1.5–2.5 times greater than Na+. There was no significant correlation between grain yield and leaf sap ion concentration among eighteen barley cultivars. Thus, leaf ion concentrations should not be used as screening tools in breeding programs for increasing salinity tolerance in barley. The highest-yielding cultivars under non-saline conditions were also most productive under moderately saline conditions, though not under high-saline conditions. Although grain yields of the eighteen barley cultivars in the TLS were substantially lower than in the DI, the salinity tolerances estimated in both systems were significantly correlated (P < 0.05), indicating that the simple and inexpensive TLS irrigation system could be successfully used in screening for salinity tolerance in barley.

13 Pags., 3 Tabls., [ES] El riego por goteo enterrado (RGE) ha despertado en los últimos años un interés creciente en España debido a que su baja presión de trabajo y su menor coste energético, junto con otras potenciales ventajascomparativas, puede hacerlo más rentable que otros sistemas de riego (aspersión en particular). Este trabajo revisa las principales ventajas y limitaciones del RGE, con un énfasis particular en los problemas dediseño, manejo y mantenimiento del sistema, así como en la salinización potencial del suelo superficialen zonas áridas o semiáridas regadas con aguas de baja calidad. El RGE bien diseñado, manejado y man-tenido, ha demostrado ser rentable y sostenible. Sin embargo, el RGE tiene inconvenientes relacionadoscon las características del agua de riego, del suelo y de los cultivos que pueden comprometer su sostenibilidad y rentabilidad. Las ventajas y limitaciones del RGE deben por lo tanto evaluarse en cada casoparticular con el objetivo de proporcionar recomendaciones sólidas a los agricultores., [EN] Subsurface drip irrigation (SDI) has attracted an increasing interest in Spain in the last years due to its low operating pressure and lower energy cost that, coupled to other potential advantages, can makeit more profitable than other irrigation systems (sprinkler systems in particular). This work reviews themain benefits and constraints of SDI, with special emphasis on design, management and maintenance problems, as well as on the potential salinization of surface soils in arid and semiarid areas irrigated with low quality waters. Well designed, operated and maintained SDI systems have shown to be profitable and sustainable. Never the less, SDI has drawbacks in relation to certain irrigation water, soil and crop characteristics that can jeopardize its sustainability and profitability. Therefore, the advantages and limitations of SDI must be evaluated on a case-by-case basis with the objective of providing solid recommendations to farmers.

9 Pags.- 3 Tabls.- 2 Figs., Brief pre- and post-irrigation sprinkling treatments using freshwater were tested to determine if these practices could reduce the uptake of salts through leaves when saline water is used to sprinkler irrigate crops. Maize and barley were sprinkler irrigated 2 to 3 times per week for 30 min with saline water (4.2 dS m−1, 30 mmol L−1 NaCl and 2.8 mmoles L−1 CaCl2 for maize and 9.6 dS m−1, 47 mmoles L−1 NaCl and 23.5 mmoles L−1 CaCl2 for barley) in separate experiments with plants grown in pots outdoors. The soil surface of all pots was covered to prevent salinization of the soil by the sprinkling water. One half of the sprinkled plants was grown in nonsaline soil to study the effects of pre-wetting and post-washing when ion uptake was primarily through leaves. The other half of the sprinkled plants was grown in soil salinized by drip irrigation, in order to evaluate the effects of pre-wetting and post-washing when Na+ and Cl- uptake was through both leaves and roots. Post-washing with freshwater (5 min) reduced the leaf sap concentrations of Cl- in saline-sprinkled plants from 56 to 43 mmol L−1 in maize and from 358 to 225 mmol L−1 in barley (averages for plants grown in nonsaline and saline soil). Na+ concentrations in leaf sap were reduced from 93 to 65 mmoles L−1 (maize) and from 177 to 97 mmoles L−1 (barley) by the post-washing. Pre-wetting had a small effect on ion uptake through leaves, the only significant reduction in seasonal means being in leaf Na+ concentrations for plants grown in nonsaline soil. Pre-wetting and post-washing, when combined, reduced leaf Cl- concentrations to levels similar to those of nonsprinkled plants grown in saline soil; however, Na+ concentrations in leaves remained 3.5 times (maize) and 1.5 times (barley) higher than those of nonsprinkled plants. When pre-wetting and post-washing were not applied, sprinkled barley plants grown in saline soil had grain yields which were 58% lower than nonsprinkled plants grown in saline soil, but the reduction in grain yield was only 17% when the freshwater treatments were given. We conclude that a brief period of post-washing with freshwater is essential when saline water is employed in sprinkler irrigation. By comparison, the benefits from pre-wetting were small in these experiments. ei]T J Flowers, This work was financially supported by the STD program of the European Union and by the Interministry Commission of Science and Technology of Spain. The first author was supported for two years by the Spanish government, through the fellowship ‘Temporary Stays of Foreign Scientists and Technical Experts in Spain’ of the Ministry of Education and Science.

This chapter presents a discussion of a set of technological actions aimed at living with drought in the irrigated agricultural region of the Ebro Basin in Spain. The basin faces recurrent drought episodes that have led farmers to take action on the structural and water management aspects of water conservation. Structural works have taken the form of large irrigation modernization plans, affecting about one-fourth of the currently irrigated land. Modernization typically implies the construction of collective, remote-controlled, pressurized irrigation networks and the installation of on-farm sprinkler/drip irrigation systems. The impacts of these modernization projects on the Ebro Basin hydrology and on the economy and productivity of irrigated agriculture are discussed. In parallel, actions have been set up to improve water management, mostly at the water-user association (WUA) level. The cooperative design, elaboration, and dissemination of a database software supporting daily water management operations in WUAs is presented, and the utilities for drought management are discussed. Finally, a plan for action benefiting from improvements on both structures and water management capacities is presented. This new action comprises automated irrigation scheduling and operation, and is based on a combination of remotely controlled networks, WUA management and meteorological databases, and irrigation engineering tools. The proposed action has already undergone significant research and could result in the generalization of scientific irrigation scheduling and in the complete automation of irrigation operation. Technology can support farmers in their efforts to adapt to drought conditions and still obtain sustainable profits.

50 Pags., 1 Tabl., 8 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/00221694, The measurement of the soil solution electrical conductivity (σw) is critical for a better management of irrigation water and the effective monitoring and control of soil salinity. The objective of this work is to present the design and validation of a new time domain reflectometry (TDR) probe (WECP) for accurate and non-destructive measurements of σw. The probe consists in 14 porous ceramics disks (0.5 bar bubbling pressure) arranged along the axis of a three-rod TDR probe. Using the Mualem and Friedman (1991) model, σw was estimated from the volumetric water content (θ) and the bulk electrical conductivity (σa) measured in the ceramic disk set of known pore-geometry. The τ and β factors, which describe the complex geometry of the ceramic matrix, were calculated by immersing the probe in NaCl solutions of different electrical conductivities, and in a pressure cell wetted and drained with these NaCl solutions, respectively. The reliability of the WECP was validated under laboratory and field conditions. The laboratory experiment consisted of the TDR probe inserted in a pressure cell packed with mixed sand and 2-mm sieved loam soil that was subsequently wetted and drained with different NaCl solutions at various pressure heads. The σw estimated by WECP was compared to the σw measured in the draining solutions after they stabilized in the soil porous system. The field experiment compared the σw estimated by WECP with the corresponding σw values measured in the soil solution extracted with three ceramic tension lysimeters (TLs) after successive wetting and drainage cycles. The τ and β factors calculated for the ceramic disks set were 1.957 and 4.282, respectively. High and significant correlations were found in both laboratory (R2 = 0.98; P < 0.001) and field (R2 = 0.97; P < 0.001) experiments between the σw estimated by the WECP and the corresponding σw values measured in the column-drainage or TL-extracted soil solutions, respectively. These results demonstrate that the WECP is a feasible instrument to accurately estimate soil solution salinity independently of the soil water content and the porous medium in which the TDR probe is installed., This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grant AGL2010-22050-CO3-02/AGR). C. Peña was awarded with a FPI fellowship by the Spanish Ministry of Science and Innovation.

42 Pags., 9 Tabls., 5 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, One of the main constraints of irrigated agriculture is off-siteNpollution due to export of nitrate in irrigation return flows (IRF). Models capable of simulating the growth of crops and the N loads in IRF as affected by irrigation and N fertilization may be valuable tools in watershed studies. The Agricultural Policy Environmental eXtender (APEX) model was used to assess bestmanagement practices for reducing off-siteN loads in the IRF of three Mediterranean irrigated watersheds (Akarsu in Turkey, La Violada in Spain and Sidi Rached in Algeria). The watersheds (ranging from 4013 to 10,971 ha) were monitored along three hydrological years to determine the volume of IRF and the NO3-N concentrations and loads in IRF. APEX was calibrated with the data of the first two years and validated with the last year's data. APEX adequately simulated crop evapotranspiration and the volume of IRF and N loads in the IRF (errors < 20%). Simulated annual values were in general more accurate than simulated monthly values. APEX predicted that improving irrigationmanagement (change of irrigation system and/or scheduling) will decrease N loads in IRF over current values by 45% (Akarsu), 40% (La Violada), and 8% (Sidi Rached). However, improved N fertilization only will reduce N loads in IRF by 17% (Akarsu) or below 5% (La Violada and Sidi Rached). Improving irrigationmanagement will increase IRF NO3-N concentrations by 19% in La Violada and will decrease or will remain the same in the other two watersheds. APEXsimulations identified the main soils (shallow and low water holding capacity soils) and crops (heavily fertilized or shallow-root crops) N polluters within the studied watersheds. Overall, APEX simulated that the improvement of irrigation performance was the bestmanagementstrategy to decrease off-siteNpollution while maintaining or increasing crop yields in the three studied Mediterranean watersheds., This study was supported by the European Commission research project (INCO-CT-2005-015031).

35 Pags., 5 Figs., 5 Tabls. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809, Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. The main N inputs and outputs were measured or estimated in the semi-arid LaVioladairrigation district (Spain). Data on two periods (1995–1998 and 2006–2008) were compared and related to observed changes during the decade in cropping patterns and N fertilization and irrigationmanagement. N fertilization exceeded crop N uptake due to over-fertilization of corn (426 kg N/ha in 1995–1998 and 332 kg N/ha in 2006–2008) and alfalfa (62 kg N/ha). Between the two periods, N fertilization decreased by 56%, primarily due to a change from corn to alfalfa and barley. Accordingly, N losses in the irrigationreturnflows (IRF) diminished from 31% of the applied fertilizer in 1995–1998 to 20% in 2006–2008. NO3− concentrations and NO3-N loads in the IRF decreased from 40 mg/L and 106 kg N/ha in 1995–1998 to 21 mg/L and 22 kg N/ha in 2006–2008, due to lower N fertilization, lower corn area and improved irrigation efficiency. N contamination in the IRF will be minimized by increasing the irrigation efficiency and decreasing the corn area and its N fertilization rates, particularly when supplemental organic N is applied at pre-sowing., This work was sponsored by the Spanish Ministry of Science and Education project AGL2006-11860/AGR, the European Regional Development Fund (FEDER) and the European Union project INCO CT-2005-015031.

44 Pag., 5 Figs., 3 Tabl. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Long-term analysis of hydrologic series in irrigated areas allows identifying the main water balance components, minimizing closing errors and assessing changes in the hydrologic regime. The main water inputs [irrigation (I) and precipitation (P)] and outputs [outflow (Q) and potential (ETc) crop evapotranspiration] in the 4000-ha La Violada irrigation district (VID) (Ebro River Basin, Spain) were measured or estimated from 1995 to 2008. A first-step, simplified water balance assuming steady state conditions (with error ɛ = I + P − Q − ETc) showed that inputs were much lower than outputs in all years (average ɛ = −577 mm yr−1 or −33% closing error). A second-step, improved water balance with the inclusion of other inputs (municipal waste waters, canal releases and lateral surface runoff) and the estimation of crop's actual evapotranspiration (ETa) through a daily soil water balance reduced the average closing error to −13%. Since errors were always higher during the irrigated periods, when canals are full of water, a third-step, final water balance considered canal seepage (CS) as an additional input. The change in water storage in the system (ΔW) was also included in this step. CS and ΔW were estimated through a monthly soil–aquifer water balance, showing that CS was a significant component in VID. With the inclusion of CS and ΔW in the water balance equation, the 1998–2008 annual closing errors were within ±10% of total water outputs. This long-term, sequential water balance analysis in VID was an appropriate approach to accurately identify and quantify the most important water balance components while minimizing water balance closing errors., This work was sponsored by the Spanish Ministry of Science and Education project AGL2006-11860/AGR, the European Regional Development Fund (FEDER) and the European Union project INCO CT-2005-015031.

25 Pag., 6 Tabl., 1 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Irrigated agriculture is threatened by soil salinity in numerous arid and semiarid areas of the Mediterranean basin. The objective of this work was to quantify soil salinity through electromagnetic induction (EMI) techniques and relate it to the physical characteristics and irrigation management of four Mediterranean irrigation districts located in Morocco, Spain, Tunisia and Turkey. The volume and salinity of the main water inputs (irrigation and precipitation) and outputs (crop evapotranspiration and drainage) were measured or estimated in each district. Soil salinity (ECe) maps were obtained through electromagnetic induction surveys (ECa readings) and district-specific ECa–ECe calibrations. Gravimetric soil water content (WC) and soil saturation percentage (SP) were also measured in the soil calibration samples. The ECa–ECe calibration equations were highly significant (P < 0.001) in all districts. ECa was not significantly correlated (P > 0.1) with WC, and was only significantly correlated (P < 0.1) with soil texture (estimated by SP) in Spain. Hence, ECa mainly depended upon ECe, so that the maps developed could be used effectively to assess soil salinity and its spatial variability. The surface-weighted average ECe values were low to moderate, and ranked the districts in the order: Tunisia (3.4 dS m−1) > Morocco (2.2 dS m−1) > Spain (1.4 dS m−1) > Turkey (0.45 dS m−1). Soil salinity was mainly affected by irrigation water salinity and irrigation efficiency. Drainage water salinity at the exit of each district was mostly affected by soil salinity and irrigation efficiency, with values very high in Tunisia (9.0 dS m−1), high in Spain (4.6 dS m−1), moderate in Morocco (estimated at 2.6 dS m−1), and low in Turkey (1.4 dS m−1). Salt loads in drainage waters, calculated from their salinity (ECdw) and volume (Q), were highest in Tunisia (very high Q and very high ECdw), intermediate in Turkey (extremely high Q and low ECdw) and lowest in Spain (very low Q and high ECdw) (there were no Q data for Morocco). Reduction of these high drainage volumes through sound irrigation management would be the most efficient way to control the off-site salt-pollution caused by these Mediterranean irrigation districts., This study was supported by the European Commission research project INCO-CT-2005-015031.

22 Pag., 5 Tabl., 3 Fig. The definitive version is available at www.springerlink.com, Olive is considered moderately tolerant to salinity, but most studies are short in duration and report its tolerance on the basis of targeted irrigation water salinity (ECiw) rather than on measured root zone soil salinity (ECe). We evaluated the growth (tree height and trunk diameter) and yield (fruit and oil weights) response of two drip-irrigated young olive cultivars (Arbequina and Empeltre) subject to three ECiw treatments (2, 4 and 10 dS m−1). The ECe of 23 Arbequina and 20 Empeltre trees was intensively monitored during the 2003–2007 study period using an EM38 sensor and converting its readings into ECe through sensor calibration. For growth, the slopes of the linear regression equations (−3% to −5%) and the ECe50 estimates (12.5–14.0 dS m−1) were similar in both cultivars and vegetative traits. Likewise, for yield the slopes of the linear regression equations (−4% to −7%) and the ECe50 estimates (7.9–9.6 dS m−1) were similar in both cultivars and yield traits. Based on mean ECe50 estimates, olive vegetative growth was ranked as moderately tolerant (mean ECe50 = 13.2 dS m−1), whereas olive and oil yields were ranked as moderately sensitive (mean ECe50 = 8.7 dS m−1)., This study was financed by projects RTA01-001 and RTA04-050 of INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Spain).

18 Pag., 1 Tabl., 4 Fig., This article analyses the effects of irrigation modernization processes on water quantity and quality, taking the Ebro river basin (NE Spain) as a case study. The objective is to contribute to needed in-depth analysis and discussion regarding the optimization of water use in agriculture. A conceptual approach based on water accounting concepts has been applied. Results show that irrigation modernization linked to an increase in land productivity involves additional water depletion if the location of the irrigated areas and the quality of the irrigation return flows allow their re-use. Additionally, modernization reduces the volume of return flows and pollutant loads and increases the quality of the receiving water bodies. The modernization of water management will be required to maximize economic, social and environmental returns from the investment in new irrigation infrastructure.

32 Pag., 9 Fig., 5 Tabl. The definitive version is available at: http://www.sciencedirect.com/science/journal/00221694, The identification of the different components in a water course is required to individualize and assess the actual contribution of irrigated agriculture to the pollution of the water course. This paper aimed at identifying and assessing the composition of the end-members in La Violada irrigation district (VID) and establishing a statistical procedure to reduce the sampling effort needed to establish drainage water quality. The quality of irrigation water, groundwater, and irrigated-land drainage water in VID was monitored during three hydrologic years to identify the components of flow in La Violada Gully, the natural exit course of VID. A network of sampling points in the secondary ditches and main drains of VID allowed identifying and separating those collecting irrigated-land drainage waters from those conveying high proportions of irrigation waters. Three end-member flows were identified in La Violada Gully during the irrigation season: (a) irrigation water arising from tail-waters, leakages and spills from the irrigation canals, very low in salts; (b) groundwater originating from the non-irrigated upper reaches of La Violada Gully watershed, high in Cl and Na+; and (c) VID drainage water, high in SO2 4 and Ca2+. The overall VID drainage water quality was accurately assessed through a simplified sampling scheme of only four sampling points that produced low errors of 0.1 dS/m for EC and 0.1 mmolc/L for Cl . The separation of La Violada Gully flow in these three components is essential for estimating the actual contribution of irrigation in VID to the salt and nitrogen loads in La Violada Gully., This work was funded by the Spanish Institute of Agricultural Research and Technology (Project INIA SC95-031) and the European Union (Project INCO CT-2005-015031). The Spanish Institute of Agricultural Research and Technology provided a fellowship for the first author.

Soil salinity is a major threat in irrigated agriculture because of its negative on-site (decreased productivity) and off-site (salinization of irrigation return flows) effects. The delineation of the spatial variability of soil salinity is best suited using non-invasive geophysical measurements of the apparent soil electrical conductivity (ECa) using mobile GPS-based systems. Two simple and cost-effective Mobile Georeferenced Electromagnetic Sensors (MGES) developed in Aragón and Navarra (Spain) are described. These devices involve electromagnetic instruments towed by all terrain vehicles and combined with GPS units and data acquisition systems that collect both ECa readings and GPS coordinates. Two applications of the MGES aimed at delineating ECa maps for (1) selecting the most suitable crops in a 43-ha saline site (Hondo de Espartosa) and (2) correlating ECa with drainage water salinity to ascertain the salinity-source areas in a new 715 ha irrigated basin (Barranco de Lerma) were examined. These examples demonstrate the MGES surveying capacities for management of salt-affected agricultural areas. La salinidad del suelo es una importante amenaza para la agricultura de regadío debido a sus efectos negativos internos (descenso de la productividad) y externos (salinización de los flujos de retorno del riego). El procedimiento más adecuado para delinear la variabilidad espacial de la salinidad edáfica es mediante la medida geofísica de la conductividad eléctrica aparente del suelo (ECa) efectuada con sistemas móviles georreferenciados. En este trabajo se describen dos Sensores Electromagnéticos Móviles Georreferenciados (MGES) sencillos y económicos desarrollados en Aragón y Navarra (España). Estos equipos incluyen instrumentos electromagnéticos arrastrados por un vehículo todo terreno, combinados con una unidad de GPS y un sistema de adquisición de datos que recopila las lecturas de ECa y las coordenadas geográficas. Se presentan dos aplicaciones del MGES en las que se levantan mapas de ECa para (1) seleccionar los cultivos más apropiados en un regadío salino de 43 ha (Hondo de Espartosa) y (2) correlacionar la ECa con la salinidad de las aguas de drenaje para identificar las áreas-fuente mas importantes de salinidad en una nueva cuenca de regadío de 715 ha (Barranco de Lerma). Estos ejemplos demuestran las capacidades de análisis del MGES para el manejo de áreas agrícolas afectadas por salinidad.

10 Pag., 6 Tabl., 4 Fig., Fertilizer leaching affects farm profitability and contributes to nonpoint-source pollution of receiving waters. This work aimed to establish nitrate nitrogen export from La Violada Gully in relation to nitrogen fertilization practices in its basin (La Violada Gully watershed, VGW, 19 637 ha) and especially in La Violada Irrigation District (VID, 5282 ha). Nitrogen (N) fertilization in VID (and VGW) was determined through interviews with local farmers for the hydrologic years 1995 and 1996 and NO3-N load in the gully was monitored from 1995 to 1998. The N fertilizer applied in VGW was 2175 Mg in 1995 and 2795 Mg in 1996. About 43% was applied in VID (945 Mg in 1995 and 1161 Mg in 1996). The most fertilized crop was corn: 398 kg N ha−1 (665 Mg) in 1995 and 453 kg N ha−1 (911 Mg) in 1996. Nitrogen fertilization was higher than N uptake for irrigated crops, especially for corn and rice. Nitrate N load in La Violada Gully averaged 427.4 Mg yr−1. Seventy-five percent of the exports took place during the irrigation season (321.8 Mg). During the non-irrigation season maximum NO3-N loads (3.1 Mg NO3-N d−1) were found after heavy rains following the N side-dressing of wheat in the rain-fed area of VGW (February). During the irrigation season NO3-N load was determined by outflow from the district (caused by irrigation) and to a lesser extent by changes in NO3 concentration (caused by fertilization), showing peaks in April (pre-sowing corn N fertilization and first irrigations) and June to August (highest irrigation months and corn side-dress N applications, maximum 6.3 Mg NO3-N d−1 in July). Adjusting N fertilization to crops' needs, improving irrigation efficiencies, and better scheduling N fertilization and irrigation in corn could reduce N export from VID., This study was funded by the Spanish Institute of Agricultural Research and Technology (INIA). A Fulbright Grant and the financial sponsorship of the Spanish Ministry of Education supported Daniel Isidoro.

10 Pag., 4 Tabl., 9 Fig., Salt loading in irrigation return flows contributes to the salinization of the receiving water bodies, particularly when originated in salt-affected areas as frequently found in the middle Ebro River basin (Spain). We determined the salt loading in La Violada Gully from the total dissolved solids (TDS) and flows (Q) during the 1995 to 1998 hydrological years. Since this gully collects flows from various sources, an end-member mixing analysis (EMMA) was performed to quantify the drainage flow from La Violada Irrigation District (VID). Three flow components were identified in La Violada Gully: drainage waters from VID (Qd); tail-waters from irrigation ditches, spill-over, and seepage from the Monegros Canal (Qo); and ground water inflows (Qg) originating in the dryland watershed. Gypsum in the soils of VID was the main source for salts in La Violada Gully (flow-weighted mean TDS = 1720 mg L−1, dominated by sulfate and calcium). The contribution of Qg to the total gully flow during the 1996 irrigation season was low (6.5% of the total flow). The 1995 to 1998 annual salt load average in La Violada Gully was 78 628 Mg, 71% of which was exported during the irrigation season. The 1995 to 1998 irrigation season salt load average in Qd was 43 015 Mg (77% of the total load). Thus, irrigated agriculture in VID was the main source of salt loading in this gully, with a yield of 11.1 Mg of salts per hectare of irrigated land for the irrigation season. Efficient irrigation systems and irrigation management practices that reduce Qd are key factors for controlling off-site salt pollution of these gypsum-rich irrigated areas., This study was funded by the Spanish Institute of Agricultural Research and Technology (INIA). A Fulbright Grant and the financial sponsorship of the Spanish Ministry of Education supported Daniel Isidoro.

9 Pags.- 6 Figs., Irrigated agriculture may negatively affect groundwater quality and increase off-site salt and nitrate contamination. Management alternatives aimed at reducing these potential problems were analysed in the 15498 ha CR-V Irrigation District (Spain) by monitoring 49 wells and modelling the hydrological regime in a representative well of the Miralbueno Aquifer. Groundwaters presented low to moderate electrical conductivity (EC) (mean = 0.89 dS/m) and high [NO3−] (mean = 94 mg/L). The groundwater depth (GWD) during the 2001 hydrological year responded to the annual cycles of precipitation and irrigation as well as to the secondary cycles derived from irrigation scheduling. GWD were consistently simulated by the groundwater BAS-A model. Model results indicate that an increase in irrigation efficiency and the pumping of groundwater for irrigation will decrease GWD and aquifer's discharge by 56–70%, depending on scenarios. These recommendations will save good-quality water in the reservoir, will be beneficially economical to farmers, and will minimize off-site salt and nitrogen contamination., his work was financed by the National Plan I + D and FEDER funds from the EU, Project 2FD1997-0547, with the collaboration of the Bardenas Irrigation District no. V. We thank Consejo Superior de Investigación y Desarrollo of the Diputación General de Aragón for awarding a fellowship to the senior author.

Soil crusting negatively affects the productivity and sustainability of irrigated agriculture, reducing water infiltration and plant emergence, and enhancing surface runoff and erosion. Clay dispersion and slaking of the aggregates at the soil surface are the main processes responsible for crusting. The infiltration rates (IR) of ten arid-zone soils in disturbed soil columns were measured and their relative susceptibilities to dispersion and slaking were determined. It was also examined whether the final soil IRs (FIR) could be estimated from various soil stability indices. The susceptibility to chemical dispersion was determined by measuring the IR of soil columns slowly pre-saturated from below with tap water and subsequently ponded with deionized (DW), canal irrigation (CW), and gypsum-saturated (GW) waters. The susceptibility to aggregate slaking was determined by comparing the IR measured in pre-saturated (slow wetting from below) and air-dry (fast wetting) soil columns ponded with CW. The FIRs of most soils decreased in the order GW>CW>DW. Seven soils were susceptible to clay dispersion induced by DW. Five soils were susceptible to clay dispersion induced by CW. Only two soils were susceptible to slaking. The fast wetting in these soils completely sealed the soil surface, reducing their IRs to zero from the start of leaching. Clay dispersion rather than aggregate slaking was the principal process inducing sealing and decreasing IR in these soils when subject to low-salinity waters. The indices WSA (water stable aggregates), MDC (mechanically dispersed clay) and MWDstir (mean weight diameter of stirring aggregates after a prewetting treatment) gave consistent and significant relationships with FIRs. El encostramiento del suelo afecta negativamente a la rentabilidad y sostenibilidad de la agricultura de regadío, reduciendo la infiltración y emergencia del cultivo, y aumentando la escorrentía y erosión. La dispersión de arcillas y la desagregación de la superficie del suelo por una humectación rápida ("slaking") son los principales procesos responsables del encostramiento. Se han medido las tasas de infiltración de 10 suelos en columnas de suelo alterado, y se han determinado sus susceptibilidades a la dispersión y "slaking". Asimismo, se ha examinado si las tasas de infiltración final (IF) pueden ser estimadas a partir de índices de estabilidad estructural. La susceptibilidad a la dispersión se determinó comparando las IFs de suelos previamente saturados por capilaridad con agua de grifo y posteriormente lavados con aguas desionizada (AD), de riego (AC), y saturada en yeso (AY). La susceptibilidad al "slaking" se determinó comparando las IFs de suelos presaturados (humectación lenta por capilaridad) y secos al aire (humectación rápida) lavados con AC. Las IFs de los suelos disminuyeron en el orden: AY>AC>AD. Siete suelos fueron susceptibles a la dispersión inducida por el AD, cinco suelos fueron susceptibles a la dispersión inducida por el AC, y solamente dos suelos fueron susceptibles al "slaking". La dispersión química fue el principal proceso inductor del encostramiento y de la reducción de la IF de dichos suelos al lavarlos con aguas de baja salinidad. Se han encontrado correlaciones consistentes y significativas entre los índices AEA (agregados estables al agua), ADM (arcilla dispersa mecánicamente) y DMPagit (diámetro medio ponderado de agregados frente a agitación) y las IFs de los suelos.

28 Pag., 10 Fig. The definitive version is available at: http://www.springerlink.com/content/0032-079x/, High-density olive orchards are increasing around the world, many of which may be potentially affected by salinity and waterlogging (hypoxia), two important stresses common in irrigated fields in arid and semi-arid climates. However, the response of olive to these stresses under field conditions is not well established. Therefore, our objective was to evaluate the vegetative growth response of young olive trees (Olea europaea L., cv. Arbequina) grown in a spatially-variable waterlogged, saline-sodic field. We monitored the growth in trunk diameter of 341 three-year’s old olives between September 1999 and September 2000. Field contour maps were developed delineating soil salinity (ECa), relative ground elevation (RGE) and water table depth (WTD). Soil samples were also collected and analyzed for ECe and SARe in order to characterize the salinity and sodicity profiles and develop the ECa-ECe calibration equation. The infiltration rate (IR) of the crusted and uncrusted soil and the penetration resistance (PR) were also measured. The field was characterized by spatially variable ECe (2 to 15 dS m-1), SARe (3 to 40), RGE (-4 to +4 cm) and WTD (0.5 to 1.9 m, with corresponding ground water EC values between 12 and 6 dS m-1). Steady-state IR of crusted soil was only 7% of the uncrusted soil. Since the field was heavily irrigated by flooding, waterlogging conditions were related to low RGE values. Soil salinity was negatively correlated (R2 = 0.83, P < 0.001) with RGE (ponded water) and WTD (upward flux), due to the evapo-concentration of water and salts at the soil surface. Thus, inverted salinity profiles developed in high salinity areas. Fifty five percent of the olives were dead 3.5 years after planted, and most of them were located in areas of high ECe (> 10 dS m-1), low RGE (< - 1.5 cm) and low WTD (< 1.2 m). The surviving trees had vegetative salinity tolerance values of ECe threshold = 4 dS m-1 and slope = -12% (i.e., percent decline per unit increase in ECe above the treshold), indicating that the Arbequina olive is moderately tolerant to salinity. The RGE and WTD thresholds for olive’s survival were > 0.1 cm and > 1.6 m, respectively. Thus, very small changes in ground elevation had a significant effect on olive’s survival or death. The coupled effects of salinity and waterlogging (hypoxia) stresses were most detrimental for olive’s growth., This study was partially supported by INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Spain).

22 Pag., 5 Tabl., 4 Fig. The definitive version is available at: http://www.springerlink.com/content/0014-2336/, The assessment of the level and spatial variability of soil salinity and the knowledge of the salinity-yield response functions of crops are required to ascertain the best management strategies aimed at optimizing crop's productivity in saline environments. This work analyzed the spatial distribution of ECe in six irrigated, salt-affected fields of the middle Ebro River Valley (Spain) using electromagnetic survey and geostatistical techniques, and the implications of this salinity variability in plant breeding strategies for increased productivity. The average field ECe varied between 4.9 and15.4 dS m-1, with within-field coefficients of variation between 37 and 79%. The yield simulation analysis of 20 barley and durum wheat cultivars showed that almost 60% of the total yield came from the less saline areas (ECe < 6 dS m-1). The model-estimate Ym (maximum yield under non-saline conditions)and the simulated yields were significantly correlated (p, The first author was granted by Consejo Asesor de la Investigación, Gobierno de Aragón.

12 Pags.- 4 Tabls.- 3 Figs., Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m−1 (30 mM NaCl and 2.8 mM CaCl2) and for barley in 1994, 9.6 dS m−1 (47 mM NaCl and 23.5 mM CaCl2). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S). Saline sprinkling increased leaf sap Na+ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl− concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na+ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na+ over Cl− whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na+ and Cl− than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na+ and Cl− transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers, This work was financially supported by the STD program of the European Union and by the Interministry Commission of Science and Technology of Spain. The first author was supported for two years by the Spanish government, through the feliowship ‘Temporary Stays of Foreign Scientists and Technicai Experts in Spain’ of the Ministry of Education and Science.

9 Pags.- 2 Tabls.- 4 Figs., Barley is a crop that has been classified as tolerant to soil salinity, but under sprinkler irrigation with saline water it can readily absorb salts through its leaves and develop injury. Experiments using a triple-line-source sprinkler system were conducted on barley between 1989 and 1991 to determine: (1) the specific effects of foliage wetting on the mass of different shoot components; (2) the relative contribution of root and foliar absorption processes to foliar Cl accumulation; and (3) the extent by which these processes affect Cl partitioning in the shoot at the end of the season. Some plants were covered with plastic during the irrigation process to prevent foliar wetting while others remained uncovered. Salinity affected the partitioning of dry matter in the shoots regardless of whether plants were covered during the irrigation process. The organs associated with reproduction, e.g., heads and peduncles, comprised a larger fraction of the total shoot biomass under high salinity than under low salinity, indicating that plants under salinity stress were able to redistribute their dry matter to favor reproductive growth. The Cl concentration of the young leaves sampled from uncovered plants was linearly related (i.e., r 2>0.71) to the Cl concentration of the irrigation water. Equivalent leaves from covered plants also contained a substantial amount of Cl but concentrations were weakly correlated (i.e., r 2, At low salinity, there were no differences in leaf Cl concentrations between covered and uncovered treatments. In young leaves, differences between these treatments progressively increased with increasing salinity, indicating that the relative contribution of Cl in the leaf from foliar absorbed salts increased with increasing Cl in the irrigation water. Only in the youngest leaves sampled at the end of the season from plants grown at high salinity was the Cl concentration in uncovered plants (foliar plus root-absorbed Cl) found to be more than twice that in covered plants (only root-absorbed Cl) indicating that most of the Cl in young leaves originated from foliar absorption. In addition, only in the youngest leaves (e.g., flag leaves) was the slope of the relationship between leaf-Cl concentration and Cl concentration of the sprinkling water of uncovered plants more than twice that of covered plants, also indicating that foliar-Cl absorption was more substantial than root-Cl absorption. At high salinity, the difference in leaf Cl concentration between covered and uncovered plants was maximum in the youngest leaf (flag leaf), but differences became progressively smaller with increasing leaf age until ultimately concentrations of chloride in leaves older than the flag leaf-2 were highest in covered plants. In older tissue, it was difficult to distinguish which process, foliar or root absorption, was most responsible for leaf-Cl accumulation. These processes may not be entirely independent of one another and much of the Cl in the oldest leaves of uncovered plants could have been derived from foliar sources during the first month of sprinkling, reaching maximal levels, and thereby restricting root-absorbed Cl. Furthermore, since these leaves at the end of the season are more injured and drier than those from covered plants, late-season sprinkler irrigations may have been responsible for leaching some of the Cl out of these necrotic leaves.

8 Pags.- 1 Tabl.- 6 Figs., Crops that are sprinkler irrigated with saline water often suffer greater yield losses than when they are irrigated by soil surface methods, because harmful levels of salts are directly absorbed through the wetted leaves. We investigated whether salt damage to barley, sprinkler irrigated with saline water, was minimized with a short pre-irrigation with fresh water. A triple line-source sprinkler system was used to test the influence of three irrigation treatments on harvested grain yield, leaf water content and Cl and Na concentrations of barley sampled at two different dates. These treatments were compared at five levels of applied water salinity and consisted of : (i) RO (root salt absorption only) : plants were covered to avoid salt spray on leaves and saline water was applied directly to the soil ; (ii) PREW (pre-washing with fresh water) : plants were pre-irrigated for 3 min with fresh water in addition to the regular 30 min irrigation with saline sprinkler water plus the 3 min post-washing with fresh water ; (iii) NOPREW (no pre-washing with fresh water), where the 3 min pre-irrigation was not applied. Exposure to saline spray plus soil salinity (PREW and NOPREW treatments) decreased grain yields more than soil salinity only (RO treatment). Increased salinity decreased grain yields substantially less in the PREW treatment than in the NOPREW treatment. The EC of the applied water that reduced grain yield by 50 per cent was 12.9 dS m-' in the PREW treatment and 10.8 dS m−1 in the NOPREW treatment. Differences in grain yield were associated with lower concentrations of foliar salt in leaves from the PREW treatment. The first several minutes of sprinkler irrigation are, therefore, critical in the foliar absorption of salts. Cl and Na accumulated in the leaves in the same proportion in the first sampling of 16 April, but plants absorbed Cl more readily than Na in the second sampling of 29 May. This preferential accumulation of Cl was greater in the RO treatment, indicating that roots absorbed Cl more readily than did leaves, in comparison with Na absorption. These results have important implications in the management of overhead sprinkler irrigation, since short pre-irrigations with good quality water may substantially reduce the adverse effects of saline sprinkling water., This research was supported by the Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria (INIA) and the European Community. The Spanish Ministry of Education partially financed the sabbatical leave of S. Granan.