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Knowledge of soil water conductive porosity is of paramount importance for understanding the water and solute movement in soil. The objective of this study was to describe and evaluate an alternative pore index, i.e., the representative mean pore radius for two consecutive soil water tensions (lambda(Delta psi)), for characterizing the water-transmitting macro- and mesoporosity of soil. The hydraulic conductivity (K) and related hydraulic parameters were measured using a tension disk infiltrometer at -14, -4, -1, and 0 cm water pressure heads at a soil depth of 2 cm on a long-term conservation tillage experiment (after 9 yr of trial) under conventional tillage (CT), reduced tillage (RT), and no-tillage (NT) treatments. The soil was loam (Xerollic Calciorthid). The measurements were performed within the first half of a 16- to 18-mo-long fallow period. Unlike the model based on the classical capillary rise theory, which assumes no differences between measurement sites (e.g., tillage treatments) for the corresponding equivalent pore radius (CD) for macro- and mesopores, significant differences in lambda(Delta psi) values for macro- and mesopores were found between the three tillage systems tested. The number of water-transmitting macro- and mesopores per unit area estimated by means of the capillary rise approach was significantly greater than that calculated using the lambda(Delta psi) pore index. Although significantly higher values of lambda(Delta psi) for both macro- and mesopores were observed under NT a significantly lower near-saturation K was found under NT than CT and RT treatments due to the lower density of water-transmitting macro- and mesopores. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants no. AGF98-0261-C02-02 and AGL 2001-2238-CO2-01 and PNFPI predoctoral fellowship and research contract awarded to the first author) and the European Union (FEDER funds). ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987 ; There is limited information on the effects of tillage practices on soil hydraulic properties, especially changes with time. The objective of this study was to evaluate on a long-term field experiment the influence of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on the dynamics of soil hydraulic properties over 3 consecutive 16–18 month fallow periods. Surface measurements of soil dry bulk density (ρb), soil hydraulic conductivity (K(ψ)) at −14, −4, −1 and 0 cm pressure heads using a tension disc infiltrometer, and derived hydraulic parameters (pore size, number of pores per unit of area and water-transmission porosity) calculated using the Poiseuille's Law were taken on four different dates over the fallow period, namely, before and immediately after primary tillage, after post-tillage rains and at the end of fallow. Under consolidated structured soil conditions, NT plots presented the most compacted topsoil layer when compared with CT and RT. Soil hydraulic conductivity under NT was, for the entire range of pressure head applied, significantly lower (P < 0.05) than that measured for CT and RT. However, NT showed the largest mean macropore size (0.99, 0.95 and 2.08 mm for CT, RT and NT, respectively; P < 0.05) but the significantly lowest number of water-conducting pores per unit area (74.1, 118.5 and 1.4 macropores per m2 for CT, RT and NT, respectively; P < 0.05). Overall, water flow was mainly regulated by macropores even though they represented a small fraction of total soil porosity. No significant differences in hydraulic properties were found between CT and RT. In the short term, tillage operations significantly increased K (P < 0.05) for the entire range of pressure head applied, which was likely a result of an increase in water-conducting mesopores despite a decrease in estimated mesopore diameter. Soil reconsolidation following post-tillage rains reduced K at a rate that increased with the intensity of the rainfall events. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants no. AGF98-0261-C02-02 and AGL 2001-2238-CO2-01 and PNFPI predoctoral fellowship and research contract awarded to the first author) and the European Union (FEDER funds). ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987 ; In Central Aragon, winter cereal is sown in the autumn (November–December), commonly after a 16–18 months fallow period aimed at conserving soil water. This paper uses the Simple Soil–Plant–Atmosphere Transfer (SiSPAT) model, in conjunction with field data, to study the effect of long fallowing on the soil water balance under three tillage management systems (conventional tillage, CT; reduced tillage, RT; and no-tillage, NT). This was on the assumption that soil properties would remain unchanged during the entire fallow season. Once the model was validated with data obtained before primary tillage implementation, the differences between simulated and observed soil water losses for the CT and RT treatments could be interpreted as the direct effect of the soil tillage system. The model was calibrated and validated in a long-term tillage experiment using data from three contrasting long-fallow seasons over the period 1999–2002, where special attention was paid to predicting soil hydraulic properties in the pre-tillage conditions. The capacity of the model to simulate the soil water balance and its components over long fallowing was demonstrated. Both the fallow rainfall pattern and the tillage management system affected the soil water budget and components predicted by the model. The model predicted that about 81% of fallow seasonal rainfall is lost by evaporation in long-fallow periods with both a dry autumn in the first year of fallow and a rainfall above normal in spring. Whereas, when the fallow season is characterised by a wet autumn during the first year of fallow the model predicted a decrease in soil water evaporation and an increase in water storage and deep drainage components. In this case, the predicted water lost by evaporation was higher under NT (64%) than under RT (56%) and CT (44%). The comparison between measured and simulated soil water loss showed that the practice of tillage decreased soil water conservation in the short term. The long-term analysis of the soil water balance showed that, in fallow periods with a wet autumn during the first year of fallow, the soil water loss measured under CT and RT was moderately greater than that predicted by the model. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGF98-0261-CO2-02 and AGL2001-2238-CO2-01 and PNFPI pre-doctoral fellowship awarded to the first author) and the European Union (FEDER funds). ; Peer reviewed

16 Pags., 4 Tabls., 4 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145X ; The Ebro River valley in Northeast Spain experiences regularly strong west-northwest winds that are locally known as cierzo. When the cierzo blows, wind erosion may potentially occur on unprotected agricultural lands. In this paper the first results of field measurements of soil characteristics and saltation transport in the Ebro River valley near Zaragoza are presented. An experiment was conducted on a silt loam soil in the summers of 1996 and 1997. Two plots of 135×180 m were both equipped with a meteorology tower, three saltiphones (acoustic sediment sensors) and ten sediment catchers. The plots were different with respect to tillage practices. One plot received mouldboard ploughing followed by a pass of a compacting roller (conventional tillage—CT), whereas the other plot only received chisel ploughing (reduced tillage—RT). Soil characterizations indicated that soil erodibility was significantly higher in the CT plots than in the RT plots. Consequently, no significant saltation transport was observed in the RT plots during both seasons. In the CT plot, four saltation events were recorded during the 1996 season and nine events during the 1997 season. Most events were preceded by rainfall during the previous one or two days, which reduced saltation transport significantly. It is concluded that the occurrence of wind erosion in the Ebro River valley depends on the timing and type of tillage, distribution of rainfall and soil-surface crusting. ; The WELSONS project is funded by the European Union under Contract No. ENV4‐CT95‐0182. ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/11610301 ; In Central Aragón (NE Spain), where strong and dry winds are frequent all year round, fallow lands are susceptible to wind erosion due to insufficient crop residues on the surface and loose, finely divided soils by multiple tillage operations. Effects of conventional tillage (mouldboard ploughing followed by a compacting roller) and reduced tillage (chisel ploughing) on soil surface properties affecting wind erosion were studied during three experimental campaigns in a dryland field of Central Aragón. Reduced tillage provided higher soil protection than conventional tillage through a lower wind erodible fraction of soil surface (on average, 10% less) and a significantly higher percentage of soil cover with crop residues and clods (30% higher). Random roughness was also higher after reduced tillage than after conventional tillage (15% vs. 4%). These results indicate that reduced tillage can be an effective soil management practice for wind erosion prevention during the fallow period in semiarid Aragón. The study shows, likewise, that significant changes in soil aggregate size distribution associated with wind erosion processes may occur in short periods of time. Thus, temporal variability of soil surface properties, including crust and clods stability, needs to be considered in wind erosion research in agricultural soils. ; This work was supported by the WELSONS project funded by the European Union (Contract No. ENV4-CT95-0182). The first author is grateful to the Spanish Ministry of Education and Culture for her PNFPI contract. ; Peer reviewed

The definitive version is available at: http://www.ametsoc.org/ ; During the second phase of the EFEDA experiment (ECHIVAL Field Experiment in a Desertification Threatened Area), the spatial variability of the soil water retention and hydraulic conductivity characteristics of layers 2-12 and 17-27 cm depth was characterized. A simplified method, based on particle size distribution and simple infiltration tests was used. It provided these characteristics at the nodes of a 1 km grid over 10x10 km2 around the town of Tomelloso (Castilla- La Mancha, Spain). A total number of 78 sample points were used to address the problem of soil surface properties variability and its consequences on the monthly and annual water balance. The SiSPAT (Simple Soil Plant Atmosphere Transfer model) 1-D Soil-Vegetation-Atmosphere Transfer (SVAT) model was run with a one-year climatic forcing for the 78 soil profiles until equilibrium was reached. As no runoff was generated, the spatial variability of the water budget components only concerned soil evaporation, transpiration and deep drainage. It was found that i) the choice of the type of boundary condition at the bottom of the soil profile was greatly influencing the final variability, ii) the variability of transpiration was the largest in situations of water stress for the vegetation, iii) soil evaporation was the most sensitive component when plants were well supplied with water. Various aggregation methods of soil surface parameters (use of the arithmetic mean, median of the parameters or parameters associated to the average soil texture of the Clapp and Hornberger (1978) classification) were assessed. The use of median parameters in a single 1-D simulation was found to provide the best agreement with the average of the 78 simulations performed for each grid cell using locally measured soil properties. The use of average soil texture parameters led to a significant bias, especially in the case of water stress. ; This study was funded by the European Union in the context of the ECHIVAL Experiment in a Threatened Desertification Area (EFEDA) project (EPOCH-CT 90-0030 and EV5V-CT93-0272). ; Peer reviewed

39 Pags.- 4 Tabls.- 4 Figs. The defintive version is available at: http://www.sciencedirect.com/science/journal/01678809 ; There is a strong need to identify the combination of tillage and N fertilization practices that reduce the amount of nitrous oxide (N2O) emissions while maintaining crop productivity in dryland Mediterranean areas. We measured the fluxes of N2O in two field experiments with 3 and 15 years since their establishment. In the long-term experiment, two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three mineral N fertilization rates (0, 60 and 120 kg N ha−1) were compared. In the short-term experiment, the same tillage systems (CT and NT) and three N fertilization doses (0, 75 and 150 kg N ha−1) and two types of fertilizers (mineral N and organic N with pig slurry) were compared. N2O emissions, water-filled pore space, soil mineral N content, grain yields, N-biomass inputs and soil total nitrogen (STN) stocks were quantified and the N2O yield-scaled ratio as kg of CO2 equivalents per kg of grain produced was calculated. In both experiments tillage treatments significantly affected the dynamics of N2O fluxes. Cumulative losses of N as N2O were similar between tillage treatments in the long-term field experiment. Contrarily, although not significant, cumulative N losses were about 35% greater under NT than CT in the short-term experiment. NT significantly increased the production of grain and the inputs of N to the soil as above-ground biomass in both experiments. Averaged across fertilizer treatments, CT emitted 0.362 and 0.104 kg CO2 equiv. kg grain−1 in the long-term and the short-term experiment, respectively, significantly more than NT that emitted 0.033 and 0.056 kg CO2 equiv. kg grain−1, respectively. Nitrogen fertilization rates did not affect the average N2O fluxes or the total N losses during the period of gas measurement in the long-term experiment. Contrarily, in the short-term experiment, N2O emissions increased with application rate for both mineral and organic fertilizers. The use of pig slurry increased grain production when compared with the mineral N treatment, thus reducing the yield-scaled emissions of N2O by 44%. Our results showed that in rainfed Mediterranean agroecosystems, the use of NT and pig slurry are effective means of yield-scaled N2O emissions reduction. ; D. Plaza-Bonilla was awarded with a FPU fellowship by the Spanish Ministry of Education. This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01/02), the Aragon Government and La Caixa (grant GA-LC-050/2011), the Department of Agriculture of the Catalonia Government (grant 2012 AGEC 00012) and the European Union (FEDER funds). ; Peer reviewed

The definitive version is available at: http://vzj.scijournals.org/ ; Time Domain Reflectometry (TDR) is a valuable technique that allows simultaneous estimation of the apparent permittivity (a) and the bulk electrical conductivity (a). However, in highly conductive media the signal is completely attenuated which precludes permittivity measurements. This paper shows that a can be estimated in conductive media by applying the long-time TDR waveform analysis to a TDR probe partially insulated with a high-dielectric coating. Four 10-cm-long three-rod TDR probes with identical geometry but different percentages of rod-coating were tested: an uncoated sensor (P0) and probes with 50% (P50), 75% (P75) and 95% (P95) of the rod-length, respectively, coated with an insulator with a relative permittivity (r) equal to 32.3. A good relationship (r2 = 0.99) was found between the a estimated, if possible, with P0 immersed in several conductive and nonconductive media and the corresponding values estimated with P50, P75 and P95. The cell constant value (m-1) for P0 (5.10), P50 (9.60), P75 (16.92) and P95 (51.31), which were experimentally determined in different NaCl-water solutions, were on average 10% greater than the corresponding values calculated using a numerical model. The results show that, for a values ranging between 0.4 and 0.75 S m-1, simultaneous measurements of a and a were only possible using the partially coated probes. A good correlation was found between the a estimated with P0 inserted in different soil columns wetted with highly saline solutions (i.e. a > 0.2 S m-1) and those values estimated with P50, P75 and P95 (R2 = 0.96, RMSE = 1.08 and SD = 0.38). For a values lower than 0.2 S m-1 the accuracy of the partially coated TDR probes for estimations of a decreases as increases the percentage of the rod-coating, with errors up to 292% when a determined by P95 was compared to that estimated by P0. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grant AGL2007-66320-CO2-02/AGR) and the European Union (FEDER funds). ; Peer reviewed

Losses of soil organic carbon (SOC) have contributed to CO2 emissions from soils to the atmosphere and to global climate change. We hypothesized that in semiarid agroecosystems of the Mediterranean region, a shift from the traditional management system (including conventional tillage [CT] and a cereal–fallow rotation) to a more conservative system, including no-till (NT) and continuous cropping, could reduce CO2 emissions during the cropping season. Thus, in this study, we studied the effects of tillage and cropping systems on C inputs and soil CO2 fluxes during three cropping seasons at three different sites in the Ebro River valley (northeast Spain). Carbon inputs ranged from 650 to 6000 kg ha–1 and seasonal average CO2 flux ranged from 0.10 to 1.76 g CO2 m–2 h–1. Differences in rainfall led to marked differences in C inputs and soil fluxes among growing seasons. Although differences among tillage treatments were weak, CO2 fluxes under NT were always lower. Intensification of cropping systems led to an increase in C input. A move from CT to NT together with cropping intensification is suitable to increase C inputs and to reduce soil CO2 fluxes in semiarid Mediterranean agroecosystems. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01 and AGL 2004-07763-C02-02) and the European Union (FEDER funds). J. Álvaro-Fuentes was awarded an FPI fellowship by the Spanish Ministry of Science and Education. ; Peer reviewed

The final version of this article is available at: http://www.sciencedirect.com/science/journal/01671987 ; This paper presents a new type of pressure cell associated with a zigzag-shaped time domain reflectometry (TDR) probe for determining the soil-water retention (θ(ψ)) curve of disturbed thin soil samples. The pressure cell, designed for pressures ranging between 0 and −500 kPa, consisted of a zigzag copper rod (150-mm long, 2 mm in diameter) vertically installed in a clear plastic cylinder (60-mm high, 50 mm in internal diameter) with six vertical copper rods (60-mm long, 2 mm in diameter) arranged around the inner wall of the plastic cylinder. The cylinder was closed at the base with a nylon cloth and placed on a porous ceramic disc. The inner rod and the six-rod grille of the cell were connected respectively to the inner and outer conductors of a coaxial cable. The results showed that the correlation between the apparent dielectric constant measured with a standard three-rod TDR probe and the zigzag-shaped TDR probe, both immersed in five different non-conductive fluids, was excellent (R2 = 0.99). On the other hand, the volumetric water content measured with the TDR probe of the pressure cell filled up with sand, 2-mm sieved loam and clay-loam soils was highly correlated to the corresponding values calculated from the gravimetric water content and the soil bulk density (R2 = 0.97; RMSE = 2.32 × 10−2). The parameters of the θ(ψ) curves measured for these three different soils with the TDR-pressure cell were within the range of values found in the literature. The cell was also used to study the θ(ψ) changes of a 2–4-mm sample of loam soil aggregates after a slow and a fast-wetting process. While negligible changes in both the soil structure and θ(ψ) were observed following slow wetting, fast wetting resulted in disintegration of aggregates and drastic changes in the shape of the θ(ψ) curve. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR) and the European Union (FEDER funds). ; Peer reviewed

The final version is available at: http://www.sciencedirect.com/science/journal/01671987 ; Long-term tillage negatively affects soil aggregation, but little is known about the short-term effects of tillage. We investigated the effects of intensive tillage (moldboard plowing) and conservation tillage (chisel plowing) on aggregate breakage during tillage in a long-term study located in the semiarid Ebro river valley (NE Spain). The type of tillage resulted in different soil aggregate distributions. In the 0–5-cm and 5–10-cm soil layers, chisel plowing decreased dry mean weight diameter (DMWD) 29% and 35%, respectively, while moldboard plowing decreased DMWD by only 2% and 16%, respectively. The decrease in DMWD was mainly due to breaking of large aggregates ranging (2–8 mm) into small aggregates (<0.5 mm). Tillage method had no effect on water stability of 1–2 mm aggregates. The differences in DMWD demonstrate that the choice of the tillage implement can be a key factor in improving soil management and productivity. The surprising result that aggregate breakdown was greater with chisel than moldboard plowing needs further research to determine the mechanisms controlling aggregate breaking during tillage. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01, AGL 2004-07763-C02-02, AGL2007-66320-CO2-02/AGR) and the European Union (FEDER funds). The first author was awarded a FPI fellowship by the Spanish Ministry of Science and Education. ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/00167061 ; During decades, in semiarid agroecosystems of the Ebro valley, intensive soil tillage and low crop residue input has led to a loss of soil structure. Conservation tillage and cropping intensification can improve soil structure in these areas. The objective of this study was to determine the influence of three different tillage systems (conventional tillage, CT; reduced tillage, RT; and no-tillage, NT) under two cropping systems (barley–fallow rotation, CF; and continuous barley, CC) on soil aggregation dynamics during two consecutive growing seasons (2003–2004 and 2004–2005). At the same time, the role that different soil and climatic factors play on soil aggregation in these semiarid areas was studied. Soil samples were collected at the soil surface (0–5 cm depth) from a long-term tillage experiment with a loamy soil (Xerollic Calciorthid). Two aggregation indexes were studied: dry aggregate size distribution and water aggregate stability from both air-dried and field-moist macroaggregates. A decrease in tillage intensity resulted in a higher mean size of dry aggregates and a greater water aggregate stability in both cropping systems particularly under NT. During the whole experiment, the dry aggregate size distribution (measured as the mean weight diameter, MWD) and the water stability of field-moist and air-dried soil aggregates (WASAD and WASFM, respectively) were greater under NT than under RT and CT due to a higher soil organic matter content under NT. Intensification of cropping system resulted in a greater water aggregate stability (both WASAD and WASFM) but it did not have any effect in the MWD. Differences among tillage treatments were more pronounced under the CC system than under the CF rotation due to the lower soil organic matter content and microbial biomass when long-fallowing was used. Variations in soil aggregation dynamics during the cropping season were mainly affected by crop growth and the associated activity of soil microorganisms. These findings indicate that the use of alternative management practices as NT and CC are viable strategies to improve soil aggregation from semiarid Ebro valley. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01, AGL2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR) and the European Union (FEDER funds). The first author was awarded a FPI fellowship by the Spanish Ministry of Science and Education. ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/00489697 ; During decades, in semiarid rainfed Aragon, intensive soil tillage and low crop residue input have led to the loss of soil structure and soil degradation. Conservation tillage and cropping intensification can improve soil structure in these areas. The objective of this study was to determine the influence of three different tillage systems (traditional tillage, reduced tillage and no-tillage) under two cropping systems (fallow-barley rotation and barley monoculture) on soil aggregation dynamics during a cropping season. A decrease in tillage intensity resulted in a higher mean size of dry aggregates and a greater water aggregate stability in both cropping systems particularly under no-tillage. ; Financial support of the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01 y AGL 2004-07763-C02-02) and the European Union (FEDER funds) is gratefully acknowledged. The first author was awarded a FPI fellowship by the Spanish Ministry of Science and Education. ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987 ; In semiarid Mediterranean agroecosystems, low and erratic annual rainfall together with the widespread use of mouldboard ploughing (conventional tillage, CT), as the main traditional tillage practice, has led to a depletion of soil organic matter (SOM) and with increases in CO2 emissions from soil to the atmosphere. In this study, we evaluated the viability of conservation tillage: RT, reduced tillage (chisel and cultivator ploughing) and, especially, NT (no-tillage) to reduce short-term (from 0 to 48 h after a tillage operation) and mid-term (from 0 h to several days since tillage operation) tillage-induced CO2 emissions. The study was conducted in three long-term tillage experiments located at different sites of the Ebro river valley (NE Spain) across a precipitation gradient. Soils were classified as: Fluventic Xerocrept, Typic Xerofluvent and Xerollic Calciorthid. Soil temperature and water content were also measured in order to determine their influence on tillage-induced CO2 fluxes. The majority of the CO2 flux measured immediately after tillage ranged from 0.17 to 6 g CO2 m−2 h−1 and was from 3 to 15 times greater than the flux before tillage operations, except in NT where soil CO2 flux was low and steady during the whole study period. Mid-term CO2 emission showed a different trend depending on the time of the year in which tillage was implemented. Microclimatic soil conditions (soil temperature and water content) had little impact on soil CO2 emission following tillage. In the semiarid Mediterranean agroecosystems studied, NT had low short-term soil CO2 efflux compared with other soil tillage systems (e.g., conventional and reduced tillage) and therefore can be recommended to better manage C in soil. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL 2001-2238-C02-01 and AGL 2004-07763-C02-02) and the European Union (FEDER funds). The first author was awarded a FPI fellowship by the Spanish Ministry of Science and Education. ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/11610301 ; Winter barley is the major crop on semiarid drylands in central Aragon (NE Spain). In this study we compared, under both continuous cropping (BC) (5–6-month fallow) and a crop–fallow rotation (BF) (16–18-month fallow), the effects of three fallow management treatments (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) on the growth, yield and water use efficiency (WUE) of winter barley during three consecutive growing seasons in the 1999–2002 period. Daily precipitation measurements and monthly measurements of soil water storage to a depth of 0.7 m were used to calculate crop water use (ET) and its components. The average growing season precipitation was 195 mm. Above-ground dry matter (DM) and corresponding WUE were high in years with high effective rainfalls (>10 mm day−1) either in autumn or spring. However, the highest values of WUE for grain yield were mainly produced by effective rainfalls during the time from stem elongation to harvest. Despite the similarity in ET for the three tillage treatments, NT provided the lowest DM production, corresponding to a higher soil water loss by evaporation and lower crop transpiration (T), indicated by the lowest T/ET ratio values found under this treatment. No clear differences in crop yield were observed among the tillage treatments in the study period. On average, and regardless of the type of tillage, BF provided the highest values of DM and WUE and yielded 49% more grain than BC. These differences between cropping systems increased when water-limiting conditions occurred in the early stages of crop growth, probably due to the additional soil water storage under BF at sowing. Although no significant differences in precipitation use efficiency (PUE) were observed between BC and BF, PUE was higher under the BC system, which yielded 34% more grain than the BF rotation when yields were adjusted to an annual basis including the length of the fallow. The crop yield under BF was not dependent on the increase in soil water storage at the end of the long fallow. In conclusion, this study has shown that, although conventional tillage can be substituted by reduced or no-tillage systems for fallow management in semiarid dryland cereal production areas in central Aragon, the practice of long-fallowing to increase the cereal crop yields is not longer sustainable. ; This research was funded by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGF98-0261-C02-02 and AGL 2001-2238-C02-01 and PNFPI predoctoral fellowship awarded to the first author) and the European Union (FEDER funds). ; Peer reviewed