• Authors:
    • García-Vila, M.
    • Fereresa, E.
  • Source: European Journal of Agronomy
  • Volume: 36
  • Issue: 1
  • Year: 2012
  • Summary: Water resources used in irrigated agriculture are increasingly scarce, particularly in many countries where irrigation has undergone recent expansion. To optimize the limited resources available, optimization models provide useful tools for technical and economic analyses. One of the key inputs of these models is the yield response to water which is often simulated with empirical water production functions. At present, dynamic crop simulation models, such as AquaCrop (Steduto et al., 2009) offer alternative predictions of crop responses to different irrigation strategies as inputs to economic optimization. A model at farm scale was developed and applied to an area in South-western Spain to assist farmers in pre-season decision making on cropping patterns and on irrigation strategies. Yield predictions were obtained from the AquaCrop model which was validated for four different crops. The model simulated the impact on farm income of: (a) irrigation water constraints; (b) variations in agricultural policies; (c) changes in product and water prices; and, (d) variations in the communication to farmers of the specific level of irrigation water allocation. The applications of the models to the study area showed that currently, the changes in cropping patterns induced by the agricultural policy will encourage water savings more than an increase in water prices. Under water restrictions, the best strategy combines planting of low water use crops in part of the area to release water to grow more profitable crops with greater water needs. The model predicted a strong negative impact on farm income of delaying a decision on the level of seasonal water allocation by the water authority, reaching up to 300 ha(-1) in the case of the study area. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Soriano, M. A.
    • Santos, C.
    • Carmona, M. A.
    • Garcia-Vila, M.
    • Lorite, I. J.
  • Source: Water Resources Management
  • Volume: 26
  • Issue: 8
  • Year: 2012
  • Summary: The Local Irrigation Advisory Services (LIAS) carry out essential work to achieve an efficient use of irrigation water at field and irrigation scheme level, which is crucial in Mediterranean irrigation systems. However, it is unusual to find agronomic and economic assessments of LIAS advice. In this work, the LIAS operating in the Genil-Cabra Irrigation Scheme (southern Spain) was evaluated during the first 5 years of its advice. Acceptance by farmers of the LIAS recommendations was evaluated by using agronomic indicators, such as ARIS (Annual Relative Irrigation Supply). ARIS(LIAS) (actual irrigation applied v. recommendation of LIAS) with values ranging from about 0.23 for wheat and sunflower, and 0.94 for maize, also detecting a high variability between farmers, which indicated a scant acceptance of the LIAS recommendations. The economic evaluation of irrigation was made through two economic indicators, Irrigation Water Productivity (IWP) and Irrigation Water Benefit (IWB). IWP values varied significantly between different crops: around 0.23 a,not sign m(-3) in wheat, sunflower and maize, about 0.53 a,not sign m(-3) in cotton and sugar beet, and values higher than 2.0 a,not sign m(-3) in garlic, for optimal irrigation schedules. For IWB, trends were similar, emphasizing the low IWB values in wheat and sunflower (average values of 0.06 and 0.13 a,not sign m(-3), respectively). Consideration of these economic indicators by LIAS could not only help to obtain more suitable and economically profitable irrigation schedules, but also contribute towards a greater acceptance of advisory services by farmers, by shifting the emphasis from maximizing production to maximizing irrigation profitability.
  • Authors:
    • Conesa, M. R.
    • Domingo, R.
    • Perez-Pastor, A.
    • Pagan, E.
    • Caro, M.
  • Source: Agricultural Water Management
  • Volume: 111
  • Year: 2012
  • Summary: A two year experiment on Fortune mandarin trees (Clementina * mandarina Dancy ( Citrus clementina Hort. Ex. Tanaka * Citrus reticulata Blanco)) grafted onto Cleopatra mandarin ( Citrus reshni Hort. ex. Tanaka) rootstock was carried out with the aim of studying the suitability of midday stem water potential (psi stem) and trunk diameter reference baselines for irrigation scheduling. Plants were drip-irrigated with saline water during the second year (EC 25°C ~ 4 dS m -1). Measurements of psi stem, trunk daily growth rate (TGR) and maximum daily trunk shrinkage (MDS) were related with meteorological variables. Among them, MDS presented the best behavior. The mean temperature during the period 10.00-15.00 h solar time ( Tmd) was the environmental variable that best correlated with MDS, although there were no differences with other T-related variables (daily mean and daily maximum values). MDS data from stage III did not correlate with meteorological variables and fit-linear regressions became better with data from stages I and II (March-October), this being the period which covers 80% of total crop water requirements. Despite the different conditions that the trees were submitted to during the experimental period, i.e. irrigation water with different salinity and crop load, inter-annual differences were not observed in the reference baselines obtained.
  • Authors:
    • Alarcon, J. J.
    • Gil, M. I.
    • Allende, A.
    • Pedrero, F.
  • Source: Agricultural Water Management
  • Volume: 109
  • Year: 2012
  • Summary: The effects of applying different types of treated wastewater on citrus trees were studied in Murcia, in the south-east of Spain. Two treatments with wastewater effluents of different quality were applied for three consecutive years. In the first case, the wastewater received a secondary treatment (conventional activated sludge). In the second case, the irrigation water was a mix of well water and wastewater from a tertiary treatment plant (conventional activated sludge with ultraviolet tertiary treatment). The characteristics of the tertiary treated wastewater make it better for irrigation than the secondary treated wastewater. It was considered that high salinity, Cl and B concentration could be the main restrictions associated with treated wastewater irrigation in both cases, although leaf toxicity levels were not observed. The soil nitrate concentration increased over the experimental time period in both water irrigation treatments. The production was affected by the wastewater quality and the total crop yield was lower in the plots irrigated with secondary treated wastewater. However, in these plots, the fruit-quality indexes such as external colour, weight, peel thickness, firmness, soluble solids, pH, total acidity and maturity index were significantly better than those observed in the plots irrigated with tertiary treatment. The soil microbiological analysis revealed an absence of faecal coliforms, Escherichia coli and helminth eggs in the experimental plots irrigated with tertiary treated wastewater, but with secondary treated wastewater the soil accumulation of faecal coliforms exceeded health standards. In both cases, there was an absence of microbiological contamination on fruits.
  • Authors:
    • Espadaler, X.
    • Ribes, J.
    • Ribes, E.
    • Piñol, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 158
  • Year: 2012
  • Summary: The Heteroptera assemblage of a citrus grove and how it was affected by ant-exclusion was examined during transformation from conventional to organic agriculture. The results showed that the Heteroptera assemblage changed dramatically over the eight years of the study: at first, it mainly consisted of herbivorous lygaeids and predatory anthocorids but became dominated by predatory mirids in 2008-2009. The predator/herbivore ratio increased steadily over the eight years of the study. Ants can form mutualistic relationships with heteropteran pests. However, exclusion of ants from canopies did not affect the Heteroptera assemblage at the beginning of the study, but had a profound effect later on. In particular, ant-exclusion increased the abundance of most predatory Heteroptera, except for the myrmecomorphic mirid Pilophorus perplexus, which was approximately five times more abundant in control than in ant-excluded trees; the analyses showed that the only mimicked ant species was Lasius grandis.
  • Authors:
    • Limon, M.
    • Blanco-Moure, N.
    • Lopez, M.
    • Gracia, R.
  • Source: Soil & Tillage Research
  • Volume: 118
  • Year: 2012
  • Summary: Conservation tillage has been encouraged as a management alternative to preserve soil and water resources in semiarid Aragon (NE Spain). In fact, its adoption by farmers, and especially of no tillage (NT) systems, has increased in recent years. However, little information concerning the soils on which these techniques are applied is available for this region. The objective of this study was to assess the potential of NT to increase organic carbon content at the soil surface (0-20 cm) in rainfed Aragon. To this aim, 22 pairs of adjacent farm fields under NT and conventional tillage (CT) were compared in different cereal production areas. The fields were under continuous NT between 5 and 19 years but half were over 10 years. Soil organic carbon (SOC) in NT ranged from 7.06 to 18.53 g kg -1 (0-20 cm depth) and was higher than 12 g kg -1 in nearly 30% of the fields. These contents represented between 8% less (only one case) and 55% more SOC under NT than under CT with an average gain of 20% in favour of NT. The highest SOC contents were found in the NT fields of longer duration (>10 years) and/or managed with practices that enhance the return of more crop biomass to the soil (complete residue return, cropping intensification and manure application). The identification of the current management practices used by farmers has allowed us to know the diversity of the NT-based cropping systems and the reality of the conservation agriculture in our region. Overall, results from this on-farm study indicate that NT can be recommended as a viable alternative to CT to increase organic carbon at the soil surface in cereal production areas of Aragon.
  • Authors:
    • Moret-Fernandez, D.
    • Angurel, L. A.
    • Blanco-Moure, N.
    • Victoria Lopez, M.
  • Source: GEODERMA
  • Volume: 189
  • Year: 2012
  • Summary: Tensile strength (TS) of soil aggregates is recognized as a useful parameter to detect structural changes associated with soil management. Although conservation tillage has been encouraged as a management alternative to preserve soil and water resources in semiarid Aragon (NE Spain), little information concerning soils on which these techniques are applied is available for this region. The main objective of this study was to assess the effect of long-term no tillage (NT) on TS, rupture energy (E) and organic carbon (OC) of soil surface aggregates (0-5 cm depth) in five different cereal production areas of Aragon. In four of the sites, the study was conducted under on-farm conditions where pairs of adjacent fields under NT and conventional tillage (CT) were compared. In the last site, the study was carried out in research plots from a long-term tillage experiment where a third tillage treatment was also considered (reduced tillage). In all cases, a nearby undisturbed soil under native vegetation was included. Results indicate that NT reduced aggregate IS and E with respect to CT systems through lower soil disturbance and higher OC content. Aggregate size (16-8, 8-4, 4-2 and 2-1 mm in diameter) and aggregate-associated OC explained 70-80% of the variation in TS and E. Strength properties varied with OC in quadratic way with minimum values at about 20 g kg(-1) of OC. This behavior can be explained by the significant interactions found between clay and OC in such a way that in the soils with the highest values of clay and OC, aggregate strength increased considerably. This study shows that, under the rainfed conditions of semiarid Aragon, NT improves soil physical conditions by reducing aggregate strength at the soil surface. This means, for example, that NT could provide a more favorable environment for seedling emergence and root growth than the traditional practices in the area. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Pardini, G.
    • Gispert, M.
    • Emran, M.
  • Source: GEODERMA
  • Volume: 170
  • Year: 2012
  • Summary: Carbon dioxide measurements from soil surface may indicate the potential for soil respiration and carbon consumption according to microbial biomass and root activity. These processes may be influenced by land use and cover change, and abandonment especially in the upper soil organic layer. Seven environments from cultivation to late abandonment, with the same soil type classified as Lithic Xerorthent, were tested to ascertain the respiration capacity according to the current use and cover, and to establish the ability to preserve and eventually increase the organic matter pools after abandonment. Given the importance of carbon dioxide measurements at soil surface, a comparison between the classic soda lime method (SL) and a rapid method based on infrared sensor analyzer (IR) was performed from autumn 2008 to autumn 2009 in the field. The field measurements of CO2 proved significant correlations between the values from the two techniques under the same natural conditions and along the period of observation. However, the values of CO2 measured by the soda lime method were always higher than those obtained by the infrared analyzer. This pattern was attributed to the difference in time of measurement, larger in the former method, and type of measurement technique. Despite that the trend of measured CO2 values was rather similar along the year. On average, the highest values of CO2 emission in the field were recorded in the warmest periods of the year and with soil surface moisture not lower than 3% independently on the method used. High soil surface temperature with soil moisture below 3% decreased drastically the CO2 production from the dry soil. The cultivated environments and soil under forests have resulted higher CO2 producers than abandoned soils depending on the age of abandonment, climatic conditions, and within abandonment perturbations. Those abandoned soils preserved by perturbations like wildfire showed a higher potential for accumulating organic carbon, as indicated by the lowest emission of CO2 with respect to SOC content, during the period of observation. Results demonstrated the reliability of the methods used to evaluate the soil carbon dioxide production capacity and allowed to classify through environments with increasing potential for carbon sequestration. The classification was rather similar by using both methods indicating a higher susceptibility to carbon loss in the following order: soil under Vines (V)> under Olives (O)> under Pine trees (PI) > under Cork Trees (S)> under Pasture (PR)> under Cistus scrub (MC)> under Erica scrub (MB) by using the SL method and V> O > PI > S> MC> MB> PR by using the IR method. Indications about the need of management of abandoned areas were also considered in order to recover the landscape heterogeneity. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Madejón, E.
    • Deurer, M.
    • López-Garrido, R.
    • Murillo, J. M.
    • Moreno, F.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 118
  • Year: 2012
  • Summary: Long-term field experiments are important to provide information about how soil carbon (C) dynamics is affected by soil tillage systems. In this study we directly diagnose the influence of the topsoil's (0-5cm depth) C concentration on soil quality in an Entisol under Mediterranean conditions, testing a new statistical method. The objective was to estimate the impact of conservation tillage (RT) as a C management practice, versus a traditional tillage (TT) system on biophysical soil properties. We analyzed the impact of the soil C management on biological (microbial biomass C, dehydrogenase and ß-glucosidase activities), physical soil properties (aggregates stability, conductive mean pore diameter, aggregation index) and CO 2 fluxes. The concentrations for total organic carbon (TOC), the active carbon (AC) normalised by the total carbon (AC TOC -1), served as a combined proxy for the soil C management related to the tillage system. Soil C management accounted for 0-46% of the change of biophysical soil properties in RT versus TT. The RT led to a C increase (18.9%) of microbial activities, especially in the top 0-5cm depth. Related to the physical soil properties, less C in TT led to a lower aggregation index, although this tendency was not observed for other physical parameters. The impact of soil C management was better correlated with soil microbial than with the physical properties. Our analysis directly quantified for the first time that the increase in the soil's carbon concentration could only explain a small fraction of the beneficial change in biophysical soil properties due to RT. In general the RT contributed to the long-term sustainability of the agroecosystem by improving biological and physical soil characteristics under dryland semi-arid Mediterranean conditions.
  • Authors:
    • Easter, M.
    • Alvaro-Fuentes, J.
    • Paustian, K.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 155
  • Year: 2012
  • Summary: The interactive effects of climate change and atmospheric CO 2 rise could have potential effects on both soil organic carbon (SOC) storage and the capability of certain management practices to sequester atmospheric carbon (C) in soils. In this study, we present the first regional estimation of SOC stock changes under climate change in Spanish agroecosystems. The Century model was applied over a 80-yr period (i.e., from 2007 to 2087) to an agricultural area of 40,498 km 2 located in northeast Spain under five different climate scenarios. The model predicted an increase in SOC storage in the 0-30 cm soil depth in all the climate change scenarios tested (i.e., ECHAM4-A2, ECHAM4-B2, CGCM2-A2 and CGCM2-B2). Among climate change scenarios, SOC stock changes ranged from 0.15 to 0.32 Tg C yr -1. The Century model also predicted differences in SOC sequestration among agricultural classes. At the end of the simulation period, the greatest SOC stocks were found in the rainfed arable land under monoculture and no-tillage (MC-NT) class and in the grape-olive (GO) class with average stocks greater than 80 Mg C ha -1. On the contrary, both the alfalfa (AF) and the cereal-fallow (CF) classes showed the lowest SOC stocks with predicted values lower than 60 Mg C ha -1. Under climate change conditions, Spanish agricultural soils could act as potential atmospheric C sinks. Nevertheless, both the magnitude of the change in climate and the adoption of beneficial management practices could be critical in maximizing SOC sequestration.