• Authors:
    • Alvaro-Fuentes, J.
    • Paustian, K.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1/2
  • Year: 2011
  • Summary: Climate change is projected to significantly impact vegetation and soils of managed ecosystems. In this study we used the ecosystem Century model together with climatic outputs from different atmosphere-ocean general circulation models (AOGCM) to study the effects of climate change and management on soil organic carbon (SOC) dynamics in semiarid Mediterranean conditions and to identify which management practices have the greatest potential to increase SOC in these areas. Five climate scenarios and seven management scenarios were modeled from 2010 to 2100. Differences in SOC sequestration were greater among management systems than among climate change scenarios. Management scenarios under continuous cropping yielded greater C inputs and SOC gain than scenarios under cereal-fallow rotation. The shift from rainfed conditions to irrigation also resulted in an increase of C inputs but a decrease in the SOC sequestered during the 2010-2100 period. The effects of precipitation and temperature change on SOC dynamics were different depending on the management system applied. Consequently, the relative response to climate and management depended on the net result of the influences on C inputs and decomposition. Under climate change, the adoption of certain management practices in semiarid Mediterranean agroecosystems could be critical in maximizing SOC sequestration and thus reducing CO 2 concentration in the atmosphere.
  • Authors:
    • Intrigliolo, D.
    • Castel, J.
    • Ballester, C.
    • Castel, J.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 6
  • Year: 2011
  • Summary: The effects of mid-summer regulated deficit irrigation (RDI) treatments were investigated on Clementina de Nules citrus trees over three seasons. Water restrictions applied from July, once the June physiological fruit drop had finished, until mid September were compared with a Control treatment irrigated during all the season to match full crop evapotranspiration (ET c). Two degrees of water restrictions were imposed based on previous results also obtained in Clementina de Nules trees ([Ginestar and Castel, 1996] and [Gonzalez-Altozano and Castel, 1999]). During the RDI period, deficit irrigation was applied based on given reductions over the ET c, but also taking into account threshold values of midday stem water potential (psi s) of -1.3 to -1.5 MPa for RDI-1 and of -1.5 to -1.7 MPa for RDI-2. Results showed that water savings achieved in the RDI-2 treatment impaired yield by reducing fruit size. On the contrary, the RDI-1 strategy allowed for 20% water savings, with a reduction in tree growth but without any significant reduction in yield, fruit size nor in the economic return when irrigation was resumed to normal dose about three months before harvest. Water use efficiency (WUE) in the RDI trees was similar or even higher than in Control trees. RDI improved fruit quality increasing total soluble solids (TSS) and titratable acidity (TA). In conclusion, we suggest that the RDI-1 strategy here evaluated can be applied in commercial orchards not only in case of water scarcity, but also as a tool to control vegetative growth improving fruit composition and reducing costs associated with the crop management.
  • Authors:
    • Intrigliolo, D.
    • Yeves, A.
    • Sanz, F.
    • Castel, J.
    • Ballester, C.
    • Castel, J.
  • Source: Acta Horticulturae
  • Issue: 922
  • Year: 2011
  • Summary: In citrus trees, regulated deficit irrigation (RDI) can be a useful irrigation strategy to reduce water supply without affecting yield. Previous studies conducted in this sense have determined irrigation water savings achieved by RDI but less is known about the actual transpiration values of the RDI trees. This information is crucial to properly carry out a water balance of an RDI orchard. In an experiment performed during 2009 on mature 'Clementina de Nules' citrus, we determined sap flow (SF) of well irrigated and RDI trees by means of the compensation heat pulse method. SF was measured in two trees per treatment instrumented with one unit of two different gauge types per tree, determining heat velocity at four different xylem depths. SF values obtained at 30-min intervals during the entire experimental period were compared with whole canopy gas exchange measurements carried out during two representative days with custom designed Mylar plastic chambers. Plant water status was determined by midday stem water potential measurements (Psi stem). Results showed that absolute SF values clearly underestimated tree water use. After calibrating SF against canopy gas exchange determinations, corrected SF values appeared more reasonable but it also increased tree-to-tree variability (CV from 0.08 to 0.17). The transpiration ratio (SF RDI/SF control) had a somewhat decreasing trend during the water restriction period according to Psi stem, but recovering before the irrigation was resumed to normal dose. Overall, the results highlight some of the problems and uncertainties when using a limited number of sap flow sensors for detecting plant water stress and for accurately measuring transpiration.
  • Authors:
    • Benchabane, M.
  • Source: IOBC/WPRS Bulletin
  • Volume: 62
  • Year: 2011
  • Summary: After studies (2006-2009) of the states of fading of citrus fruits in the Mitidja (Algeria), we noted a troubling epidemic evolution in some orchards where the death rates reached proportions of 5 to 10%. The symptomatologic diagnosis indicates the presence of a strong likeness between the different biotic reasons possible without the presence of symptoms typical and/or of revealing signs of the known diseases (bacteria and virus). The diagnosis of laboratory confirmed their absence. The isolations achieved from the roots and soil put often in evidence the presence of Fusarium flora dominated by Fusarium solani and Fusarium oxysporum species. The implication of these species is joined to the pedological features and to the technical practices, notably the irrigation.
  • Authors:
    • Olitrault, P.
    • Msatef, Y.
    • Handaji, N.
    • Benazzouze, A.
    • Omari, F.
    • Beniken, L.
    • Benyahia, H.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 4
  • Year: 2011
  • Summary: Alkalinity of Moroccan soils is the major abiotic constraint on citrus production area. The best choice of citrus rootstocks adequate and resistant is a better solution to avoid this problem. The aim of this study is to develop a fast test of citrus rootstocks screening towards alkalinity. The alkaline stress was applied on ten citrus rootstocks two month old, using irrigation with a Hoagland and Arnon solution added with 1 g CaCO 3/L and adjusted at various pH levels 6, 7 and 9. Observations concerned symptoms incidence and severity of iron chlorosis after two months of rearing. Results permitted to classify Poncirus trifoliata and Flying dragon as the most sensitive to alkalinity stresses, whereas, Citrus volkameriana and Citrus macrophylla were resistant. These conclusions are equivalent with those obtained with old citrus rootstocks in field trials.
  • Authors:
    • Kuper, M.
    • Billaud, J.
    • Faysse, N.
    • Abdellaoui, E.
    • Bouzidi, Z.
    • Errahj, M.
  • Source: Cahiers Agricultures
  • Volume: 20
  • Issue: 1/2
  • Year: 2011
  • Summary: The design and diffusion of technical innovations in large-scale irrigation schemes in Morocco have generally been understood as necessarily stemming from centralized public policies. This situation tends to mask farmers' local initiatives. We analyzed local networks for innovation and coordination practices among local actors, in the case of the introduction of citrus plantations in an agrarian reform cooperative of the Gharb irrigation scheme. These networks and practices appeared as the motor for innovation around which revolved social and technical stakes and an issue of identity construction. Revealing these dynamics provides guidance for renewing the approaches to support farmers and more generally rural communities.
  • Authors:
    • Scicolone, B.
    • Consoli, S.
    • Capra, A.
  • Source: Acta Horticulturae
  • Issue: 922
  • Year: 2011
  • Summary: Citrus orchards are economically one of the most important crops in South Italy, where climate is semi-arid with scarce rain and high evaporative demand. One way to optimize water resources in this region is to adopt deficit irrigation (DI) strategies, such as regulated deficit irrigation (RDI). In Mediterranean regions, DI criteria have been widely applied and crop physiological responses to water deficit application have been studied in depth, but the profitability of these strategies in commercial orchards is still largely unknown. The objective of this study was to determine the economic feasibility of DI treatment on orange orchards in Sicily (South Italy), by estimating optimum levels of applied water which provide maximum profit under limited resource availability (e.g. land or water). The applied methodology follows the economic analysis on DI suggested by English in 1990. The analysis of the profit/total costs ratio showed that Deficit Irrigation strategies would increase the generated income, thus being more profitable (up to a maximum of 100%) than the current irrigation water supply management in the area.
  • Authors:
    • Domenikiotis, C.
    • Mplanta, A.
    • Dalezios, N.
  • Source: Journal of Information Technology in Agriculture
  • Volume: 4
  • Issue: 1
  • Year: 2011
  • Summary: Water for food production represents by far the largest share among all uses and its demand keeps growing with increasing population. The lack of water can affect disfavour the economic and social stability of entire regions. New technologies (Earth Observation, Geographic Information Systems) provide the possibility of time and spatial observation for the decision support and management. In this paper applied principles of precision agriculture through variable-rate inputs by the efficient monitoring of crop needs in space and time, defined zones of sustainable production by means of parallelepiped supervised classification using two indices, the soil maps and the DEM and described the process for the computation of crop evapotraspiration ETp for cotton fields in central Creece, a high agricultural productivity area that produces high quality products. The methodology was also used in Project PLEIADeS and new projects SMART and HYDROSENSE. For the data collection cotton fields were used. NOAA/AVHRR images consist the data base for the estimation of Water Limited Growth Environment (WLGE) and Landsat TM satellite images were processed for the extraction of reflectance, NDVI, RGB, ETp, Fractional cover, Kc maps. The objectives of this paper target to calculation of water balance with the use of satellite data and GIS, efficient use of water in water limited environments, improvement of irrigation systems with the use of new technologies, contribution to rational management of water resources in agriculture. Methodology can be applied in large scale areas and extend to other crops using satellite data. The results are in good agreement with ground-truth observations.
  • Authors:
    • Muriel-Fernández, J. L.
    • Jiménez-Bocanegra, J. A.
    • Durán-Zuazo, V. H.
    • Romero, R.
    • García-Tejero, I.
  • Source: Acta Horticulturae
  • Issue: 922
  • Year: 2011
  • Summary: Three different deficit-irrigation strategies were studied: sustained deficit irrigation (SDI), regulated deficit irrigation (RDI), and low-frequency deficit irrigation (LFDI) in different commercial citrus orchards located in the Guadalquivir river basin SW Spain. Each irrigation treatment was based on different water-stress ratio (WSR), which is the ratio of water supplied to deficit-irrigation treatment with respect to the control treatment (100% ET C). Midday stem-water potential (Psi Stem) was measured during the irrigation periods and was used to characterize plant-water status. Also, integrated stem-water potential (Psi Int) was calculated for all treatments and used as a timing water-stress indicator for the crop. Yield and fruit quality were evaluated at harvest in each treatment taking into account the temporal and spatial variability, associated mainly with local weather conditions, and agronomic orchard management. Relationships among water applied, Psi Int and yield response were performed to quantify the effects of deficit irrigation on yield and fruit-quality parameters. Analysis of data showed that, in all cases, the irrigation-water restriction significantly affected yield and some fruit-quality parameters (total soluble solids, titratable acidity, and maturity index). The results confirmed that the water productivity (WP) was positively related to water amount and irrigation strategy applied. Consequently, when WSR of 0.70 was applied (moderate deficit irrigation) RDI strategy showed better results than the SDI. However, with WSR of 0.60 (severe water reduction), LFDI strategy provided the best crop response. Under Mediterranean climate and water scarcity conditions, the application of DI strategies allowed water savings up to 1000 m 3 ha -1 yr -1. In DI treatments, the total water applied was better correlated with WP than with yield, indicating that this parameter should be used when trying to improve irrigation management.
  • Authors:
    • Muriel-Fernández, J. L.
    • Durán-Zuazo, V. H.
    • García-Tejero, I.
    • Martínez-García, G.
    • Jiménez-Bocanegra, J. A.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 4
  • Year: 2011
  • Summary: Citrus is a crop of major economic importance in Spain, cultivated during the dry season when irrigation is essential to guarantee yields of high quality. As water resources are progressively more insufficient, more effective water management in agriculture is crucial. Deficit irrigation in many agricultural crops has frequently proved to be an efficient tool for improving water-use efficiency. We hypothesise that, despite the effectiveness of deficit irrigation, the most suitable strategy in citrus orchards remains to be defined for Mediterranean environment. In this study, for the period from 2006 to 2008, a 12-year-old orange orchard, Citrus sinensis L. Osb. cv. Navelina, grafted onto Carrizo citrange, C. sinensis L. Osb. * Poncirus trifoliata L. Osb., were subjected under two deficit-irrigation strategies defined as follows: (1) low-frequency deficit irrigation applied according to the plant-water status, and (2) sustained-deficit irrigation with a water-stress ratio of 0.6, defined as the ratio of actual water-limited supply in this treatment related to the water supply of the control treatment. The control treatment was irrigated at 100% of ET C for the entire irrigation season (ET C: crop evapotranspiration). Midday stem-water potential (Psi stem) and stomatal conductance ( gS) were used to estimate the water status of the trees. The lowest Psi stem and g S values were registered in the deficit-irrigation treatments with a seasonal pattern consistent with the irrigation dynamics applied in each case. Psi stem and gS values significantly differed from those of the control trees. Although the integrated stress levels were similar in deficit-irrigation treatments, differences in yield and fruit quality were found, having a more positive response to low-frequency deficit irrigation with an increase of 25% in yield in comparison to the sustained-deficit irrigation treatment. Here, we thus demonstrate the significant differences in water productivity. Indeed, water productivity parameter not only depends on the amount of water, but also on the irrigation strategy applied, which promoted substantial water savings without significant impact on yield. The present study highlights that low-frequency deficit irrigation should be adopted as a most appropriate strategy for achieving sustainable water management and attains reasonable yields and improves quality in citrus orchards under Mediterranean semiarid climate.