• Authors:
    • Cherif, S.
    • El-Ayni, F.
    • Jrad, A.
    • Trabelsi-Ayadi, M.
  • Source: Water Environment Research
  • Volume: 84
  • Issue: 8
  • Year: 2012
  • Summary: Groundwater is the main source of water in Mediterranean, water-scarce, semiarid regions of Tunisia, Africa. In this study of the Korba coastal aquifer, 17 water wells were studied to assess their suitability for irrigation and drinking purposes. Assessment parameters include pH, salinity, specific ion toxicity, sodium adsorption ratio, nutrients, trace metals pollutants, and fecal indicators and pathogens. Results indicate that salinity of groundwater varied between 0.36 dS/m and 17.4 dS/m; in addition, its degree of restriction is defined as "none", "slight to moderate", and "severe" for 18, 23, and 59% of the studied wells, respectively. To control salts brought in by irrigation waters, the question arises as to how much water should be used to reach crop and soil requirements. To answer this question, a new approach that calculates the optimum amount of irrigation water considering the electrical conductivity of well water ( ECw), field crops, and the semiarid meteorological local conditions for evapotranspiration and rainfall is developed. This is applied to the authors' case study area; barley and lettuce were selected among the commonly grown crops because they are high- and low-salinity tolerant, respectively. Leaching requirements were found to be independent of the crop selected, and depend only on the season, that is, 250 to 260 mm/month in the driest season, with a minimum of 47 mm/month though all seasons. A high bacteriological contamination appears in almost all samples. However, if disinfected and corrected for pH, all the well waters can be used for animal farming (including livestock and poultry), although only 29% could be used for human consumption.
  • Authors:
    • Özbek, N.
    • Göre, M. E.
    • Erdoğan, O.
  • Source: Bitki Koruma Bülteni
  • Volume: 52
  • Issue: 1
  • Year: 2012
  • Summary: The effects of barley and common vetch on Verticillium wilt intensity were examined at Nazilli Cotton Reserach experiment fields during 2006-2007. Applications used in experiment were planted as barley, barley+common vetch, common vetch (traditional production), common vetch (growing at last irrigation) and control (conventional cotton production). After a four weeks residue decomposition period, seeds of Nazilli 84-S cotton variety were planted in a randomized complete block design with four replications. The data for disease intensity were determined during the stage of 5-10%, 50-60% cotton boll opening and after harvest. Seed cotton yield and fiber quality properties were also determined. Disease intensity identified according to symptoms on leaf and cross section of stems was determined lower level in organic growing plots and it was followed by control growing plot. During experiments, green manure applications of barley and barley+common vetch provided with a larger decrease on disease intensity than control growing plot. This also shows that cotton growing increase disease intensity every year. In common vetch and control plots, average yield values were determined higher according to barley+common vetch and barley growing plots. Cotton fiber properties have not been affected by these treatments.
  • Authors:
    • Frisvold, G. B.
    • Konyar, K.
  • Source: Water Resources Research
  • Volume: 48
  • Issue: 5
  • Year: 2012
  • Summary: This study examined how agriculture in six southwestern states might adapt to large reductions in water supplies, using the U.S. Agricultural Resource Model (USARM), a multiregion, multicommodity agricultural sector model. In the simulation, irrigation water supplies were reduced 25% in five Southern Mountain (SM) states and by 5% in California. USARM results were compared to those from a "rationing" model, which assumes no input substitution or changes in water use intensity, relying on land fallowing as the only means of adapting to water scarcity. The rationing model also ignores changes in output prices. Results quantify the importance of economic adjustment mechanisms and changes in output prices. Under the rationing model, SM irrigators lose $65 in net income. Compared to this price exogenous, "land-fallowing only" response, allowing irrigators to change cropping patterns, practice deficit irrigation, and adjust use of other inputs reduced irrigator costs of water shortages to $22 million. Allowing irrigators to pass on price increases to purchasers reduced income losses further, to $15 million. Higher crop prices from reduced production imposed direct losses of $130 million on first purchasers of crops, which include livestock and dairy producers, and cotton gins. SM agriculture, as a whole, was resilient to the water supply shock, with production of high value specialty crops along the Lower Colorado River little affected. Particular crops were vulnerable however. Cotton production and net returns fell substantially, while reductions in water devoted to alfalfa accounted for 57% of regional water reduction.
  • Authors:
    • Blanco-Lopez, M. A.
    • Perez-Rodriguez, M.
    • Garcia-Cabello, S.
    • Lopez-Escudero, F. J.
  • Source: European Journal of Plant Pathology
  • Volume: 133
  • Issue: 4
  • Year: 2012
  • Summary: Verticillium dahliae Kleb. causes Verticillium wilts in many herbaceous and woody species. Many hosts of the pathogen are commonly cultivated in Andalucia (southern Spain), particularly major crops such as cotton, vegetables, almond, peach and, particularly, olive, in which the fungus causes Verticillium wilt of olive. Infective structures of the pathogen (microsclerotia), produced in the late phases of the infection cycle in senescent tissues of the infected plants, can be spread over short or long distances by a number of dispersal methods. Irrigation water is one of the factors implicated in this spread of V. dahliae. Indeed, increasing irrigation dosages in crops or an inadequate irrigation schedule have been identified as cultural practices favouring Verticillium wilt onset and severity in olive and other hosts. Most of the cultivated areas in the Guadalquivir Valley of Andalucia are irrigated by pumping stations using modern infrastructures that supply water to thousands of hectares of farm land, which are usually associated with irrigation communities. This study demonstrates that the pathogen survives in the sediment and particles suspended in water used for irrigation in different facilities of an irrigation community, that were involved in distributing water (main canal and reception tank of a investigated pumping station, irrigation pools and sand from filters). Thus microsclerotia moves from the pumping station to individual plots (olive and cotton cultivated farm) as viable microsclerotia, free or embedded in soil particles and plant debris, suspended in the irrigation water, or deposited in the sludge in piping systems or water storage ponds. We have detected amounts of inoculum in the solid pellet samples in these facilities that ranged from 2.7 to 6.7 microsclerotia per gram. Besides this, water from drippers in cultivated plots released into the soil a variable amount of infective propagules of the pathogen over time that accounted for 3.75 microsclerotia/m 3 in some of the recording times. Therefore, irrigation water becomes an important source of inoculum that is very effectively involved in medium and long-distance spread of the pathogen.
  • Authors:
    • Arriaga, J.
    • Muriel-Fernández, J. L.
    • Durán-Zuazo, V. H.
    • García-Tejero, I. F.
  • Source: Scientia Horticulturae
  • Volume: 133
  • Year: 2012
  • Summary: This study examines the suitability of trunk dendrometers for assessing fruit growth under deficit irrigation (DI) for two consecutive years in a mature citrus orchard. Two DI programmes were applied during the maximum evapotranspirative demand period: sustained-deficit irrigation, applied at 50% ET C on average, and low-frequency deficit irrigation, applied according to plant-water status, establishing different irrigation-restriction cycles. Additionally, a control treatment at 100% ET C was monitored for the entire irrigation season. Trunk daily growth (TDG) and fruit daily growth (FDG) were estimated together with stem-water potential at midday (Psi stem) and the maximum daily shrinkage of the trunk (MDS). Significant relationships were determined for Psi stem vs. TDG ( R2=0.60), and vs. FDG ( R2=0.78). In addition, significant relationships were established between TDG vs. FDG ( R2=0.60), and between the daily increment of MDS (DeltaMDS) and FDG ( R2=0.50), revealing the strong connection between trunk and fruit variations caused by water stress. According to these findings, the DI effects on fruit growth can be monitored by means of TDF or temporal evolution of Psi stem, promising automation possibilities for appropriately regulating irrigation under DI programmes, and predicting its effects on fruit size by continuous field measurement.
  • 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:
    • Houdret, A.
  • Source: Water Alternatives
  • Volume: 5
  • Issue: 2
  • Year: 2012
  • Summary: Water and land grabbing is often an indication of growing control by an elite group over natural resources for agricultural production, marginalising their previous users. It may drive and exacerbate social, economic and political disparities and so increase the potential for conflict. In Southern Morocco's Souss valley, the overuse of water resources is causing aquifer levels to sink and agricultural land to be abandoned. At the same time, irrigated agriculture is still expanding, often permitting the lucrative growing of citrus fruits. This export-oriented agriculture mostly benefits the economic elite, increasing their political influence. Small farmers, on the other hand, face growing threats to their livelihoods. A public-private partnership (PPP) project reallocating water through a 90 km pipeline from a mountain region to plantations in the valley has been implemented to enhance water supply and save dying citrus plantations. However, it is accentuating disparities between farmers. We trace the dynamics of marginalisation linked to this PPP and use emerging water conflicts as a lens to analyse the appropriation of water resources and the underlying political and economic relationships and strategies. On the basis of the case study, we show that water conflicts are as much struggles over political influence as over the resource itself and, consequently, that the related phenomenon of 'water grabbing' is not only driven by economic interests but also determined by a political agenda of regime stability and economic control. However, we also point to the opportunities presented by recent social and political changes in Morocco, including the influence of the 'Arab Spring', and argue that such processes as increasing transparency, decentralisation and the empowerment of local civil society support the re-appropriation of water, livelihoods and power. We conclude by examining the limits of this PPP model, which has been internationally praised by financial institutions, and calling for a careful evaluation of its ecological and social impacts before such experience is replicated elsewhere.
  • Authors:
    • Al-Ain, F.
    • Al-Chammaa, M.
    • Khalifa, K.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 43
  • Issue: 16
  • Year: 2012
  • Summary: A field experiment was carried out to study the effect of different rates of potassium (K) fertilizer [0, 50, 100, and 150 potassium oxide (K2O) ha(-1)] in the presence of increased supply of nitrogen (N) (120, 180, and 240 kg N ha(-1)) on cotton (Gossypium hirsutum L.) yield and the N and K use efficiencies using the N-15 isotopic dilution technique. Potassium fertilizer increased cotton yield, which was significant and more pronounced with the application of N in the high level (N3). The greatest cotton yield (6442 kg ha(-1)) was obtained in N2K3 treatment with an increase of 14% over the control. In addition, K fertilizer significantly increased N uptake efficiency in the N2 and N3 treatments. The greatest N uptake efficiency (98%) was in N2K3 treatment. The greatest K uptake efficiency (42%) was occurred in N3K1 treatment. In conclusion, the use of K fertilizer could be useful when growing cotton in soils of moderate to high N content to improve N uptake efficiency and consequently increase cotton yield.
  • 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:
    • Basheer, A. M.
    • Mohamed, E. M.
    • Abukaf, N.
  • Source: Egyptian Journal of Biological Pest Control
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: A study to survey parasitoid species associated with the citricola scale insect, Coccus pseudomagnoliarum (Kuwana) (Homoptera: Coccidae) was carried out in untreated citrus orchards, at 4 districts (Alrama-Ean Alaros-Hmaimimm and Albassa), at Lattakia, Syria, seasons 2010 and 2011. Weekly sampling was undertaken by collecting infested leaves and twigs. Rate of parasitism, population trend of the parasitoid complex and the role of each species was determined. The survey revealed the presence of 10 parasitoid species; 2 aphelinids ( Coccophagus lycimnia and Coccophagus sp.), 5 encyrtids ( Metaphycus sp., M. helvolus, Microterys nietneri, Baryscapus sp. and Encyrtus sp.), one pteromalid ( Prochiloneurus sp.) and 2 eulophids ( Abrostocetus sp. and Tetrastichus sp.).