• Authors:
    • Tortosa, F.
    • Villafuerte, R.
    • Barrio, I.
  • Source: Wildlife Biology
  • Volume: 18
  • Issue: 1
  • Year: 2012
  • Summary: Damage caused by wildlife foraging can lead to significant agricultural losses and the problem can be further complicated if the damage-inducing animal is a valuable resource in its own right. Provision of alternative food sources such as cover crops might be a means of reducing the damage which appears to be linked to scarcity of alternative foods in intensively-managed agroecosystems. Cover crops may provide other benefits to agroecosystems, i.e. preventing soil erosion but can potentially have some undesired consequences, i.e. water competition with the cash crop. In our study, we tested the effectiveness of cover crops in reducing the damage caused by foraging European rabbit Oryctolagus cuniculus to vineyards in a semi-arid agroecosystem in southern Spain. Experimental treatments consisted of a combination of the presence/absence of sown cover crops (70% oat Avena sativa and 30% garden vetch Vicia sativa) with/without rabbit exclusion. In the 2009 growing season, we assessed rabbit-induced damage using a browsing index on vine shoots, rabbit use of plots was estimated based on faecal pellet counts and grapevine yield was measured at harvest. Rabbits ate the cover crops, and rabbit use was highest in the plots sown with the oat and vetch cover crop. However, the effect of the presence of the cover crop on the amount of damage caused by rabbits was limited and, moreover, the presence of the cover crop had a negative effect on grapevine yield. Exclosure fences effectively reduced rabbit damage by keeping rabbit densities close to zero, but even a low rabbit number (~1 rabbit/ha) can cause significant damage. Although cover crops provided rabbitswith an alternative food source, they acted as attractants for rabbits and were not effective in reducing the damage caused to vineyards by higher rabbit numbers. Therefore, adding cover crops might not be an effective measure in controlling rabbit-induced damage in semi-arid wine-growing regions.
  • Authors:
    • Baraibar, B.
    • Torra, J.
    • Atanackovic, V.
    • Westerman, P.
  • Source: IOBC/WPRS Bulletin
  • Volume: 75
  • Year: 2012
  • Summary: In dryland cereals in NE Spain, the harvester ant, Messor barbarus L., is responsible for a high percentage of seed removal. A direct density dependent response of seed predators to seed patches may help regulate weed populations. In this study, we investigated if seed removal rate by harvester ants is influenced by weed seed density. For this reason, 60 circular areas of 1 m 2 were created inside four 50*50 m blocks after cereal harvest Lolium multiflorum L. seeds were applied at 1000, 2000, 5000, 10000 or 20000 seeds/m 2, in ten randomly selected areas each; the remaining 10 were used to test the methodology used to retrieve the seeds. After 24h, the remaining seeds were collected using vacuum cleaners or a D-vac and seed removal rates were estimated. In three of the four blocks, seed removal was extremely high (99-100%), and the response was therefore density independent Here, nests densities ranged from 468 to 900 nests/ha. In the fourth block seed removal was 91%, and here nest density was lower (284 nests/ha).
  • Authors:
    • Intrigliolo, D.
    • Castel, J.
    • Ballester, C.
    • Castel, J.
    • Testi, L.
  • Source: Acta Horticulturae
  • Issue: 951
  • Year: 2012
  • Summary: Transpiration of well watered (C) and regulated deficit irrigated (RDI) trees was determined by means of the compensation heat pulse method during 2009 and 2010 in commercial citrus groves of 'Clementina de Nules' (CN) and 'Navel Lane Late' (NLL). In both species, sap flow (SF) was measured in two trees per treatment instrumented with two gauges per tree. CN trees were equipped with two different types of gauges (type1 shorter than type2) determining heat velocity from crossing time at four different xylem depths according to Green et al. (2003). In NLL oranges, all the gauges were identical and the data were processed according to the compensation heat pulse+calibrated average gradient (CAG) method (Testi and Villalobos, 2009). Plant water status was determined by midday stem water potential measurements (Psistem). Results showed that the absolute SF values, and especially those from type2 gauges in CN, clearly underestimated tree water use. Tree to tree variability registered in CN (CV=0.09) was lower than in NLL (CV=0.17) which also showed a 17% of within tree variability. The average nocturnal-to-diurnal sap flow ratio was between 7% and 13%. The evolution of relative SF (e.g. SF RDI/SF C) was in agreement with differences in Psistem (r 2=0.78 in CN and 0.84 in NLL). This SF ratio showed the expected decreasing trend during the water restriction period and the recovery when irrigation was reestablished to normal dose. Overall, the results show that sap flow sensors can detect plant water stress but they also highlight some of the problems for accurately measuring transpiration.
  • Authors:
    • Aragues, R.
    • Isidoro, D.
    • Barros, R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 155
  • Year: 2012
  • Summary: 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 La Violada irrigation 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 irrigation management. 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 irrigation return flows (IRF) diminished from 31% of the applied fertilizer in 1995-1998 to 20% in 2006-2008. NO 3- concentrations and NO 3-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.
  • Authors:
    • Villalobos, F.
    • Gomez-Macpherson, H.
    • Boulal, H.
  • Source: Field Crops Research
  • Volume: 130
  • Year: 2012
  • Summary: In the Mediterranean region, conservation agriculture principles like minimum soil disturbance or retaining residues on soil surface are rarely applied in irrigated annual cropping systems. This paper compares a conservation agriculture practice, permanent bed planting (PB), with a conventional system in which the ridges are reformed annually (CB). Comparisons were made throughout a crop sequence of cotton (Gossypium hirsutum L)-maize (Zea mays L) - cotton in which PB was introduced before the maize cropping. Traffic was controlled during the study. Both maize and cotton crops produced higher leaf area index and biomass under PB than CB and Sand 24% higher yield respectively though the yield benefit for maize was not significant. The PB system did not improve Water-use Efficiency but delayed water use until the later growth stages. Soil organic matter (SUM) was significantly higher in PB compared to CB one year after the introduction of the system, and this difference was due to higher SUM in the 0-0.05 m layer, particularly in the furrows. The lack of negative effects of PB on yield and the positive effects on SUM, coupled with increased water infiltration and reduced erosion shown in previous studies, point to the beneficial adoption of PB in the region assuming the patterns are confirmed in the longer term. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Jimenez-Martinez, J.
    • Elorza, F.
    • Candela, L.
    • Igel, W.
  • Source: Computers and Electronics in Agriculture
  • Volume: 86
  • Year: 2012
  • Summary: According to the general circulation models (CGMs) for future climate projections, a temperature increase, precipitation decrease, and an increase in the variability of extreme events may be expected in the future, likely reducing available water resources. For the western Mediterranean, future climate change projections indicate that temperature increase may range from 1.5°C to 3.6°C, and the precipitation decline will reach between 10% and 20%, which may result in a significant reduction of natural groundwater recharge. With the use of modelling tools, the amount of groundwater recharge under different climate change scenarios and varying agricultural management practices can be predicted, and water budget attributes can be estimated, which may allow for quantifying impacts, and assist in defining adaptation strategies. For the Inca-Sa Pobla basin (Balearic Islands, Spain), under future climate change projections, agricultural management alternatives of crop type distribution and irrigation demands are required for planned adaptation strategies. In the area, where irrigation water for agricultural practices originates from groundwater resources, adaptation measures based on a change from mixed crops to potatoes and a 20% decrease of agricultural land cultivation have proven to be efficient for the hydrologic system and associated wetland sustainability.
  • Authors:
    • Carr, M.
  • Source: Experimental Agriculture
  • Volume: 48
  • Issue: 3
  • Year: 2012
  • Summary: The results of research on the water relations and irrigation need of Citrus spp. are collated and reviewed in an attempt to link fundamental studies on crop physiology to drought mitigation and irrigation practices. Background information is given on the centres of origin (south-east Asia) and of production of citrus (areas with subtropical Mediterranean-type climates). The effects of water stress on the development processes of the crop are summarised followed by reviews of the plant water relations, crop water requirements, water productivity and irrigation systems. The topic is complicated by the diversity of species and cultivars (including rootstocks) that are embraced within Citrus spp. The effects of water availability on vegetative growth are understood in general terms, but the relationships have not yet been quantified. Similarly, the need for a 'rest period' to induce flowering is understood, but its magnitude (in terms of a drought stress index or day-degrees) does not appear to have been specified with precision. Again, the effects of drought on flower and fruit formation and retention are understood in general terms, but the relationships have not been quantified in useful ways for specific cultivars. Rooting depth and distribution have only been described in a limited number of situations. Environmental factors influencing stomatal conductances are generally well described and relationships with some growth processes established. Compared with other crops, low stomatal/canopy conductance restricts water use of Citrus spp. Some (limited) progress has been made in quantifying crop water requirements in specific conditions. Despite many recent attempts to specify how little water can be applied at specific growth stages to optimise water productivity through regulated deficit irrigation, no consensus view has emerged. The yield response to 'full' irrigation is of the order 6-7 kg fresh fruit m -3 as a result of an increase in the number of fruit of marketable size. There are also improvements in fruit quality. The most effective way of irrigating a citrus orchard is with a microirrigation system (drip or microsprinklers), but both methods require answers to the question: what proportion of the root zone needs to be irrigated? Both methods, especially drip, allow water to be applied (with fertigation) at very frequent intervals (including several times a day), although formal evidence of the benefits to be obtained from this level of intensification is lacking.
  • Authors:
    • Williams, J.
    • Cetin, M.
    • Ibrikci, H.
    • Lounis, A.
    • Hartani, T.
    • Isidoro, D.
    • Topcu, S.
    • Sellam, F.
    • Barros, R.
    • Cavero, J.
    • Araguees, R.
  • Source: Agricultural Water Management
  • Volume: 103
  • Year: 2012
  • Summary: One of the main constraints of irrigated agriculture is off-site N pollution 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 best management practices for reducing off-site N 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
  • 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.