• Authors:
    • Castel, J. R.
    • Ballester, C.
    • Jiménez-Bello, M. A.
    • Intrigliolo, D. S.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 10
  • Year: 2011
  • Summary: Leaf temperature is a physiological trait that can be used for monitoring plant water status. Nowadays, by means of thermography, canopy temperature can be remotely determined. In this sense, it is crucial to automatically process the images. In the present work, a methodology for the automatic analysis of frontal images taken on individual trees was developed. The procedure can be used when cameras take at the same time thermal and visible scenes, so it is not necessary to reference the images. In this way, during the processing in batch, no operator participated. The procedure was developed by means of a non supervised classification of the visible image from which the presence of sky and soil could be detected. In case of existence, a mask was performed for the extraction of intermediate pixels to calculate canopy temperature by means of the thermal image. At the same time, sunlit and shady leaves could be detected and isolated. Thus, the procedure allowed to separately determine canopy temperature either of the more exposed part of the canopy or of the shaded portion. The methodology developed was validated using images taken in several regulated deficit irrigation trials in Persimmon and two citrus cultivars (Clementina de Nules and Navel Lane-Late). Overall, results indicated that similar canopy temperatures were calculated either by means of the automatic process or the manual procedure. The procedure developed allows to drastically reduce the time needed for image analysis also considering that no operator participation was required. This tool will facilitate further investigations in course for assessing the feasibility of thermography for detecting plant water status in woody perennial crops with discontinuous canopies. Preliminary results reported indicate that the type of crop evaluated has an important influence in the results obtained from thermographic imagery. Thus, in Persimmon trees there were good correlations between canopy temperature and plant water status while, in Clementina de Nules and Navel Lane-Late citrus cultivars canopy temperature differences among trees could not be related with tree-to-tree variations in plant water status.
  • Authors:
    • Chauhan, P. S.
    • Jitendra, S.
  • Source: The Indian Forester
  • Volume: 137
  • Issue: 7
  • Year: 2011
  • Summary: An attempt was made to analyze the vivipary of Citrus sinensis with intent to highlight the utility of harvesting fruits at proper stage. The vivipary observed in sweet orange fruit may be due to increased humidity in garden atmosphere or might be due to coincidental rain, heavy irrigation, and sudden lowering of temperature.
  • Authors:
    • Arpaia, M. L.
    • Sanden, B.
    • Kallsen, C. E.
  • Source: HortScience
  • Volume: 46
  • Issue: 8
  • Year: 2011
  • Summary: The objective of this study was to measure effects of late-season water stress on fruit yield, size, quality, and color of an early-maturing navel orange cultivar, Citrus sinensis (L.) Osbeck 'Beck-Earli'. Three irrigation regimes were initiated in August in the southern San Joaquin Valley of California in 2006, 2007, and 2008. Increasing levels of water stress resulted in decreasing midday shaded leaf water potential (SLWP) ranging from -1.4 MPa in early September to a minimum of -2.5 MPa at harvest. Generally, over the course of the 3 years, late-season water stress decreased fruit grade and increased soluble solids concentration (SSC), titratable acidity (TA), the BrimA index, and orange color. Fruit juiciness and SSC:TA ratios were unaffected by late-season water stress. The intensity of the water stress in 2007 decreased fruit yield by number and weight and decreased the percentage of large fruit. When trees exposed to 2 years of late-season water stress were fully irrigated the next year, fruit yield and quality were similar to trees that had not experienced late-season water stress for the 3 years of the study.
  • Authors:
    • Shimazu, H.
    • Yagyu, H.
    • Numano, N.
    • Kamiya, T.
  • Source: Agricultural Information Research
  • Volume: 20
  • Issue: 3
  • Year: 2011
  • Summary: We developed a mobile phone-based field datalogger system for mandarin orange production. The system focuses on collecting data that can be used to determine the watering schedule for cultivation using multi combined with drip irrigation. In the study area at Kumano, in Japan's Mie Prefecture, automated field monitoring was performed using Field Server, a server computer installed in the field and a sensor network to collect weather information. However, indicators such as fruit size, fruit hardness, leaf roll, and soil or tree volumetric water content are still collected by visual inspection, creating a burden for the field workers. The system we developed lets them input measurements of these indicators directly in the field. The data is then stored by Field Server along with data from other users and environmental data measured by Field Server or Japan's AMeDAS system. The results can be visualized as a timeline using a Web-based system, and the users can compare their results with data from other users, and can then consult with experts in their area.
  • Authors:
    • Nogueira, J. M. F.
    • Smiti, S.
    • Neffati, M.
    • Khadhri, A.
    • Araujo, M. E. M.
  • Source: Natural Product Research: Formerly Natural Product Letters
  • Volume: 25
  • Issue: 1/2
  • Year: 2011
  • Summary: Cymbopogon is an aromatic plant valued for its citrus scent aroma. In this article, the effect of saline irrigation water on yield and quality of Cymbopogon schoenanthus L. was evaluated. Compounds of essential oils were identified by gas chromatography-mass spectrometry and/or 13C-NMR spectroscopy. Results showed that the growth of the aerial part was not affected at a concentration of 50 mmol NaCl. Under salt stress, the content of major chemical compounds was affected differently by the treatment level.
  • Authors:
    • Shaaban, S. H. A.
    • El-Fouly, M. M.
    • Khalifa, R. K. M.
    • Hamouda, H. A.
  • Source: Journal of American Science
  • Volume: 7
  • Issue: 5
  • Year: 2011
  • Summary: The present work aimed to determine the nutritional status of Balady mandarin orchards, through soil testing and leaf analysis, in order to work out a proper fertilization programs. A field study was conducted at El-Tall El-Kepeer, Ismailia governorate, covering 19 Balady mandarin orchards grown on sandy soils under drip irrigation. These soils are of poor fertility. However, fertilization of these orchards still depends upon the grower's inherited knowledge and in very small scale on the extension information. The trees were fifteen years old. The orchard soils had very high pH values, low to high level of EC and Na, and were low in total CaCO 3 and very low in O.M. The values for available nutrients in soil were found to be as very low of P, Fe, Mn, Zn and Cu. Values of K, Mg ranged between very low to medium levels, However values of Ca ranged between medium to high levels. The leaf macronutrient values were low in N, ranged between optimum to high in P and Mg, ranged between low to high in K, However values of Ca was ranged between low and optimum. The leaf micronutrient contents were as follow, Fe ranged from optimum to high; Mn, Zn and Cu were ranged from low to the beginning of optimum levels. The nutrient correlations of the leaves revealed some antagonisms between K and Ca, Mg and both of Mn and Zn. Also, the nutrient correlations of the leaves and fruits revealed some antagonisms between N in leaves and Zn in fruits, P and K in leaves and Mn in fruits, K in leaves and N, Cu in fruits, Ca in leaves and K in fruits.
  • Authors:
    • Krajewski, A. J.
    • Krajewski, S. A.
  • Source: Acta Horticulturae
  • Issue: 894
  • Year: 2011
  • Summary: Over the past 18 years, citrus canopy management strategies (CMS) were developed improving tree health, productivity, fruit quality and management efficiency of orchards in tropical Southern Africa and Australia. These CMS are based on understanding of knowledge of tree phenology and natural growth habit, recognition of fruiting habits of "strong" and "weak" bearing branch units (SBBU and WBBU respectively), tree physiology, floral biology, environmental physiology, effects of canopy illumination, branch sap flow patterns, and of effects on these of climate, weather, topography, altitude and local pest and disease cycles. Secondly, CMS were derived with an understanding of effects on tree physiology of specific pruning and regrowth management practices. Thirdly, cost-effective methods were developed of optimising growth, form and function of non-bearing trees, trees in full production, and old trees declining due to age and/or shading. The strategy is to create, after planting, strong, balanced tree frameworks, and to maintain these through the orchard's life by selectively pruning multiple light- and spray "channels" into the trees' canopies. As new "internal" growth arises and develops, fruiting is displaced to sheltered, well-lit and ventilated canopy interiors. Pruning specifically removes WBBU, and stimulates production of SBBU, directly subtended by scaffold branches in which sap flow is strong. These SBBU bear large, unblemished fruit of uniform high quality. Rejuvenation pruning of old trees is discussed, as is protection of leaf flush from the pests citrus leaf miner, thrips, leafhoppers and pathogens Citrus black spot (CBS), Asiatic citrus canker (ACC) and Huanglongbing (HLB). Also discussed are improvements observed to soil following additions of coarse, organic wood chip mulches derived from triturated prunings, and necessary adjustments in support of CMS to fertiliser practices, irrigation, pest-, disease- and orchard floor management.
  • Authors:
    • M. F. López-Climent (1) V. Arbona (1) R. M. Pérez-Clemente (1) A. Gómez-Cadenas aurelio.gomez@uji.es (1)
    • M. F. López-Climent (1) V. Arbona (1) R. M. Pérez-Clemente (1) A. Gómez-Cadenas aurelio.gomez@uji.es (1)
    • M. F. López-Climent (1) V. Arbona (1) R. M. Pérez-Clemente (1) A. Gómez-Cadenas aurelio.gomez@uji.es (1)
    • M. F. López-Climent (1) V. Arbona (1) R. M. Pérez-Clemente (1) A. Gómez-Cadenas aurelio.gomez@uji.es (1)
    • López-Climent, M. F.
    • Arbona, V.
    • Pérez-Clemente, R. M.
    • Gómez-Cadenas, A.
  • Source: Biologia Plantarum
  • Volume: 55
  • Issue: 1
  • Year: 2011
  • Summary: The effect of increased Cd 2+ concentrations in the watering solution on citrus physiology was studied by using two citrus genotypes, Cleopatra mandarin and Carrizo citrange. Cadmium content in roots and leaves was tested together with measurements of leaf damage, gas exchange parameters, and hormonal contents. Citrus roots efficiently retained Cd 2+ avoiding its translocation to the shoots and Cleopatra mandarin translocated less Cd 2+ than Carrizo. With increasing Cd 2+ concentration all gas exchange parameters were decreased more in Carrizo than in Cleopatra mandarin. Cd-induced increases in abscisic acid and salicylic acid contents were observed in leaves but not in roots of both genotypes.
  • Authors:
    • Shukla, S.
    • Harris, W. G.
    • Obreza,T. A.
    • Sartain, J. B.
    • Schumann, A. W.
    • Mann, K. K.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 174
  • Issue: 6
  • Year: 2011
  • Summary: Variability in soil properties is a complication for fertilization, irrigation, and amendment application. However, only limited progress has been made in managing soil variability for uniform productivity and increased water-use efficiency. This study was designed to ameliorate the poor-productivity areas of the variable sandy soils in Florida citrus groves by using frequent small irrigations and applying organic and inorganic soil amendments. Two greenhouse experiments were set up with sorghum and radish as bioassay crops in a randomized complete block design (RCBD). The factors studied were two soil-productivity classes (very poor and very good), two water contents (50% and 100% of field capacity), two amendments (phosphatic clay and Fe humate), and two amendment rates (10 and 25 g kg -1 for sorghum and 50 and 100 g kg -1 for radish). Amendments applied at 50 and 100 g kg -1 increased the water-holding capacity (WHC) of poor soil by 2- to 6-fold, respectively. The lower rates (10 and 25 g kg -1) of amendments were not effective in enhancing sorghum growth. The higher rates (50 and 100 g kg -1) doubled the radish growth as compared to the control. The results indicate that rates greater than 50 g kg -1 of both amendments were effective in improving water retention and increasing productivity. Irrigation treatment of 100% of field capacity (FC) increased the sorghum and radish growth by about 2-fold as compared with the 50%-water content treatment. The results suggest that the root-zone water content should be maintained near FC by frequent small irrigations to enhance water availability in excessively drained sandy soils. In addition, application of soil amendments in the root zone can enhance the water retention of these soils. Furthermore, managing variable sandy soils with WHC-based irrigation can increase water uptake and crop production in the poor areas of the grove.
  • Authors:
    • Angelocci, L. R.
    • Marin, F. R.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 6
  • Year: 2011
  • Summary: Crop evapotranspiration (ETc) was measured as evaporative heat flux from an irrigated acid lime orchard ( Citrus latifolia Tanaka) using the aerodynamic method. Crop transpiration (T) was determined by a stem heat balance method. The irrigation requirements were determined by comparing the orchard evapotranspiration (ETc) and T with the reference evapotranspiration (ETo) derived from the Penman-Monteith equation, and the irrigation requirements were expressed as ETc/ETo (Kc) and T/ETo (Kcb) ratios. The influence of inter-row vegetation on the ETc was analyzed because the measurements were taken during the summer and winter, which are periods with different regional soil water content. In this study, the average Kc values obtained were 0.65 and 0.24 for the summer and winter, respectively. The strong coupling of citrus trees to the atmosphere and the sensitivity of citrus plants to large vapor pressure deficits and air/leaf temperatures caused variations in the Kcb in relation to the ETo ranges. During the summer, the Kcb value ranged from 0.34 when the ETo exceeded 5 mm d -1 to 0.46 when the ETo was less than 3 mm d -1.