19982015
  • Authors:
    • Lo Giudice, V.
  • Volume: 67
  • Issue: 4
  • Year: 2011
  • Summary: This paper provides information on the behaviour of Clemenrubi, a new clementine selection introduced from Spain, based on field experiences (including the experiments conducted in 2008-10 in Sicily, Italy, on Carrizo citrange rootstock) and existing literatures. Clemenrubi may be a valid selection for the Italian citrus due to its precocious maturation as early as September, but the sunburn and splitting of its fruits must be controlled. Studies in the coming years will be necessary to determine the behaviour of Clemenrubi in different growing conditions. Some suggestions are given to prevent sunburn and splitting of the fruits, including foliar application of calcium nitrate at 2% in June and July, as well as careful management of irrigation and fertilizer application.
  • Authors:
    • Nagler, P. L.
    • Hunsaker, D. J.
    • Neale, C. M. U.
    • Glenn, E. P.
  • Source: Hydrological Processes
  • Volume: 25
  • Issue: 26
  • Year: 2011
  • Summary: Crop coefficients were developed to determine crop water needs based on the evapotranspiration (ET) of a reference crop under a given set of meteorological conditions. Starting in the 1980s, crop coefficients developed through lysimeter studies or set by expert opinion began to be supplemented by remotely sensed vegetation indices (VI) that measured the actual status of the crop on a field-by-field basis. VIs measure the density of green foliage based on the reflectance of visible and near infrared (NIR) light from the canopy, and are highly correlated with plant physiological processes that depend on light absorption by a canopy such as ET and photosynthesis. Reflectance-based crop coefficients have now been developed for numerous individual crops, including corn, wheat, alfalfa, cotton, potato, sugar beet, vegetables, grapes and orchard crops. Other research has shown that VIs can be used to predict ET over fields of mixed crops, allowing them to be used to monitor ET over entire irrigation districts. VI-based crop coefficients can help reduce agricultural water use by matching irrigation rates to the actual water needs of a crop as it grows instead of to a modeled crop growing under optimal conditions. Recently, the concept has been applied to natural ecosystems at the local, regional and continental scales of measurement, using time-series satellite data from the MODIS sensors on the Terra satellite. VIs or other visible-NIR band algorithms are combined with meteorological data to predict ET in numerous biome types, from deserts, to arctic tundra, to tropical rainforests. These methods often closely match ET measured on the ground at the global FluxNet array of eddy covariance moisture and carbon flux towers. The primary advantage of VI methods for estimating ET is that transpiration is closely related to radiation absorbed by the plant canopy, which is closely related to VIs. The primary disadvantage is that they cannot capture stress effects or soil evaporation. Copyright (C) 2011 John Wiley & Sons, Ltd.
  • Authors:
    • Otero, A.
    • Goni, C.
  • Source: ISHS Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: Supplementary irrigation in Citrus sinensis (L.) Osbeck 'Spring' navel and Citrus unshiu Marcow trees were studied according to fruit development stages on the northwestern region of Uruguay (32S, 58W) from 2000 to 2009. The effective rainfall (Pe) variability between consecutive years is bigger than the reference evapotranspiration (ETo) variability; despite the annual water balance seems to be adequate for excellent yields. Water deficit occurs at different intensities during fruit growth stages I, II and III. Supplementary irrigation was necessary in 'Spring' navel and satsuma 'Owari' during stage I and II, although 'Spring' navel requires occasionally irrigation during stage III. The major irrigation impact was to increase the fruit weight but not the number of fruits. The increment in the marketable fruit was related to the best size distribution of the fruits, also it was verified an attenuation on the alternate bearing. An inverse and significant relationship was found between the ETo/Pe ratio and the relative yield reduction in the stage I (R 2=0.73) and in stage II (R 2=0.91); and between the ETo/Pe and the fruit weight in satsuma 'Owari', (R 2=0.56) (R 2=0.85) respectively. The yield reduction between trees without irrigation and all year irrigated represents 20% in 'Spring' navel and 40% in satsuma 'Owari'. Maximum water application of 1000-1200 m 3 ha -1 was required for irrigated trees on stage I and between 1800-2000 m 3 ha -1 for the stages I+II. In a close up view, supplementary water is required to reach maximum marketable yield and alternate bearing reduction in citrus production in temperate conditions.
  • Authors:
    • Loveys, B. R.
    • Hutton, R. J.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 10
  • Year: 2011
  • Summary: In Australian irrigated citriculture, fruit yield and quality outcomes are not tightly related to levels of plant available water, which raises the possibility of using mild water stress applied to part of the root zone, i.e. partial root zone drying, to stimulate physiological mechanisms that reduce tree water use by changing the relationship between stomatal conductance and ambient evaporative conditions. The PRD technique alternates irrigation such that one side of the tree root zone is allowed to dry whilst the other side is irrigated. This significantly reduces the wetted soil volume at any point in time, whilst always maintaining a readily available water supply to part of the root zone. By adopting this irrigation strategy water use of mature Navel orange trees C. sinensis (L.) Osbeck was reduced and water use efficiency was increased. The technique did not induce excessive fruitlet drop and crop yield was unaffected. Both fruit size and juice percentage slightly decreased whereas total soluble solids percentage (TSS) and juice acid percentage increased. As water use was reduced and juice quality attributes were increased, this technique has obvious benefits for juice fruit production. PRD offers an advantage over conventional deficit irrigation strategies because it helps reduce water use by separating the biochemical signaling responses to water deficit in the dry part of the root zone from the physical effects of reduced stomatal conductance due to lower water availability, allowing developmental processes associated with plant growth to remain unperturbed. Irrigating a reduced root zone volume in this way reduces crop water requirement. However, it is also important to understand that this technique pushes the crop to its limits and should only be applied to well established healthy trees. When applying PRD irrigation, it is important that water is supplied with sufficient frequency and depth of wetting to meet the water needs of the whole plant.
  • 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:
    • 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.