• Authors:
    • Ribeiro Junior, P.
    • Teixeira, M.
    • Coelho, R.
    • Armindo, R.
  • Source: ENGENHARIA AGRICOLA
  • Volume: 32
  • Issue: 3
  • Year: 2012
  • Summary: This study aimed to evaluate the spatial variability of leaf content of macro and micronutrients. The citrus plants orchard with 5 years of age, planted at regular intervals of 8*7 m, was managed under drip irrigation. Leaf samples were collected from each plant to be analyzed in the laboratory. Data were analyzed using the software R, version 2.5.1 Copyright (C) 2007, along with geostatistics package GeoR. All contents of macro and micronutrients studied were adjusted to normal distribution and showed spatial dependence. The best-fit models, based on the likelihood, for the macro and micronutrients were the spherical and matern. It is suggest for the macronutrients nitrogen, phosphorus, potassium, calcium, magnesium and sulfur the minimum distances between samples of 37; 58; 29; 63; 46 and 15 m respectively, while for the micronutrients boron, copper, iron, manganese and zinc, the distances suggests are 29; 9; 113; 35 and 14 m, respectively.
  • Authors:
    • Ohta, H.
    • Sumi, H.
    • Inafuku-Teramoto, S.
    • Taira, I.
    • Asikin, Y.
    • Takara, K.
    • Wada, K.
  • Source: Journal of Agricultural & Food Chemistry
  • Volume: 60
  • Issue: 32
  • Year: 2012
  • Summary: Citrus peels are important sources of various pleasant aroma compounds and valuable bioactive substances. To investigate differences in the composition and content of Shiikuwasha ( Citrus depressa Hayata) peels from different cultivation lines, the composition of volatile aroma components, flavanones, and polymethoxylated flavones (PMFs) in four Shiikuwasha cultivation lines was examined. The composition of volatile aroma components in cold-pressed extracts of Shiikuwasha peels was analyzed using gas chromatography-flame ionization detection and gas chromatography-mass spectrophotometry. The extracts contained mainly monoterpene hydrocarbons (93.40-97.25%), including limonene (46.52-68.26%) and gamma-terpinene (21.48-30.52%). Differences in the composition of volatile aroma compounds in the Shiikuwasha cultivation lines were revealed using principal component analysis. Additionally, the composition of flavanones and PMFs was determined using high-performance liquid chromatography methods. Neohesperidin (96.58%) was the predominant flavanone in 'Izumi kugani' peel, while the other peels had high hesperidin contents (89.26-98.66%). Moreover, the PMFs of Shiikuwasha peels were composed of nobiletin (56.74-64.77%) and tangeretin (23.17-34.70%).
  • Authors:
    • Mustian, J.
    • Bordovsky, J.
  • Source: Applied Engineering in Agriculture
  • Volume: 28
  • Issue: 3
  • Year: 2012
  • Summary: The recent increase in the use of subsurface drip irrigation (SDI) for cotton production in the Texas High Plains has resulted in questions concerning drip lateral position and orientation relative to crop rows. Field experiments were conducted at Halfway, Texas to evaluate traditional SDI installations with crop rows spaced at 0.76 and 1.02 m; crop row to lateral offsets of 0.0, 0.13, 0.25, and 0.38 m; and crop rows perpendicularly crossing SDI laterals spaced at 0.76, 1.02, and 1.52 m. Traditionally installed SDI with cotton rows spaced at 0.76 m resulted in generally higher yield than those spaced at 1.02 in; however, differences were not significant over the 5-year period. Yields were significantly different between individual rows of adjacent row pairs irrigated with single SDI laterals when row offsets were greater than 0.25 m on 0.76-m row spacing. However, cotton plants from rows closest to the SDI lateral largely compensated for yield losses of rows farthest from the lateral. When considering perpendicularly crossing 1.52-m spaced laterals with 0.76-m wide crop rows, only modest declines in cotton lint yield (1.5% and 3.3%) occurred compared to traditional parallel row-lateral orientation with the same lateral and row spacing. With crop rows perpendicular to laterals, SDI lateral spacings resulted in average yields of 1802, 1869, and 1903 kg ha(-1) at distances of 1.52, 1.02, and 0.76 m, respectively. Orienting rows perpendicular to drip laterals using 0.76-m crop row widths resulted in significantly higher yields and irrigation water use efficiencies than 1.02-m row widths at high irrigation capacity. As water availability declines, these results will provide producers additional information on SDI installation and management.
  • Authors:
    • Maringoni, A.
    • Verona, L.
    • Nesi, C.
    • Theodoro, G.
    • Brugnara, E.
  • Source: IDESIA
  • Volume: 30
  • Issue: 1
  • Year: 2012
  • Summary: The citrus canker, caused by Xanthomonas axonopodis pv. citri, is one of the main citrus diseases and has threatened the world's citriculture. In this study, the damage caused by citrus canker was quantified in a sweet orange culture, cv. Valencia [ Citrus sinensis (L.) Osb.], grafted over 15 year-old Rangpur lime ( C. limonia Osb.), in the municipality of Guatambu, SC, Brazil, in the crop of 2004/05. Evaluations of the number of fruits per plant (NF), fruit yield per plant (P), citrus canker incidence on the fruit (IFR), and incidence (IL) and severity (SV) of citrus canker on 80 leaves per orange tree were performed in the harvest period, applying diagrammatical scales. Plants had large variation in SV (0.16%-1.09%), IL (12.50%-56.25%) and IFR (12.30%-56.09%). Linear regressions were significant between IL * SV, NF * SV, P * IFR, and NF * IFR. There was no significant difference (p>0.05) between the mean estimated values of IL in different quadrants of the crowns of the orange trees (N, S, L and O). Each 1% increase in IFR reduced 2.16 kg and 21.3 fruits per tree.
  • Authors:
    • Gitz, D.
    • Booker, J.
    • Bednarz, C.
    • Lascano, R.
    • Bufon, V.
  • Source: Irrigation Science
  • Volume: 30
  • Issue: 4
  • Year: 2012
  • Summary: Crop irrigation with subsurface drip (SDI) is increasing in the semiarid Texas High Plains (THP). Information on drip-tubing positioning, irrigation strategies, and wetted soil area is needed to increase rainwater effectiveness when well capacities are inadequate to meet full irrigation requirements. Time and resources necessary to test SDI strategies for different conditions through field experimentation is too large. However, a mechanistic model such as Hydrus-2D can quantify the effect of different installation geometries and irrigation strategies. Our objective was to experimentally validate the Hydrus-2D in an Amarillo soil in THP so that the model can be used to evaluate different irrigation frequency and timing strategies for SDI cotton. Results showed that Hydrus-2D simulated volumetric soil water content within +/- 3% of measured values, and simulation bias represented the smaller portion of the simulation error, indicating that the model can be used to evaluate irrigation strategies.
  • Authors:
    • Silva, S.
    • Stuchi, E.
    • Mourao Filho, F.
    • Cantuarias-Aviles, T.
    • Espinoza-Nunez, E.
    • Bremer Neto, H.
  • Source: Scientia Horticulturae
  • Volume: 142
  • Year: 2012
  • Summary: Despite considerable research conducted on 'Tahiti' lime [ Citrus latifolia (Yu Tanaka) Tanaka] in several countries, few long-term studies have focused on rootstock effects on fruit production and quality under non-irrigated conditions. As for many other fruit crops, rootstock studies for 'Tahiti' lime are often based on the evaluation of several horticultural responses simultaneously, instead of considering multivariate statistical approaches which may provide with more comprehensive information. Consequently, a trial was installed to evaluate the horticultural performance of non-irrigated 'Tahiti' lime trees budded onto the following 12 rootstocks: 'HRS 801' and 'HRS 827' hybrids; 'Rubidoux', 'FCAV' and 'Flying Dragon' trifoliates; 'Sun Chu Sha Kat' and 'Sunki' mandarins; 'Cravo Limeira' and 'Cravo FCAV' 'Rangpur' limes; 'Carrizo' citrange, 'Swingle' citrumelo, and 'Orlando' tangelo. The trial was installed in 2001, in an 8 m * 5 m spacing with no supplementary irrigation. Measurements of yield, fruit quality oriented to different consuming markets, canopy volume and tree tolerance to drought, were performed. A multivariate cluster analysis identified both 'Rangpur' lime rootstocks as those inducing larger cumulative yield and higher percentage of fruits for the domestic market, with highest drought tolerance to the trees. Despite of their high susceptibility to drought stress under non-irrigated conditions, the 'Flying Dragon' and 'FCAV' trifoliate rootstocks performed outstandingly for 'Tahiti' lime, inducing higher yield efficiency, early bearing and larger percentage of high-quality fruits for foreign markets, with smaller trees more suitable for high-density plantings.
  • Authors:
    • Sutton, B.
    • Neilsen, J.
    • Mahan, J.
    • Burke, J.
    • Conaty, W.
  • Source: Crop Science
  • Volume: 52
  • Issue: 4
  • Year: 2012
  • Summary: A plant-based thermal optimum approach to irrigation scheduling provides potential benefits in that water applications are scheduled on the basis of plant response to water status. Such irrigation systems require a defined thermal optimum for the crop and while such optimum values have been identified for cotton (Gossypium hirsutum L.) cultivars in the United States, there is no information of this type for cultivars common in Australian production. This paper outlines a threefold approach to determining the optimum temperature (T-opt) of the commercial Australian cotton cultivar Sicot 70BRF in an Australian production system. It combines the use of a laboratory-based fluorescence assay, field-based net C assimilation rate (A) and stomatal conductance to water vapor (g(s)), and canopy temperature (T-c)-yield relations. The fluorescence assay showed a T-opt between 28 and 30 degrees C while leaf gas exchange rates peaked at a leaf temperature (T l) of 29 degrees C. The T-c-yield relations peaked at 26 degrees C, with yield reductions observed when T-c > 28 degrees C. We conclude the T-opt of the Australian upland cotton cultivar Sicot 70BRF to be 28 +/- 2 degrees C. This T-opt will provide valuable information for use in thermal optimum irrigation scheduling systems.
  • Authors:
    • Krutz, L.
    • Park, S.
    • Sij, J.
    • DeLaune, P.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 4
  • Year: 2012
  • Summary: Identifying management practices that conserve and protect water resources are very important to a wide variety of stakeholders within semiarid environments. The objective of this study was to develop water management strategies for transitioning tillage systems in cotton (Gossypium hirsutum L.) production within the Texas Rolling Plains when in a subsurface drip irrigation (SDI) system. Five irrigation regimes (0, 33, 66, 100, and 133% evapotranspiration [ET] replacement) and four tillage systems (conventional till, reduced till, no-till, and no-till with a terminated cover crop) were evaluated. The study was conducted for 3 yr and treatments were replicated three times in a randomized complete block design. Lint yields were not affected by the main effects of tillage or the interaction of tillage and ET replacement. In contrast ET replacement was a significant factor for lint yields, irrigation water use efficiency, and net returns. Greatest lint yields and net returns were achieved at 100% ET replacement. Fitted models indicated that optimum lint yields and net returns were achieved at 104.5% ET and 102% ET, respectively. Irrigation at 83% ET was within the 95% confidence interval for lint yield. Net returns were significantly higher for no-till systems compared with conventional till. Thus, adoption of conservation tillage systems should not negatively affect lint yield or net returns in deficit irrigated SDI cotton systems within the Texas Rolling Plains, particularly during the transition from intensively tilled systems to conservation tilled systems.
  • Authors:
    • de Figueiredo, M.
    • Figueiredo, M.
    • Detomini, E.
  • Source: Revista de Politica Agricola
  • Volume: 21
  • Issue: 1
  • Year: 2012
  • Summary: The main purpose of this study is to identify the optimum allocation of limited amount of land and irrigation water across a number of alternative farm enterprises, maximising the whole-farm profitability by considering present relative prices, changes in river water availability, irrigation system efficiency and a highly variable climate. It was developed an optimisation model by using linear programming language to maximise the whole-farm profit of farm located in Wee Waa (NSW, Australia), for three different scenarios (dry, average and wet years) over two seasons. The whole-farm profit is highly sensitive to climate variability and also to prices and yields variability, especially in relation to cotton.
  • Authors:
    • Silva, J. A. A.
    • Modesto, R. T.
    • Miguel, F. B.
    • Grizotto, R. K.
    • Vieira Jr., J. B.
  • Source: Revista Brasileira de Engenharia Agrícola e Ambiental
  • Volume: 16
  • Issue: 7
  • Year: 2012
  • Summary: The effect of a technological package implemented in a Valencia orange orchard was studied and compared with the conventional system, based on the production and quality of the fruits harvested. The technologies implemented included the densification, fertilization during implantation and training, phytosanitary treatment, weed management, irrigation and pruning. The results for the fruits from the first harvest showed that the Technified System and Irrigation (TS+I) resulted in significant increase in crop yield. This increase was higher in orchards with a higher density of 727 plants ha -1 (5.5*2.5 m spacing) or 667 plants ha -1 (6.0*2.5 m spacing). In general, irrigation concomitant with TS resulted in larger sized fruits and consequently less fruit per standard sized box, and lower soluble solids and titrable acidity. There was no effect on juice yield with the production system or spacing. It is concluded that, in this first evaluation, orchard management technologies concomitant with irrigation (TS+I) is interesting because promoted an increase in crop yield compared to conventional systems.