• 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:
    • 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.
  • Authors:
    • Finlay, L. A.
    • Weaver, T. B.
    • Hulugalle, N. R.
    • Lonergan, P.
  • Source: Soil Research
  • Volume: 50
  • Issue: 4
  • Year: 2012
  • Summary: Comparative studies of soil quality and energy use in two- and three-crop rotations in irrigated cotton ( Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are sparse. Our primary objective was to quantify selected soil quality indices (salinity, sodicity, exchangeable cations, nitrate-N, pH), crop yields, and greenhouse gas emissions in four irrigated cotton-based cropping systems sown on permanent beds in a Vertosol with subsoil sodicity near Narrabri in north-western New South Wales. A secondary objective was to evaluate the efficacy of sowing vetch in rotation with cotton over a long period on the incidence of black root-rot in cotton seedlings. Results: presented in this report pertain to the period June 2005-May 2011. The experimental treatments were: cotton-cotton; cotton-vetch ( Vicia benghalensis L.); cotton-wheat ( Triticum aestivum L.), where wheat stubble was incorporated; and cotton-wheat-vetch, where wheat stubble was retained as in-situ mulch. Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in-situ mulch. Soil pH, electrical conductivity (EC 1:5), Cl -, NO 3--N, exchangeable cations, exchangeable sodium percentage (ESP), electrochemical stability index (=EC 1:5/ESP), and EC 1:5/ESC (exchangeable sodium concentration) were evaluated in samples taken from the 0-1.2 m depth before sowing cotton during late September or early October of each year. Incidence of black root-rot was assessed 6 weeks after sowing cotton. Compared with sowing cotton every year, including wheat in cotton-based cropping systems improved cotton yield and reduced soil quality decline, emissions of carbon dioxide equivalents (CO 2-e) per unit area, and CO 2-e emissions per unit of cotton yield. Including vetch in the rotation was of negligible benefit in terms of yield and CO2-e emissions per unit of yield. The rate of soil quality decline was unaffected by including vetch in a cotton-wheat rotation but was accelerated when included in a cotton-cotton sequence. Among all cropping systems, soil quality was best with cotton-wheat and cotton-wheat-vetch but poorest with cotton-vetch. Although CO2-e emissions associated with growing 1ha of cotton could be reduced by 9% by growing vetch because of substituting fixed atmospheric N for N fertiliser derived from fossil fuels, this advantage was partly negated by the emissions from farming operations associated with growing a vetch crop. Relative to a two-crop rotation (one cotton-one rotation crop), negligible benefits in terms of yield, soil quality, greenhouse gas emissions, and black root-rot control accrued from a three-crop rotation (one cotton-two rotation crops). Incidence of black root-rot increased as the number of cotton crops sown increased. In addition to the cropping systems, soil quality indices and yield were significantly influenced by irrigation water quality and climate.
  • Authors:
    • Singh, M.
    • Jhala, A. J.
  • Source: Weed Technology
  • Volume: 26
  • Issue: 3
  • Year: 2012
  • Summary: Soil-applied herbicides are commonly used for broad-spectrum residual weed control in Florida citrus. Groundwater contamination from some soil-applied herbicides has been reported in citrus growing areas in Florida. Indaziflam is a new soil-applied herbicide recently registered for broad-spectrum weed control in Florida citrus. There is no information available on leaching behavior of indaziflam in sandy soil. Experiments were conducted to compare leaching of indaziflam with five commercially used residual herbicides in a Florida Candler soil under simulated rainfall of 5 or 15 cm ha -1. Herbicide movement down soil columns was measured by visually evaluating injury and harvesting aboveground biomass of the bioassay species annual ryegrass. Ryegrass was not injured and plant biomass was not affected beyond 30 cm when indaziflam at a recommended rate of 73 g ai ha -1 was leached through the soil column. Leaching of indaziflam increased with increasing amounts of rainfall. For example, indaziflam leached up to 12.20.8 cm (values are expressedSD) and 27.22.6 cm at 5 and 15 cm ha -1 rainfall, respectively. The herbicide ranking from high to low mobility at 15 cm ha -1 of rainfall was bromacil=norflurazon>indaziflam>simazine=pendimethalin>diuron. Overall results suggested that indaziflam leaching was limited in Florida Candler soil in this study; however, field experiments are required to confirm the leaching of indaziflam under natural rainfall situation.
  • 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:
    • Sil, A. C. da
    • Azevedo, F. A. de
    • Correa, F. E.
    • Kupper, K. C.
  • Source: Scientia Horticulturae
  • Volume: 134
  • Year: 2012
  • Summary: The objective of this research was to study the viability of Bacillus subtilis (ACB-69) to control the casual agent in postbloom fruit drop, Colletotrichum acutatum under field conditions. During the 2007/2008 crop season, B. subtilis was tested in 5% (5*10 8 cfu ml -1) and 10% (1*10 9 cfu ml -1) concentrations on 'Pera' sweet orange ( Citrus sinensis (L.) Osbeck) plants grafted on Rangpur lime ( Citrus limonia Osb.), in Botucatu, Sao Paulo, Brazil. The same treatments were repeated in the 2008/2009 crop season with and without adding a carbon source (molasses 5%) to 'Valencia' sweet orange plants grafted on Rangpur lime. Additional experiment was conducted to determine the most appropriate flower growth stage to apply the biocontrol agent. The biological products were applied with an air assisted sprayer in all experiments with the intention of evaluating the practicality of this type of sprayer. A weekly application of B. subtilis (5*10 8 cfu ml -1) reduced the quantity of symptomatic flowers by 47% while the chemical treatment only had an 18% reduction. On the other hand, B. subtilis (10% or 1*10 9 cfu ml -1) applied weekly or applied one week before to the "green bud bloom" stage (like a preventive control) provided a greater average number of effective fruits (ANEF). The addition of a carbon source at the time of application, did not favor the antagonistic activity of bacteria. In controlling postbloom fruit drop, the best time to apply B. subtilis was observed in the open flower stage when the percentage of symptomatic flowers was evaluated. However, when the bacterium was applied in all flowering stages there was a greater average number of effective fruits. The use of air assisted sprayer helped implement the antagonistic on a commercial scale.
  • Authors:
    • Vervoort, W.
    • Ancev,T.
    • Lee, L. Y.
  • Source: Agricultural Water Management
  • Volume: 109
  • Year: 2012
  • Summary: An integrated biophysical and economic model is used to determine the effects of using more water efficient irrigation systems and trade in water rights on the environmental performance of irrigation enterprises in the Mooki catchment within the Murray-Darling Basin, Australia. We find that improved water use efficiency increased profit in the presence of modern irrigation technologies and water trading. Salinity risk downstream is reduced due to the fall in saline discharge from the catchment, and irrigation water is traded away from ecologically significant regions. It is important that the institutional setup gives confidence in the security of water supplies. When irrigators can be assured about the security of their water entitlements in the context of water reform policies, incentives emerge for them to invest in water efficient irrigation technologies and to participate in the water market. Environmental performance can thereby be improved without the need for financial support from the government. Further, minimal government intervention is required to address salinity; given the conjunctive nature of secondary salinity and water use it can be cost-efficient to address both environmental flow and salinity mitigation with a single policy instrument. (C) 2012 Elsevier BM. All rights reserved.