Browsing by Author "Kogan, M"

Now showing 1 - 11 of 11
  • Thumbnail Image
    Item
    Adsorption of glyphosate in Chilean soils and its relationship with unoccupied phosphate binding sites
    (EMPRESA BRASIL PESQ AGROPEC, 2003) Kogan, M; Metz, A; Ortega, R
    The objective of this work was to investigate glyphosate adsorption by soils and its relationship with unoccupied binding sites for phosphate adsorption. Soil samples of three Chilean soils series-Valdivia (Andisol), Clarillo (Inceptisol) and Chicureo (Vertisol) - were incubated with different herbicide concentrations. Glyphosate remaining in solution was determined by adjusting a HPLC method with a UV detector. Experimental maximum adsorption capacity were 15,000, 14,300 and 4,700 mug g(-1) for Valdivia, Clarillo, and Chicureo soils, respectively. Linear, Freundlich, and Langmuir models were used to describe glyphosate adsorption. Isotherms describing glyphosate adsorption differed among soils. Maximum adjusted adsorption capacity with the Langmuir model was 231,884, 17,874 and 5,670 mug g(-1) for Valdivia, Clarillo, and Chicureo soils, respectively. Glyphosate adsorption on the Valdivia soil showed a linear behavior at the range of concentrations used and none of the adjusted models became asymptotic. The high glyphosate adsorption capacity of the Valdivia soil was probably a result of its high exchangeable Al, extractable Fe, and alophan and imogolite clay type. Adsorption was very much related to phosphate dynamics in the Valdivia soil, which showed the larger unoccupied phosphate binding sites. However relationship between unoccupied phosphate binding sites and glyphosate adsorption in the other two soils (Clarillo and Chicureo) was not clear.
  • Thumbnail Image
    Item
    Clomazone selectivity among six cucurbit crops
    (COLEGIO POSTGRADUADOS, 2005) Figueroa, R; Kogan, M
    To determine clomazone tolerance of cucurbit crops, at different rates (0.3, 0.45, 0.6 and 0.9 kg ai ha(-1)) and to evaluate weed control efficacy of those treatments, six field studies were conducted in the 1998-1999 season. Clomazone at 0.45 kg ai ha(-1) provided an excellent weed control (>90%) compared with the untreated plots. Yield and number of fruit per plot in all crops were not affected (p <= 0.05) by clomazone treatment regardless of the rate used, except in honeydew (Cucumis melo L. vat. inodorus Naud). As for leaf injury, with the exception of zucchini (Cucurbita pepo L.) and winter squash (C. maxima Duch, Ex. Poiret), all other crops [cucumber (Cucumis sativus L.), honeydew (Cucumis melo L. vat. inodorus Naud), watermelon (Citrullus lanatus Thunb. Matsumara and Nakai) and cantaloupe (Cucumis melo L. vat. reticulatus Naud), exhibited leaf bleaching 10 d after treatment; cantaloupe and watermelon were the least tolerant crops. However, the bleaching effect was transient and did not affect yield. Clomazone can be used selectively as a preemergence herbicide on winter squash, zucchini and cucumber at rates ranging from 0.3 to 0.9 kg ai ha(-1); and on honeydew, watermelon and cantaloupe from 0.3 to 0.6 kg is ha(-1).
  • No Thumbnail Available
    Item
    Dew and spray volume effect on glyphosate efficacy
    (2001) Kogan, M; Zúñiga, M
    The influence of three simulated dew levels and 150, 300, and 450 L/ha spray volume on glyphosate control of oat plants was determined from pot experiments. Results showed that the effect of dew level on glyphosate efficacy was related to application volume. Glyphosate efficacy at the low and medium application volume (150 and 300 L/ha) was not affected by dew level. However, glyphosate efficacy decreased when applied at the high spray volume (450 L/ha), regardless of dew level. However. high dew level reduced efficacy only when glyphosate was applied at 450 L/ha.
  • Thumbnail Image
    Item
    Differential phytotoxicity of glyphosate in maize seedlings following applications to roots or shoot
    (WILEY, 2005) Alister, C; Kogan, M; Pino, I
    The transport and differential phytotoxicity of glyphosate was investigated in maize seedlings following application of the herbicide to either roots or shoots. One-leaf maize seedlings (Zea mays L.) were maintained in graduated cylinders (250 mL) containing nutrient solution. Half of the test plants were placed in cylinders (100 mL) containing different C-14-glyphosate concentrations; the remainder received foliar appliation of C-14-glyphosate. After 26 It, the roots and the treated leaves were washed with distilled water, and the plants placed again in cylinders (250 mL) containing fresh nutrient solution for 5 days. Plants were weighed, and split into root, seed, cotyledon, coleoptile, mesocotyl, first leaf and apex. The recovery of 14 C-glyphosate was over 86%. For both application treatments, the shoot apex was the major sink of the mobilized glyphosate (47.9 +/- 2.93% for root absorption and 45.8 +/- 2.91% for foliar absorption). Expressed on a tissue fresh weight basis, approximately 0.26 mug a.e. g(-1) of glyphosate in the apex produced a 50% reduction of plant fresh weight (ED50) when the herbicide was applied to the root. However, the ED50 following foliar absorption was only 0.042 mug a.e. g(-1) in the apex, thus maize seedlings were much more sensitive to foliar application of the herbicide.
  • Thumbnail Image
    Item
    Effect of glyphosate applied over emerged asparagus spears
    (ELSEVIER SCI LTD, 2004) Alister, C; Kogan, M
    The effect of glyphosate applied directly to asparagus spears on their growth and crowns regrowth capacity was studied during the 2001 and 2002 seasons. Homogeneous asparagus crowns, cultivar UC 157 F1, were planted in individual plastic bags two seasons before application. The effect of spear height (smaller and larger than 12 cm), and one or two glyphosate application as well as the effect of time between the application and spear harvest (2, 24, 48 and 72 h) were determined. The Spears were treated with a commercial formulation of glyphosate (isopropylamine salt) at 2.4 kg ai ha(-1). The experimental design was a factorial with an arrangement of complete randomized blocks with four replications. A clear deformation was observed in the sprayed spears after treatment with glyphosate, which was more evident as the time interval between application and harvest increased. Applied spears harvested within 2h after application did not show any evident deformation. The crown regrowth capacity was not affected by glyphosate application directly to spears, eventhough some did show strong damage at the apex. These results show that glyphosate application directly to spears during the harvest season will not produce damage to the asparagus plants. However, residues of glyphosate on harvested spears might be an important issue. (C) 2003 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Efficacy of imidazolinone herbicides applied to imidazolinone-resistant maize and their carryover effect on rotational crops
    (ELSEVIER SCI LTD, 2005) Alister, C; Kogan, M
    A field study was performed in imidazolinone-resistant maize in order to evaluate the effectiveness and carryover effect on rotational crops of two formulated mixtures of imidazolinone herbicides: imazapyr plus imazapic and imazapyr plus imazethapyr. During the 2003 season the mixtures were applied broadcast to five leaves maize plants at doses of 114 and 228 g ha(-1), both tanks mixed with a 31% petroleum hydrocarbon adjuvant at 125 and 250 mL ha(-1), respectively. Overall weed control varied from 85%, up to 95%. Weed species controlled were Setaria sp., Chenopodium album, Solanum, sp., Amaranthus retroflexus and Digitaria sanguinalis, and Echinochloa cruss-galli whilst Eragrostis sp. was not controlled. Soil activity of the herbicides (carryover) was detected over 10 months after application, imazapyr/imazapic mixture being the most persistent. The sensitivity of rotational crops, from high to low, was the following: Beta vulgaris > Capsicum annum > Lycopersicum esculentum > Cucumis melo > Hordeum vulgare > Medicago sativa > Lolium multiflorum > A vena sativa > Pisurn sativurn > Allium cepa > Zea mays. (C) 2004 Elsevier Ltd. All rights reserved.
  • No Thumbnail Available
    Item
    ERI: Environmental risk index. A simple proposal to select agrochemicals for agricultural use
    (2006) Alister, C; Kogan, M
    Agricultural production must respond to high-quality and improved environmental requirements. To choose adequate pest control strategies, it is necessary that there is knowledge to enable management of many agrochemicals parameters that offer sufficient information to take correct decisions. However, information about leaching, persistence, chronic and acute toxicology parameters, bioconcentration and others are hard to perform and analyze for persons without knowledge related with agrochemicals. The Environmental Risk Index (ERI) reported here permits the usage of available parameters of each different agrochemical. These include persistence (DT50), leaching, volatility, octanol-water coefficient (K-ow), reference dose (Rfd), lethal dose (LD50) for non-target organism (mammals, birds, aquatic animals and insects). These can be compared in a simple way for many agrochemicals and ranked according to environmental risk. To assess the use of this index, ERI values were calculated for several agrochemicals used in USA and Europe and related to their detection in ground and surface water. These showed good correlations. This result allows consideration of the ERI as a useful screening tool to incorporate the environment into local or regional regulations and change criteria for individual agrochemical use according to soil, weather or crop management condition. (c) 2005 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Glyphosate-resistant Lolium multiflorum in Chilean orchards
    (BLACKWELL PUBLISHING LTD, 2003) Perez, A; Kogan, M
    Lolium multiflorum (Italian ryegrass) seeds suspected of being resistant to glyphosate were collected from fruit orchards at two locations, San Bernardo (SB) and Olivar (OL), Chile, that had been treated an average of three times per year with the isopropylamine salt of glyphosate during the previous 8-10 years. Laboratory experiments were conducted for each orchard population and a susceptible population, a commercial cultivar called Tama (TM), using Petri dishes containing filter paper saturated with 5 mL of glyphosate solution (0-160 mg a.e. L-1 ). Pot dose-response experiments were also conducted in the greenhouse. The three L. multiflorum populations were treated with glyphosate (0.00-4.32 kg a.e. ha(-1) ). The dose needed to reduce shoot length (Petri dish experiment) and fresh weight (pot dose-response experiment) by 50% was determined for each population. Compared with the TM population, the Petri dish experiment found that the SB and OL populations were five- and sixfold, respectively, more resistant to glyphosate, whereas the pot dose-response experiment found that the SB and OL populations were two- and fourfold, respectively, more resistant to glyphosate. These results confirm a new case of glyphosate resistance in a novel species, L. multiflorum , and correspond to the first case of glyphosate resistance reported from South America.
  • Thumbnail Image
    Item
    Interaction between glyphosate and fluroxypyr improve mallow control
    (ELSEVIER SCI LTD, 2002) Chorbadjian, R; Kogan, M
    The interaction between glyphosate and fluroxypyr for mallow control (M. pairviflora L.) was evaluated under field and greenhouse conditions. In the field, fluroxypyr at 0.2 and 0.3 kg ae/ha, and glyphosate at 1.08 kg ae/ha, were applied separately and mixed. In the greenhouse experiments, fluroxypyr at 0.11, 0.14 and 0.21 kg ae/ha and glyphosate at 0.72, 1.08 and 1.44 kg ae/ha were applied separately and in mixtures. In the field, neither glyphosate nor fluroxypyr controlled mallow, when they were applied separately. In the greenhouse, when the herbicides were applied separately, only fluroxypyr at the highest rate (0.21 kg ae/ha) was effective for mallow control. On the other hand, a positive effect on mallow control was observed when the mixtures of glyphosate and fluroxypyr were applied in field and greenhouse experiments, compared to the efficacy of each compound applied separately. According to Colby's method, results showed that the combined application of glyphosate and fluroxypyr acted synergistically for mallow control. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Simazine dynamics in a vineyard soil at Casablanca valley, Chile
    (WILEY, 2005) Alister, C; Lopez, R; Kogan, M
    Field dissipation, soil movement and laboratory leaching studies were performed to elucidate the effect of two rainfall amounts in the behaviour and environmental fate of simazine under climatic conditions at Casablanca Valley, Chile. Dissipation and soil movement were studied in a field vineyard with a sandy loam soil (Inceptisol; 74.08% sand; 14.87% silt and 11.04% clay). Simazine was applied to bare soil at 2.0 kg AI ha(-1), and its concentration was measured using immunoassay (ELISA) at 0, 10, 20, 40 and 90 days after application under two rainfall amounts, natural field conditions (39 mm) and modified conditions (39 + 180 mm). Simazine leaching was studied using soil core PVC lysimeters (0.9 m height; 0.22m diameter). Field dissipation data were adjusted with a bi-exponential model. Half-life (DT50) values varied between 31.3 (+/- 2.5) and 19.0 (+/- 4.2) days under natural and modified conditions, respectively. Simazine K-d varied from 0.42 to 2.15 (K-oc 32.6-216.2) in the soil profile. Simazine was detected at a 90-cm soil depth in concentrations of 0.0085 (+/- 0.0043) mg kg(-1) and 0.0321 (+/- 0.001) mg kg(-1) under field and modified conditions, respectively. The maximum simazine leachate concentrations were 0.013 (+/- 0.00084) mg litre(-1) (0.012% of total applied simazine) and 0.0084 (+/- 0.00082) mg litre(-1) (0.11% of total applied simazine) for field and modified conditions respectively. These data indicate that water quantity has a significant effect on the DT50 and the amount of simazine that moved through the soil profile, but not on the soil depth reached by this herbicide. (c) 2005 Society of Chemical Industry.
  • No Thumbnail Available
    Item
    Weed control intensity effects on young radiata pine growth
    (2002) Kogan, M; Figueroa, R; Gilabert, H
    An experiment was conducted to quantify the effect of different weed control intensities (WCI) during the first three growing seasons in a Pinus radiata plantation. At the end of the third growing season, results showed that stem volume index of check plants was similar to that of plants that received spot applications in the first and second year. On the other hand, when plots were treated with herbicide spot application (first year) plus band or total area application (second year), the stem volume index was two and three times larger, respectively. However, if the first year WCI consisted of total area application, the second and third year treatment had less effect on yield. The largest biomass yield was obtained when plots were submitted to total area WCI during the first and second year. (C) 2002 Elsevier Science Ltd. All rights reserved.