Pre-emergence Spray Research Articles

Weed management in potato (Solanum tuberosum) grown at different fertility levels in North-east hills

A field experiment was conducted during the summer season (March July) of 1995 and 1996 at Upper Shillong for controlling weeds in potato (Solanum tuberosum L.) crop grown at varying manuring schedule. All the weed- management practices significantly reduced the weed density and its biomass production within all the manuring schedules. Weed-control efficiency was 68, 65 and 58% with metribuzin. Farmyard manure alone or with fertilizers .significantly increased the tuber yield compared with without farmyard manure. All the weed-management practices significantly increased the tuber reduction. Increase in tuber yield was 122, 97 and 94% with metribuzin, paraquat and cultural practices respectively over the control. The best combination was medium fertility level (1 00, 120 and 150 N, P,O, and K,O/ha and 15 tonnesfha farmyard manure) along with pre-emergence spray of metribuzin which gave 17.2 tonnesfha tuber yield.

Integrated weed management in fingermillet (Eleusine coracana)

A field experiment was conducted on fingermillet [Eleusine coracana (L.) Gaertn] during kharif 1996 and 1997 at Ranichauri under rainfed conditions. Pre-emergence spray of 0.5 kg a.i./ha of isoproturon alone and mixed with sand, and post-emergence spray of 0.75 kg a.i./ha of 2, 4-D Na-salt alone and with CaSO, gave simllar grain and stover yields but markedly higher than control. However, isoproturon alone recorded comparatively higher net returns than all other herbicidal treatments and control. Two intercultivation along with 1 hand weeding gave the minimum weed count and weed dry weight and also gave significantly higher grain yield (21.06 @ha) and monetary return (Rs 3,6@0/ha) as compared to other treatments.

Effect of weed-management practices on nutrient depletion by weeds, yield and economics of winter-irrigated cotton (Gossypium hirsutum)

A field experiment was conducted on sandy-loam soils during winter seasons of 2001-02 and 2002-03 at Bhubaneshwar, to explore effective weed management in irrigated cotton. Eleusine indica L. Dactyloctenium aegyptium (L.) Beauv., Digitaria sanguinalis L., Cynodon dactylon L. Pers. Cyperus rotundus L., Cyperus iria L., Ageratum conyzoides L., Heliotropium indicum L. and Gnaphalum indicum L. were the major weed flora in the unweeded control plot. Post-emergence directed spray of paraquat dichloride Q 0.2 kglha at 30 days after sowing with follow up hand-weeding at 60 days after sowing recorded the lowest weed population, maximum weed-control efficiency, highest plant height, leaf-area index, number of sympodia, bolls/plant and boll weight, and significantly increased seed-cotton yield, net return, benefit : cost ratio with maximum NPK uptake compared to other weed control and unweeded control due to lesser weed competition. It was followed by pre-emergence spray of alachlor Q 1.0 kglha at 3 days after sowing with a hand-weeding at 40 days after sowing, Weeds if not controlled within 60 days after sowing, could deplete NPK to the extent of 87.1, 17.9 and 61.7 kglha at 90 days after sowing.

COMPARISON OF GAUCHO, ADAGE, AND LORSBAN FOR GRAIN SORGHUM STAND PRESERVATION IN THE PRESENCE OF THE RED IMPORTED FIRE ANT, 1999

COMPARISON OF GAUCHO, ADAGE, AND LORSBAN FOR GRAIN SORGHUM STAND PRESERVATION IN THE PRESENCE OF THE RED IMPORTED FIRE ANT, 1999: The efficacies of two seed treatments and one surface-applied spray were evaluated against the RIFA in grain sorghum at the Macon Ridge location of the Northeast Research Station near Winnsboro, LA. Grain sorghum was planted no-till at a rate of 70,000 seeds/acre with a John Deere 4050 planter into a bermuda-grass sod containing a high density of RIFA colonies. The test was planted on 27 May in a RCB design with 4-row plots (40-inch centers) x 20 ft and 4 replications. Lorsban 4E was applied as a pre-emergence surface spray (PRE) immediately after planting with a CO2 charged system calibrated to deliver 10 gpa at 34 psi through 8003 nozzles (1/row) in a 20-inch band centered over the seed drill. Other treatments were applied as commercial seed treatments (SEEDT). RIFA densities were estimated on 11, 16, and 25 Jun using a single unruled index card (3 x 5 inches) baited with a teaspoon of peanut butter evenly distributed on one side of the card and was placed, baited side down, in each plot. The number of RIFA was recorded 30 to 60 minutes after placing the card in each plot. Mean values of the three samples are reported. Plant population densities were recorded on 8 Jul by sampling the entire 2 center rows of each plot. Plant heights were estimated on 8 Jul by measuring 20 randomly selected plants from the 2 center rows of each plot. Intra-row skips between plants were recorded on 8 Jul by counting the number of skips > 12 inches between plants in the 2 center rows. RIFA numbers were transformed [log (x + 1)] prior to ANOVA and LSD. Untransformed means are presented for RIFA density. Other data were subjected to ANOVA and LSD without transformation.

Red Imported Fire Ant Management in Grain Sorghum Using Selected Insecticide Treatments, 1997

Abstract The efficacy of selected insecticide treatments was evaluated against the RIFA in grain sorghum. The experiment was conducted at the Macon Ridge location of the Northeast Research Station near Winnsboro, LA. Grain sorghum was planted no-till with a John Deere 7300 planter into a bermuda-grass and containing a high density of RIFA mounds. The test was planted on 30 May in a RCB design with 4-row plots (40-inch centers) X 15 ft and 4 replications. Karate 1 EC and Furadan 4°F were applied as in-furrow sprays at planting (IFSAP) using a CO2 charged system calibrated to deliver 5 gpa of total solution at 35 psi through 8002E flat fan nozzles (1/row). Lorsban 4 EC was applied as pre-emergence surface spray (PRE) immediately post-plant with a CO2 charged system calibrated to deliver 10 gpa at 35 psi through 8001 flat fan nozzles (1/row) in a band 20 inches wide over the row center. Other treatments were applied either as T-banded granules at planting (TBAND) or seed treatments (SEEDT). RIFA densities were estimated on 18 Jun by placing an unruled index card (3 X 5 inches) baited with a teaspoon of creamy peanut butter evenly distributed on one side of the card. One card was placed, baited side down, in each plot and the number of ants attracted after 30 minutes was recorded. Plant population densities were recorded on 2 Jul by sampling the entire 2 center rows. The heights of 20 randomly selected plants from the 2 center rows of each plot were measured on 3 Jul. Intra-row skips between plants were recorded on 3 Jul by counting the number of skips between plants > 12 inches in the 2 center rows. RIFA density data were transformed [log (x + 1)] prior to ANOVA and LSD. Actual means were presented in table.

Evaluation of Selected Hopper Box and Insecticide Treatments for Control of the Red Imported Fire Ant (RIFA) in Grain Sorghum, 1996

Abstract Selected insecticide treatments were evaluated for management of the RIFA in grain sorghum at the Macon Ridge Location of the Northeast Research Station in Franklin Parish, LA. Grain sorghum was planted no-till with a John Deere 7300 planter into a bermuda grass sod containing a high density of RIFA mounds. The test was planted on 11 Jun in a RCB design with 4-row plots (13.33 ft X 15 ft) and 4 replications. Lorsban 4EC, Admire 2F and Furadan 4F were applied as in-furrow sprays at planting (IFSAP) with a CO2 charged system, calibrated to deliver 5 gpa at 25 psi through 8002E flat fan nozzles (1/row). Lorsban 4EC was also applied as pre-emergence surface spray (PRE) immediately post-plant with a CO2-charged system, calibrated to deliver 10 gpa at 35 psi through 8001 flat fan nozzles (1/row) in a band 20 inches wide over the row center. Other treatments were applied either as in-furrow granules at planting (IFGAP), T-banded granules at planting (T-BAND) or seed treatments (SEED T). RIFA densities were estimated on 9 Jul by placing an unruled index card (3 X 5 inches) baited with peanut butter in each plot and recording the number of ants attracted after 30 minutes. Plant population densities were recorded on 9 Jul by sampling the entire 2 center rows. Plant heights were estimated on 9 Jul by measuring 20 plants in each plot. Intra-row skips between plants were recorded on 9 Jul by counting the number of skips > 12 inches in the 2 center rows.

Evaluation of Selected Hopper Box and Insecticide Treatments for Control of the Red Imported Fire Ant in Grain Sorghum, 1995

Abstract Selected hopper box and insecticide treatments were evaluated for management of the RIFA in no-till sorghum at the Macon Ridge Location of the Northeast Research Station in Franklin Parish, LA. Grain sorghum was planted no-till with a John Deere 7300 planter into a bermuda grass sod containing a high density of RIFA mounds. The test was planted on 19 May in a RCB design with 4-row plots (13.33 ft X 15 ft) and 4 replications. Lorsban, Admire and Furadan were applied as in-furrow sprays at planting (IFSAP) with a CO2 charged system calibrated to deliver 5 gpa at 35 psi through 8002E flat fan nozzles (1/row). Lorsban was also applied as pre-emergence surface spray (PRE) immediately post-plant with a CO2 charged system calibrated to deliver 10 gpa at 35 psi through 8001 flat fan nozzles (1/row) in a band 20 inches wide over the row center. Other treatments were applied either as in-furrow granules at planting (IFGAP), T-banded granules at planting (T-BAND) or seed treatments (SEEDT). RIFA densities were estimated on 29 May by placing an unruled index card (3X5 inches) baited with peanut butter in each plot and recording the number of ants attracted after 2 h. Plant population densities were recorded on 15 Jun by sampling the 2 center rows. Plant heights were estimated on 15 Jun by measuring 20 plants in each plot. Intra-row skips between plants were recorded on 15 Jun by counting the number of skips > 12 inches in the 2 center rows. Sorghum seed yields were obtained on 9 Aug from the 2 center rows of each plot.

Evaluation of Selected Insecticides for Control of Red Imported Fire Ant in Grain Sorghum, 1994

Abstract The efficacy of selected insecticides and application methods for management of RIFA in no-till sorghum was evaluated in two tests at the Macon Ridge Branch of the Northeast Research Station in Franklin Parish, LA. Both tests were planted in a Gigger silt loam (pH = 5.0, 1.4% organic matter) in an area that had been covered with a hairy vetch (Vicia villosa) winter cover crop. Plots consisting of 4 rows (40 inch centers) by 35 ft were planted on 28 Apr in a RCB with 4 replications. Lorsban 4EC and Asana XL were applied as in-furrow sprays at planting (IFSAP) with a CO2 charged system calibrated to deliver 5 gpa at 35 psi through 8002E flat fan nozzles (1/row). Lorsban 4EC and Asana XL were also applied as pre-emergence surface sprays (PRE) with a CO2 charged system calibrated to delvier 10 gpa at 35 psi through 8001 flat fan nozzles (1/row) in a 20 inch band immediately post-plant. Other insecticide treatments were applied either as in-furrow granules at planting (IFGAP), T-banded granules at planting (T-BAND) or seed treatments (SEEDT). RIFA numbers were estimated on 11 May by placing an unruled index card (3 × 5 inches) baited with peanut butter in each plot and recording the no. of ants attracted after 3 h. Plant stand densities were recorded on 19 May by sampling the entire 2 center rows in each plot. Plant heights were estimated on 25 May by measuring 20 plants in each plot. Sorghum seed yields were recorded on 15 Aug by harvesting the 2 center rows of each plot.

EFFECT OF TIME OF NITROGEN APPLICATION, METHODS OF WEED CONTROL AND SOWING ON YIELD AND ECONOMICS OF MAIZE

Field experiments were conducted at the Agricultural College and Research Institute, Coimbatore to study the yield and economics of methods of weed control (hand weeding twice at 20 and 40 days after sowing (DAS), atrazine pre-emergence spray @ 0.5 kg ai/ha) and sowing (direct seeding and transplanting maize with 5 day old seedlings) and time of nitrogen application and their combined influence. Hand weeding twice at 20 and 40 DAS, transplanting of 5- day-old seedlings and application of nitrogen in three splits as 25% basal + 50% at knee high stage + 25% at tasseling stage recorded significantly higher yields, gross returns, net returns and benefit cost ratio.

Control of Chara with oxadiazon and copper sulphate in waterlogged rice fields in India

Experiments were carried out during 1982–1984 in Chara-infested areas under farmer's-field conditions. Under the worst crop-weed competition, the alga accumulated ∼ 1060 kg dry matter ha −1 and removed 21.14 kg N ha −1 causing a reduction in rice yield of ∼41%. For safe, effective and economic control of Chara, a pre-emergence spray application of oxadiazon at 2 kg ha −1 was found to be highly effective and comparable to the efficacy of copper sulphate at 16 kg ha −1. The dose of copper sulphate could be reduced to 0.75 kg ha −1 when applied in combination with an equal amount of oxadiazon. Combined application of these two herbicides was found to be much more effective than their single application. Postemergence application of the herbicides by means of mud balls, sand mix or the usual spray was ineffective.

Metolachlor Transport in Surface Runoff

AbstractIn 1987 metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] was applied to a 5.5‐ha corn field in southern Ontario, Canada, in two separate areas—as a preemergence surface spray with cross‐contour plowing and as a pre‐plant incorporated treatment with contour plowing. The application rate for both treatments was 2.64 kg a.i. ha−1. Metolachlor concentrations in soils and in the dissolved and adsorbed phases in runoff from natural rainstorms were monitored throughout the growing season. Persistence in soils decreased exponentially after application, although there was evidence of temporary accumulation of metolachlor in footslope areas. Dissolved concentrations in runoff decreased with time, while temporal trends in adsorbed concentrations reflected changes in metolachlor persistence in soils. Average ratios of adsorbed to dissolved herbicide concentrations ranged from 7 to 57, and were dependent upon hydrological and pedologic conditions within the treatments. Sediment carried between 9 to 58% of the total metolachlor yield from runoff plots during individual storms, and 20 to 46% of the total yield over the monitoring period. Herbicide incorporation and contour plowing led to significant reductions in dissolved and adsorbed concentrations, and in total metolachlor loss in runoff, relative to application as a preemergence spray with cross‐contour plowing. Incorporation was associated with an increase in the relative importance of sediment in metolachlor transport. Variations in herbicide losses and the relative importance of transport vectors within a given treatment were linked to local hydrological processes.

Effect of Herbicides on the Production of Common Buffelgrass (Cenchrus ciliaris)

Dicamba (3,6-dichloro-o-anisic acid), 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], 3,6-dichloropicolinic acid, picloram (4-amino-3,5,6-trichloropicolinic acid), triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] were applied at rates of 0.3, 0.6, 1.1, and 2.2 kg/ha pre- and postemergence to greenhouse-grown common buffelgrass (Cenchrus ciliarisL. ♯3PESCI). Buffelgrass tolerated preemergence sprays of 3,6-dichloropicolinic acid up to and including 1.1 kg/ha. All other treatments except picloram and 2,4,5-T at 0.3 kg/ha were phytotoxic to emerging buffelgrass. Buffelgrass tolerated early postemergence applications of 2,4-D, picloram, and tebuthiuron at 0.3 kg/ha; dicamba and 2,4,5-T at 0.6 kg/ha; and 3,6-dichloropicolinic acid at 2.2 kg/ha based on oven-dry shoot production 1 month after treatment. Regrowth of buffelgrass from stubble 1 month after original harvest of the early postemergence treatment occurred only with all rates of 3,6-dichloropicolinic acid and 2,4,5-T at 0.3 kg/ha. When treated at 45 days after planting, buffelgrass tolerated dicamba, 2,4-D, 2,4,5-T, 3,6-dichloropicolinic acid, and picloram at 2.2 kg/ha, but top growth production was significantly reduced by most rates of hexazinone and tebuthiuron. Relative differences in regrowth of buffelgrass 1 month after the original harvest were similar to those of the original harvest. Mature buffelgrass (90 or 150 days old) responded similarly to herbicides as the 45-day-old buffelgrass.

Response of Kleingrass and Buffelgrass to Herbicides1

AbstractKleingrass and buffelgrass are sometimes difficult to establish in the field from seeding because of poor seedling vigor and severe competition from weeds. Greenhouse studies were conducted to evaluate the tolerance of kleingrass (Panicum coloratum L. ‘Selection 75’) and buffelgrass (Cenchrus ciliaris L. ‘Nueces’) seedlings to nine herbicides applied pre and postemergence at rates of 0, 0.28, 0.56, 1.12, and 2.24 kg/ha. Herbicides investigated were atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine], ametryn [2‐(ethylamino)‐4‐(isopropylamino)‐6‐(methylthio)‐s‐triarine], prometryn [2,4‐bis(isopropylamino)‐6‐(methylthio)‐s‐triazine], and propazine [2‐chloro‐4,6‐bis(isopropylamino)‐s‐triazine]; linuron [3‐(3,4‐dichlorophenyl)‐l‐methoxy‐l‐methylurea], pendimethalin [N‐(lethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine], alachlor [2‐chloro‐2',6'‐diethyl‐N‐(methoxymethyl)acetanilide], metolachlor [2‐chloro‐N(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐l‐methylethyl)acetamide], and propachlor [2‐chloro‐N‐isopropylacetanilide].Kleingrass and buffelgrass were grown in a 1:1:1 Houston black clay (Udic Pellustert): sand: peat moss mixture in small pots. Five to 10 plants were typically grown in each pot with five replications (pots) per treatment. All herbicides were sprayed in water at a spray volume of 93.5 L/ha. Herbicide injury counts were made by visually estimating percent desiccation and/or dead plants per pot 14 days after treatment.Kleingrass seedlings were tolerant to preemergence sprays of propazine up to and including 0.56 kg/ha. All other herbicides and rates applied preemergence were phytotoxic to emerging kleingrass. At the early postemergence stage, kleingrass tolerated rates up to and including 2.24, 0.56 and 0.28 kg/ha of propazine, propachlor and metolachlor, respectively, but did not tolerate other herbicides included in the study. Response of buffelgrass to pre and postemergence applications of propazine was similar to kleingrass. Buffelgrass, however, tolerated early postemergence sprays of propachlor and atrazine at 0.28 and 0.56 kg/ha; pendimethalin and alachlor at 1.12 kg/ha each; and metolachlor at 2.24 kg/ha. Propazine was the only herbicide that showed promise for both preemergence and postemergence applications in kleingrass and buffelgrass.

An Effective Pre-emergence Weedicide Mix for Use in Pinus Nurseries

SUMMARY Chlorthal, diphenamid, propazine and sulfallate (CDEC) were tested as Pre-emergence sprays for the control of weeds in three slash pine (Pinus elliottii) nurseries located in south-east Queensland. The best weedicide treatment was a combined chlorthal 22,4 kg/ha plus propazine I,I kg/ha mix which provided up to twenty weeks broad spectrum weed control and proved selective to the pine crop. Use of this effective weedicide mix has been safely extended to include the treatment of caribbean (P. caribaea), loblolly (P. taeda) and radiata (P. radiata) pine sowings.

Effect of Certain Herbicides on White Horsenettle (Solanum elaeagnifolium Cav.) under Potted Conditions

Two pot culture experiments were conducted to evaluate the efficacy of high doses of different herbicides in the control of White horsenettle. Tordon 22K. in combination with either bromacil or 2,4-D and San H. 9789 completely prevented the establishment of the root cuttings in the experiment where herbicides were applied as pre-emergence spray. In others the reduction in establishment was more than 90 per cent. In the other experiment, Tordon 22K and San H. 9789 completely destroyed the weeds as post-emer- gence spray to the established weeds. The weed control ranged from 23 to 77 per cent in the rest of the treatments.

Studies on the Crop-Weed Competition and Chemical Weed Control in Irrigated and Dryland Bajra (Pennisetum typhoideum L.).

Experiments conducted at Coimbatore during kharif 1973 revealed that a weed free condition upto 35 days was required for getting economic yield in direct sown irriga- ted Bajra (var HB. 3). Application of atrazine at 0,5 kg a. i.fha as pre-emergence spray was found to be the best effective and economic weed control treatment under irrigated condition. For dry crop, pre-sowing application of atrazine 0.5 kg o. 1/he is recommended. Post-emergence application of 2, 4-D at 1 kg a. i/ha was not effective in controlling weed in both irrigated and dry crop.

Effect of Weed Control Under Different Moisture Levels on Maize

A field experiment conducted to study the effect of weed control under different moisture levels on maize indicated that pre-emergence spray of atrazine was effective in controlling dicot weeds and to a certain extent monocot-weeds. There was increase in yield of grain and straw at 80 per cent available soil moisture regime. There was incre- ase in yield of grain in weeded plots over no-weeding while there was phenomenal incre ase in yield of straw in herbicide applied plot over hand weeded and un-weeded plots. There was significant interaction between moisture levels and the effect of weeds on the crop.

Effect of Fungicides, Herbicides and Combinations on Root Growth of Cotton1

AbstractWe studied the effect of soil‐applied herbicides and fungicides on cotton (Gossypium hirsutum L.) root growth under ambient greenhouse conditions. Root growth of cotton was not affected by soil treatment with the fungicides 1‐Chloro‐2‐Nitropropane (Lanstan)3 or Pentachloronitrobenzen+ e 5‐Ethoxy‐3‐trichloromethyl‐l‐l‐l,2,4‐thiadiazole (Terraclor Super X)3. Trifluralin (α,α,α, trifluoro‐ 2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) applied at 0.84 kg/ha did not affect cotton roots when applied preplant and incorporated; however, the higher rate (1.68 kg/ha) significantly reduced total root growth. Fluometuron [l,l‐dimethyl‐3‐(α,α,α,‐trifluoro‐m‐tolyl)urea] was not injurious to cotton at the rate evaluated. Root growth of cotton was significantly reduced by treatment with 3.36 kg/ha of prometryne [2‐4‐bis(isopropylamino)‐6‐(methylthio)‐s‐triazine] applied as a preemergence spray. There were no significant interactions between fungicides and herbicides; however, interaction as evidenced by a reduction in total growth did occur between trifluralin and prometryne. Based on pesticides evaluated in this series of experiments, deleterious interactions as have been reported by other researchers to occur between herbicides and insecticides do not occur.

Título en español.

Los herbicidas 2-cloro-4,6-bis(isopropilamino)-s-triazine (Propazine), 2-cloro-4-etilamino-6-isopropilamino-s-triazine (Atrazine) y 3-(3-4-diclorofenil)- l,l-dimetilurea (Diuron) fueron evaluados en siembras de sorgo (Sorghum bicolor (L.) Moench.) de la variedad SA 406 en la Estación Experimental Federal de Mayagüez, Puerto Rico. Las pruebas preliminares indicaron que las aspersiones de Propazine o de Atrazine aplicados como preemergente, a razón de 3 libras por acre, fueron eficaces para combatir los yerbajos de hoja ancha y las gramíneas, mientras que el Diuron fue menos eficaz contra los yerbajos de hoja ancha. El Propazine fue menos nocivo al sorgo que el Atrazine. Pruebas adicionales demostraron que la eficacia del Propazine fue mayor durante la sequía (usando riego) que durante la temporada lluviosa. Durante la estación seca, un predio testigo desyerbado con azada produjo la mayor cantidad de forraje, pero este rendimiento no fue significativamente mayor que la que se produjo mediante los tratamientos con 1 y 3 libras de Propazine por acre. Sin embargo, durante la estación lluviosa, el rendimiento del predio testigo desyerbado fue significativamente mayor que el de los predios sometidos a otros tratamientos. No se notaron efectos residuales del herbicida en las siembras de avena (Avena sativa (L.)) hechas 6 meses más tarde en los predios que habían sido tratados con 1 y 3 libras de Propazine por acre. La eficacia demostrada por el Propazine cuando se aplicaron de 2 a 3 libras por acre, unido a su bajo costo, parecen hacer de este herbicida un medio económico para combatir los yerbajos en las siembras de sorgo en los trópicos, siempre que el tipo de suelo, la precipitación pluvial, los yerbajos, etc. sean similares a los que prevalecieron en estos estudios.

Título en español

Durante 16 meses y bajo condiciones de invernadero se cultivaron plantas de caña de azúcar en un suelo arcilloso y en otro francoarenoso, ambos tratados con Diurón, Este estudio tenía tres objectivos: 1, Evaluar los efectos del Diurón sobre la producción de azúcar; 2, determinar los efectos del Diurón sobre las enzimas por un período prolongado; 3, medir los efectos residuales del Diurón sobre la producción de azúcar en varios tipos de suelos. Las plantas se regaron con un equivalente de alrededor de 75 pulgadas de lluvia al año. El Diurón se aplicó a los suelos en aspersiones preemergentes, a razón de 0, 2, 6 y 18 libras por acre. Se obtuvieron los resultados siguientes: 1. El Diurón impidió marcadamente la producción de azúcar en las plantas de 2 meses de sembradas. El efecto disminuyó a los 6 meses y desapareció a los 12 y a los 16 meses. 2. Los análisis de la hoja indicaron que la absorción del Diurón disminuyó marcadamente después de 2 meses; y a los 16, sólo rastros del yerbicida llegaban al tejido foliar. 3. A los 2 meses las plantas absorbieron el Diurón más fácilmente en el terreno franco que en el arcilloso. A los 16 meses las muestras de hojas tomadas del terreno franco no acusaron la presencia del Diurón, indicando así que se había extinguido totalmente el yerbicida aplicado. 4. La gran absorción del Diurón en el terreno franco fue acompañada de una supresión mayor del azúcar, en comparación con las muestras obtenidas en el arcilloso. 5. El tipo de suelo afectó marcadamente la actividad de la fosfatasa, la ATP-asa, la amilasa, la invertasa, la peroxidasa y la fosforilasa del almidón. Ninguno de los cambios en las enzimas fue consistente, lo que sugirió que los efectos debidos al tipo de suelo eran indirectos. 6. El Diurón causó reacciones anormales en las enzimas, pero, también, los cambios eran inconsistentes. La teoría es que la reacción de la planta a la acción inicial del Diurón incluye la síntesis anormal de las enzimas y la de las substancias que bloquean los puntos en que actúa el yerbicida. 7. En términos generales, la actividad enzimática disminuyó según la edad de las plantas. Las muestras del primer retoño, que representan 4 meses de crecimiento nuevo, no indicaron una actividad comparable a la obtenida en el material original a los 4 meses de edad.