Evaluation of Water and Nitrogen Use Efficiency,Digestibility and Some Quantitative and Qualitative Characteristics of Forage Beet Cultivars Under Different Irrigation Methods and Nitrogen Levels

The aim of this study was to evaluate the water and nitrogen use efficiency and some quantitative and qualitative characteristics of forage beet cultivars under the influence of different irrigation methods and nitrogen levels in two cropping years, 2017–18 and 2018–19, at Agricultural Research Station in Karaj, Iran. Experimental factors included the first factor with four irrigation methods (normal leakage, alternate furrow irrigation, fixed furrow irrigation, type (drip-strip)), the second factor was the amount of nitrogen fertilizer with three levels (150, 200 and 250?kg N ha^?1) and the third factor included three forage beet cultivars (Sbsi052, Jamon and Kyros). Among irrigation treatments, alternate furrow irrigation and fixed furrow irrigation had the highest sugar content with 9.28% and 9.17%, respectively. The highest yield of digestible organic matter was obtained in leakage irrigation treatment, nitrogen fertilizer of 250?kg ha^?1 and in Kyros at the rate of 19.45?t ha^?1. The highest yield of root digestible dry matter, potassium, sodium and free nitrogen was observed in leakage irrigation treatment and consumption of 200?kg ha^?1 nitrogen was observed in foreign cultivars. The highest crude protein was observed in alternate furrow irrigation conditions with a consumption of 200?kg ha^?1 nitrogen in cultivar Sbsi052 at 13.08%. Leakage irrigation and type tape had the highest consumption efficiency and efficiency of nitrogen uptake with application of 150 and 200?kg ha^?1 N, and the highest water use efficiency was also observed in leakage irrigation and type tape with application of 250?kg ha^?1 N in domestic and foreign cultivars. The type irrigation method showed better quantitative and qualitative yield than the furrow irrigation methods.

     

Weed competition and control in sugarcane

Losses of about 40% in cane yields due to natural stands of weeds were found in experiments conducted in sugarcane var. Co 527 in the year of planting at Guneid Sugarcane Research Station, Sudan. Weed competition lowered millable stalks per metre row by 32%, stalk height by 24%, stalk thickness by 15% and number of nodes per stalk by 14%. Tillering was the growth phase most affected by weed competition. Cane yields were increased as number of hand weedings increased, but four weedings were not markedly better than three. The average yield (67·04 t ha^?1) obtained from four weedings was not significantly (P= 0·05) better than that of three weedings carried out at 3, 6 and 9 weeks after cane planting. Juice analysis components were also affected by weeds and a 15% reduction in sucrose recovery was recorded. Reductions in the other components were only 4–7%. Atrazine and diuron (3·3 kg ha^?1), metribuzin (2·4 kg ha^?1) and metribuzin (1·3 kg ha^?1) in tank mixture with diuron (1·5 kg ha^?1) gave excellent residual weed control of the dominant weed species, Ipomoea cordofana Choisy., Brachiaria eruciformis (Sm.) Griseb., Corchorus fascicularis Lam., Ocimum basilicum L. and Dinebra retroflexa (Vahl) Panz., for most of the first growing season. Excellent control of weeds achieved by the herbicide treatments resulted in comparable yields to frequently-weeded cane. These herbicides were not phytotoxic to sugarcane var. Co 527.     

Reduced rates of residual and post-emergence herbicides for weed control in vineyards

In 1997 and 1998, five field studies were conducted at four Portuguese wine‐growing regions in order to evaluate the effectiveness of the chemical control of vineyard weeds under Mediterranean conditions using either reduced doses of residual herbicides or only foliar herbicides. Amitrole (3440 g a.i. ha^?1), amitrole + glyphosate mono‐ammonium salt (1720 + 900 g a.i. ha^?1), amitrole (3400 g a.i. ha^?1), amitrole + diuron (2580 + 1500 g a.i. ha^?1), amitrole + simazine (2580 + 1500 g a.i. ha^?1), amitrole + terbuthylazine (2580 + 1500 g a.i. ha^?1) and amitrole + diuron + simazine (2580 + 1300 + 1400 g a.i. ha^?1) were assayed and compared with the following reference herbicides: glyphosate isopropylamine salt (1800 g a.i. ha^?1), amitrole + diuron (2520 + 1680 g a.i. ha^?1), diuron + glyphosate + terbuthylazine (1275 + 900 + 1425 g a.i. ha^?1), amitrole + simazine (1900 + 3900 g a.i. ha^?1) and glyphosate + simazine (800 + 2200 g a.i. ha^?1). The herbicides were applied during late winter. The results indicated that good control was achieved by the application of foliar herbicides alone or of reduced rates of a mixture of residual herbicides with foliar herbicides for at least 2 months. Three months after application, the efficacy of post‐emergence herbicides and lower rates of residual herbicides decreased significantly in clay soils and under heavy rainfall conditions. Convolvulus arvensis– a weed that is becoming increasingly significant in Portuguese vineyards – was poorly controlled, even when glyphosate was used. Despite this, it can be assumed that in those regions in which the trials were conducted, it is possible to employ weed control strategies that entail the elimination or a reduction in the rate of residual herbicides.     

Activated-carbon and ash-carbon effects on the adsorption and phytotoxicity of diuron

Carbon produced by burning paspalum (Paspalum dilatatum L.) under a wide range of conditions (ash-C) adsorbed appreciable quantities of diuron from aqueous solution. However, commercially activated-C was a more efficient adsorbent than any of the ash-C products whose activity was related to their conditions of formation. Broadcast activated-C at a C/diuron ratio ≤5/1 (w/w) prevented death of barley (Hordeum vulgare L.) seedlings receiving the highest diuron treatment (32 kg ha^?1); although 0–8 kg ha^?1 killed the plants in its absence. Only one of the two ash-C products tested caused a significant reduction in the phytotoxicity of ≥16 kg diuron ha^?1. Death of plants was delayed. However, the bioassay was not sufficiently sensitive to measure the smaller reduction in phytotoxicity caused by the other ash-C treatment. Effets d'un charbon actif et de charbons de cendres sur l'adsorption et la phytotoxicité du diuron Les charbons des cendres obtenues en faisant brüler du paspalum (Paspalum dilatatum L.) dans une série étendue de conditions ont adsorbé des quantités appreciates de diuron a partir d'une solution aqueuse. Toutefois, un charbon actif du commerce se révéla comme un adsorbant plus efficace qu'aucun des charbons obtenus dont l'activité fut en rapport avec les conditions de leur obtention. Un poudrage avec du charbon actif dans une proportion pondérale de 5 parties au minimum de carbon pour une partie de diuron a prévenu la destruction de plantules d'orge (Hordeum vutgare L.) ayant reçu le traitement á la dose la plus élevée de diuron (32 kg/ha) alors qu'en l'absence de charbon actif, les plantules furent tuées á la dose de 0.8 kg/ha. Un seul des deux charbons de cendres essayés provoqua une reduction significative de la phytotoxicité du diuron á la dose de 16 kg/ha. La mort des plantes fut retardée. Toutefois l'essai biologique ne fut pas suffisamment précis pour mesurer la réduction plus faible de phyiotoxicité résultant du traitement avec l'autre charbon de cend res. Die Wirkung ton Aktivkohle und Aschekohlenstoff auf die Adsorption und Phytotoxizität von Diuron Aschekohlenstoff, der auf versehiedene Weise durch Verbrennen von Paspalum ditatatum L. gewonnen wurde, adsorbierte aus wässerigen Lösungen beträchtliche Mengen an Diuron. Die vom Handel bezogene Aktivkohle wiir uber ein starkeres Adsorbens als jedes der Aschekohlenstolf-Produkte. Ihre Wirksamkeit hing von der Art der Herstellung ab. Wenn Aktivkohle in einem Verhältnis zu Diuron von ≥5/1 (Gew./Gew.) breitwörfig ausgebracht wurde, konnte bei der höchsten Diuronbchandlung (32 kg ha^?1) das Absterben von Gerstesämlingen (Hordeum vutgare L.) verhindert werden, während hereits 0.8 kg ha^?1 Diuron alieine die Pflanzen abtöteten. Nur eines der beiden geprüften Aschekohlenstoff-Produkte bewirkte bei ≤16 kg ha^?1 Diuron eine gesicherte Reduktion der phytotoxischen Wirkung indem das Absterben der Pflanzen verzögert wurde. Um die geringere Wirkung des anderen Produkls zu erfasscn. war der Biotest zu unempfindlich.     

Impact of Irrigation Timing and Weed Management Practices on Chlorophyll Content and Morphological Traits of Tomato (Solanum lycopersicum Mill.)

Weeds are a major biotic constraint; compete with crop for the same resources and ultimately reduce productivity. This study evaluated the impact of irrigation intervals and weed management treatments on chlorophyll content and morphological growth of tomato to find an appropriate integrated weed management strategy. Two-year field experiments (2018/2019) were conducted at district Mardan (34°15′38″ N and 72°6′36″ E). Tomato F1 hybrid (Taj?3592) was transplanted during March. The experiments were laid out in a randomized complete-block design in split-plot arrangement with three replications. The main block comprised three irrigation intervals (3, 6, and 9 days) and the sub-block included weed management treatments: transparent polythene, black polythene, weeding except Orobanche, sole weeding of Orobanche, weeding of all weeds, copper oxychloride 1.5?kg a.i ha^?1 (single dose), copper oxychloride 1.5?kg a.i ha^?1 (split doses), copper oxychloride?+?humic acid 25?kg ha^?1 (single dose), copper oxychloride?+?humic acid 25?kg ha^?1 (split doses), copper sulphate 2?kg ha^?1 (single dose), copper sulphate 2?kg ha^?1 (split doses), ammonium sulphate 200?kg ha^?1 (single dose), ammonium sulphate 200?kg ha^?1 (split doses), pendimethalin 33 EC 1.44?kg a.i ha^?1, glyphosate 48 SL 1.5?kg a.i ha^?1, and weedy check. Lowest relative weed density (RWD) of O. cernua (2.23%) and highest RWD of O. cernua (38.01%) were recorded in the 3? and 9?day irrigation intervals, respectively. However, 3?day irrigation interval resulted in highest fresh weed biomass (5794?kg ha^?1). Moreover, the 6?day irrigation interval significantly increased chlorophyll content by 11 and 5%, leaf area by 23 and 6%, and number of branches plant^?1 by 30 and 22% compared to 9? and 3?day irrigation intervals, respectively. Among the weed management treatments, black polythene resulted in the highest weed control efficiency (96%), increasing chlorophyll content by 16%, leaf area by 33%, and number of branches plant^?1 by 64% vs. weedy check. Consequently, 6?day irrigation intervals?×?black polythene could be the best weed management strategy, followed by transparent polythene, weeding of all weeds, pendimethalin, glyphosate, and ammonium sulphate.

     

Effect of nitrogen fertilizer application on growth, biomass production and N-uptake of torpedograss (Panicum repens L.)

A glasshouse study was conducted to evaluate the effects of different rates (0, 50, 100, 200 and 400 kg ha^?1) of nitrogen (N) fertilizer application on the growth, biomass production and N‐uptake efficiency of torpedograss. The growth responses of torpedograss to the N application were significant throughout the observation periods. Torpedograss grown for 60 days obtained the highest total biomass of 23.0 g plant^?1 with an application of 200 kg ha^?1 N, followed by 20.4 g plant^?1 with an application of 100 kg ha^?1 N; when it was grown for 90 days a significantly higher biomass of 102.3–106.0 g plant^?1 was obtained with the 200–400 kg ha^?1 N than the biomass (68.0 g plant^?1) obtained with the fertilizer applied at a lower rate. When the torpedograss was grown for 130 days the highest biomass was 230.0 g plant^?1 with the 400 kg ha^?1 N application, followed by a biomass of 150.0 g plant^?1 with the 200 kg ha^?1 N application, but the above‐ground shoot in all treatments was over mature for animal food. The ratio of the above‐ground shoot to the underground part increased with the increase in N application up to 400 kg ha^?1 during the 90 days after planting (DAP), but the above‐ground shoot biomass was the same with the 200 and 400 kg ha^?1 N. The agronomic efficiency of the N application decreased to 5–38 with the increase in N application to 400 kg ha^?1, which was less than half the agronomic efficiency with the 200 kg ha^?1 N. The agronomic efficiency of N was very low (5–22) during the 60 DAP, which indicated that the N application would not be economically viable in this period for torpedograss as a pasture, and short‐duration plants could be cultivated in torpedograss‐infested fields to minimize weed‐crop competition. The nitrogen concentration (%) in the torpedograss increased with the increase in N application, but N‐uptake efficiency was the opposite and the value was very low with the 400 kg ha^?1 N. The above results lead us to conclude that the N application rate of 200 kg ha^?1 is the most effective for torpedograss growth.     

Chemical weed control in transplanted onion (Allium cepa L.) in the Sudan Gezira

Unrestricted weed growth reduced the yield of transplanted onions (Allium cepa L.) by 26–48%. Hand-weeding once, 42 days after transplanting reduced the yield loss to 15%. Application of oxadiazon (1.1–1.3 kg ai ha^?1), pendimethalin (1.2–1.8 kg ai ha^?1), oxyfluorfen (0.14–0.43 kg ai ha^?1) and chlorthal-dimethyl (8.3–13.1 kg ai ha^?1) resulted in yields comparable to the hand-weeded control (82–126%). When sprayed at transplanting these herbicides gave excellent and persistent control of grasses (86–100%). However, they were less effective on broad-leaved weeds (38–94% control). Désherbage chimique de l'oignon repiqué (Allium cepa L.) dans la Gezireh soudanaise La croissance incontrôlée des mauvaises herbes réduit le rendement des oignons repiqués de 26–48%. Un désherbage manuel, 42 jours après le repiquage, ramène la baisse de rendement à 15%. L'application d'oxadiazon (1,1–1,3 kg ma ha^?1), de pendiméthalin (1,2–1,8 ka ma ha¹), d'oxyfluorfen (0,14–0,43 ka ma ha^?1) et de chlortal-diméthyle (8,3–13,1 kg ma ha^?1), a permis d'atteindre des rendements comparables aux témoins désherbés manuellement (82–126%). Lorsqu'ils ont été administrés au moment du repiquage, ces herbicides ont permis un contrôle efficace et persistant des monocotylédones (86–100%). Toutefois, ils se sont montrés moins efficaces à l'égard des dicotylédones (38–94% du témoin). Chemische Unkrautbekämpfung in verpflanzten Zwiebeln (Allium cepa L.) in der Region Gezira (Sudan) Ungehinderte Unkrautentwicklung in verpflanzten Zwiebeln (Allium cepa L.) verringerte die Ernte um 26–48%. Eine Handjätung, 42 Tage nach dem Auspflanzen, reduzierte den Ernteverlust auf 15%. Die Applikation von Oxadiazon (1,1–1,3 kg ai ha^?1), Pendimethalin (1,2–1,8 kg ai ha^?1), Oxyfluorfen (0,14–0,43 kg ai ha^?1) und Chlorthal- dimethyl (8,3–13,1 kg ai ha^?1) erbrachte Ernten, die mit denjenigen, der von Hand gejäteten Kontrollparzellen vergleichbar waren (82–126%). Diese Herbizide, zur Ausflanzzeit ausgebracht, ergaben eine ausgezeichnete und andauernde Kontrolle von Gräsern (86–100%), während die Wirkung gegen breitblättrige Unkräuter geringer ausfiel (38–94%).     

Relative importance of crop seed, manure and irrigation water as sources of weed infestation

Three possible sources of field contamination by weed seeds were studied during 1983–86 in two areas of Fars Province, Iran. These sources were crop seed, irrigation water and sheep manure. Manure was found to be the most important, adding almost 10 million seeds ha^?1 at each application. Farmer-saved seed of wheat, the main crop of the area, added an average of 182,000 weed seeds ha^?1. Irrigation water added no more than 120 seeds ha^?1, but was able to carry seeds over long distances without affecting viability.     

Application timing of asulam for torpedograss (Panicum repens L.) control in sugarcane in Okinawa island

Field and glasshouse experiments were conducted from 1995 through 1996 to evaluate application timing of asulam (methyl sulfanilylcarbamate) for torpedograss (Panicum repens L.) control in relation to plant age in sugarcane. Above‐ground shoots of torpedograss were completely controlled with asulam at 2–4 kg active ingredient (a.i.) ha^?1 applied 60 or 80 days after planting (DAP) in artificially infested pots. But some newly developed rhizome buds survived after asulam application resulting in 1–25 and 76–100% or more regrowth in 60 and 80 DAP‐applied pots, respectively. Whereas the herbicide at 2–4 kg a.i. ha^?1 applied within 60 DAP completely controlled above‐ground shoots, applied 80 DAP at 2 kg a.i. ha^?1 it did not completely control the weed in the artificially infested field. Regrowth levels were 1–25 and 76–100% or more in 60 and 80 DAP‐applied plots, respectively. Asulam at 2–3 kg a.i. ha^?1 applied 20, 40, 60 or 80 DAP in a naturally infested field completely controlled above‐ground shoots and regrowth levels were 76–100 or more, 51–75, 1–25 and 26–50% in these same DAP applied plots, respectively. The herbicide applied at 4 kg a.i. ha^?1 caused chlorosis on younger sugarcane leaves (one‐leaf stage), but when applied at 2–3 kg a.i. ha^?1, no injury symptoms were shown. The herbicide at 2–4 kg a.i. ha^?1 applied within 60 DAP resulted in remarkably higher yield and shoot biomass of sugarcane than that applied 80 DAP. This study suggested that asulam at 2–3 kg a.i. ha^?1 should be applied 60 days after planting for the maximum control of torpedograss regrowth and better yield of sugarcane. This study also indicated that torpedograss cannot be completely controlled with a single application of asulam in a naturally infested field because of rhizome fragmentation by cross plowing and distribution of rhizomes into different soil layers that require different times to emerge. The shoots emerging after asulam application could not be controlled. Another study is required to determine the interval between sequential applications of asulam for better control of torpedograss in a naturally infested field.     

Recovery of Ralstonia solanacearum from canal water in traditional potato-growing areas of Egypt but not from designated Pest-Free Areas (PFAs)

Surveys over three seasons of irrigation, drainage and artesian well water throughout the major potato-growing areas of Egypt indicated that Ralstonia solanacearum bv. 2 race 3 (phylotype II sequevar 1), cause of potato brown rot, was limited to the canals of the traditional potato-growing areas in the Nile Delta region, with positive findings more commonly associated with the network of smaller irrigation canals flowing through potato-growing areas. Pathogen populations in the canals of the Delta (~100–200 cfu l^?1) were generally variable throughout the year with presence linked to potato cultivation in the immediate area. The pathogen was not detected in irrigation or drainage water associated with potato cultivation in the newly reclaimed desert areas (designated as Pest-Free Areas, PFAs) or in the main branches of the Nile upstream from these areas. In vitro studies showed that temperature and microbial activity were the main factors affecting survival of the pathogen in canal water. In experiments at temperatures of 4, 15, 28 and 35°C, survival was longest at 15°C and shortest at 35°C. Survival at 4 and 28°C tended to be intermediate between these extremes as was survival when the bacterium was grown at fluctuating temperatures. Aeration, solarisation and pH variation between 4 and 9 appeared to have little effect on survival. Survival in autoclaved or filter-sterilised canal water was longer than in untreated water irrespective of other factors with survival times exceeding 300 days at 15°C in some experiments. Evidence is presented indicating that survival in water-saturated sediment may be longer than in the overlying water suggesting that sediment may provide a protective niche for the pathogen in some circumstances. The maximum survival time in non-sterile Egyptian canal water at high inoculum pressure was estimated to be up to 300 days at optimum temperature for survival (15–30°C) suggesting the potential for long-distance spread in Egyptian surface waters from sources of contamination.     

Residues of diuron and phytotoxic degradation products in aquatic situations. I. Analytical methods for soil and water

Thin-layer and gas-liquid chromatography, ultraviolet analysis and bioassay with Chlorella spp. have been used to investigate the pathway of degradation of diuron to phytotoxic derivatives when diuron was used as a soil-residual herbicide in irrigation canals. Observations suggest that 1-(3,4-dichlorophenyl)-3-methylurea and 1-(3,4-dichlorophenyl)urea make a contribution to total residues equivalent to a maximum of about 40 and 55%, respectively, of diuron concentrations. Application of a phyto-toxicity rating suggests that in this environment, measurement of diuron specifically would underestimate the total phytotoxicity of residues by a maximum of about 7%.     

Residues in blackcurrants,fodder peas,spinach and potatoes treated with sublethal doses of 2,4,5-T to simulate wind drift damage

Blackcurrants, treated with 0.1 kg of 2,4,5-T ha^?1 (as esters of mixed C₄–C₆ alcohols; ‘Tormona 80’), contained 0.1 mg of 2,4,5-T residues kg^?1 in the berries at ripeness 29 days after treatment. Total residues in the berries were not reduced during growth and ripening, although the residue concentrations declined in the same period due to growth dilution. In spinach leaves from old plants, treated with 0.1 kg ha^?1, 0.05 mg of 2,4,5-T kg^?1 was found 14 days after treatment. Fodder peas showed no residues (< 0.002 mg kg^?1) at harvest 62 days after treatment with 2,4,5-T esters. After application of 0.1 kg ha^?1 on potato plants, the disappearance of 2,4,5-T was rapid during the first month, but residues were translocated into the tubers and reached a constant level of 0.02 mg kg^?1 after 1 month until harvest at 108 days after treatment. In all crops, visible effects were observed after treatment with 0.1 kg ha^?1. After the application at 0.01 kg ha^?1, phytotoxic effects were observed only in blackcurrants, but negligible residues were found in all the test crops.     

Effects of fluazifop-butyl on shoot growth and rhizome buds of Elymus repens (L.) Gould

A series of glasshouse experiments was conducted to evaluate the activity of fluazifop-butyl, butyl 2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy] propionate, against Elymus repens. Foliar applications of doses 0·25–1·0 kg ha^?1 consistently gave better control than did soil applications. The most obvious phytotoxic symptoms were chlorosis and necrosis, beginning with the youngest leaves 5–6 days after spraying, which spread to all leaves within 2 weeks. Translocation was measured by defoliating plants at different times after spraying and assessing regrowth and by evaluating rhizome-bud viability. At low doses (0·125 and 0·25 kg ha^?1) translocation to rhizomes occurred mainly between 6 and 48 h. When fluazifop-butyl was sprayed at a dose range of 0·125–1·0 kg ha^?1, at least 90% of the rhizome buds had accumulated a lethal dose within 72 h of spraying. In another experiment, with a dose of 0·25 kg ha^?1, 31, 72 and 92% of rhizome buds were found to be non-viable when sampled 2, 24 and 48 h respectively after spraying. At 1·0 kg ha^?1 all the buds had accumulated sufficient herbicide to prevent sprouting 48 h after spraying.     

A rapid bioassay for the detection of photosynthesis inhibitors in water

A modified leaf disc buoyancy procedure for the detection of photosynthesis-inhibiting residues in water is described. The modifications proposed, mainly the presence of sodium hydrogen carbonate in the infiltration solution, increased the sensitivity of the method and reduced the time required. The substituted urea and 1,3,5-triazine herbicides diuron, linuron, monuron, atrazine, ametryn and atraton were detected below 0.7 mg litre^?1 using cucumber (Cucumis sativus L., cv. ‘Dalia’) leaf discs. A concentration as low as 0.09 mg diuron litre^?1 could be detected. Although bean (Phaseolus vulgaris L., cv. ‘Bulgarian’) leaf tissue was less sensitive in this bioassay than cucumber, 0.3 mg diuron litre^?1 could still be detected. The test, being very rapid (less than 30 min per determination) and relatively sensitive, could be used for the detection of photosynthesis inhibitors in recycled water used for irrigation.     

Residues and efficacy of fluazifop-butyl in strawberries

Residues of fluazifop-butyl were determined in strawberries from New Brunswick and Nova Scotia, Canada and North Carolina, U.S.A. using a High Performance Liquid Chromatography (HPLC) system. Strawberries harvested within 28 days of treatment (pre-harvest interval= PHI) had detectable residues of fluazifop, ranging from 0.05 ppmw with a split application of 0.25 kg ha-¹ and a 18-day PHI to 3.24 ppmw with a split application of 0.5 kg ha^?1 and a 12-day PHI. Fluazifop was not detected in samples treated 287 days or more before harvest (prior growing season) at 0.25–1.65 kg ha^?1 (three applications of 0.55 kg ha^?1). Fluazifop-butyl did not provide acceptable control (50% with two applications of 0.25 kg ha^?1) of Elymus repens (L.) Gould in a commercial planting in New Brunswick. Control of Digitaria sanguinalis (L.) Scop. was better than 90% with two applications of 0.30 kg ha^?1 in North Carolina. Fluazifop-butyl did not injure strawberries at any of the rates or sites tested. Résidus et efficacité du fluazifop-butyle en culture de fraises Les résidus du fluazifop-butyle dans des fraises provenant de New Brunswick et Nova Scotia au Canada et de North Carolina aux Etats-Unis ont été déterminés en utilisant un système de chromatographie liquide à haute performance (HPLC). Des fraises récoltées avant 28 jours après le traitement (PHI 28) contenaient des résidus de fluazifop décelables, allant de 0.05 ppmw après un apport fractionné de 0,25 kg ha^?1 et PHI 18 à 3,24 ppmw après un apport fractionné de 0,5 kg ha^?1 et PHI 12. Nulle trace de fluazifop n'a été décelée dans des échantillons traités au moins 287 jours avant la récolte, c'est-à-dire pendant la saison précédente, aux doses de 0,25 à 1,65 kg ha^?1 (trois pulvérisations à 0,55 kg ha^?1). Le fluazifop-butyle n'a pas permis une destruction convenable d'Elymus repens (L.) Gould dans une exploitation commerciale au New Brunswick (50% suivant deux pulvérisations à 0,25 kg ha^?1). La destruction de Digitaria sanguinalis (L.) Scop. avec deux pulvérisations à 0,30 kg ha^?1 en North Carolina dépassait 90%. Le fluazifop-butyle n'a provoqué de dégâts dans les fraises à aucune des doses testées ni à aucune localité. Rückstände und Wirkung von Fluazifop-Butyl in Erdbeeren Erdbeeren von Neu-Braunschweig, Neu-Schott-land (Kanada) und Nord-Karolina (U.S.A.) wurden mittels Hochleistungs-Flüssigkeits-Chromatographie (HPLC) auf Rückstande von Fluazifop-Butyl untersucht. Innert 28 Tagen nach der Behandlung (Intervall vor der Ernte = PHI) geerntete Erdbeeren enthielten messbare Rückstande von Fluazifop; sie betrugen zwischen 0,05 ppmw nach einer Split-Applikation von 0,25 kg ha^?1 und einem PHI von 18 Tagen und 3,24 ppmw nach Split-Applikation von 0,5 kg ha^?1 und 12 Tagen PHI. Es wurden keine Rückstände in Proben gefunden, die 287 oder mehr Tage vor der Ernte mit 0,5–1,65 kg ha^?1 (drei Applikationen von je 0,55 kg ha^?1) behandelt worden waren (vor der Wachstumsperiode). Fluazifop-Butyl erzielte keine genügende Kontrolle von Elymus repens (L.) Gould (50% Erfolg nach zwei Behandlungen mit 0,25 kg ha^?1) in einer Produktionspflanzung in Neu-Braunschweig. Der Erfolg gegen Digitaria sanguinalis (L.) Scop. war in Nord-Karolina nach zwei Applikationen von 0,30 kg ha^?1 höher als 98%. Fluazifop-Butyl schädigte die Erdbeeren an keinem der Standorte und mit keiner Dosierung.     

Chemical control of nodding thistle (Carduus nutans L.) in New Zealand pastures

Broadcast sprays of several herbicides were applied at different times of the year at several sites in Hawkes Bay, Canterbury and Otago. For good thistle control, date of application was more important than types of herbicide. In Hawkes Bay, applications made in April, May and June tended to be the most effective. Under slightly cooler Canterbury conditions, April, September and October were the best application dates. In the Otago trials, spring emergence of thistle seedlings meant that the most consistent results came from September or October applications. At all sites, applications made in July or August were relatively ineffective, probably because of low winter temperatures and slow thistle growth rates. MCPA (potassium salt) at 1·0 kg ha^?1 was the standard herbicide used in all experiments. MCPA at 0·5 kg ha^?1, MCPB (sodium salt) at 0·5 and 1·0 kg ha^?1 and 2,4-D at 0·5 kg ha^?1 did not kill as many thistles as MCPA at 1·0 kg ha^?1. MCPA at 1·5 kg ha^?1 and MCPB (butyl) ester + clopyralid at 0·5 + 0·015 or 1·0+0·03 kg ha^?1 gave consistently better control than MCPA at 1·0 kg ha^?1 2,4-D at 1·0 or 1·5 kg ha^?1, MCPB at 1·5 or 2·0 kg ha^?1, and MCPA + MCPB at 0·33 + 1·0 or 0·67 + 0·5 kg ha^?1 gave results very similar to MCPA at 1 kg ha^?1. Thistle control varied between sites and years. Some of the variation may have been due to different proportions of first and second year thistles present at spraying, and to variation in genetically determined herbicide susceptibility. Chemical control of thistles was short term only, because of dormant seeds in the soil.     

Triazine resistance in biotypes of Solanum nigrum and four Amaranthus species found in Spain

Triazine-resistant (R) biotypes of Amaranthus albus L. (tumble pigweed), A. blitoides S. Wats. (prostrate pigweed), A. hybridus L. (smooth pigweed), A. retroflexus (redroot pigweed), and Solanum nigrum L. (black nightshade) were found in Spain. The former two R biotypes were found in simazine-treated, non-tilled olive orchards, whereas the latter three came from atrazine-treated maize (Zea mays L.) crops. All R biotypes survived at rates up to 5.0 kg ha^?1 of soil-incorporated atrazine or simazine, whereas their susceptible (S) or ‘wild type’ counterparts were completely controlled at levels of 0.25 kg ha^?1 atrazine, in the case of A. hybridus, A. retroflexus and S. nigrum, and 2.5 kg ha^?1 in the case of A. albus and A. blitoides. The higher tolerance to triazines of these latter S biotypes appears to be attributable to herbicide detoxification. Photosynthetic electron transport in R biotypes was little affected by atrazine and simazine, but was inhibited by diuron, as shown by fluorescence induction measurements in whole leaves. In Hill reaction assays, the R biotypes showed a high level of resistance to atrazine and simazine (resistance factors in the range 350–900), and very slight resistance to diuron (resistance factors in the range 1.1–1.6). It is concluded that all R biotypes have evolved a chloroplastic mode of resistance similar to that previously described for other triazine-resistant weed biotypes. Résistances aux triazines des biotypes de Solanum nigrum et 4 espèces d'Amaranthus trousiées en Espagne Des biotypes résistant aux triazines (R) d'Amaranthus albus L., d'A. blitoïdes S. Wats, d'A. hybrydus et d'A. retroflexus et de Solanum nigrum L. ont été trouvés en Espagne. Les 2 premiers biotypes (R) ont été trouvés dans des oliveraies non labourées traitées à la simazine, tandis que les 3 derniers viennent de cultures de maïs traitées à l'atrazine. Tout les biotypes R ont survécu à des doses jusqu'à 5 kg ha^?1 d'atrazine ou de simazine incorporée au sol tandis que leurs équivalents sensibles (S) ou ‘types sauvages’étaient complètement détruits à des doses de 0,25 kg ha^?1 d'atrazine dans le cas d'A. hybridus, A. retroflexus et S. nigrum et de 2,5 kg ha^?1 dans le cas d'A. albus et A. blitoïdes. La tolérance plus élevée aux triazines de ces 2 derniers biotypes apparaît être attribuable à la détoxification de l'herbicide. Le transport des d'électrons photosynthétiques dans les biotypes R a été peu affecté par l'atrazine et la simazine mais a été inhibé par le diuron, comme l'ont montré des mesures d'induction de fluorescence dans des feuilles entières. Dans des essais de réaction de Hill, les biotypes R ont exprimé une haute résistance à l'atrazine et à la simazine (facteurs de résistance de 350 à 900) et une très faible résistance du diuron (facteurs de résistance de 1,1 à 1,6). Il est conclu que tous les biotypes R ont développé un mode de résistance chloroplastiques identique à celui déjà décrit par d'autres biotypes d'adventices résistant aux triazines. Triazinresistenz bei Biotypen von Solanum nigrum und vier Amaranthus-Arten in Spanien Triazinresistente Biotypen (R) von Amaranthus albus L. (Weißer Amarant), A. blitoides S. Watson (Westamerikanischer A.), A. hybridus L. (Grünähriger A.), A. retroflexus L. (Zurückgekrümmter A.) und Solanum nigrum L. (Schwarzer Nachtschatten) wurden in Spanien gefunden. Die ersten beiden R-Biotypen stammten aus Simazin-behandelten Olivengärten ohne Bodenbearbeitung, die drei anderen von Atrazin-behandeltem Mais (Zea mays L.). Alle R-Biotypen ertrugen biszu 5,0kg ha^?1 Atrazin oder Simazin, in den Boden eingcarbeitet, während empfindliche (S) oder ‘wilde’ Pflanzen mit 0,25 kg ha^?1 Atrazin (A. hybridus, A. retroflexus, S. nigrum) und 2,5 kg ha^?1 (A. albus, A. blitoides) bekämpfbar waren. Die höhere Triazintoleranz der beiden letzten Arten ist wahrscheinlich, auf eine Herbizidde-toxifikation zurückzuführen. Der photosynthetische Elektronentransport in den R-Biotypen wurde durch Atrazin und Simazin nur wenig beeinflußt, durch Diuron jedoch unterbunden, wie durch Messungen der Fluoreszenzinduktion der ganzen Blätter gefunden wurde. Bei der Untersuchung der Hill-Reaktion wurde bei den R-Biotypen für Simazin und Atrazin Resistenzfaktoren zwischen 900 und 350 festgestellt, für Diuron aber nur kleine Faktoren (1,1 bis 1,6). Daraus wurde geschlossen, daß alle R-Biotypen eine chloroplastische Resistenz entwickelt haben, wie sie schon früher für andere Triazin-resistente Unkrautbiotypen beschrieben worden ist.     

Control of Avena fatua L. and Cirsium arvense (L.) Scop. with mixtures of 3,6-dichloropicolinic acid and four herbicides for control of A. fatua

Control of Avena fatua (L.) (wild oat) with diclofop methyl applied at 0·7 kg ha^?1 at the two-leaf stage and difenzoquat at 0·84 kg ha^?1 at the four-leaf stage in wheat (Triticum aestivum L.) under field conditions was good and not affected when either of these herbicides was mixed with 3,6-dichloropicolinic acid as the monoethanolamine salt at 0·14, 0·20 or 0·30 kg ha^?1. In the glasshouse, mixtures containing 3,6-dichloropicolinic acid at rates as high as 0·6 kg ha^?1 also did not affect control of A. fatua. When barban at 0·35 kg ha^?1, or flamprop methyl at 0·56 kg ha^?1 was mixed with similar rates of 3,6-dichloropicolinic acid and applied at the two-leaf and four-leaf stage of A. fatua respectively, a reduction in control of A. fatua (antagonism) occurred under both field and glasshouse conditions. The herbicides for control of A. fatua did not influence the fresh weight suppression of C. arvense shoots obtained in the glasshouse with 3,6-dichloropico-colinic acid at 0·3 kg ha^?1. Early tolerance of wheat (cv. Neepawa) was acceptable with all mixtures. Wheat yields with diclofop methyl or difenzoquat alone or in mixture with 3,6-dichloropicolinic acid were increased over the yields from the A. fatua-infested control.     

Chemical manipulation of weed emergence

Field studies were conducted over a 4-year period to determine whether weed emergence could be increased by incorporating germination stimulants into the soil. Sodium azide (4.5–36 kg azide ha^?1), ammonium nitrate (34–67 kg nitrate ha^?1), and butylate (0.2–0.4 kg ai ha^?1) were used. Sodium azide was the most consistent stimulant of indigenous weed emergence over all experiments and seasons, but there was great variability in its effects and the highest application rate sometimes inhibited emergence. Consistent stimulation of broad-leaf weed emergence occurred following September applications of 4–5 kg azide ha^?1 of sodium azide. Sodium azide at 4.5 kg azide ha^?1 increased grass plus broad-leaf weed emergence 43% based on summer applications in three growing seasons. No general recommendation for stimulating the emergence of weeds can be made because stimulation was a function of rate of application, season of the year, and post-treatment environment. Influence de traitments chimiques sur la levée des mauvaises herbes Des études portant sur une durée de quatre ans ont été conduites afin de déterminer si l'incorporation dans le sol de stimulants de germination pouvait augmenter la levée des mauvaises herbes. Les produits essayés ont été le nitrure de sodium (4, 5–36 kg de nitrure ha^?1), le nitrate d'ammonium (34–67 kg nitrate ha^?1), et le butylate (0, 2–0, 4 kg ma ha^?1). C'est avec le nitrure de sodium que la stimulation de la levée des graines en place a été observée le plus régulièrement, au cours de plusieurs expériences effectuées en différentes saisons; cependant, une grande variabilité de l'effet de ce produit a été notée, et les doses d'application les plus élevées ont parfois inhibé les levées. Appliqué en septembre à la dose de 4, 5 kg nitrure ha^?1, le nitrure de sodium stimule d'une manière régulière la levée des dicotylédones. Des traitements d'été opérés durant trois années ont montré qu'à cette dose, il augmente la levée des mono et des dicotylédones de 43%. Il n'est cependant pas possible de donner des recommandations générales pour la stimulation des levées de mauvaises herbes, car cette stimulation dépend de la dose appliquée, de la saison pendant laquelle elle est opérée, et des conditions qui régnent après le traitement. Chemische Beeinflussung des Auflaufens von Unkräutern In einer über vier Jahre laufenden Feldstudie wurde untersucht, ob durch das Einarbeiten von Keimungsstimulatoren das Auflaufen von Unkräutern beschleunigt werden kann. Zu die-sem Zweck wurden Natriumazid (4, 5–36 kg azid ha^?1), Ammoniumnitrat (34–67 kg nitrat ha^?1) und Butylat (0, 2–0, 4 kg ai ha^?1) verwendet. Natriumazid war in allen Versuchen das am regelmässigsten wirksame Auflaufstimulans für die an den verschiedenen Standorten vorkommenden Unkräuter, wobei die höchsten Applikationsraten hin und wieder das Auflaufen hemmten. Applikationen von 4, 5 kg azid ha^?1 Natriumazid im September erhöhten die Auflaufrate regelmässig; sie wurde in drei Vegetations-perioden bei grasartigen und breitblättrigen Unkräutern um 43%, vergleichen mit den Sommerapplikationen, gesteigert. Es kann keine all-gemein gültige Anwendungsempfehlung gegeben werden, da der Stimulationseffekt stark von Dosierung, Jahreszeit und den Umweltsbedingungen nach der Applikation abhängt.     

Littleseed canarygrass (Phalaris minor) resistance to clodinafop‐propargyl in wheat fields in north‐western India: Appraisal and management

Littleseed canarygrass (～canarygrass) evolved populations that are resistant to isoproturon during the early 1990s in north‐western India. Clodinafop‐propargyl (～clodinafop) was recommended for controlling these populations. It has been used extensively in wheat for the last several years. Recently, poor or no control of canarygrass by clodinafop has been observed in large areas, which could be related to cross‐resistance or multiple resistance. This study was designed to test whether resistance has evolved in canarygrass populations against clodinafop and to explore control of the resistant populations with sulfosulfuron and pinoxaden. Among the 311 canarygrass populations that were tested, 86, 55 and 34 showed variable phytotoxicity (0–99%) due to 0.030, 0.060 and 0.120 kg ha^?1 clodinafop, respectively. Based on the resistance index, 11 populations were “highly resistant”, 60 were “resistant” and the rest (240) were “susceptible” to clodinafop. Five and six clodinafop‐resistant populations showed slight resistance to 0.0125 kg ha^?1 sulfosulfuron and 0.025 kg ha^?1 pinoxaden, respectively. But, sulfosulfuron at 0.025 and 0.050 kg ha^?1 and pinoxaden at 0.050 and 0.100 kg ha^?1 controlled all the canarygrass populations. Clodinafop used for 4 years increased the chance of resistance evolving, whereas its rotation with sulfosulfuron reduced the chance of resistance evolving. This study showed that considerable canarygrass populations have evolved a low‐to‐high degree of resistance against clodinafop. The further use of clodinafop would lead to the spread of resistance in larger areas through the dispersal of resistant seeds. Clodinafop should be replaced with 0.025 kg ha^?1 sulfosulfuron or 0.050 kg ha^?1 pinoxaden. Besides, where canarygrass has not evolved resistance, the yearly rotation of sulfosulfuron with clodanafop or pinoxaden might delay the evolution of resistance.