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1.
The effects of three weeding systems with and without top-dressed nitrogen were examined in 40 experiments on bread wheat and durum wheat planted by farmers in the Chaouia (semi-arid area of Morocco) in 1984–1985 and 1985–1986 growing seasons. In both years, hand-weeding to simulate collection of forage reduced weed numbers by 30% and removed 63% of the weed dry weight. Treatment with 2, 4-D removed 66% of the weeds and reduced weed dry weight by 82%, in 1985–1986. Hand-weeding for forage produced 427 kg ha?1 weed dry matter in both years, but wheat grain yields were 179 kg ha?1 lower than with 2.4-D treatments. Over both years, the cost of each kg weed forage was 0·43 kg grain yield loss. Without weeding grain yields were 130 kg ha?1 lower than 2, 4-D treatments. Weed control with 2,4-D increased wheat grain yields over both non-weeded and hand-weeded treatments by an average of 154 kg ha?1. Overall, there were no significant effects of nitrogen on wheat or weed yields nor interactions between top-dressed nitrogen and weeding systems. A total of 157 weed species belonging to 29 botanical families were identified on the 40 experimental sites over both years; 89% were dicotyledons. Papaver rhoeas L. (common poppy), 2, 4-D susceptible plant, was the most annual weed in wheat fields in Chaouia.  相似文献   

2.

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.

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3.
Weeds are a major constraint to increasing production of lentil (Lens culinaris Medik.) in Sudan, Field studies were conducted to determine the yield loss due to weeds, to identify the critical period of weed interference, to evaluate the activity of different herbicide mixtures in controlting weeds and their selectivity for lentil, and to evaluate different methods of weed control for developing an integrated weed management practice. At Rubatab. unrestricted weed growth accounted for up to 84% loss in yield. The critical period of weed control was between 2 and 4 weeks after sowing. However, a weeding regime experiment at Dongola, a cooler location with a longer growing season, indicated that the critical period was between 4 and 6 weeks after sowing. suggesting that the critical period might vary with the environmental conditions. The herbicides imazethapyr (0.05 kg a.i. ha-1), terbutryn (1.0 kg a.i. ha-1) and prometryn (1.0 kg a.i. ha-1), each in a tank mixture with pendimethalin (1.2 kg a.i. ha-1), were tolerated by lentil, controlled weeds effectively and significantly increased yields at Wad Hamid. Their efficacy in controlling weeds at Rubatab was low, however, because of the presence of Tephrosia apollinea (Del.) DC. and Melilotus indica (L.) All., which tolerated these herbicides. Efficacy was also reduced in heavier soils. One supplementary hand-weeding at 4 weeks after sowing enhanced the performance of these herbicides under such conditions. A tank mixture of oxyfluorfen (0.24 kg a.i. ha-1) with either terbutryn (1.0 kg a.i. ha-1) or prometryn (1.0 kg a.i. ha-1) also provided good weed control and increased yield of lentil at Wad Hamid. Application of a higher dose (1.5 kg a.i. ha-1) of terbutryn and prometryn caused phytotoxicity. Irrigation before seed-bed preparation reduced grass and broad-leaved weeds by 58% and 40% respectively, and gave a 30% increase in grain yield over no irrigation. Pre-emergence application of oxyfluorfen (0.24 kg a.i. ha-1) and a supplementary hand-weeding at 4 weeks after sowing gave excellent control of weeds and increased lentil yield by 57% over the weedy control. Thus, use of presowing irrigation, pre-emergence herbicide and one hand-weeding form an effective integrated package for controiling weeds in northern Sudan.  相似文献   

4.
R. F. NORRIS 《Weed Research》1991,31(6):317-331
Sugarbeet and weeds were treated with phenmedipham plus desmedipham either as single applications or as split applications in which 50% of the equivalent single application rate was applied at each application. Split application did not alter the phytotoxicity to the crop when environmental conditions did not predispose the Sugarbeet to injury by the herbicide. Split applications at 1-1 or 1-4 kg ha?1 spaced from 0-5 to c. 5 days apart caused more injury to the crop than the respective single applications when environmental conditions were such that injury to the crop resulted from the single applications. Injury to Sugarbeet following application of 0-72 kg ha?1 of phenmedipham plus desmedipham was always low, regardless of the type of application. Susceptible weeds were controlled by single applications of 1 1-1 ?4 kg ha?1, but 0-72 kg ha?1 did not reliably provide adequate control. Split applications c. 3-8 days apart gave improved control. Control achieved by 0-72 kg ha?1 of the herbicide applied as split treatments equalled or exceeded that produced by single applications of 1-4 kg ha?1. Improvement in the control of tolerant weed species by split applications of phenmedipham plus desmedipham was species dependent. Use of low-rate split applications of phenmedipham plus desmedipham thus resulted in reduced injury to the Sugarbeet, and the introduction of less herbicide into the ecosystem, while maintaining or improving the control of susceptible weeds.  相似文献   

5.
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.  相似文献   

6.
The benefits of conservation agriculture (CA) and associated technologies are not equal for all agro ecosystems. This study used a field experiment to examine winter-wheat yield and weeds under conservational and conventional systems in the central region of Spain. The three tillage treatments were conventional tillage (CT), minimum tillage (MT) and no-tillage (NT). The climatic conditions influenced wheat yield, yield components, soil water content and weeds. When the autumn-winter rainfall was abundant and constant (69.7% of annual rainfall), wheat grain yield (4465?kg?ha?1) and yield components (3897?kg?ha?1 of straw biomass and 584.5 ear m?2) were highest. Wheat grain yield was highest with NT: 3549.9?kg?ha?1 (compared to MT: 2955.1?kg?ha?1 and CT: 2950.3?kg?ha?1) and ear number per m2 was significantly lower with MT (332 no ear m?2, compared to 426 and 411.6?ear?m?2 in CT and NT-systems respectively). Soil water content, at earing stage, was the highest in NT (27.36% of soil moisture) while MT showed the lowest content (11.83% of soil moisture). The higher weed measurements (means of 2.557 plants m?2; 1.443 species m?2 and 2.536 g m?2) was with higher annual rainfall (488?mm). Throughout the experiment it was the dominant presence, in MT-wheat plots, of Lolium rigidum Gaudin (with means from 4.87 to 7.71 plants m?2), which reduced the ear number per m2. Our study revealed that in the short term, under semi-arid conditions, only the adoption of NT system (rather than MT) showed economic benefits.  相似文献   

7.
Abstract

In northern Queensland, the addition of 2,4,5‐T butyl ester was found to be unnecessary to maintain the control of Echinochloa colona (L.) Link and Cyperus Iria L. In dry seeded rice when propanil rates were reduced below the registered rate of 4 kg a.i. ha?1. Adequate weed control was obtained with 1.3 kg a.i. ha?1 propanil alone. No adverse effects on rice yield were found with any of the propanil × 2,4,5‐T treatments. Low rates of propanil, 1.3 and 0.72 kg a.i. ha?1, compared favourably with pre‐emergence treatments of thiobencarb, butachlor, oxyfluorfen and pretilachlor (plus a safener) when weed yields were low. Where water management was poor and Ischaemum rugosum Salisb. was the dominant weed, oxyfluorfen applied pre‐emergence at 0.96 kg a.i. ha?1 produced a higher rice and a lower weed yield than the low rates of propanil. In three of the five experiments, weed growth was insufficient to depress rice yields significantly.  相似文献   

8.

Lack of control options for cool-season broadleaf weeds is a major deterrent to autumn-sown chickpea. Weed control and chickpea tolerance to PRE (pre-emergence) and POST (post-emergence) application of isoxaflutole and oxyflurofen, PRE metribuzin, POST pyridate, and flumetsulam were investigated at three locations, including Kermanshah, Kurdistan, and Hamedan provinces during 2017–2018. Untreated and weed-free checks were added for comparison. Pyridate and PRE oxyflurofen 125?g ai ha?1 caused the minor visual crop injury according to EWRS score (1–1.8), while the highest crop injury occurred with metribuzin (EWRS score 3.5–8.5) in whole locations. The most effective herbicides for weed reduction were pyridate (70–75%), PRE oxyfluorfen (69–76%), and POST oxyfluorfen (65–73%) at Kermanshah, PRE oxyfluorfen at 125 and 175?g ai ha?1 (70–78%), POST oxyfluorfen (70–76%) and pyridate (70–78%) at Kurdistan, PRE oxyfluorfen at 125 and 175?g ai ha?1 (88–96%), metribuzin (91–100%) and Pyridate (80–97%) at Hamedan. Pyridate and PRE oxyfluorfen at 125?g ai ha?1 resulted in the highest chickpea grain yield at the three locations. In general, PRE oxyfluorfen (125?g ai ha?1) was similar to pyridate in terms of efficacy in weed control and grain yield enhancement.

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9.
Abstract

Chickpea suffers severe competition due to Chenopodium album L. infestation. Two to three hoeings are generally given to check C. album but increasing labour costs and scarcity of farm labour make the manual weeding difficult. Usage of herbicides appears to be a logical solution. Pre‐emergence applications of pendimethalin or ametryn alone at 1.5 kg ai ha?1 or one handweeding at 35–40 days after seeding following either 1 kg ai ha?1 of pendimethalin, ametryn or fluchloralin or metribuzin at 0.3 kg ai ha?1 applied pre‐emergence gave effective control of C. album and seed yields similar to clean‐weeded chickpeas. There was an 84% reduction in seed yield of chickpea without weeding.  相似文献   

10.
Field experiments at Lacombe on a Ponoka loam soil (9·6% organic matter) during 1982 and 1983 investigated the tolerance of spring wheat (Triticum aestivum L.) cv. Neepawa in a weed free situation to trifluralin applied at 0·0–3·0 kg ai ha?1 in the autumn or spring and incorporated to a depth of 10 cm. Rates of trifluralin above 1·0 kg ai ha?1 applied in the autumn or spring reduced the percent stand of wheat compared to an untreated control. Two weeks after emergence the crop showed 37 or 47% injury indicated by delayed growth, following application at 1·0 kg ai ha?1 in the autumn or spring, respectively. The wheat recovered throughout the course of the growing season. At harvest, trifluralin applied in the autumn or spring at rates below 1·0 kg ai ha?1 caused a yield increase while higher rates caused a yield decrease compared to the untreated control. Spring application caused a greater yield loss than autumn application. The tolerance of spring wheat to trifluralin at rates required for weed control (1·1 kg ai ha?1 or higher) on this soil type is marginal.  相似文献   

11.
Portulaca oleracea (common purslane) is a summer annual weed with wide geographic distribution and is problematic in many crops worldwide. Field experiments were conducted to determine the effects of different management practices on P. oleracea emergence in soyabean fields. Two tillage systems [conventional tillage (CT) and no‐till (NT)], three soyabean seeding rates (SR) (200 000, 300 000 and 400 000 seeds ha?1) and three imazethapyr doses (0, 50, and 100 g a.i. ha?1 applied pre‐emergence) were considered as experimental factors. Portulaca oleracea emergence was affected by management practices including tillage system, soyabean SR and imazethapyr dose. Conventional tillage required a thermal time (TT) of 195.95 and 221.30 d °C to reach 50% emergence in 2016 and 2017, respectively, while for NT, the respective TT requirements were 182.34 and 203.32 d °C. On increasing soyabean SR from 200 000 to 400 000 seeds ha?1, the TT requirements for 50% emergence (T50) of P. oleracea also increased. The T50 at the herbicide dose of 100 g a.i. ha?1 was 193.05 and 220.67 d °C in 2016 and 2017, respectively, while for the non‐herbicide treatment, the respective TT requirements were 165.98 and 202.94 d °C. From an integrated weed management perspective, a combination of CT with a SR of 400 000 seeds ha?1 and a 100 g a.i. ha?1 imazethapyr dose not only resulted in the lowest P. oleracea seedling density m?2 but also caused the longest delay in the time to reach the T50. Findings from our study may facilitate the development of effective P. oleracea management strategies.  相似文献   

12.
The influence of no-tillage and conventional tillage on the outcome of early weed interference in maize (Zea mays L., cv. TZB), cowpea [Vigna unguiculata (L.) Walp, cv. VITA-5] and their intercrop at populations of 40000, 50 000 and 30 000 + 40 000 plants ha?1 was investigated on a loamy sand Oxic Ustropept in a subhumid tropical environment between April and July 1980. Both tillage treatments received 60 kg N, 30 kg P2O5 and 30 kg K2O ha?1. Although the weed spectrum was wider under no-tillage, weed weight was only 52% of the weight recorded under conventional tillage 6 weeks after sowing and the average food energy yield reductions caused were 28 and 65%, respectively. Cropping pattern had no effect on plot weediness. With minimum or no weed interference, maize performance was better in conventional than no-tillage but worse with prolonged weed interference. Cowpea responded more to weed interference than to tillage practice. Regardless of tillage practice and weed interference duration (up to 6 weeks) after sowing, maize monoculture produced the highest food energy yield, followed by maize/cowpea intercrop and cowpea monoculture in that order.  相似文献   

13.
Fluazifop-butyl, haloxyfop and sethoxydim with adjuvant oil were applied for three successive growing seasons to established strawberries infested with Elymus repens. The weed was virtually eradicated by three applications of haloxyfop (0.8 kg a.e. ha?1) in successive years. A similar effect was given by five applications of haloxyfop (0.4 kg a.e. ha?1) and fluazifop-butyl (1.6 kg AI ha?1) in three growing seasons. Lower rates of haloxyfop and fluazifop-butyl, and a high rate of sethoxydim (1.6 kg AI ha?1) applied five times were less effective, the ground cover of E. repens shoots not being reduced by the end of the experiment although weight of living rhizome was only 10-30% of that on untreated plots. Fruit yields on treated plots generally reflected the level of E. repens control, but there was some evidence of crop phytotoxicity from herbicide treatments. During the experiment E. repens untreated plots increased from about 30-100% ground cover and reduced yield 13, 28 and 68% in successive years compared with weed-free plots.  相似文献   

14.
Studies on competition between Ridolfia segetum Maris, and sunflower (Helianthemum annuus L.) were conducted at eight locations in southern Spain in 1990 and 1991. in order to define competition models and to estimate from these economic thresholds as affected by crop inputs and potential yields. Competition losses in sunflower crops ranged from 19% to 56% of weed–free yields. There were slightly better correlations between percentage sunflower reduction and weed density than with weed dry weight, (?0.66 and ?0.59, respectively). The weed competitive index, or sunflower crop dry weight reduction per unit dry weight of R. segetum, was 1.09. The percentage yield losses due to weed density (NPRt) were fitted to multiple linear, quadratic, exponential and hyperbolic models. The hyperbolic equation, %RSY=100 (1+1/b*NPRt)?1, where b=0.14 and is the R. segetum competitive ability index, had the lowest error sum of squares (SSE), and gave the best biological explanation for the competition response. Early emergence (before mid–March) made weeds about 1.5 times more competitive than late emergence. The economic threshold to offset the cost of a shallow post–emergence tillage, assuming 70% control efficiency, ranged from about 2.5 plants m ?2 for low–yielding crops(1200kgha?1) to less than one plant m?2 for higher–yielding crops (2800 kg ha?1).  相似文献   

15.
The present study assessed the effect of arbuscular mycorrhizal fungi (AMF) on broomrape (Orobanche aegyptiaca Pers.) control to determine its effects on tomato (Lycopersicon esculentum L.) growth indices. This experiment was carried out using a randomized complete block design with four replications. The treatments included three strains of AMF (Glomus mosseae, Glomus intraradices and Glomuse hoe ) at three levels (100, 200 and 300 kg ha?1). The control treatments (without mycorrhiza) were with and without broomrape (weed infest and weed free). The results showed that the use of G. intraradices and G. mosseae decreased broomrape seed germination, the number of nodules and the dry weight of the broomrape and increased root area and dry weight of the tomato plant when compared to G. hoe and the control treatments without broomrape. The tomato yield in G. intraradices 300 kg ha?1 treatment increased by 10 and 205% than weed free and weed infest treatments, respectively. Finally, G. intraradices and G. mosseae at, respectively, 200 and 300 kg ha?1 are recommended for land under tomato cultivation that has been contaminated with broomrape.  相似文献   

16.
Atrazine carryover often limits growers to production of atrazine-tolerant crops the year following application, and allows the increase of triazine-tolerant weed species such as Panicum miliaceum L. (wild proso millet). Tiriazine-resistant Brassica napus L. cv. ‘Triton’ (oilseed rape) was tested to characterize the nature of interspecific interference with P. miliaceum. In a greenhouse study, atrazine at 2.2 kg ha?1 depressed oilseed rape fruit (siliqua) number and fruit dry weight, and delayed flowering, but did not significantly affect height or weight of shoots, Oilseed rape fruit weight was reduced at 200 P. miliaceum plants m?2. fruit number and shoot weight were inhibited at 400 weeds m?2. and height was reduced and flowering delayed at 600 weeds m?2. Number and weight of fruits were reduced by one-third after 8 weeks of interference as compared to oilseed rape grown with the weed for 4 weeks. Oilseed rape height was reduced by 29% and shoot weight by 55% by 600 weeds m?2 and 2–2 kg ha?1 atrazine, while fruit number and weight were reduced by 72%. Oilseed rape shoot weight was reduced by 74% by 600 weeds m?2 for 12 weeks of interference, while fruit number and weight were reduced by 85% and 82%. respectively. In a field study, fluazifop reduced early season P. miliaceum cover by 72%, but did not increase oilseed rape cover. Mid-season P. miliaceum shoot weight was decreased by 97% by fluazifop and oilseed rape shoot weight was increased by 34%. P. miliaceum control increased oilseed rape biomass by 38% at 89 days, but biomass of oilseed rape sown at 11.2 kg ha?1 with 2.2 kg atrazine ha?1 was not decreased by P. miliaceum interference at 89 days.  相似文献   

17.
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.  相似文献   

18.
M. ANDREWS 《Weed Research》1990,30(5):331-340
Avena saliva cv. Amuri and A. fatua were sprayed with diclofop methyl (1.0 kg a.i. ha?1) alone and in combination with 2,4-D (1.1 kg a.i. ha?1), bentazone (1.0 kg a.i. ha?1), chlorsulfuron (15 g a.i. ha?1) or dicamba (0.3 kg a.i. ha?1). Effects of the herbicides on leaf extension rate during the first 8 to 10 days after spraying and subsequent growth (dry weight) after 57–75 days were determined by comparison with unsprayed plants. Diclofop-methyl applied alone did not cause a decrease in leaf extension rate of A. saliva or A. fatua until at least 4 days after spraying. All broadleaf weed herbicides in combination with diclofop-methyl caused a decrease in leaf extension rate of both species within 2 days of spraying. Ten days after spraying, leaf extension rates for plants sprayed with a broadleaf weed herbicide plus diclofopmethyl (all combinations) were lower than for unsprayed plants but greater than for plants sprayed with diclofop-methyl alone. With the exception of A. fatua sprayed with bentazone, long-term growth of plants sprayed with a broadleaf weed herbicide plus diclofop-methyl (all combinations) was lower than for unsprayed plants but greater than for plants sprayed with diclofop-methyl alone. Bentazone applied with diclofop-methyl caused a substantial decrease in leaf extension rate of A. fatua within 24 h of spraying but at harvest, dry weight of plants from this treatment was similar to or less than that for plants sprayed with diclofop-methyl alone. Application of diclofop-methyl with bentazone at a rate of 0.3 kg a.i. ha?1 also caused a reduction in leaf extension rate of A. fatua within one day of spraying. At this rate of bentazone, dry weight of plants at harvest was intermediate to that of unsprayed plants and those sprayed with diclofop-methyl alone. It is proposed that decreased leaf expansion rate during the first few days afte spraying is the cause of broadleaf weed herbicide antagonism of diclofop-methyl.  相似文献   

19.
The effects of sub‐lethal dose of herbicide and nitrogen fertilizer on crop–weed competition were investigated. Biomass increases of winter wheat and a model weed, Brassica napus, at no‐herbicide treatment with increasing nitrogen were successfully described by the inverse quadratic model and the linear model respectively. Increases in weed competitivity (β0) of the rectangular hyperbola and parameter B in the dose–response curve for weed biomass, with increasing nitrogen were also successfully described by the exponential model. New models were developed by incorporating inverse quadratic and exponential models into the combined rectangular hyperbola with the standard dose–response curve for winter wheat biomass yield and the combined standard dose—response model with the rectangular hyperbola for weed biomass, to describe the complex effects of herbicide and nitrogen on crop–weed competition. The models developed were used to predict crop yield and weed biomass and to estimate the herbicide doses required to restrict crop yield loss caused by weeds and weed biomass production to an acceptable level at a range of nitrogen levels. The model for crop yield was further modified to estimate the herbicide dose and nitrogen level to achieve a target crop biomass yield. For the target crop biomass yield of 1200 g m?2 with an infestation of 100 B. napus plants m?2, the model recommended various options for nitrogen and herbicide combinations: 140 and 2.9, 180 and 0.9 and 360 kg ha?1 and 1.7 g a.i. ha?1 of nitrogen and metsulfuron‐methyl respectively.  相似文献   

20.
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%).  相似文献   

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