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1.
T K Das  D K Das 《Weed Research》2018,58(3):188-199
Variable dormancies result in periodicity in the germination of weeds and make weed control a repetitive practice. Under some conditions, repeated applications of selective herbicides can lead to the dominance of perennial weeds like Cyperus rotundus . Our hypothesis was that applying a chemical dormancy breaker (DB ) plus herbicide mixture would better control a mixture of weed species. Three experiments were designed to develop a cost‐effective DB treatment and to evaluate its dose with herbicides tank‐mixtures for effective weed management. KNO 3 and gibberellic acid GA 3 as dormancy breakers offered comparable effects, but KNO 3 was more economical than GA 3. KNO 3 at a 6% concentration was more effective in promoting weed germination than a 3% concentration in soyabean. A combination of KNO 3 (6%) and pre‐emergence pendimethalin 0.75 kg a.i. ha?1 + imazethapyr 0.10 kg a.i. ha?1 controlled annual weeds by 99% and reduced C. rotundus growth by 83%. This treatment gave significantly higher soyabean yield and net returns. Similarly, a tank‐mixture comprising of clodinafop 0.06 kg a.i. ha?1 + metsulfuron 0.006 kga.i. ha?1 was more effective against weeds than pre‐emergence tank‐mix application of pendimethalin 0.75 kg a.i. ha?1 + carfentrazone‐ethyl 0.02 kg a.i. ha?1 and isoproturon 0.75 kg a.i. ha?1. The use of pre‐emergence tank‐mixture of pendimethalin 0.75 kg a.i. ha?1 + imazethapyr 0.10 kg a.i. ha?1 should exhaust seed/tuber bank if repeated and reduce the application cost of herbicides by 50% and the dose, residue and cost of pendimethalin by 25%.  相似文献   

2.
Various control strategies for Achillea millefolium L. (yarrow) were investigated in a dense stand of the weed at Lincoln College in 1977–1978. In early spring plots were either rotary cultivated or left undisturbed. In late spring, plots of both previous treatments were either left undisturbed, rotary cultivated or sprayed with glyphosate at 1·5 kg ha?1. The whole experiment was rotary cultivated twice 1 week later and sown with Hordeum vulgure L. cv. Zephyr (barley) at 144 kg seed ha?1. MCPA + dicamba at 0·9+0·15 kg ha?1 was applied to half of each plot when the second node was detectable (Zadok 32). Rotary cultivation and glyphosate both substantially reduced the regrowth of A. millefolium but glyphosate reduced regrowth by a greater proportion when applied to undisturbed plants than when applied to plants regenerating after cultivation. Both gave a more than 95% reduction compared to the control (rotary cultivation only at sowing time) in the amount of A. millefolium present in the barley stubble in the autumn. MCPA + dicamba caused seedling mortality but did not affect the numbers of primary shoots from rhizome fragments. The grain yield of the barley increased from 2·91 t ha?1 when A. millefolium was not controlled to 4·23 t ha?1 with good control. The barley yield appeared to be restricted by competition from regenerating A. millefolium and by a nitrogen deficiency induced in some regimes by nitrogen immobilization in decaying rhizomes.  相似文献   

3.
Field experiments were conducted in the early and late cropping seasons of 1979 on a loamysand Oxic Ustropept in a subhumid environment in Nigeria, using 40000, 50000 and 30000 + 40000 plants ha?1 of maize (Zea mays L. cv. TZB), cowpea (Vigna unguiculata (L.) Walp. cv. VITA-5) and maize/cowpea intercrop respectively. These indicated that weed interference effects on crops under no-tillage depended on cropping season, cropping pattern and crop species. In the early and late seasons respectively, thirty-five and twenty-nine different weed species were recorded and weed dry weights of approximately 10·4 and 5·7 t ha?1 from the plots kept weedy throughout the season reduced corresponding food energy yields by 60 and 82%. Except for the intercrop, which in the early season showed significant yield reduction when exposed to 4 weeks’ weed interference after sowing, all cropping patterns needed more than 4 weeks’ interference to show significant yield reductions, regardless of cropping season. In the early season, weed interference accounted more for the yield reductions in monocultures than it did for those in the intercrop, but in the late season all cropping patterns were equally sensitive to weed association. Maize, which performed much better in the early season, showed greater yield reductions than cowpea under early weed interference but less under full-season interference irrespective of cropping pattern and season. Cowpea seed quality was more reduced by intercropping than by weed interference in the early season but neither of these factors affected seed quality significantly in the late season.  相似文献   

4.
Long‐term research aimed to determine whether narrow row spacing and harvest weed seed destruction, in combination with herbicide use, would be sufficient to drive a Lolium rigidum population to extinction. A trial was run from 1987 to 2013, with treatments including crop row spacings of 9, 18, 27 or 36 cm and crop residue burning or retention. Herbicides were applied to reflect regional practices. The initial trial design was randomised, but treatments were maintained in each plot over the following years. Lolium rigidum seed production at harvest was assessed from 2003 to 2013. Average crop yield was higher in the unburnt plots (1638 kg ha?1) than the burnt plots (1530 kg ha?1) and greater at narrow row spacing, with an average yield of 1658, 1637, 1548 and 1492 kg ha?1 in the 9‐, 18‐, 27‐ and 36‐cm spacings. Lolium rigidum seed at harvest was reduced in the burnt plots (57 seeds m?2) compared with the unburnt plots (297 seeds m?2) and was reduced at narrow row spacing, with an average of 58, 78, 223 and 333 seeds m?2 in the 9‐, 18‐, 27‐ and 36‐cm row spacings. By 2013, L. rigidum seed production was reduced to an average of 0 seeds m?2 in the narrow row spacing, burnt plots.  相似文献   

5.
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   

6.
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   

7.

Two field trials were conducted in 2018 and 2019 to develop practical and economically efficient weed control programs in corn. The experiment included six treatments (cowpea, rice straw, sorghum extract, hoeing, foramsulfuron herbicide and weedy check). The treatments were arranged in randomized complete block design with four replicates. Findings showed that reduction in total weed number was evident with application of hoeing, cowpea and rice straw in 2018 and 2019 seasons, in addition to foramsulfuron herbicide and sorghum extract in 2019. Cowpea, hoeing, foramsulfuron herbicide and rice straw recorded higher reduction in dry biomass of grassy weeds in both seasons. Reductions in N, P and K uptake by weeds because of rice straw and cowpea treatments were similar to hoeing treatment in both seasons. The increases in ear grain weight and grain yield ha?1 due to cowpea and hoeing treatments were similar to rice straw one. In 2019 season, cowpea treatment was the superior practice for improving N, P and K uptake of maize, significantly leveling hoeing for K uptake. The values of gross returns and benefit/cost ratio of cowpea and sorghum extract, respectively, were higher than rice straw application. In conclusion, cowpea as a live mulch achieved acceptable weed control in maize by reducing weeds growth and lowering their ability to deplete the soil nutrients. Also, cowpea treatment improves growth and yield of maize with better utilization of nutrients. Thus, cowpea could be exploited as an eco-friendly method of weed management programs in maize cultivation.

  相似文献   

8.
Phalaris minor, the most serious weed in wheat in north‐western India, has developed extensive isoproturon resistance due to continuous isoproturon use. For its control, alternative herbicides (flufenacet, metribuzin and sulfosulfuron) at different application rates and timing were evaluated in wheat. In addition, herbicide carryover risk onto rotational crops (sorghum; maize and green gram, Vigina radiata) was also assessed. Isoproturon at 1 and 2 kg a.i. ha?1 provided only 10.5% and 51.8%P. minor control respectively. Of the other herbicides, early post‐emergent [15–21 days after sowing (DAS)] flufenacet at 180–480 g a.i. ha?1 provided acceptable control of P. minor, but failed to control broad‐leaved weeds and was phytotoxic to the wheat crop. Metribuzin at 210 g a.i. ha?1 was effective in controlling both Phalaris and dicotyledonous weeds. Mixtures of both flufenacet and metribuzin at reduced rates were better than flufenacet for weed control and grain yield. The efficacy of flufenacet and metribuzin was drastically reduced with later growth stages of P. minor (four to five leaf). Whereas sulfosulfuron at 25–30 g a.i. ha?1, applied either early post‐emergence (19 DAS) or post‐emergence (30–42 DAS), was quite effective. Overall, sulfosulfuron was the most effective treatment with regard to weed control and crop yield. However, maize and sorghum grown in rotation after harvest of sulfosulfuron‐treated wheat plots showed 65–73% crop biomass inhibition. The residual effect of sulfosulfuron was also noticed on Trianthema portulacastrum (Horse purslane), causing 73.5% dry matter reduction. By contrast, no carryover damage with flufenacet was observed on maize, sorghum and green gram. Glasshouse pot experiments and field trials investigating crop sensitivity to pre‐plant applications of sulfosulfuron found the decreasing order: sorghum > maize > green gram. The risk of carryover onto rotational crops should be considered when choosing alternative herbicides for P. minor control in wheat.  相似文献   

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.
In 393 field experiments in Baden‐Württemberg region in south‐western Germany, herbicide efficacy, yield loss and crop tolerance of maize (Zea mays) were investigated between 1981 and 2011. The collected data served to determine changes in weed frequencies, in herbicide use, yield loss functions and economic thresholds (ETs). Over 60 weed species were reported. Chenopodium album and Galium aparine were the most frequent broad‐leaved weeds, the former becoming more frequent over time. Species of the genera Lamium, Polygonum, Veronica and Matricaria occurred in about every fifth trial. Alopecurus myosuroides and Echinochloa crus‐galli were the most frequent grass weeds; the former declining in frequency by 1.1% per year, the latter increasing by 1.5%. Results suggest a weed population shift towards thermophilic species. aceto‐lactate‐synthase and 4‐HPPD‐inhibitor herbicides became important in the 1990s. Pendimethalin and bromoxynil have been integral components of weed control since the 1980s. ETs, the point at which weed control operations provide economic returns over input costs, ranged between 3.7% and 5.8% relative weed coverage. Without weed control, no yield increase was found over 24 years. Yield increased by 0.2 t ha ? 1 year ? 1, if weeds were controlled chemically. Despite intensive use of effective herbicides in maize, problematic weed species abundance and yield losses due to weed competition have increased in Baden‐Württemberg over a period of 30 years.  相似文献   

11.
Pre-emergence activity of pendimethalin on propanil-resistant jungle rice (Echinochloa colona) was demonstrated in glasshouse trials. Both susceptible and resistant populations, collected from Costa Rica, were controlled by 1·25 kg ha-1, the usual application rate used in the field where Rottboellia cochinchinensis is also a problem. When applied post-emergence, propanil performance was improved by the addition of low doses of pendimethalin to the herbicide mixture. A propanil-resistant selection was controlled by 0·23 kg ha-1 pendi-methalin+0·54 kg ha-1 propanil at the one-to-two leaf stage, and 0·23 kg ha-1 pendimethalin+1·08 kg propanil at the three-to-four leaf stage compared to 1·08 kg and 2·16 kg ha-1 respectively when propanil was applied alone. This suggests that pendimethalin improves post-emergence control in the field compared to the standard propanil treatment and can provide residual pre-emergence control of late-germinating individuals, so reducing the propanil selection pressure. For effective jungle rice control, growers apply propanil (3·84 kg ha-1) at 10 and 20 days after planting (DAP) followed by one application of fenoxaprop-P-ethyl (0·045 kg ha-1) at 35 DAP. Field experiments, conducted in dry-seeded upland rice in southern Costa Rica, demonstrated that under high jungle-rice population pressure, one application of pendimethalin at 1·5 kg ha-1 provided an effective replacement for propanil, resulting in reduced weed-control costs. ©1997 SCI  相似文献   

12.
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   

13.
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   

14.
This study was undertaken to explore the potential of Aglaia odorata Lour. granules in various soil types (sand, sandy loam and clay) at 0.25, 0.5 and 1 t ai ha?1 to inhibit two major maize weeds, Digitaria adscendens and Trianthema portulacastrum L., in an experimental greenhouse. The results indicated that the emergence and seedling growth of both weeds were inhibited but varied with the soil type: the inhibitory effect of the A. odorata granules was stronger when applied in sand, followed by sandy loam and clay. The weed species responded differently to the A. odorata granule application. Generally, the inhibitory effect was greater for D. adscendens than for T. portulacastrum. Additionally, the potential of the A. odorata granules for weed control in maize field plots was evaluated. The three major weeds that were found in the experimental field were D. adscendens, T. portulacastrum and Amaranthus gracilis. The highest A. odorata granule dose (1 t ai ha?1) had a significant inhibitory effect on the emergence and growth of all of the weed species and their emergence was reduced by 96.7%, 47.2% and 56.2%, respectively, compared with the control treatment (unweeded). The dry weight of the weeds was reduced in a similar manner to their emergence. In contrast, the emergence of maize was not affected by any of the A. odorata granule applications. Rather, at an application rate of 1 t ai ha?1, the maize yield increased significantly and the effect was similar to that observed with an atrazine herbicide application under field conditions.  相似文献   

15.
Two field experiments were carried out a year apart on the alkaloid poppy (Papaver somniferum) in 2012 and 2013 in north-west Hungary, to assess the efficacy of mesotrione and tembotrione herbicides for post-emergence weed control. Our experiments tested (1) a single application of mesotrione at 144 g active ingredient (a.i.) ha–1, (2) two separate applications of mesotrione at 144 g a.i. ha–1, (3) a single application of tembotrione at 88 g a.i. ha–1, (4) two separate applications of mesotrione at 88 g a.i. ha–1, and (5) the combination of a single application of mesotrione at 144 g a.i. ha–1 followed by a single application of tembotrione at 88 g a.i. ha–1. Both non-treated and hand-weeded plots were used as controls. Among the most important weeds, Chenopodium album was most successfully controlled in the majority of the test treatments, but Fallopia convolvulus and Polygonum aviculare tolerated each herbicide application in 2012, likely due to the dry weather conditions. Because of the botanical similarity to the crop, none of the treatments proved to be significant against Papaver rhoeas. One dosage of tembotrione alone never reduced the dry weights of the target weed species or weed numbers significantly. The cuticular wax layer of the opium poppy can provide a natural defence against these herbicides, but some temporary phytotoxic yellowish discoloration occurred after tembotrione treatments. Our results show that mesotrione in combination with tembotrione is the most effective treatment and should be employed in poppy cultivation.  相似文献   

16.
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   

17.
J. E. DALE 《Weed Research》1985,25(3):231-238
Experimental granules were made from moistened calcareous loess (pH 8·5) containing 2% w/w gum xanthan and chloramben sodium salt at w/w concentrations of 0·4–3·6%. Haloxyfopmethyl * * Approved WSSA common name.
(DOWCO-453 ME) {Methyl 2-(4-((3-chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)-phenoxy)propanoate) was dissolved in tung oil at a range of concentrations and poured on the dried chloramben granules with stirring. In the glasshouse, dry granules containing chloramben plus haloxyfop-methyl spread pre-emergence at the rate of 0·8 + 0·4 kg ha?1 reduced the dry weight of maize (Zea mays L.), red rice (Oryza sativa L.), Abutilon theophrasti Medic., and Sesbania exaltata (Raf.) Cory by 89, 100, 94, and 68%, respectively, with no injury to soybeans [Glycine max (L.) Merr.]. Coated granules spread pre-emergence controlled A. theophrasti and volunteer maize grown from seed sown in soil up to 10 cm deep. In a preliminary field test, the experimental granules reduced numbers of weeds in soybeans and improved crop yield. Ten weeks after treatment, chloramben granules coated with haloxyfop-methyl gave 97% control of Sorghum halepense (L.) Pers compared to 80% by uncoated granules. Linuron granules coated with haloxyfop-methyl gave 85% control compared to 12% by uncoated granules. Yields in plots treated with coated and uncoated chloramben were 3280 and 2700 kg ha?1, respectively. In coated and uncoated linuron plots, yields were 2920 and 2340 kg ha?1, respectively. Except for the uncoated linuron plot, all yields were significantly higher than 2050 kg ha?1 obtained in the weedy untreated plot.  相似文献   

18.
Abstract

In field experiments conducted at the Nyankpala Agricultural Station, Ghana, during 1976–77, soil moisture conditions appeared to be the deciding factor in determining the frequency of handweeding needed to obtain maximum seed cotton yields. In 1976, when planting was early and the late, heavy rains in October prolonged weed growth, two handweedings at 4 and 8 weeks after seeding (w.a.s.) gave comparable yields to continuous weeding and significantly better yields than an alachlor + fluometuron herbicide mixture. Supplementary weeding did not enhance the mixture's performance.

In 1977, planting was relatively late and in the peak of the rainy season and so late weed growth was reduced. A single handweeding at 4 w.a.s. gave as good a yield as repeated handweeding treatments under these conditions. The alachlor + fluometuron mixture also gave adequate weed control and again supplementary weeding did not improve it significantly.

In herbicide evaluation experiments, the safety and performance of pendimethalin and dinitramine herbicides were much influenced by the rainfall pattern immediately following application. With a relatively drier period following application in 1976, the higher rate of these herbicides depressed yields. This rate produced optimum yields in 1977, however, when a very wet period followed application.

Prodiamine and the alachlor + fluometuron mixture were the herbicides least affected by soil moisture and they consistently produced good yields.  相似文献   

19.
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   

20.
An increasing water crisis, as well as the unavailability and high cost of labor, in Pakistan has forced rice‐growers to plant rice directly into the field. However, severe weed infestation causes disastrous effects on the productivity of this rice system. In this study, three herbicides (pendimethalin, penoxsulam and bispyribac‐sodium) were evaluated for weed control in direct‐planted rice on a sandy loam soil. Weedy check and weed‐free plots were established for comparison. Weed infestation decreased the rice yield by 75.2%. However, the application of herbicides suppressed the weed infestation, with a simultaneous increase in the rice yield. The postemergence application of bispyribac‐sodium was the most effective herbicide in reducing the total weed density and dry weight over the weedy check, followed by penoxsulam and pendimethalin, respectively. Bispyribac‐sodium increased the number of productive tillers, 1000‐grain weight, number of grains per panicle and grain yield over the control, as well as improved the water productivity and economic returns of direct‐planted rice. The weeds' proliferation increased the number of unproductive tillers and decreased the plant height. In conclusion, the postemergence application of bispyribac‐sodium can be used effectively to control weeds, increase water productivity and improve the economic returns and yield of direct‐planted rice on a sandy loam soil in Pakistan.  相似文献   

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