ABSTRACT
This study was conducted in order to investigate the effects of 12 herbicide applications (linuron, prometryn, metribuzin, linuron+prometryn, prometryn+prometryn, metribuzin+prometryn, linuron+fluazifop-p-butyl, prometryn+fluazifop-p-butyl, metribuzin+fluazifop-p-butyl, linuron+quizalofop-p-ethyl, prometryn+quizalofop-p-ethyl and metribuzin+quizalofop-p-ethyl) and hand weeding (once, twice and repeated) in comparison with a weedy control on yield and yield components of lentils (cv. Erzurum-89) in 2000 and 2001 under Erzurum`s dry conditions, Turkey. Data were collected on the density and dry weight of weed species, density of lentil, plant height, branch and pod number per plant, 1000-grain weight, seed yield, total biomass yield and harvest index in both years. Weed control applications significantly decreased intensity and dry weight of weeds and increased yield and all yield parameters compared with the unweeded control excepting 1000-grain weight, corresponding increases in yield by 48.3% (metribuzin+quizalofop-p-ethyl) and 74.5% (metribuzin+fluazifop-p-butyl) with significant benefits with chemical herbicides. Pre-emergence+post-emergence combinations, however, gave no clear advantages over single applications of linuron, prometryn and metribuzin. Metribuzin reduced plant stand in wetter conditions of the second year. In conclusion, linuron and prometryn were effective in controlling weeds on lentils without apparent toxic effects. Hand weeding once was also equally effective.
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DOI: 10.3923/ajps.2004.187.192
URL: https://scialert.net/abstract/?doi=ajps.2004.187.192
INTRODUCTION
Lentil (Lens culinaris L.) is among few legume species adapted well to dry conditions in traditional rainfed cereal based farming system in Turkey. Due to extensive government support for the production of lentils in order to reduce large areas left anually to fallow, its acreage and production have sharply increased over the last two decades. Currently, lentil is grown on 517.000 ha land in dry areas and its production reached 380.000 t[1]. However, long term national yields increased only marginally in consequence of unfavourable cultural practices, especially weed control[2].
Lentils because of their small stature do not grow tall and do not build up a protective canopy to prevent establishment of weeds. Therefore, lentils are poor competitors and good weed control is essential for successful production[3,4]. Lentil growth rates are slow during early stages of vegetative growth and weeds can quickly overgrow the crop if not adequately controlled. Yield losses due to weeds in lentil of 40-80% have been reported[5-7].
Hand weeding is practiced in traditional production areas, but is impractical in the extensive production areas[8,9]. Hand weeding is labour-intensive and therefore an expensive operation when done by hired labour and, if delayed, the operation does not prevent adverse effect of the weeds on crop yield[4]. The use of appropriate herbicides can eliminate this early weed competition and prevent yield losses[3]. It is therefore necessary that effective herbicides should be used to reduce unwanted competition.
This study investigated the efficacy of some herbicide and herbicide combinations in comparison with agronomical weed control under Erzurum conditions.
MATERIALS AND METHODS
This study was carried out on the experimental farm of Atatürk University in Erzurum in Eastern Anatolia (29o55' N and 41o16' E with an altitude at 1850 m a.s.l) in 2000 and 2001 using lentil (Lens culinaris cv. Erzurum-89). With an average temperature and total rainfall of 5.7oC and 439.6 mm (Table 1), plant growth in the region is restricted to the period between May and October.
Table 1: | Climatic data on the experimental site |
Table 2: | Active ingredients, trade name, application doses and periods of herbicides investigated |
The second year of experiment received higher and more even distribution of rainfall in the growing months of May, June and July. The experimental soil was a sandy loam with organic matter content ranging between 1.68 and 1.87% and lime content between 0.34 and 0.66% (pH=6.36-6.62). Available P2O5 content ranged between 87 and 119 kg ha-1 and K2O content between 1422 and 1596 kg ha-1. Seeds were inoculated with a culture in peat obtained from Soil and Fertilizer Research Institute, Ankara and all plots received 60 kg P2O5 ha-1 in triple superphosphate form[10].
In the experiment, 16 treatments (Table 2) were investigated in three randomized complete blocks. Sowing was done by hand after mixing seeds with 15% glucose solution and bacterial culture in plots having 6 rows of 5 m length with 20 cm inter row spacing so as to give 350 seeds m-2 [11] on 26 April 2000 and 26 April 2001. Pre-emergence herbicides were applied on 27 April 2000 and 28 April 2001 and post-emergence herbicides were applied on 13 June 2000 and 14 June 2001 at the recommended doses (Table 2) with a hand operated shoulder sprayer. No rain was recorded 2 days before or after the herbicide applications. No irrigation or other chemical application was done during the plant growth until harvest. Data on weed species in each plot were collected at the flowering stage of lentil. Weeds were cut from ground level in each plot of 1/2 m2 area and were taken to the laboratory for separation and dry weight determinations. At the harvest stage, plant density was determined and 10 plants were taken from harvest area of each plot for plant height, branch and pod number measurements. Plots were harvested by hand excluding one row from each side and 50 cm from both ends giving an harvest area of 3.2 m2 on 26 July 2000 and 28 July 2001. Plants were dried for 2-3 days for 1000-grain weight, seed yield, biomass yield and harvest index measurements.
The data were subjected to analysis of variance using MSTATC Statistical Package and mean values were separated according to Duncans multiple range test.
RESULTS AND DISCUSSION
As an average of both years, Amaranthus retroflexus L. (46.8%), Chenopodium album L. (35.2%), Polygonum spp. (4.9%) and Convolvulus arvensis L. (3.3%) were the most dominant broad-leaved weed species in the unweeded control (Table 3). Other species which were of comparatively less density in the plots included Amaranthus graecizans L., Anchusa arvensis (L.) Bieb., Centaurea depressa Bieb., Chenopodium foliosum (Moench) Aschers., Chondrilla juncea L., Cirsium arvense (L.) Scop., Crambe orientalis L., Euphorbia virgata Waldst. et Kit., Falcaria vulgaris Bernh., Fumaria officinalis L., Geranium tuberosum L., Hyoscyamus niger L., Lactuca serriola L., Malva neglecta Wallr., Medicago sativa L., Myosotis arvensis (L.) Hill., Rumex crispus L., Salvia sp., Sideritis montana L., Sisymbrium altissimum L., Tragopogon bupthalmoides (DC) Boiss. and Tragopogon dubius Scop.
Table 3: | The intensity of weed (number m-2) and the efficacy of different herbicides and weeding by hand on weed species as an average of 2000 and 2001 |
1Avena fatua L., Hordeum vulgare L. 2 Data not statistically analysed |
Table 4: | Efficacy of different herbicides and weeding by hand on the dry weight of weeds (g m-2) |
Mean values in each column with the same letters are not statistically different at P < 0.01. 1 Data not statistically analysed. ns, non significant |
A total of 12 herbicide applications and 3 hand weeding treatments (once, twice and repeated) were tested for these weed species control in lentil (Table 2). The existing weed population was significantly affected by applied treatments. All of the herbicide treatments were effective on Amaranthus retroflexus L., Chenopodium album L., Polygonum spp. and the other weed species, but ineffective on Convolvulus arvensis L. when compared with the unweeded control (Table 3). The efficacy of herbicides tested was rated in comparison with the control as <40% is weak, 40-70% medium, 70-90% good, >90% excellent[12]. Thus, weed control efficiency was excellent under metribuzin+prometryn (90.4%) whereas metribuzin+fluazifop-p-butyl (89.9%), metribuzin (88.4%), prometryn+quizalofop-p-ethyl (88.3%), metribuzin+quizalofop-p-ethyl (88.2%), prometryn (84.0%), prometryn+fluazifop-p-butyl (82.6%), prometryn+prometryn (82.0%), linuron+quizalofop-p-ethyl (81.0%), linuron+prometryn (73.4%), linuron+fluazifop-p-butyl (71.6%) and linuron (70.6%) were of relatively good efficacy (Table 3). Hand weeding once, twice and repeated provided 78.8, 80.5 and the 90.4% weed control, respectively when compared with the unweeded control.
In other studies metribuzin was reported to effectively control (>90%) broad-leaved annual weed species in lentil[3,13,14]. In Sudan, prometryn, pendimethalin and prometryn+oxyfluorfen applications significantly reduced intensity of weeds between 91 and 99% compared with the unweeded control[4]. Under Spains conditions the best weed control results in lentil were obtained using prometryn, trifluralin, methabenzthiazuron and linuron[15].
All cultural and chemical weed control treatments markedly reduced weed dry weight as compared with the unweeded control in both years (Table 4). However, soil moisture affected efficiency of the herbicides investigated. Relatively balanced and higher rainfall received in 2001 (Table 1), as an average of herbicide applications, herbicidal effectiveness was greater (92.6%) compared with dry conditions experienced in 2000 (74.7%). Other researchers[3,16] also reported that dry conditions reduced the effectiveness of herbicides and weed control might be poor. Total weed dry weight mass was 96.1 g m-2 in the control plots with no herbicide spraying or hand weeding compared with 17.2 g m-2 in herbicide sprayed plants on average (Table 4). Thus, herbicidal control of weeds was 82.1% on average. In terms of dry weed mass metribuzin+fluazifop-p-butyl was more effective (91.7%) followed by prometryn+prometryn (89.3%), prometryn+fluazifop-p-butyl (88.3%), metribuzin+prometryn (85.6%), metribuzin+quizalofop-p-ethyl (85.4%) and the others.
Table 5: | Effect of herbicides and hand weeding on plant density, plant height, branch and pod number per plant of lentil |
Table 6: | Effect of herbicides and hand weeding on 1000-grain weight, seed yield, total biomass yield and harvest index of lentil |
Mean values in each column with the same letters are not statistically different at P < 0.05. *P < 0.05; ** P < 0.01. ns, non significant |
Hand weeding once, twice and repeated provided 93.4, 97.9 and 98.5% weed dry weight control, respectively when compared with the unweeded control. Hand weeding once was almost as effective in controlling weeds as herbicide applications, hand weeding twice and repeated. Other researchers also reported that hand weeding once controlled weeds effectively in lentil[17-19].
As an average of both years, except for 1000-grain weight, weed control treatments significantly affected all the parameters investigated (Table 5 and 6). Variation occured, however, between years. Except for plant height, relatively low rainfall in May, June and July of the first year (Table 1) reduced all the parameters compared with the second year. Except for plant height, 1000-grain weight and seed yield, year x treatment interaction was significant.
In the first year of experiment, plant density ranging between 205.0 and 223.3 number m-2 depending on the treatments was not affected by weed control treatments. However, metribuzin had toxic effect in relatively wet conditions of the second year. Therefore, metribuzin and metribuzin+post-emergence applications significantly reduced plant density between 32.9% (metribuzin+quizalofop-p-ethyl) and 36.9% (metribuzin+prometryn) compared with the weeded control (Table 5). Under wet conditions and on soils with minimal organic matter, metribuzin may leach deeper into the profile and cause crop injury[3,14].
Weed control treatments significantly affected plant height, branch and pod number per plant in both years. As an average of both years, unweeded control had the lowest plant height, branch and pod number per plant and all of the weed control treatments significantly increased above parameters compared with the unweeded control (Table 5). However, the effect of the weed control treatments on branch and pod number per plant significantly changed between years. In wet conditions of the second year, reduction of plant density depending on the toxic effect of metribuzin reflected to branch and pod number per plant and consequently treatments having metribuzin had the highest branch and pod number values (Table 5). In sowing density studies, it was reported that branch and pod number per plant increased depending on the reduction of plant density[20-22]. As an average of years, 1000-grain weight ranging between 45.1 and 48.3 g showed unsignificant differences among the weed control treatments (Table 6).
All herbicidal and cultural weed control treatments significantly increased seed and total biomass yields compared with the unweeded control. Seed yield increases in herbicide applications ranged between 48.3% (metribuzin+quizalofop-p-ethyl) and 74.5% (metribuzin+fluazifop-p-butyl) over the unweeded control (456.5 kg ha-1). However, pre-emergence+post-emergence combinations gave no significant yield increases compared with single applications of linuron, prometryn and metribuzin (Table 6) possibly due to the high levels of broad-leaved weed species in the experimental fields (Table 3). Fluazifop-p-butyl and quizalofop-p-ethyl which are used post-emergence to control grass weed in broad-leaved crops do not have any effect on broad-leaved weed species[23] and therefore, they do not increase seed yield in fields where broad-leaved weed species are dominant[16]. Hand weeding once gave seed yield similar to chemical applications, hand weeding twice and weeded control (Table 6). In other studies hand weeding once which controlled weeds effectively and produced grain yield almost equal to herbicide applications was also found to be sufficient for lentil[17-19]. Total biomass yield was the highest in prometryn+prometryn application (2779.3 kg ha-1) and the lowest in the unweeded control (1738.2 kg ha-1) as an average of both years. Except for metribuzine and metribuzin+quizalofop-p-ethyl, all herbicide applications gave total biomass yields similar to the weeded control (Table 6). However, the effects of metribuzin alone and metribuzin+post-emergence applications on total biomass yield significantly changed between years. Although all herbicide applications having metribuzin significantly increased total biomass yield compared with the unweeded control in the first year, these applications gave total biomass yields similar to the unweeded control depending on the toxic effect of metribuzin in relatively wet conditions of the second year.
As an average of years, the effect of weed control treatments on harvest index was significant. The unweeded control had the lowest harvest index (25.7%). Except for linorun+prometryn, prometryn+prometryn, linuron+fluazifop-p-butyl and linuron+quizalofop-p-ethyl, weed control treatments gave significantly higher harvest index values than the unweeded control (Table 6). But, the effect of treatments on harvest index significantly changed between years. Reduction of plant densitiy and total biomass yield depending on the toxic effect of metribuzin in the wet conditions of the second year was compensated with increasing of harvest index and metribuzin alone and metribuzin+post-emergence treatments had the highest harvest index values. (Table 6). Therefore, reduction of plant density did not have any negative effect on seed yields in the treatments having metribuzin, except for metribuzin+quizalofop-p-ethyl giving seed yield similar to the unweeded control in the second year of experiment (Table 6). This finding is in agreement with that of Kantar et al.[24] who reported that higher harvest index compensated yield disadvantages at lower plant densities in lentil.
In conclusion, two years of trials showed that herbicide applications considerably increased lentil yields compared with the unweeded control under Erzurums dry conditions. However, pre-emergence+post-emergence combinations gave no significant yield increases compared with the single applications of linuron, prometryn and metribuzin. On the other hand, metribuzin which controlled weeds effectively had toxic effect and significantly reduced plant density in relatively wet conditions of the second year. Thus, it was concluded that linuron and prometryn alone which considerably increased seed yield compared with the unweeded control and had no toxic effect were appropriate for weed control in lentil. Furthermore, hand weeding once may equally be effective in controlling weeds subject to economical availability of labour.
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