Efficacy evaluation of some herbicides for weed management and yield attributes in broad bean (Vicia faba)

IntroductionBroad bean (Vicia faba, L.) is grown and consumed principally in developing countries in Latin America, Africa, and Asia. Farmers often consider weeds to be the major biological constraint to growing legume crops successfully. Chemical control of weeds became widespread in the world because it brings about rapid and desirable control of weeds; and today chemical weed control is one of the most popular methods of controlling weeds. Weed interference in dry bean can reduce seed yield as much as 83%. There is limited number of post emergence herbicides available for broad bean production. More research is needed to identify POST herbicides that provide broadleaves weed control in broad beans. The objectives of this study were to evaluate the efficacy of some broadleaved herbicides applied POST at the proposed manufacturer’s recommended rate and to assess broad bean yield response to these herbicides since no information is available in the literature on these chemicals.
Materials & MethodsField experiment was conducted in 2011-2012 at the Shoushtar Branch, Islamic Azad University, Iran (320 3´ N, 480 50´ E). The experiment was performed in randomized complete block design with four replications. Treatment consisted of 1) Basagran (bentazon) SL 48% 1.5 Lha-1 Haloxyfop-R-methyl (super gallant) EC 10.8% 0.6 Lha-1 2) Bentazon SL 48% 1.5 Lha-1 Sethoxydim (nabo-S) OEC 12.5% 1.5 Lha-1 3) Bentazon SL 48% 1.5 Lha-1 Fenoxaprop-p-ethyl (whip super) EC 12% 0.7 Lha-1 4) Imazthapyr(pursuit) SL 10% 0.6 Lha-1 5) Pursuit SL 10% 0.4 applied POST, with two control plots weed-free and weed-infested throughout the crop cycle, respectively. Plots were maintained weed free by cultivation and hand hoeing as required to eliminate the confounding effect of weed interference. Bean shoot dry weight was determined by cutting plants at the soil surface from 1m of row per plot. Plants were dried at 75 0C to constant moisture and then weighed. Broad bean height was measured for 10 plants in each plot 5 WAT and averaged. Broad bean was considered mature when 90% of the pods in the untreated control had turned from green to a golden color. Beans were harvested from each plot, weight and seed moisture content were recorded, and seed yields were adjusted to 13% moisture. Data were analyzed as an RCBD using PROC MIXED in SAS 9.2. The comparison of means was conducted by Duncan method at 1 and 5% probability level.
Results & DiscussionHerbicide treatments applied to broad bean resulted in significant (P ≤ 0.05) reduction in weed biomass and density relative to the untreated control (Table1, 2). The blend of Bentazon㚆S and Pursuit with the dose of 0.6 Lha-1 has been more successful in the control of weed than other treatments, and has decreased the weed biomass by over %98.7 in compare to weedy check. Other studies have found that 50 g ai ha-1 of imazethapyr (pursuit) applied post emergence will provide season-long control of broad leaf weed in pinto beans. There was no statistical difference in weed control between pursuit applied alone or tank-mixed of Bentazon with Nobo-S (Table 3). The least level of control were observed in blend of Bentazon娘 super and pursuit with the dose of 0.4 Lha-1(Table 4). Weed management practitioners must adjust pursuit herbicide doses based on weed species composition. Among experimental treatments there was a significant difference in terms of impact on the density of weed (Table 1). Mean comparison of treatments showed that pursuit with the dose of 0.6 Lha-1 decreased the density of weed by 66.2%. Seed yield was equal in all POST herbicide treatments, and there was no statistical difference in seed yield among herbicide treatments. The lowest and highest seed yield recorded 2403 and 2545 kg ha−1 in tank-mixed of Bentazon䫪 gallant and pursuit with the dose of 0.6 Lha-1, respectively (Table 4). In the weedy treatment seed yield was 1494.9 kg ha−1, and on hoeing treatment it was 3239 kg ha−1 (Table 4). Because the highest yield of herbicide treatments was only 78% of the hoeing treatment, it is likely that more efficient weed management programs can be developed. Higher seed yield in herbicide treated plots in compare to weedy check, may be an outcome of efficient weed control achieved there. These results are in conformation with those of some researchers who reported that herbicides offer sizeable increase in crop productivity corresponding to their weed control spectrum.
ConclusionsIt is concluded that the most effective herbicide treatment was pursuit with the dose of 0.6 Lha-1, which provided maximum reduction in total weed dry matter. However, all herbicide treatments increased broad bean biological and seed yield as compared with the weedy check.