Journal of Research in Weed Science

Abstract The bio-efficiency of imazethapyr and its ready mix combination products with pendimethalin and imazamox against weeds, their effect on growth, yield and phytotoxic effects on black gram and residual effect on succeeding mustard crop were studied during 2013-14. Significantly lower weed count and dry weight was recorded with application of imazethapyr + pendimethalin (pre-mix) at 800 g/ha, pendimethalin at 1000 g/ha and imazethapyr + pendimethalin (pre-mix) at 900 g/ha. Imazethapyr + pendimethalin (pre-mix) 1000 g/ha and 800 g/ha, pendemethlin 1000 g/ha and imazethapyr 50 and 70 g/ha (pre emergence) behaving statistically similar with pendimethalin 1000 g/ha (pre emergence) and hand weeding at 20 and 40 days after sowing resulted in significantly higher seed yield of black gram. Seed yield of blackgram was negatively associated with total weed count and weed dry weight (P≤0.01). With every one weed increase per square meter, the blackgram seed yield was expected to reduce by 16.8 kg/ha. Net returns, B:C and net returns over weedy check were highest under imazethapyr + pendimethalin 900 g/ha. The economic threshold levels i.e. No m^-2 and g m^-2 with the weed management practices studied varied between 1.7 – 18.0 m^-2 and 1.0-10.0 g m^-2. Imezethapyr + pendimethalin 1000 g/ha and imazethapyr + imazamox 50 g/ha had lowest weed persistence index (WPI). Imazethapyr + pendimethalin 900 g/ha resulted in highest crop resistance index. Weed management index (WMI), Agronomic management index (AMI), and Integrated weed management index (IWMI) were highest following imazethapyr 40 g/ha. Overall impact index (Ii) was highest under imazethapyr 50 g/ha followed by imazethapyr + pendimethalin 900 g/ha, imazethapyr + pendimethalin 1000 g/ha and pendimethalin 1000 g/ha. Weed index (WI) indicated 70.8% loss in yield of blackgram. The residual effects of herbicide treatments on succeeding mustard crop were not observed.

Abstract Growing two or more cultivars of the same crop species in mixture reduces intra-specific competition for growth resources by inducing variation in spatial and temporal patterns of crop growth, increases competitive ability of crops against weeds and thus enhances crop yield. This study was conducted to evaluate the potentiality of wheat cultivar mixtures to reduce weed growth and increase the wheat yield under different irrigation regimes, and determine the best row mixture ratio of two wheat cultivars for better weed suppression and higher productivity of wheat. Factors included seven cultivar mixture ratios viz. sole BARI Gom 25, sole BARI Gom 30, 1:2, 2:1, 2:3, 3:2 and 1:1 of BARI Gom 25 to BARI Gom 30, and three water management practices viz. no irrigation, one irrigation at crown root initiation (CRI) stage, and two irrigation at CRI and flowering stages arranged in a split-plot design with three replications. Results clearly indicated that cultivar mixture can improve the competitive ability of wheat plants against weeds and can increase wheat productivity. Both cultivars showed better growth, higher weed suppression and increased yield when grown in mixture irrespective of ratios compared to their monoculture. Based on the combined grain yield, different mixture ratios performed in the order 1:1, 2:3, 1:2 and 2:1 BARI Gom 25 to BARI Gom 30 under two irrigation regimes. BARI Gom 25 and BARI Gom 30 inter-planted in 1:1 row ratio under two irrigation appeared as the best practice resulting 9% and 5.83% yield advantages over sole culture of BARI Gom 25 and BARI Gom 30, respectively; while mixture ratio of 3:2 resulted in 6.43% and 3.36% weed dry matter reduction over sole culture of BARI Gom 25 and BARI Gom 30, respectively. In conclusion, cultivar mixture strategy can be adopted as an effective tool for better weed management and increased yield of wheat. 

Abstract Glyphosate resistant Echinochloa colona is widespread in fallow systems of northern Australia from intensive glyphosate use. The inheritance of glyphosate resistance and the potential for gene transfer through pollen from resistant to susceptible individuals were investigated. A glyphosate resistant population A533.1, containing a mutation in EPSPS, was used as the resistant parent and Echi S as the susceptible parent. Gene flow via pollen between adjacent susceptible and resistant individuals was examined by treating progeny from the susceptible individuals at 240 g ha^-1 glyphosate with 1.38% gene flow detected. Survivors were selfed and the progeny segregated 3:1 for survival to 240 g ha^-1 glyphosate, consistent with single dominant gene inheritance. Hand crosses between resistant and susceptible individuals produced a single F₁ seed which carried the mutation in EPSPS. The F₂ generation from the hand cross had a response to glyphosate, intermediate between the two parents and similar to that expected for a single largely dominant gene. Sequencing the EPSPS cDNA detected at least two EPSPS genes expressed in E. colona, only one of which carried the mutation. Glyphosate resistance in this population of E. colona is inherited as a single largely dominant allele.

Abstract To evaluate most economical and efficient weed management practices in dry direct seeded rice, a field experiment was conducted at research block of AFU Rampur, Chitwan during the Kharif 2016 season. The treatments consisted of two establishment practices viz., zero till and conventional tillage and eight weed management practices such as weedy check, weed free, Pendimethalin followed by hand weeding at 20 DAS 1 kg a.i ha^-1, Pendimethalin followed by 2, 4-D ethyl ester at  25 DAS 1 kg a.i ha^-1, pendimethalin followed by bispyribac-Na at 25 DAS at 25 g a.i ha^-1, pendimethalin followed by ethoxysulfuron at 25 DAS 25 g a.i ha-¹, pendimethalin followed by penoxsulam at 25 DAS 25 g a.i ha^-1, pendimethalin followed by (ethoxysulfuron + bispyribac-Na. The experiment was conducted in split plot design with three replications. The result of experiment showed that non-significant difference was notice among the establishment method. However, significant difference was observed in weed management practices in all the traits expect number of weeds m^-2, number of weed species m^-2, and dry weight of broad leaf, narrow leaf and sedges weeds. The higher number of weeds m^-2 was found in weedy check plot which resulted in higher weed infestation at all the stages as compared to other weed management practices. Application of pendimethalin followed by hand weeding at 20 DAS recorded higher weed control efficiency which reflected in higher yield of 4202 kg ha^-1 was recorded under this treatment as compared to weedy check plot (1292.13 kg ha^-1) but rest of the treatments are statistically at par with other weed management practices.

Abstract This study was carried out to determine the impact of three-year crop rotation in sampling fields on winter wild oat (Avena sterilis L.) populations in Osmaniye wheat sown areas. The study was conducted in Osmaniye province between the years 2013-2015. A total of 103 fields in 7 districts’ wheat sown areas were determined; these sampling fields were visited every year during May-August and effects of different crops sown on winter wild oat populations were observed. Besides determining frequency of occurrence, randomly chosen general coverage in 1 decare and special coverage in 1 m2 in three points were specified. As a result of the study, it was determined that all of the crops except wheat decreased winter wild oat populations and it was found that the changes were related to the crop rotations. It was determined that corn, sunflower, soybean and peanut sown in 2nd and 3rd year instead of wheat decreased the frequency of winter wild oat at 2% and below. Moreover, when the three-year crop rotation system was analyzed, it was revealed that the maximum decrease in winter wild oat population general coverage occurred in 4 crop rotation period. It can be found that populations decrease can be up to more than 90% when compared to 2 and 3 crop rotation systems. It was concluded that crop rotations are sufficient in controlling winter wild oat that are problematic in wheat fields.

Abstract Studies were conducted to ascertain the phytotoxic action of aqueous extracts and rhizospheric soils of wasteland weeds such as Parthenium hysterophorus L., Withania somnifera L., Lantana camara L., and Achyranthes aspera L. against four summer crops viz., Gossypium hirsutum L., Helianthus annuus L., Oryza sativa L. and Zea mays L. Experiment was carried out in Agronomy Laboratory, College of Agriculture, University of Sargodha, Punjab-Pakistan. In first experiment, the 5% (w/v) aqueous extract prepared from whole plant of each weed was applied to germinating crop seeds sown in petri plates. In the second experiment soils collected from rhizosphere of these weeds were filled in plastic pots and used as germination medium for seeds of these crops. A constant temperature of 30^oC was maintained in germinator throughout the germination period of 12 days. In first experiment, significantly lower germination percentages (31.7 and 38.3%) and germination indices (4.4 and 6.4) of crops were noted with application of A. aspera and P. hysterophorus extracts, respectively. All weed extracts except L. camara caused significant reduction in shoot length, root length, seedling length and seedling biomass of crops. Root growth of the crop seedlings was influenced more than their shoot growth. In second experiment, germination percentage, shoot dry weight, seedling biomass and seedling vigor index of crops were significantly inhibited by rhizospheric soil of all weeds. Among crops, H. annuus was more susceptible to the deleterious effect of the aqueous extracts as well as rhizospheric soils of weeds. It can be concluded that wasteland weeds especially P. hysterophorus and A. aspera imparted more negative impact on the germination and seedling growth of test crops. Therefore, crop fields and their surroundings should be kept free from these weeds by clean cultivation.

Abstract The present study was conducted to evaluate the relative phytotoxic effects of different concentrations (15, 25, 50, 75 and 100%) of aqueous extract from stem and root of Parthenium hysterophorus on the rate of seed germination, length of root and shoot, and Seed Vigour Index (SVI) of Cicer aeritinum. In laboratory condition the experiment was set up in petri dishes, each petri dish contained ten seeds. Each treatment had ten replicates. A control condition was maintained using distilled water in place of stem or root aqueous extracts of Parthenium. The rate of seed germination in Cicer aeritinum in stem and root aqueous extracts of different concentrations decreased from 5% to 79%, and 0.0% to 22%, respectively. The inhibition value in root length in stem extracts varied from 11.14% to 85.96% and in root extract was from 13.14% to 64.25%. The inhibition in shoot length in stems and roots extracts varied from 14.67% to 50.19% and 73.68% to 85.86%, respectively. The Seed Vigour Index (SVI) value decreased from 16.38% to 94.99% in stem extract and 32.11% to 77.37% in root extract. The stem extract of Parthenium was more phytotoxic than the root extract in Cicer aeritinum. When the data collected were analysed using Tukey HSD and Post HOC Tests the phytotoxic impacts of plant parts (stem and root); treatments (15, 25, 50, 75 and 100% concentrations); and interactions between plant parts and treatments were highly significantly different at p < 0.000. Thus the present study indicated that the aqueous extracts of stem of Parthenium were recorded more phytotoxic than root extract on germination and growth of Cicer aeritinum.

Abstract A field experiment was conducted to assess the growth, productivity and profitability of rice (Sukhadhan-3 variety) under different methods of weed management at Bhanu-11 Rupakot, Tanahun during rainy season 2017. The experiment was laid out in randomized complete block design with three replications and ten treatments. The phenological, growth, yield and yield attributing characters were observed in the experiment. Results revealed that maximum grain yield (5.91 ton ha^-1) was obtained in application of butachlor at 4 days after transplanting (DAT) which was statistically at par with all other treatments except single manual weeding, single cono-weeding and non-weeding plots (3.66 ton ha^-1). The highest grain yield obtained from this treatment was might be due to higher number of effective grains per panicle (203 grains), less sterility (6.4%), high test weight (30.7g) with good harvest index (38.4%). Although the single application of butachlor as pre emergence spray showed highest grain yield which seems economically viable and profitable practice to the farmers but it is not environmentally safe to the whole universe.