Journal of Research in Weed Science

Abstract Herbicides have increasingly become a key component on crop production system because they offer the easiest, cheapest and timely weed management, resulting in higher yield and profit. A single herbicide application in field conditions in most of the cases is not enough to control diverse weed flora. In such situations, tank mixtures of herbicides may provide a prime option to control a broad spectrum of weeds. Cyperus rotundus L., a world’s most tenacious weed, is becoming a problematic weed in conservation crop production systems. A two-year study (2013/14 and 2014/15) was established in South-West Bangladesh to evaluate the effect of application timings and sole and tank mixtures of 2,4-D and ethoxysulfuron herbicides on weed suppression and performance of wheat. 2,4-D and ethoxysulfuron were applied solely and as tank mixtures at 10, 20, and 30 days after sowing (DAS) and these treatments were compared with completely weedy and weed-free treatments. In controlling weeds, tank mixtures of 2,4-D and ethoxysulfuron performed better than their sole application at any application timing; however, at the earliest time (10 DAS), the combination created toxicity to wheat plants, resulting in 10-22% and 11-32% less wheat plant density and biomass, respectively, compared with their sole application. Tank-mix herbicides reduced C. rotundus biomass by 87-91%, 88-100%, and 79-80% when applied at 10, 20, and 30 DAS, respectively, compared with the weedy plots. The plots applied with tank mixtures at 20 and 30 DAS produced wheat grain yield similar to that of weed-free plots, indicating that the tank mixture of 2,4-D plus ethoxysulfuron herbicides is the best option to control weeds without any toxicity to wheat plants.

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.