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Weed management is essential for sustainable crop production in all cropping systems. The use of herbicides is causing the problems of herbicide resistant weeds and environmental pollution. Plant-released phytotoxins have ability to promote or inhibit the germination and seedling growth of surrounding crops and weeds. Therefore, it is imperative to identify plant species having the herbicidal potential to use as more safe and sustainable weed management approach. The present study was planned in 2018 to investigate the germination and seedling growth of Daucus carota and Medicago polymorpha influenced by the root extract of Polygonum bistorta and fruit extract of Terminalia chebula. Different concentrations of aqueous extract (0, 2.5, 5, 10, 20, 40 and 80%) significantly reduced the germination and seedling growth of target species. Results of these experiments revealed that thefruit extract of T. chebula was more phytotoxic as compared to root extract of P. bistorta regarding seedling growth of weed. However, fruit extract of T. chebula having 80% concentration fully inhibit the germination of D. carota and M. polymorpha. One the bases of these finding it was concluded that the fruit extract of T. chebula and root extract of P. bistorta have comparatively more active substances with ability to suppress germination and growth of plants which could be exploited as prospective source of bio-herbicides.

Optimization of agronomic practices for cultivation of quinoa, a super food and climate resilient crop, is critical to obtain its maximum grain yield under the current scenario of climate change. In the present experimentation, we evaluated the appropriate sowing time of ten elite lines of quinoa, already screened from USDA germplasm. Seeds of each line were sown in the experimental area at Square No. 22, Block No. 5, Directorate of Farm, University of Agriculture, Faisalabad, Pakistan on 15 November, 30 November and 15 December during quinoa cultivation season of 2019–2020. Sowing time significantly affected the emergence percentage, days taken to anthesis, chlorophyll contents, sodium and potassium concentrations in leaf, plant height, stem diameter, number of leaves and leaf area, panicle length, grain yield and 1000-grain weight. Lines; PIA-922, PIA-924, PIA-928 and PIA-929 performed better under first sowing and produced higher grain yield as compared to other lines. Similarly, PIA-921, PIA-922, PIA-925 and PIA-932 produced maximum biomass and grain yield under second sowing date while in case of third sowing date, PIA-926, PIA-928, PIA-930 and PIA-931 were observed more responsive regarding growth and yield attributes. A diversified pattern of agronomic, growth and yield contributing attributes of quinoa lines was observed when cultivated under varying sowing dates. The collected data will be very informative for the breeders and agronomists during selection and variety development process in future.

A large number of weeds are known to be associated with crops and causing economic losses. Weeds interfere with crops through competition and allelopathy. They produce secondary metabolites known as allelochemicals, which belong to numerous chemical classes such as phenolics, alkaloids, fatty acids, indoles, terpens etc. However, phenolics are the predominant class of allelochemicals. The allelochemicals release from weed plants takes place through leaf leachates, decomposition of plant residues, volatilization and root exudates. Weeds leave huge quantities of their residues in field and affect the associated, as well as succeeding crops, in various cropping systems. Liberation of allelochemicals from weeds affects the germination, stand establishment, growth, yield and physiology of crop plants. They cause substantial reduction in germination and growth of the crop plants by altering various physiological processes such as enzyme activity, protein synthesis, photosynthesis, respiration, cell division and enlargement, which ultimately leads to a significant reduction in crop yield. In crux, allelopathic weeds represent a potential threat for crop plants and cause economic losses.