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Abstract

Background: Parthenium hysterophorus L., commonly known as parthenium weed, poses severe economic and environmental hazards to the agro-ecosystems of Pakistan. Objective: To estimate the yield loss and critical competition period of this weed in the spring sown maize crop. Method: Field studies were conducted at an agronomic research area in the College of Agriculture at the University of Sargodha in Punjab-Pakistan during two consecutive year spring seasons (2014 and 2015). Treatments were comprised of viz., control plots (weed free), and parthenium competition durations of 2, 3, 4, 5 and 6 weeks after crop emergence (WAE), as well as weedy check for the full growing season of the crop. Results: Study results showed that the prolongation in parthenium competition duration from 2 WAE to the full crop season resulted in an increase in dry weight up to 541% and 450% in the years 2014 and 2015, respectively. Plant height, stem diameter, biological yield, 1000 grain weight and grain yield decreased significantly at 2 or more WAE parthenium competition periods. The maximum reduction in plant height (8.8 and 11.3%), stem diameter (30.6 and 12.7%), cob number m-2 (35.8 and 33.9%), grain rows cob-1 (26.6 and 29.4%), 1000 grain weight (15 and 9.8%), grain (34.1 and 39.1%) and biological yield (31.4 and 27.9%) were recorded with the longest parthenium competition duration (6 WAE) during the years 2014 and 2015, respectively. Conclusion: Based upon the results above, it is concluded that the critical competition period of parthenium in spring maize, as determined by a three-parameter logistic model, is 17 to 28 and 16 to 26 days after crop emergence during the years 2014 and 2015, respectively. Therefore, this weed must be controlled during these periods in order to avoid significant grain yield loss.