Document Type : Research Paper



In order to determine the critical period of weed control (CPWC) in Corn (Zea mays L.), an experiment was carried out in a randomized complete blocks design with 14 treatments and three replications during 2013 growing season in the Nahavand climatic conditions. Two series of the treatments including weed-free and weed-infested were applied in the regular time distances of 10, 20, 30, 40, 50 and 60 days after Corn emergence. Two check treatments including full and no control of weed during the whole season were also included. The nonlinear models kind of Logistic and Gompertz were applied to determine the start and end of critical period of weed control respectively. Major weed species were field bindweed (Convolvulus arvensis L.), red root pigweed(Amaranthus retroflexus L.), pigweed(Amaranthus blitoides L.) and lambsquarters(Chenopodium album L.) with greater biomass and size. The results showed that periods of weed- free and weed- infested differently affected the dry weight and number of weeds in all treatments. The critical periods of weed control in Corn by accepting a 5% acceptable yield loss, it is necessary to control weeds in a period between 14-47 days after planting or 117- 566 growth degree day(4-12 leaf stage) and by accepting a 10% acceptable yield loss it is necessary to control weeds in a period between 23-36 days after planting or 220- 419 growth degree day(6-10 leaf stage).


1 . آقاعلیخانی م، یدوی ع ر و مدرس ثانوی ع م (1384) دورة بحرانی مهار علف­های هرز لوبیاچیتی (Phaseolus vulgaris L.) در لردگان. علمی کشاورزی. 28(1): 1-13.
2 . جمالی ع، احمدوند گ، سپهری ع و جاهدی آ (1389) دورة بحرانی کنترل علف­های هرز ذرت (Zea mays L.). حفاظت گیاهان (علوم و صنایع غذایی). 24(4): 457-464.
3 . خزائی م، حبیبی ح، زند ا، کردناییج ع، امینی دهقی م و هادیزاده م ح (1391) تعیین دورة بحرانی کنترل علف­های هرز آویشن باغی (Thymus vulgaris L.). دانش علف­های هرز. 8: 25-37.
4 . عباس­پور م و رضوانی مقدم پ (1383) دورة بحرانی کنترل علف­های هرز ذرت در شرایط مشهد. پژوهش­های زراعی ایران. 2(2): 182-195.
5 . هادیزاده م ح و رحیمیان مشهدی ح (1371) دورة بحرانی کنترل علف هرز سویا. بیماری­های گیاهی. 34: 92-106.
6 . Amador-Ramirez MD (2002) Critical period of weed control in transplanted chili pepper. Weed Research. 42: 203-209.
7 . Bukun B (2004) Critical period of weed control in cotton in Turkey. Weed Research. 44: 404-412.
8 . Chris H, Allan S, Hamill J, Zhang C and Duocet N (2001) Critical period of weed control in no-till soybean (Glycine max)and corn (Zea mays L.). www.
9 . Cousens R (1988) Misinterpretations of results in weed research through inappropriate use of statistics. Weed Research. 28: 281-289.
10 . Dawson JH (1964) Competition between irrigated field beans and annual weed. Weeds. 12: 206-208.
11 . Dunan CM, Westra P, Moore F and Chapman P (1996) Modelling the effect of duration of weed competition, weed density and weed competitiveness on seeded, irrigated onion. Weed Research. 36: 1259-1260.
12 . Hall MR, Swanton CJ and Anderson GW (1992) The critical period of weed control in grain corn. Weed Science. 40: 441-447.
13 . Knezevic SZ, Evance SP, Blankenship EE, Van Acer RC and Lindquist JL (2002) Critical period for weed control: the concept and data analysis. Weed Science. 50: 773-786.
14 . Mahmoodi S and Rahimi A (2009) Estimation of critical period for weed control in corn in Iran. World Academy of Science, Engineering and Technology. 49: 67-72.
15 . Nieto HJ, Brondo MA and Gonzalez JT (1968) Critical periods of the crop growth cycle for competition from weeds. Pest Articles and News Summaries. 14: 159-166.
16 . Ocho DL (1990) Critical period of weed competitions on sweet Corn (Zea mays Var. sacharat sturn) st. Augustine (Trinidad and Tobago). 84p.
17 . Ratkowfky DA (1983) Non-liner regression modeling. Marcel Dekker, Inc. 270p
18 . Singh M, Saxena MC, Abu-Irmaileh BE, Al-Thahbi SA and Haddad NI (1996) Estimation of critical period of weed control. Weed Science. 44: 273-283.
19 . Swanton CJ and Weise SF (1991) Integrated weed management: the rational and approach. Weed Technolgy. 5: 648-656.
20 . Zimdahl RL (1988) The concept and application of the critical weed-free period. Weed management in Agroecosystems: Ecological Approaches (eds. MA  Alteri and ML eibman): Page 145-155. CRC Press, Boca Raton, FL, US.