Critical periods for weed control in cotton in Turkey

Abstract

Field studies were conducted over 4 years in southeastern Turkey in 1999-2002 to establish the critical period for weed control (CPWC). This is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. A quantitative series of treatments of both increasing duration of weed interference and of the weed-free period were applied. The beginning and end of CPWC were based on 5% acceptable yield loss levels which were determined by fitting logistic and Gompertz equations to relative yield data representing increasing duration of weed interference and weed-free period, estimated as growing degree days (GDD). Total weed dry weight increased with increasing time prior to weed removal. Cotton heights were reduced by prolonged delays in weed removal in all treatments in all 4 years. The beginning of CPWC ranged from 100 to 159 GDD, and the end from 1006 to 1174 GDD, depending on the weed species present and their densities. Practical implications of this study are that herbicides (pre-emergence residual or post-emergence), or other weed control methods should be used in Turkey to eliminate weeds from 1-2 weeks post-crop emergence up to 11-12 weeks. Such an approach would keep yield loss levels below 5%.

Períodos de interferência das plantas daninhas em algodoeiro de fibra colorida 'BRS Safira'

“…1), verifica-se que no início do ciclo da cultura (aos 20 DAE), o capim-pé-de-galinha (ELEIN), a jetirana (IPOPE), quebra-panela (RCHGR) e o caruru (AMADE) já estavam estabelecidos. Conforme salientam Morgan et al (2001) e Bukun (2004) plantas daninhas que desenvolvem-se no início das culturas com crescimento lento, como no caso do algodoeiro, influenciam negativamente, presumivelmente pela redução da fotossíntese da cultura. V e rificou-se acúmulo de matéria seca durante todo o ciclo para o capimpé-de-galinha (ELEIN), permanecendo constante para o quebra-panela atingindo valores de 25,60% (aos 60 DAE) e 33,43% (80 DAE), já a jetirana teve o máximo de acúmulo de matéria seca aos 60 dias após a emergência com 31,62% de toda comunidade.…”

“…Estudando o período crítico de competição das plantas daninhas em algodoeiro irrigado usando a cultivar de ciclo curto, CNPA Precoce 1, Azevedo et al (1994) verificaram que a presença das plantas daninhas nos primeiros 20 dias após a emergência das plântulas não reduziu a produtividade da cultura, quando comparado ao controle sem competição durante todo o ciclo da cultura, independente da largura das fileiras estudadas (0,5; 0,8 O algodoeiro por ter crescimento inicial lento, até os primeiros 20 dias após a emergência das plântulas, e apresentar metabolismo fotossintético C 3 d e b a ixa eficiência transpiratória, é extremamente sensível ao estresse biótico causado pela interferência das plantas daninhas, exigindo muitas vezes que o controle seja realizado logo no início da cultura (BELTRÃO, 2004;BUKUN, 2004). Keeley e Thullen (1991), afirmam que a competição por luz no início do ciclo do algodão, é mais prejudicial ao algodoeiro, que a competição por água e nutrientes.…”

The Effect of Various Weedy Periods on Growth and Yield of Soybean in Agroforestry System with Kayu Putih

“…In a weedy until harvest treatment, the soil moisture content was used by soybean and weeds, causing a relatively lower moisture content compared with other weedy treatments. The degree of crop yield reduction due to weeds interference depended on various factors, such as type of weeds, their density and distribution, time of emergence of weeds relative to crop, as well as soil characteristics such as type, soil moisture status, pH, and fertility level (Papamichail et al, 2002;Bukun, 2004).…”

“…Studies conducted in different crops under diversified environmental conditions might not be applicable to all kind of systems due to location differences, including soil and climatic conditions, as well as weed populations (Van Acker et al, 1993;Evans et al, 2003;Knezevic et al, 2003;Bukun, 2004;Tursun et al, 2016). According to Hendrival et al (2014), critical period of soybean crop in the paddy field after rice plantation to weed competition occurred on 2-6 week after planting.…”

“…The critical period of weed control (CPWC) indicates the optimum time for applying weed control measure (Cardoso et al, 2011). Therefore, information on these periods can be effective to improve the efficiency of weed management practices (Hall et al, 1992;Amador-Ramírez, 2002;Bukun, 2004).…”