Red Rice (Oryza sativa) Emergence Characteristics and Influence on Rice Yield At Different Planting Dates

Abstract

Cultivated rice yield losses due to red rice infestation vary by cultivar, red rice density, and duration of interference. The competition effects of red rice could be influenced further by emergence characteristics, red rice biotype, and planting time of cultivated rice. We aimed to characterize the emergence of red rice biotypes at different planting dates and evaluate the effect of red rice biotype, rice cultivar, and planting date on cultivated rice yield loss. Field experiments were conducted at the Southeast Research and Extension Center, Rohwer, AR, and at the Arkansas Rice Research and Extension Center, Stuttgart, AR, in the summer of 2005 and 2006. The experimental design was a split-split plot with three or four replications. Planting time, ClearfieldTM(CL) rice cultivar, and red rice biotype were the main plot, subplot, and sub-subplot factors, respectively. There were three planting times from mid-April to mid-May at 2-wk intervals. CL rice cultivars, CL161 and hybrid CLXL8, and 12 red rice biotypes were planted. The emergence rate and coefficient of uniformity of germination differed among some red rice biotypes within a planting time. Planting date affected the emergence characteristics of red rice biotypes. The mean emergence rate of red rice was 0.043 d−1in the mid-April planting and 0.058 d−1in the late April planting. For the mid-April planting, 50% of red rice biotypes emerged in 20 ± 2 d compared with 15 ± 2 d for CL rice cultivars. Yield losses due to red rice biotypes generally increased in later planting dates, up to 49%. Yield losses due to interference from red rice biotypes ranged from 14 to 45% and 6 to 35% in CL161 and CLXL8, respectively. Cultivated rice became less competitive with red rice in later plantings, resulting in higher yield losses.

Competitive ability of cultivated rice against weedy rice biotypes: A review

“…The highest plant height and tiller number (90.08 ± 12.32 cm and 3.70 ± 1.42, respectively) were found in transplanted weedy rice variants with no competition while the lowest plant height (55.88 cm) and tiller number (2.08) were observed in improved rice in DSP interacting with weeds. Shivrain et al (2009) reported that 12 ecotypes of weedy rice produced 226 to 462 tillers m -2 while the cultivar of inbred rice produced 250 tillers m -2 in a competition of 1/19 weedy vs. rice. The effects of weed density on rice growth, higher tillering capacity, and shoot development potential of weedy rice generally decreases grain yield in rice production.…”

Germinação de arroz irrigado e de biótipos de arroz-vermelho submetidas a diferentes temperaturas

“…Entretanto, nessa mesma condição, o biótipo 3 apresentou similaridade ao genótipo de arroz, demonstrando que há diferenças no comportamento de biótipos de arroz-vermelho. Estudo realizado por Shivrain et al (2009), também constataram variação de emergência entre biótipos de arroz-vermelho em diferentes épocas de semeaduras do arroz irrigado.…”

“…O controle do arroz-vermelho torna-se dificultado devido a similaridade fisiológica com o arroz cultivado (SCHWANKE et al, 2008), e devido a diversidade de biótipos com características morfológicas distintas presentes em uma população de arroz-vermelho (FONTANA et al, 2007;MENEZES et al, 2002;SHIVRAIN et al, 2009).…”

“…Outra característica importante que dificulta as práticas de controle é a dormência das sementes de arrozvermelho (AGOSTINETTO et al, 2001;FOGLIATTO;VIDOTTO;FERRERO, 2011;GIANINETTI et al, 2007;MARCHESAN et al, 2011), que proporciona a distribuição da germinação e da emergência ao longo do tempo (BEWLEY, 1997), diminuindo a uniformidade de emergência (SHIVRAIN et al, 2009), dificultando ainda mais o controle.…”

“…O coeficiente de uniformidade de emergência (CUE) também foi obtido pela contagem diária do número de plântulas emergidas até que esse número permanecesse constante, porém para o cálculo do CUE utilizou-se a equação 2, proposta por Shivrain et al (2009), em que baixo valor de CUE indica menor uniformidade de emergência.…”