Germination Ecology of Southern Crabgrass (Digitaria ciliaris) and India Crabgrass (Digitaria longiflora): Two Important Weeds of Rice in Tropics

Southern and India crabgrass are important grass weeds of rice in many tropical countries. Environmental factors influenced seed germination and seedling emergence of these weeds. Seeds of both species germinated at a range of alternating temperatures (25/15, 30/20, and 35/25 C day/night), though the germination of southern crabgrass was reduced at the lowest alternating temperatures (25/15 C). Light stimulated germination of both species; however, a small proportion of southern crabgrass seeds germinated in the dark. Germination of India crabgrass was influenced to a greater degree by increasing salt and water stresses than was southern crabgrass. Seeds of both species germinated over a wide range of pH between 5 and 10. Seedling emergence of both species (98% for southern crabgrass and 94% for India crabgrass) was greatest for seeds placed on the soil surface. Seed burial depth of 2 cm completely inhibited emergence of India crabgrass, whereas for southern crabgrass, this depth was 8 cm. Knowledge gained from this study is expected to contribute to developing components of integrated weed management strategies for these species.

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Seed Germination, Seedling Emergence, and Response to Herbicides of Triquetrous Murdannia (Murdannia triquetra) in Rice

Weed Science ◽

10.1614/ws-d-16-00048.1 ◽

2016 ◽

Vol 65 (1) ◽

pp. 141-150 ◽

Cited By ~ 2

Author(s):

Wei Tang ◽

Jie Chen ◽

Jianping Zhang ◽

Yongliang Lu

Keyword(s):

Seed Germination ◽

Weed Management ◽

Seedling Emergence ◽

Management Strategies ◽

Soil Surface ◽

Rice Fields ◽

Integrated Weed Management ◽

Burial Depth ◽

Nacl Concentration ◽

Dark Regime

Triquetrous murdannia is an annual weed commonly found in rice fields in China. Laboratory and screenhouse experiments were carried out to determine the effect of light, temperature, osmotic and salt stress, seed burial depth, amount of rice residue, and depth of flooding on seed germination and seedling emergence of triquetrous murdannia and to evaluate the response of this weed to commonly available POST herbicides in China. Germination was greater than 93% under a wide day/night temperature range of 20/10 to 30/20 C in the light/dark regime. The time to onset of germination decreased as temperature increased. Germination was slightly stimulated when seeds were placed in light/dark conditions compared with seeds placed in the dark. The osmotic potential and NaCl concentration required for 50% inhibition of maximum germination were −0.5 MPa and 122 mM, respectively. The highest germination (68%) was observed from seeds sown on the soil surface, but decreased with increasing burial depth. Only 7% of seedlings emerged from a depth of 4 cm, and no seedlings emerged from seeds buried deeper than 6 cm. Seedling emergence decreased from 93 to 35% with increasing quantity of rice residue (1 to 6 103kg ha−1) applied on the soil surface. Seedling emergence was reduced by 40, 48, 64, and 70% at flooding depths of 1, 2, 4, and 6 cm, respectively, for the seeds sown on the soil surface. Fluroxypyr and MCPA herbicides provided 100% control of triquetrous murdannia at the 2- to 6-leaf stages; however, to achieve 100% control with bispyribac-sodium, MCPA+bentazone or MCPA+fluroxypyr, herbicides had to be applied by the 4-leaf stage. The results of this study could help in developing more sustainable and effective integrated weed management strategies for the control of triquetrous murdannia in rice fields in China.

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Crowfootgrass (Dactyloctenium aegyptium) Germination and Response to Herbicides in the Philippines

Weed Science ◽

10.1614/ws-d-11-00048.1 ◽

2011 ◽

Vol 59 (4) ◽

pp. 512-516 ◽

Cited By ~ 15

Author(s):

Bhagirath Singh Chauhan

Keyword(s):

Seed Germination ◽

Weed Management ◽

Seedling Emergence ◽

Management Strategies ◽

Soil Surface ◽

The Philippines ◽

Integrated Weed Management ◽

Burial Depth ◽

Early Application ◽

Dark Regime

Crowfootgrass, a C4species, is one of the principal weeds of dry-seeded rice in Asia. Weed management decisions for this species can be derived from knowledge of its seed germination biology. Experiments were conducted in the laboratory and screenhouse to determine the effects of light, alternating day/night temperatures, water stress, seed burial depth, and rice residue on seed germination and seedling emergence of crowfootgrass and to evaluate the response of this weed to commonly available selective POST herbicides in the Philippines. Light stimulated seed germination, but it was not an absolute requirement for germination. Germination in the light/dark regime was greater at alternating day/night temperatures of 25/15 C (92%) than at 30/20 (70%) or 35/25 C (44%). The osmotic potential required for 50% inhibition of maximum germination was −0.23 MPa, although some seeds germinated at −0.6 MPa. Seedling emergence was greatest for the seeds placed on the soil surface (64%), and emergence declined with increased burial depth in soil. No seedlings emerged from a burial depth of 6 cm or greater. Seedling emergence of crowfootgrass was reduced by the addition of rice residue to the soil surface at rates equivalent to 4 to 6 Mg ha−1. Fenoxaprop-p-ethyl + ethoxysulfuron at 45 g ai ha−1provided excellent control of crowfootgrass when applied at the four- (99%) and six-leaf (86%) stage. The information gained from this study could contribute to developing components of integrated weed management strategies for crowfootgrass. Soil inversion by tillage to bury weed seeds below their maximum depth of emergence, use of crop residue as mulch, and early application of an effective POST herbicide could serve as important tools for managing crowfootgrass.

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Seed Germination Ecology of Doveweed (Murdannia nudiflora)and Its Implication for Management in Dry-Seeded Rice

Weed Science ◽

10.1614/ws-d-14-00115.1 ◽

2015 ◽

Vol 63 (2) ◽

pp. 491-501 ◽

Cited By ~ 20

Author(s):

Sharif Ahmed ◽

Jhoana L. Opeña ◽

Bhagirath S. Chauhan

Keyword(s):

Weed Management ◽

Crop Residues ◽

Seedling Emergence ◽

Management Strategies ◽

Soil Surface ◽

Integrated Weed Management ◽

Burial Depth ◽

Similar Response ◽

Leaf Stage ◽

Dark Regime

This study was conducted in the laboratory and screenhouse to determine the effects of temperature, light, osmotic stress, salt stress, burial depth, use of crop residues as mulch, depth of flooding, and use of POST herbicides on the emergence, survival, and growth of doveweed. In the light/dark regime, germination was higher at alternating day/night temperatures of 35/25 C (95%) than at 30/20 C (72%), and no germination occurred at 25/15 C. Light strongly influenced germination (95%) and dark completely inhibited germination. No germination occurred at an osmotic potential of −0.8 MPa and a salt concentration of 150 mM and above. The highest germination (91%) was observed from the seeds sown on the soil surface and emergence decreased by 78, 86, and 92% when burial depths were increased to 0.5, 1, and 2 cm, respectively. No seedlings emerged from seeds buried at depths of more than 2 cm. The use of rice residues as mulch significantly reduced the emergence and growth of doveweed seedlings. The amount of residue required to suppress 50% of the maximum biomass was 2.5 t ha−1. Flooding had a more pronounced effect on seedling biomass than seedling emergence. Biomass was reduced by 78, 92, and 96% when flooding depths increased from 0 to 2, 4, and 6 cm, respectively, for the seeds placed on the soil surface, whereas for the seeds buried at 0.5 cm, these values were 78, 100, and 100%. Bentazon (100 g ha−1) and bispyribac-sodium (30 g ha−1) provided 100% control of doveweed when applied at the three-leaf stage. Doveweed control was less than 31% with glyphosate rates up to 2,000 g ha−1. The application of 2,4-D (500 g ha−1) provided 100% control of doveweed even when applied at the seven-leaf stage. The information from this study could help in developing more sustainable and effective integrated weed management strategies for the control of this weed and weeds with similar response in dry-seeded rice systems.

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Threelobe Morningglory (Ipomoea triloba) Germination and Response to Herbicides

Weed Science ◽

10.1614/ws-d-11-00137.1 ◽

2012 ◽

Vol 60 (2) ◽

pp. 199-204 ◽

Cited By ~ 17

Author(s):

Bhagirath Singh Chauhan ◽

Seth Bernard Abugho

Keyword(s):

Weed Management ◽

Seedling Emergence ◽

Management Strategies ◽

Soil Surface ◽

The Philippines ◽

Integrated Weed Management ◽

Burial Depth ◽

Early Application ◽

Hard Seed ◽

Ipomoea Triloba

Experiments were conducted in the laboratory and screenhouse to determine the effects of scarification; alternating day/night temperatures; light, salt, and water stress; seed burial depth; and rice residue on seed germination and seedling emergence of threelobe morningglory, and to evaluate the response of this weed to commonly available POST herbicides in the Philippines. Germination was stimulated by seed scarification, suggesting that inhibition of germination in this species is mainly due to the hard seed coat. Germination of the scarified seeds was not influenced by the tested temperatures (alternating day/night temperatures of 25/15, 30/20, and 35/25 C) and light. The concentrations of sodium chloride, ranging from 0 to 250 mM, did not influence germination of the scarified seeds of threelobe morningglory. The osmotic potential required for 50% inhibition of maximum germination was −0.35 MPa, although some seeds germinated at −0.6 MPa. Seedling emergence was greatest for the seeds placed on the soil surface (96%), and emergence declined with increased burial depth in soil. The burial depth required for 50% inhibition of maximum emergence was 2.8 cm. No seedlings emerged from a burial depth of 6 cm or greater. Residues of up to 6 Mg ha−1on the soil surface did not influence seedling emergence of threelobe morningglory. The herbicide 2,4-D at 400 g ai ha−1provided excellent control of threelobe morningglory when applied at the four-leaf (100%) and six-leaf (97%) stages. However, at the eight-leaf stage, percent control was reduced to 67% and herbicide rate had to be increased twofold to achieve 95% control. The information gained from this study could contribute to developing components of integrated weed management strategies for threelobe morningglory. Soil inversion by tillage to bury weed seeds below their maximum depth of emergence and early application of an effective POST herbicide could serve as important tools for managing threelobe morningglory.

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Germination of Fresh Horse Purslane (Trianthema portulacastrum) Seeds in Response to Different Environmental Factors

Weed Science ◽

10.1614/ws-d-11-00002.1 ◽

2011 ◽

Vol 59 (4) ◽

pp. 495-499 ◽

Cited By ~ 18

Author(s):

Jihyun Lee ◽

Bhagirath S. Chauhan ◽

David E. Johnson

Keyword(s):

Seed Germination ◽

Environmental Factors ◽

Seedling Emergence ◽

Soil Surface ◽

The Philippines ◽

Integrated Weed Management ◽

Burial Depth ◽

Seed Burial ◽

Soil Burial ◽

Two Populations

Horse purslane, a C4 species, is a branched, prostrate, and annual weed of upland field crops throughout the tropics. Experiments were conducted to determine the influence of various environmental factors on seed germination and seedling emergence of two populations of horse purslane. Seeds were collected from rice fields of the International Rice Research Institute (the IR population) and from sorghum fields of the University of the Philippines (the UP population); the two sites were 5 km apart in Los Baños, Philippines. Germination response of both populations was greater at 30/20 C and35/25 C day/night temperatures than they were at 25/15 C alternating day/night temperatures. Germination of both populations was greater in the light/dark regime than in darkness. In dark, depending on the temperature, seed germination of the UP population ranged from 37 to 62%, whereas seed germination of the IR population was < 20%. Exposure to 5 min at 117 and 119 C for the IR and UP populations, respectively, reduced germination to 50% of maximum germination. Osmotic potential of −0.26 MPa inhibited germination to 50% of the maximum for the UP population, whereas the corresponding value for the IR population was −0.37 MPa. Seeds placed on or near the soil surface had maximum emergence, and emergence declined with increase in seed burial depth. Seedling emergence of the UP and IR populations was 74% and 13%, respectively, for seeds placed on the soil surface. For both populations, no seedlings emerged from a soil burial depth of 6 cm or more. Germination and emergence responses to light and seed burial depth differed between the two populations of horse purslane. Residues on the soil surface of up to 6 Mg ha−1 did not influence seedling emergence of either populations. Knowledge gained in this study could contribute to developing components of integrated weed management strategies for horse purslane.

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Seed Germination, Seedling Emergence, and Response to Herbicides of Wild Bushbean (Macroptilium lathyroides)

Weed Science ◽

10.1614/ws-d-14-00038.1 ◽

2014 ◽

Vol 62 (4) ◽

pp. 563-570 ◽

Cited By ~ 2

Author(s):

Bhagirath S. Chauhan ◽

Ma Jenina De Leon

Keyword(s):

Seed Germination ◽

Weed Management ◽

Seedling Emergence ◽

Soil Surface ◽

The Philippines ◽

Integrated Weed Management ◽

Burial Depth ◽

Early Application ◽

Tillage Operation ◽

Macroptilium Lathyroides

Experiments were conducted in laboratory and screenhouse to determine the effects of light, temperature, salt and water stress, seed burial depth, and amount of rice residue on seed germination and seedling emergence of wild bushbean and to evaluate the response of that weed to commonly available POST herbicides in the Philippines. Germination (81 to 85%) was not influenced by light; however, it was higher at 30/20 C (88%) than at 25/15 C (82%) and 35/25 C (80%) day/night temperatures. The sodium chloride and osmotic potential required for 50% inhibition of maximum germination were 149 mM and −0.28 MPa, respectively. Seedling emergence (81%) was similar for seeds placed on the soil surface and for seeds buried up to 4 cm deep. No seedlings emerged from a burial depth of 8 cm. Rice residue applied on the soil surface up to 8 t ha−1did not affect seedling emergence (72 to 80%) of wild bushbean. The herbicide bentazon provided 100% control of wild bushbean when applied at the three- to five-leaf stages. However, to achieve 100% control by 2,4-D and metsulfuron-methyl + chlorimuron-ethyl, herbicides had to be applied at the three-leaf stage. The information gained from this study can help in developing components of integrated weed management programs for wild bushbean. A deep-tillage operation to bury weed seeds below their maximum depth of emergence and early application of an effective POST herbicide can help in managing this weed in rice fields.

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Effect of Environmental Factors on the Germination and Emergence of Drunken Horse Grass (Achnatherum inebrians)

Weed Science ◽

10.1017/wsc.2020.81 ◽

2020 ◽

pp. 1-29

Author(s):

Yonghuan Yue ◽

Guili Jin ◽

Weihua Lu ◽

Ke Gong ◽

Wanqiang Han ◽

...

Keyword(s):

Seed Germination ◽

Environmental Factors ◽

Abiotic Factors ◽

Seedling Emergence ◽

Management Strategies ◽

Germination Percentage ◽

Western China ◽

Burial Depth ◽

Achnatherum Inebrians ◽

Water Ph

Abstract Drunken horse grass [Achnatherum inebrians (Hance) Keng] is a perennial poisonous weed in western China. A comprehensive understanding of the ecological response of A. inebrians germination to environmental factors would facilitate the formulation of better management strategies for this weed. Experiments were conducted under laboratory conditions to assess the effects of various abiotic factors, including temperature, light, water, pH and burial depth, on the seed germination and seedling emergence of A. inebrians. The seeds germinated at constant temperatures of 15, 20, 25, 30, 35°C and in alternating-temperature regimes of 15/5, 20/10, 25/15, 30/20, 35/25, 40/30°C, and the seed germination percentages under constant and alternating temperatures ranged from 51% to 94% and 15% to 93%, respectively. Maximum germination occurred at a constant temperature of 25°C, and germination was prevented at 45/35°C. Light did not appear to affect seed germination. The germination percentage of seeds was more than 75% in the pH range of 5 to 10, with the highest germination percentage at pH 6. The seeds germinated at osmotic potentials of 0 MPa to -1.0 MPa, but decreasing osmotic potential inhibited germination, with no germination at -1.2MPa. After 21 d of low osmotic stress, the seeds that did not germinate after rehydration had not lost their vitality. The seedling emergence percentage was highest (90%) when seeds were buried at 1 cm but declined with increasing burial depth and no emergence at 9 cm. Deep tillage may be effective in limiting the seed germination and emergence of this species. The results of this study provide useful information on the conditions necessary for A. inebrians germination and provide a theoretical basis for science-based prediction, prevention and control of this species.

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Germination Biology of Sesbania (Sesbania cannabina): An Emerging Weed in the Australian Cotton Agro-environment

Weed Science ◽

10.1017/wsc.2018.62 ◽

2018 ◽

Vol 67 (1) ◽

pp. 68-76 ◽

Cited By ~ 2

Author(s):

Nadeem Iqbal ◽

Sudheesh Manalil ◽

Bhagirath S. Chauhan ◽

Steve W. Adkins

Keyword(s):

Seed Germination ◽

Management Strategies ◽

Moisture Stress ◽

Integrated Weed Management ◽

Burial Depth ◽

Weed Species ◽

Physical Dormancy ◽

Sesbania Cannabina ◽

Wide Range ◽

The Impact

AbstractSesbania [Sesbania cannabina(Retz.) Pers.] is a problematic emerging weed species in Australian cotton-farming systems. However, globally, no information is available regarding its seed germination biology, and better understanding will help in devising superior management strategies to prevent further infestations. Laboratory and glasshouse studies were conducted to evaluate the impact of various environmental factors such as light, temperature, salt, osmotic and pH stress, and burial depth on germination and emergence of two Australian biotypes ofS. cannabina. Freshly harvested seeds of both biotypes possessed physical dormancy. A boiling-water scarification treatment (100±2 C) of 5-min duration was the optimum treatment to overcome this dormancy. Once dormancy was broken, the Dalby biotype exhibited a greater germination (93%) compared with the St George biotype (87%). The nondormant seeds of both biotypes showed a neutral photoblastic response to light and dark conditions, with germination marginally improved (6%) under illumination. Maximum germination of both biotypes occurred under an alternating temperature regime of 30/20 and 35/25 C and under constant temperatures of 32 or 35 C, with no germination at 8 or 11 C. Seed germination of both biotypes decreased linearly from 87% to 14% with an increase in moisture stress from 0.0 to −0.8 MPa, with no germination possible at −1.0 MPa. There was a gradual decline in germination for both biotypes when imbibed in a range of salt solutions of 25 to 250 mM, with a 50% reduction in germination occurring at 150 mM. Both biotypes germinated well under a wide range of pH values (4.0 to 10.0), with maximum germination (94%) at pH 9.0. The greatest emergence rate of the Dalby (87%) and St George (78%) biotypes was recorded at a burial depth of 1.0 cm, with no emergence at 16.0 cm. Deep tillage seems to be the best management strategy to stopS. cannabina’s emergence and further infestation of cotton (Gossypium hirsutumL.) fields. The findings of this study will be helpful to cotton agronomists in devising effective, sustainable, and efficient integrated weed management strategies for the control ofS. cannabinain cotton cropping lands.

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Effect of Environmental Factors on Germination and Emergence of Shortawn Foxtail (Alopecurus aequalis)

Weed Science ◽

10.1017/wsc.2017.42 ◽

2017 ◽

Vol 66 (1) ◽

pp. 47-56 ◽

Cited By ~ 12

Author(s):

Ning Zhao ◽

Qi Li ◽

Wenlei Guo ◽

Lele Zhang ◽

Lu’an Ge ◽

...

Keyword(s):

Seed Germination ◽

Osmotic Potential ◽

Control Strategies ◽

Abiotic Factors ◽

Germination Rate ◽

Seedling Emergence ◽

Soil Surface ◽

Burial Depth ◽

Effective Measure ◽

Wide Range

Shortawn foxtail is an invasive grass weed infesting winter wheat and canola production in China. A better understanding of the germination ecology of shortawn foxtail would help to develop better control strategies for this weed. Experiments were conducted under laboratory conditions to evaluate the effects of various abiotic factors, including temperature, light, pH, osmotic stress, salt concentration, and planting depth, on seed germination and seedling emergence of shortawn foxtail. The results showed that the seed germination rate was greater than 90% over a wide range of constant (5 to 25C) and alternating (15/5 to 35/25C) temperatures. Maximum germination occurred at 20C or 25/15C, and no germination occurred at 35C. Light did not appear to have any effect on seed germination. Shortawn foxtail germination was 27% to 99% over a pH range of 4 to 10, and higher germination was obtained at alkaline pH values ranging from 7 to 10. Seed germination was sensitive to osmotic potential and completely inhibited at an osmotic potential of −0.6 MPa, but it was tolerant to salinity: germination even occurred at 200 mM NaCl (5%). Seedling emergence was highest (98%) when seeds were placed on the soil surface but declined with the increasing burial depth. No seedlings emerged when seeds were buried 6-cm deep. Deep tillage could be an effective measure to limit seed germination from increased burial depth. The results of this study will lead to a better understanding of the requirements for shortawn foxtail germination and emergence and will provide information that could contribute to its control.

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Seed Germination Ecology of Itchgrass (Rottboellia cochinchinensis)

Weed Science ◽

10.1614/ws-d-10-00095.1 ◽

2011 ◽

Vol 59 (2) ◽

pp. 182-187 ◽

Cited By ~ 30

Author(s):

Grace E-K. Bolfrey-Arku ◽

Bhagirath S. Chauhan ◽

David E. Johnson

Keyword(s):

High Temperature ◽

Seed Germination ◽

Seedling Emergence ◽

Soil Surface ◽

The Philippines ◽

Integrated Weed Management ◽

Burial Depth ◽

Soil Burial ◽

Dark Regime ◽

Temperature Pretreatment

Itchgrass is a weed of many crops throughout the tropics and one of the most important grass weeds of rainfed rice. Experiments were conducted in the laboratory and screenhouse to determine the effects of light, alternating day/night temperatures, high temperature pretreatment, water stress, seed burial depth, and rice residue on seed germination and seedling emergence of itchgrass in the Philippines. Two populations were evaluated and the results were consistent for both populations. Germination in the light/dark regime was greater at alternating day/night temperatures of 25/15 C than at 35/25, 30/20, or 20/10 C. Light was not a requirement for germination, but a light/dark regime increased germination by 96%, across temperature and population. A 5-min high temperature pretreatment for 50% inhibition of maximum itchgrass germination ranged from 145 to 151 C with no germination when seeds were exposed to ≥ 180 C. The osmotic potential required for 50% inhibition of maximum germination was −0.6 MPa for itchgrass, although some seeds germinated at −0.8 MPa. Seedling emergence was greatest for seeds placed on the soil surface, and emergence declined with increasing soil burial depth; no seedlings emerged from seeds buried at 10 cm. The addition of rice residue to soil surface in pots at rates equivalent to 4 to 6 Mg ha−1reduced itchgrass seedling emergence. Since seedling emergence was greatest at shallow depths and germination was stimulated by light, itchgrass may become a problem in systems where soil is cultivated at shallow depths. Knowledge gained in this study could contribute to developing components of integrated weed management strategies for itchgrass.

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