Comparing the emergence of Echinochloa crus- galli populations in different locations. Part I: Variations in emergence timing and behaviour of two populations

Echinochloa crus-galli (L.) P. Beauv. is one of the most important weeds. It is distributed worldwide and has adapted to diverse habitats and climatic conditions. This study aimed to compare the emergence patterns of two populations of E. crus-galli from different environments at 11 locations across Europe and the Middle East. Seeds of the two populations were collected from maize in Italy and from spring barley in Norway and were then buried in soil in autumn 2015. In the spring of 2016, the soil was disturbed around the usual seedbed preparation date in each location and emergence was recorded. The soil was again disturbed a year later and emergence was recorded for a second season. Total emergence, the times of onset, end and to 50% emergence and the period between 25% and 75% of emergence were analysed by two-way ANOVA and principal components analysis. The Italian population showed a higher emergence than the Norwegian population in Southern locations, while the ranking was reversed in Northern locations. In almost all locations, a tendency to emerge earlier was recorded for the Norwegian population, but the periods from 25% to 75% emergence were similar for both populations. Total emergence, and the times of onset and end of emergence seemed to be mainly under genotypic (plus maternal) control, suggesting there were different temperature thresholds for seedling emergence in each population. Conversely, the duration of emergence seemed to be mainly under environmental control. This research confirms the high variability between populations and suggests the need to continue identifying key characteristics for the development of efficient models for seedling emergence in specific climates and/or latitudes.The authors thank all the technicians, students and institutions that have contributed to establishing and maintaining the field experiment. We also thank Dr. Frank Forcella and James Eklund from the USDA‐ARS in Morris (MN) for providing the dataloggers and facilitating the collection of soil temperature data in each location. Our thanks also to the Spanish Ministry of Economy and Competitiveness for funding to Royo‐Esnal through the AGL2017‐83325‐C4‐2‐R; Duzce Üniversitesi, Turkey, for funding to Uludag (Project No: 2015.11.02.375); and the Norwegian Research Funding for Agriculture and the Food Industry and project partners in Research Council of Norway Project no. 267700 for supporting Tørresen in the experiment. Uludag thanks his two graduate students Miss Buyukkurt and Zambak, and Murdoch thanks MSc student, Mr Guangxing Xie, who carried out the germination assays. Finally, the authors are also grateful to the European Weed Research Society for providing funds to enable the working group participants to meet and discuss the collaborative experiment

Comparing the emergence of Echinochloa crus-galli populations in different locations. Part II: similarities and threshold parameters

The variability in the emergence process of different populations was confirmed for two Echinochloa crus-galli populations, one from Italy (IT) and the second from Norway (NO). Seeds were sown in 12 localities over Europe and the Middle East, and the emergence patterns of IT and NO were compared with those of several local populations at each location. Seeds of each population were sown in pots buried to the ground level. The base temperature (Tb) for emergence was estimated by (1) analysing logistic models applied to the field emergence of IT and NO, and (2) a germination assay set in winter 2020 at constant temperatures (8, 11, 14, 17, 20, 26, 29°C) with newly collected seeds in 2019 from the same fields where IT and NO had previously been harvested in 2015. The logistic models developed for IT and NO in each location showed that the emergence pattern of IT was similar to that of the local populations in Poland, Italy, Spain, Turkey South and Iran, while NO fitted better to those in Sweden and Latvia. No germination was obtained for IT in a germination chamber, but the estimated Tb with the logistic model was 11.2°C. For NO, the estimated Tb was 8.8°C in the germination chamber and 8.1°C in the field. Results suggest that adaptation to local environmental conditions has led to inter-population differences in Tb and parameter estimates of thermal-time models to predict the emergence of E. crus-galli should only be used for populations with similar climatic and habitat conditions.The authors thank all the technicians, students and institutions that have contributed to establishing and maintaining the field experiment. We also thank Dr. Frank Forcella and James Eklund, from the USDA‐ARS in Morris (MN), for providing the dataloggers and facilitating the collection of soil temperature data in each location. Our thanks also to the Spanish Ministry of Economy and Competitiveness for funding to Royo‐Esnal through the AGL2017‐83325‐C4‐2‐R; Duzce Üniversitesi, Turkey, for funding to Uludag (Project No: 2015.11.02.375); and the Norwegian Research Funding for Agriculture and the Food Industry and project partners in Research Council of Norway Project no. 267700 for supporting Tørresen in the experiment. Uludag thank his two graduate students, Miss Buyukkurt and Zambak, and Murdoch thank MSc student, Mr Guangxing Xie, who carried out some of the germination assays. Royo‐Esnal thank Jordi Izquierdo for providing the seeds of L3 population for the experiment in Lleida. Finally, the authors are also grateful to the EWRS, for providing funds to enable the working group participants to meet and discuss the collaborative experiment

Seed dormancy and germination in Solanum nigrum and S. physalifolium as influenced by temperature conditions

Solanum nigrum L. (black nightshade) and Solanum physalifolium Rusby (hairy nightshade) are two important weeds in many crops. They reduce crop quantity by competition and crop quality by contaminating harvested products. The timing of different control measures is a key factor in integrated weed management, which must be related with emergence of the weeds. Since emergence timing of the species is controlled by seed dormancy and temperature conditions, the effect of temperature on dormancy and germination has to be well understood. Experiments were conducted to study seed dormancy, the temperature effect on dormancy, dormancy cycle, germination characteristics, and emergence of the species. In addition, a simulation model was developed to study the effect of temperature on the dynamics of dormancy release and induction under different temperature conditions. I found differences in primary dormancy among populations of S. nigrum collected on two dates and in different locations. Fresh seeds of S. nigrum were conditionally dormant and germinated at higher alternating temperatures and in light, while seeds of S. physalifolum were deeply dormant. Seed dormancy is reduced during autumn, winter and early spring in seeds buried in the soil. The rate of dormancy release and induction is low at lower temperatures and increases as the temperature rises. High temperatures cause short-lasting breakage of dormancy followed by induction. Short-lasting dormancy induction in spring is likely to delay emergence of the species. Seedling emergence of both species showed a bi- or three-modal pattern during an extended period in late spring and early summer. This enables the species to survive natural catastrophes or escape weed control operations. This information can be used to maximize the efficacy of weed management strategies by timing weed control tactics to coincide with seedling flushes. Dormancy is mainly induced during summer due to higher temperatures. This prevents seedlings from emerging too late and being killed by frost in autumn before reproduction

Seed Dormancy and Germination in Solanum nigrum and S. physalifolium as Influenced by Temperature Conditions

Solanum nigrum L. (black nightshade) and Solanum physalifolium Rusby (hairy nightshade) are two important weeds in many crops. They reduce crop quantity by competition and crop quality by contaminating harvested products. The timing of different control measures is a key factor in integrated weed management, which must be related with emergence of the weeds. Since emergence timing of the species is controlled by seed dormancy and temperature conditions, the effect of temperature on dormancy and germination has to be well understood. Experiments were conducted to study seed dormancy, the temperature effect on dormancy, dormancy cycle, germination characteristics, and emergence of the species. In addition, a simulation model was developed to study the effect of temperature on the dynamics of dormancy release and induction under different temperature conditions. I found differences in primary dormancy among populations of S. nigrum collected on two dates and in different locations. Fresh seeds of S. nigrum wer

Modelling seedling emergence of Amaranthus retroflexus affected by soil depth

Aim of study: To determine and quantify the effect of seed burial depths on the seedling emergence pattern of Amaranthus retroflexus in field conditions. Area of study: West of Iran (Ilam). Material and methods: The seedling emergence of A. retroflexus was studied in an outdoor pot experiment, burying the seeds at 0, 2, 4, 6 and 8 cm in the soil in Ilam (Iran) in two consecutive years, 2010 and 2011. Different models were tested to predict the cumulative seedling emergence, and the log logistic model was found to be the best for this A. retroflexus population. Newly estimated Tb values, slightly different each year, but lower than those of the references, were estimated and set at 2.6 ºC and 0 ºC in 2010 and 2011, respectively. Main results: The seedling emergence in the west of Iran take place over a period from early February to late May. The level of seed dormancy can be reduced during autumn and winter burial in the soil or after a dry storage. Seed dormancy reduction resulted in a lower base temperature for germination/emergence followed by increase of the seedling emergences. Moreover, light in the soil surface and higher fluctuation in temperature at shallower soil depths may stimulate the seed germination and seedling emergence of A. retroflexus. Research highlights: Total emerged seedlings and emergence pattern are affected by soil depth and the level of dormancy. The results obtained in this study can be used to optimize the timings of the weed management activities

The role of legume cover crops in the ecological intensification of winter wheat to manage weeds under different soil tillage regime

Ecological intensification by means of legume cover crops undersown in winter wheat has the potential to control weeds and reduce the herbicides adoption in cereal cultivation. They may also provide high biomass to be used for feeding livestock in case of cash crop failure due to the climate changes consequences. Field experiments were conducted to investigate the effect of legume cover crops undersown in wheat (Triticum aestivum L. cv. Baharan)to suppress weeds under different tillage systems at the research station of Ilam University (Iran) during 2018-2019 and 2019-2020. The treatments were three soil tillage systems (conventional tillage, minimum tillage and no-tillage); and four legume cover crop [Persian clover (Trifolium resupinatum L. var. Haftchin), vetch (Vicia villosacv. Maragheh), grass pea (Lathyrus sativusL.) and bitter vetch (Vicia ervilia (L.) Willd.)]. In addition, wheat monoculture with and without weeds, monoculture of each legume cover crop and a fallow plot were included. Legume cover crops were sown at 50% and wheat at 100% of the seed rate adopted by the farmers. In 2018-2019, weed aboveground biomass was reduced of 43.0, 86.5, 68.4 and 3.5% when Persian clover, vetch, bitter vetch and grass pea, respectively, were undersown in wheat under no tillage system. The reduction for the same treatments was of 54.0, 98.0, 85.0 and 84.9 %, respectively, under minimum tillage and 70.0, 95.8, 65.8 and 50.8%, respectively, under conventional tillage. In 2019-2020, the reduction in weed aboveground biomass under no-tillage system was significant only for vetch and bitter vetch (33.4 and 10.3%, respectively), while no reduction was observed in Parsian clover and grass pea. Under minimum tillage, the reduction was 28.2, 62.0, 58.5 and 55.5% in wheat undersown with Persian clover, vetch, bitter vetch and grass pea, respectively, and 43.9, 57.4, 44.3 and 46.3%, respectively, under conventional tillage. Vetch adopted for ecological intensification of wheat showed the greatest impact in reducing weed dry weight. As expected, the highest wheat grain yield (8422 kg ha-1) was obtained in wheat monoculture with weed control followed by wheat + bitter vetch intercropping (6267 kg ha-1) under minimum tillage. The forage quality in legume crops and soil factors were also improved under intercropping system. The land equality ratio was more than one in all intercropping patterns. We concluded that the intercropping of wheat with the legume cover crops present promising environmental-friendly approaches for managing weeds in a sustainable way while maintaining the crop production system

The role of legume cover crops in the ecological intensification of winter wheat to manage weeds under different soil tillage regime

Ecological intensification by means of legume cover crops undersown in winter wheat has the potential to control weeds and reduce the herbicides adoption in cereal cultivation. They may also provide high biomass to be used for feeding livestock in case of cash crop failure due to the climate changes consequences. Field experiments were conducted to investigate the effect of legume cover crops undersown in wheat (Triticum aestivum L. cv. Baharan)to suppress weeds under different tillage systems at the research station of Ilam University (Iran) during 2018-2019 and 2019-2020. The treatments were three soil tillage systems (conventional tillage, minimum tillage and no-tillage); and four legume cover crop [Persian clover (Trifolium resupinatum L. var. Haftchin), vetch (Vicia villosacv. Maragheh), grass pea (Lathyrus sativusL.) and bitter vetch (Vicia ervilia (L.) Willd.)]. In addition, wheat monoculture with and without weeds, monoculture of each legume cover crop and a fallow plot were included. Legume cover crops were sown at 50% and wheat at 100% of the seed rate adopted by the farmers. In 2018-2019, weed aboveground biomass was reduced of 43.0, 86.5, 68.4 and 3.5% when Persian clover, vetch, bitter vetch and grass pea, respectively, were undersown in wheat under no tillage system. The reduction for the same treatments was of 54.0, 98.0, 85.0 and 84.9 %, respectively, under minimum tillage and 70.0, 95.8, 65.8 and 50.8%, respectively, under conventional tillage. In 2019-2020, the reduction in weed aboveground biomass under no-tillage system was significant only for vetch and bitter vetch (33.4 and 10.3%, respectively), while no reduction was observed in Parsian clover and grass pea. Under minimum tillage, the reduction was 28.2, 62.0, 58.5 and 55.5% in wheat undersown with Persian clover, vetch, bitter vetch and grass pea, respectively, and 43.9, 57.4, 44.3 and 46.3%, respectively, under conventional tillage. Vetch adopted for ecological intensification of wheat showed the greatest impact in reducing weed dry weight. As expected, the highest wheat grain yield (8422 kg ha-1) was obtained in wheat monoculture with weed control followed by wheat + bitter vetch intercropping (6267 kg ha-1) under minimum tillage. The forage quality in legume crops and soil factors were also improved under intercropping system. The land equality ratio was more than one in all intercropping patterns. We concluded that the intercropping of wheat with the legume cover crops present promising environmental-friendly approaches for managing weeds in a sustainable way while maintaining the crop production system

Dormancy breaking and seed germination of the annual weeds Thlaspi arvense, Descurainia sophia and Malcolmia africana (Brassicaceae)

In Iran, Descurainia sophia, Malcolmia africana, and Thlaspi arvense are abundantly found as importunate weeds in winter cereal. Understanding the timing of seed germination under natural conditions is crucial for learning how to manage these annual weeds. Therefore, this study was conducted to evaluate the effect of soil burial, dry storage, cold stratification, KNO3, GA3, and scarification on the seed dormancy and germination of these three species. Species had significantly different responses to the treatment. In D. sophia, seeds buried at a depth of 10 cm for 60 days (55%), and seeds dry stored at 20°C for 180 days (45%) showed the highest level of germination. In M. africana, the germination percentage reached 95% when seeds buried at a depth of 1 cm were soaked in a GA3 concentration of 150 ppm. T. arvense had the lowest level of germination compared to the other species. The highest percentage of T. arvense germination was obtained in seeds treated with 150 ppm GA3. Potassium nitrate partly increased germinability in seeds of M. africana, which initially were less dormant than those of T. arvense and D. sophia

Dormancy breaking and seed germination of the annual weeds Thlaspi arvense, Descurainia sophia and Malcolmia africana (Brassicaceae)

In Iran, Descurainia sophia, Malcolmia africana, and Thlaspi arvense are abundantly found as importunate weeds in winter cereal. Understanding the timing of seed germination under natural conditions is crucial for learning how to manage these annual weeds. Therefore, this study was conducted to evaluate the effect of soil burial, dry storage, cold stratification, KNO3, GA3, and scarification on the seed dormancy and germination of these three species. Species had significantly different responses to the treatment. In D. sophia, seeds buried at a depth of 10 cm for 60 days (55%), and seeds dry stored at 20°C for 180 days (45%) showed the highest level of germination. In M. africana, the germination percentage reached 95% when seeds buried at a depth of 1 cm were soaked in a GA3 concentration of 150 ppm. T. arvense had the lowest level of germination compared to the other species. The highest percentage of T. arvense germination was obtained in seeds treated with 150 ppm GA3. Potassium nitrate partly increased germinability in seeds of M. africana, which initially were less dormant than those of T. arvense and D. sophia

Competitive interaction between maize, Xanthium strumarium and Datura stramonium affecting some canopy characteristics

Abstract Field experiments were conducted in 2006 and 2007 to evaluate Xanthium strumarium and Datura stramonium single and multispecies interferences with maize. At different weed densities (4, 8, 12 and 16 plants m -2 ), X. strumarium and D. stramonium were planted in five proportions of 0:100, 25:75, 50:50, 75:25 and 0:100. Monoculture of maize at 6 plant m -2 and pure stands of X. strumarium and D. stramonium at two densities of 4 and 16 plants m -2 were also included. The results showed that X. strumarium is the most competitive weed in mixed plant community of maize, X. strumarium and D. stramonium. Maize, mainly due to its greater height at high density of weeds and because of its greater height and LAI at low density of weeds, was more successful in competition for light than the two weed species. At mixture of X. strumarium and D. stramonium under competition with maize, X. strumarium due to its greater LAI and height, showed greater ability in light interception than the other weed species. Therefore, stronger competitive ability of a weed in competition for light may be attributed to its canopy characteristics e.g. greater height and LAI expansion. In the mixed plant community, these characteristics enable the species to soon occupy the space and capture the common resources i.e. light. To control these weeds in maize, appropriate control measures have to be taken in early growth stages