scholarly journals Modeling the emergence of North African knapweed (Centaurea diluta), an increasingly troublesome weed in Spain

Weed Science ◽  
2020 ◽  
Vol 68 (3) ◽  
pp. 268-277 ◽  
Author(s):  
Carlos Sousa-Ortega ◽  
Aritz Royo-Esnal ◽  
Antonio DiTommaso ◽  
Jordi Izquierdo ◽  
Iñigo Loureiro ◽  
...  
Keyword(s):  
Cropping Systems ◽  
Seedling Emergence ◽  
Management Strategies ◽  
First Year ◽  
Weibull Function ◽  
Limited Information ◽  
North African ◽  
High Predictability ◽  
Second Year ◽  
Base Water Potential

AbstractNorth African knapweed (Centaurea diluta Aiton) is an annual weed that is widespread in southern Spain and is of increasing concern in dryland cropping systems. Despite its expanding range in Spain, there is limited information on the emergence timing and pattern of this species, knowledge of which is critical for developing more timely and effective management strategies. Therefore, there is a need to develop simple and reliable models to predict the timing and emergence of this annual weed under dryland conditions. A multi-location field experiment was established across Spain in 2016 to 2017 to assess the emergence of C. diluta. At each of 11 locations, seeds were sown in the fall, and emergence was recorded. Overall emergence averaged 39% in the first year across all sites and 11% in the second year. In both years, the main emergence flush occurred at the beginning of the growing season. A three-parameter Weibull function best described seedling emergence of C. diluta. Emergence models were developed based on thermal time (TT) and hydrothermal time (HTT) and showed high predictability, as evidenced by root mean-square error prediction values of 10.8 and 10.7, respectively. Three cardinal points were established for TT and HHT at 0.5, 10, and 35 C for base, optimal, and ceiling temperatures, respectively, while base water potential was estimated at −0.5 MPa.

scholarly journals Seed germination ecology of Conyza stricta Willd. and implications for management

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244059
Author(s):  
Safdar Ali ◽  
Fakhar Din Khan ◽  
Rehmat Ullah ◽  
Rahmat Ullah Shah ◽  
Saud Alamri ◽  
...  
Keyword(s):  
Seed Germination ◽  
Osmotic Potential ◽  
Cropping Systems ◽  
Seedling Emergence ◽  
Management Strategies ◽  
Conservation Agriculture ◽  
Weed Species ◽  
Seed Burial ◽  
Germination Ecology ◽  
Tillage Practices

Numerous cropping systems of the world are experiencing the emergence of new weed species in response to conservation agriculture. Conyza stricta Willd. is being a newly emerging weed of barley-based cropping systems in response to conservational tillage practices. Seed germination ecology of four populations (irrigated, rainfed, abandoned and ruderal habitats) was studied in laboratory and greenhouse experiments. The presence/absence of seed dormancy was inferred first, which indicated seeds were non-dormant. Seed germination was then recorded under various photoperiods, constant and alternating day/night temperatures, and pH, salinity and osmotic potential levels. Seedling emergence was observed from various seed burial depths. Seeds of all populations proved photoblastic and required 12-hour light/dark period for germination. Seeds of all populations germinated under 5–30°C constant temperature; however, peak germination was recorded under 17.22–18.11°C. Nonetheless, the highest germination was noted under 20/15°C alternating day/night temperature. Ruderal and irrigated populations better tolerated salinity and germinated under 0–500 mM salinity. Similarly, rainfed population proved more tolerant to osmotic potential than other populations. Seeds of all populations required neutral pH for the highest germination, whereas decline was noted in germination under basic and alkaline pH. Seedling emergence was retarded for seeds buried >2 cm depth and no emergence was recorded from >4 cm depth. These results add valuable information towards our understanding of seed germination ecology of C. stricta. Seed germination ability of different populations under diverse environmental conditions suspects that the species can present severe challenges in future if not managed. Deep seed burial along with effective management of the emerging seedlings seems a pragmatic option to manage the species in cultivated fields. However, immediate management strategies are needed for rest of the habitats.

scholarly journals Effect of Continuous Intensive Cultivation on the Chemical and Microbiological Properties of Oxic Dystrandept Soils in the Western Highlands of Cameroon

2021 ◽  
Vol 9 (1) ◽  
pp. 17-26
Author(s):  
NTANGMO TSAFACK Honorine ◽  
Keyword(s):  
Soil Fertility ◽  
Crop Production ◽  
Cropping Systems ◽  
Management Strategies ◽  
Chemical Properties ◽  
Available Phosphorus ◽  
First Year ◽  
Soil Productivity ◽  
One Year ◽  
Microbiological Properties

Soil fertility indices are well documented as they are directly related to land use and productivity. However, the effect of continuous intensive cultivation on the evolution of soil fertility is still poorly documented. The aim of this study was thus to assess the effect of continuous intensive cultivation on the chemical and microbiological properties of Oxic Dystrandept soils in the Western Highlands of Cameroon. Composite soil samples were taken between 0-15 cm depths on farmlands that have been subjected to continuous intensive cultivation for one, five and ten years meanwhile samples from plots that have never been cultivated served as control. The main results revealed that the ammonium contents dropped abruptly (86%-wt) from the first year of cultivation. The organic carbon (OC) content decreased from 1.81 ± 0.14 %-dm (in control) to 1.69 ± 0.09 % after one year, 1.66 ± 0.10 % after 5 years and 1.58 ± 0.07 % after 10 years. Compared to the control, available phosphorus (P) showed a 13 %-wt drop after one year, 46 % after 5 years and 85 % after 10 years. Dehydrogenase activity showed a 42 % decrease after one year, 50 % after five years and 73 % after 10 years. The other parameters were not significantly different (P<0.05) amongst treatments. Decline of soil productivity was undoubtedly related to the decrease of OC, P, microbial activity and ammonium with continuous intensive cultivation. Thus, management strategies for improved crop production should include selection suitable cropping systems and chemical methods. Keywords: Continuous intensive cultivation, enzymatic activities, soil chemical properties, Oxic Dystrandept, Cameroon western highland

Seedbanks and seedling emergence of saffron thistle (Carthamus lanatus) in eastern Australian pastures

2002 ◽  
Vol 53 (12) ◽  
pp. 1327 ◽  
Author(s):  
B. S. Grace ◽  
A. W. Sheppard ◽  
R. D. B. Whalley ◽  
B. M. Sindel
Keyword(s):  
Weed Management ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
First Year ◽  
Seed Loss ◽  
Eastern Australia ◽  
Mesh Bags ◽  
Second Year ◽  
Number Of Seeds ◽  
Over Time

Weed management has often proved difficult because of persistent seedbanks that allow recruitment to occur for many years after the weed has otherwise been controlled. The number of seeds in seedbanks of Carthamus lanatus, a widespread and troublesome weed, has not been investigated. Little is known about longevity of its seedbanks in pastures of eastern Australia.The numbers of seeds in the soil and the rate of seed loss were investigated at 3 sites in eastern Australia. Seedbanks were found to be patchy, and they had mean densities between 815 and 2290 seeds/m2 after the main germination flush. These seedbanks decreased over time and between 11 and 15% of seeds remained in the soil after 2 years without further input. More seeds were lost in the first year than in the second year, and pasture cover did not affect the rate of seed loss.Seeds buried in mesh bags and exhumed regularly showed that dormancy was lost, induced, then lost again within the 2-year experiment. Maximum seed germinability coincided with peak germination times. The likelihood of a seed producing a seedling was reduced when seeds were sown at high density. C. lanatus seeds appear to be well adapted for persistence in eastern Australian pastures by maintaining a bank of seeds that generally germinate when conditions favour seedling survival.

Predicting Emergence of 23 Summer Annual Weed Species

Weed Science ◽  
2014 ◽  
Vol 62 (2) ◽  
pp. 267-279 ◽  
Author(s):  
Rodrigo Werle ◽  
Lowell D. Sandell ◽  
Douglas D. Buhler ◽  
Robert G. Hartzler ◽  
John L. Lindquist
Keyword(s):  
Soil Temperature ◽  
Field Experiments ◽  
Seedling Emergence ◽  
Information Criterion ◽  
Weibull Function ◽  
Base Temperature ◽  
Weed Species ◽  
Penalty Cost ◽  
Second Year ◽  
Best Fit

First- and second-year seedbank emergence of 23 summer annual weed species common to U.S. corn production systems was studied. Field experiments were conducted between 1996 and 1999 at the Iowa State University Johnson Farm in Story County, Iowa. In the fall of 1996 and again in 1997, 1,000 seeds for most species were planted in plastic crates. Seedling emergence was counted weekly for a 2-yr period following seed burial (starting in early spring). Soil temperature at 2 cm depth was estimated using soil temperature and moisture model software (STM2). The Weibull function was fit to cumulative emergence (%) on cumulative thermal time (TT), hydrothermal time (HTT), and day of year (DOY). To identify optimum base temperature (Tbase) and base matric potential (ψbase) for calculating TT or HTT, Tbaseand ψbasevalues ranging from 2 to 17 C and −33 to −1,500 kPa, respectively, were evaluated for each species. The search for the optimal model for each species was based on the Akaike's Information Criterion (AIC), whereas an extra penalty cost was added to HTT models. In general, fewer seedlings emerged during the first year of the first experimental run (approximately 18% across all species) than during the second experimental run (approximately 30%). However, second-year seedbank emergence was similar for both experimental runs (approximately 6%). Environmental effects may be the cause of differences in total seedling emergence among years. Based on the AIC criterion, for 17 species, the best fit of the model occurred using Tbaseranging from 2 to 15 C with four species also responding to ψbase= −750 kPa. For six species, a simple model using DOY resulted in the best fit. Adding penalty costs to AIC calculation allowed us to compare TT and HTT when both models behaved similarly. Using a constant Tbase, species were plotted and classified as early-, middle-, and late-emerging species, resulting in a practical tool for forecasting time of emergence. The results of this research provide robust information on the prediction of the time of summer annual weed emergence, which can be used to schedule weed and crop management.

scholarly journals Effects of genetically modified herbicide-tolerant cropping systems on weed seedbanks in two years of following crops

2005 ◽  
Vol 2 (1) ◽  
pp. 140-143 ◽  
Author(s):  
L.G Firbank ◽  
P Rothery ◽  
M.J May ◽  
S.J Clark ◽  
R.J Scott ◽  
...  
Keyword(s):  
Oilseed Rape ◽  
Cropping Systems ◽  
Genetically Modified ◽  
First Year ◽  
Medium Term ◽  
Farmland Biodiversity ◽  
Winter Oilseed Rape ◽  
Herbicide Tolerant ◽  
Farm Scale ◽  
Second Year

The Farm Scale Evaluations (FSEs) showed that genetically modified herbicide-tolerant (GMHT) cropping systems could influence farmland biodiversity because of their effects on weed biomass and seed production. Recently published results for winter oilseed rape showed that a switch to GMHT crops significantly affected weed seedbanks for at least 2 years after the crops were sown, potentially causing longer-term effects on other taxa. Here, we seek evidence for similar medium-term effects on weed seedbanks following spring-sown GMHT crops, using newly available data from the FSEs. Weed seedbanks following GMHT maize were significantly higher than following conventional varieties for both the first and second years, while by contrast, seedbanks following GMHT spring oilseed rape were significantly lower over this period. Seedbanks following GMHT beet were smaller than following conventional crops in the first year after the crops had been sown, but this difference was much reduced by the second year for reasons that are not clear. These new data provide important empirical evidence for longer-term effects of GMHT cropping on farmland biodiversity.

Changes with time in the germination of buried scentless chamomile (Matricaria perforata Mérat) seeds

1995 ◽  
Vol 75 (1) ◽  
pp. 277-281 ◽  
Author(s):  
G. G. Bowes ◽  
A. G. Thomas ◽  
L. P. Lefkovitch
Keyword(s):  
Seed Bank ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Growing Season ◽  
Early Spring ◽  
First Year ◽  
Temperature Regimes ◽  
Buried Seed ◽  
Second Year ◽  
Persistent Seed Bank

Change with time in the germination of scentless chamomile (Matricaria perforata Mérat) seeds was investigated. Seeds were placed in nylon net bags, buried 7 cm deep in soil, exhumed at monthly intervals for 2 yr and allowed to germinate in temperature regimes of 10/2 °C, 20/5 °C, 25/10 °C and 35/20 °C (16/8 h), simulating temperatures found during early spring or late fall, spring or fall, summer and mid-summer on the soil surface, respectively. Exhumed and refrigerator-stored (2 °C) check seeds exhibited no yearly dormancy/nondormancy germination cycle, but mortality of buried seed increased to 36%, after 10 mo in contrast with that of the check seeds which remained low for two years. Light was required for germination during the first year but was not required for a portion of the seed during the second year. The retention of viability in buried seed explains the persistent seed bank and seedling emergence throughout the growing season when moisture and temperature are nonlimiting. Key words: Seed burial, germination, Matricaria perforata Mérat

Germination ecology of giant chickweed (Myosoton aquaticum)

Weed Science ◽  
2020 ◽  
Vol 68 (6) ◽  
pp. 619-626
Author(s):  
Hengzhi Wang ◽  
Lipeng Wang ◽  
Shuang Bai ◽  
Wenlei Guo ◽  
Jinxin Wang ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Seedling Emergence ◽  
Management Strategies ◽  
Germination Percentage ◽  
Burial Depth ◽  
Limited Information ◽  
Weed Species ◽  
Wide Ph Range ◽  
Ph Range ◽  
Deep Plowing

AbstractGiant chickweed [Myosoton aquaticum (L.) Moench], a troublesome broadleaf weed species, is widespread in winter wheat (Triticum aestivum L.) fields in China. However, limited information is available on its germination and seedling emergence ecology. Thus, three M. aquaticum populations (JS, HN, and AH) from different geographic regions were studied under laboratory conditions to determine the effects of different environmental factors on germination or seedling emergence. The seeds germinated at a relatively wide constant temperature range of 5 to 25 C; however, the optimal temperature for germination varied among the populations. Compared with constant temperatures, fluctuating temperatures with the same mean significantly improved the final germination of all populations. Light was not required for germination. The seeds germinated under a wide pH range of 3 to 10, and the optimum pH was 6 to 7, with a final germination percentage of 81% to 95%. The seeds of all populations showed similar sensitivities to osmotic potential and similar high tolerances of saline conditions. The seedling emergence of all populations decreased with increasing burial depth, and no emergence was observed when the seeds were buried more than 3 cm, but the AH population showed higher sensitivity to burial depth than the others. The results generated from this study will contribute to the development of integrated M. aquaticum management strategies for winter wheat fields in China, and deep plowing and late sowing of autumn-sown wheat are suggested for managing M. aquaticum, as it showed lower germination at a low temperature and under relatively deep burial.

scholarly journals Use of the agricultural practice of pasture termination in reducing soil N2O emissions in high-rainfall cropping systems of south-eastern Australia

Soil Research ◽  
2016 ◽  
Vol 54 (5) ◽  
pp. 585 ◽  
Author(s):  
Oxana N. Belyaeva ◽  
Sally J. Officer ◽  
Roger D. Armstrong ◽  
Rob H. Harris ◽  
Ashley Wallace ◽  
...  
Keyword(s):  
Cropping Systems ◽  
Pore Space ◽  
N2o Emission ◽  
First Year ◽  
N2o Emissions ◽  
Agricultural Practice ◽  
Fallow Period ◽  
High Rainfall ◽  
Eastern Australia ◽  
Second Year

Conversion of long-term pasture to cropping was investigated for its effects on nitrous oxide (N2O) emissions in a 2-year field experiment in the high-rainfall zone of south-western Victoria. Early termination (pasture terminated 6 months before sowing) followed by winter (ETw) and spring (ETs) crops and late termination (pasture terminated 1 month before sowing) followed by a winter crop (LTw) were compared with continuous, mown pasture (MP). Emissions of N2O were measured with an automated gas sampling and analysing system. Emissions from MP were the lowest throughout the study, resulting in annual losses of 0.13kg N2O-N ha–1 in the first and the second years of the experiment. N2O-N loss was 0.6kgha–1 from treatments without fallow in both years (LTw in 2013 and ETs in 2014). In the first year, annual losses from previous fallow in ETw and ETs plots were 7.1 and 3.6kg N2O-N ha–1, respectively. Higher annual N2O losses from treatments with fallow periods continued in the second year of the study and were 2.0 and 1.3kg N2O-N ha–1 from ETw and LTw treatments, respectively. High emissions were associated with N mineralisation and the accumulation of NO3-N in the soil during the extensive fallow period after early pasture termination or wheat harvest. Soil water content was a key factor influencing the temporal fluctuations in N2O emissions. Low emissions occurred when water-filled pore space was <30%, whereas high emissions occurred when it was >65%, suggesting that denitrification was the major source of N2O emission. Crop grain yield was not affected by the duration of fallow (and therefore timing of pasture termination) in the first year, but was lower (P<0.05) in the treatment without fallow in the second year. Terminating pasture late rather than early, thus reducing the length of the fallow period, is a practical way of reducing N2O emissions from mixed pasture–cropping systems.

scholarly journals Hydro-priming Effects on Seed Germination and Field Performance of Faba Bean in Spring Sowing

Agriculture ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 201 ◽  
Author(s):  
A. Damalas ◽  
D. Koutroubas ◽  
Fotiadis
Keyword(s):  
Faba Bean ◽  
Seedling Emergence ◽  
Field Performance ◽  
Seed Priming ◽  
Field Trials ◽  
Germination Percentage ◽  
First Year ◽  
Vigor Index ◽  
Germination Speed ◽  
Second Year

Seed priming has been used to advance germination and stand in several crops, but relevant research on faba bean (Vicia faba L.) is scarce. Laboratory and field trials were carried out for two years to study the effect of hydro-priming on faba bean germination and field performance in spring sowing. In laboratory trials, the effects of hydro-priming for 0, 8, 16, 24, 36, and 48 h on final germination percentage, germination speed, Timson’s germination index, mean germination time, mean daily germination, synchronization index, and seedling vigor index were studied. All hydro-priming treatments improved germination parameters of faba bean seeds, except for final germination percentage and mean daily germination compared with non-primed seeds. Averaged over priming duration treatments, hydro-priming improved germination speed by 16.2%, germination synchrony by 20.7%, and seedling vigor index by 13.4%. All hydro-priming durations improved germination synchrony, while hydro-priming for 8, 16, and 24 h provided the highest values of germination speed (2.56, 2.58, and 2.37 seeds day−1, respectively). Hydro-priming for 8 and 16 h provided the lowest values of mean germination time (5.81 and 5.96 days, respectively). In field trials, hydro-priming periods of 0, 8, 16, and 24 h were compared. On average, seed hydro-priming did not affect significantly seedling emergence 14 days after sowing in the first year, but significantly improved seedling emergence by 34.4% in the second year. No significant effect of seed hydro-priming was noted in the number of plants at 28 and 35 days after sowing. Seed priming for 8 h resulted in higher fresh weight at anthesis by 22.3% and 8.6% in the first and the second year, respectively, than the non-primed control. Similarly, seed priming for 8 h provided higher seed yield by 12.0% in the first year and by 5.9% in the second year compared with non-primed control. Overall, seed hydro-priming accelerated faba bean germination and seedling emergence, but the magnitude of the response was associated with the environment and was more evident under limited soil moisture after sowing, whereas the beneficial effect of priming was masked when rainfall followed sowing. Similarly, the beneficial effect of priming on seed yield was more pronounced with limited soil moisture after anthesis.

An inevitable crisis? From first to second year in counsellor training

2020 ◽  
Vol 5 (1) ◽  
pp. 74-89
Author(s):  
Hugh Crago
Keyword(s):  
Right Hemisphere ◽  
Training Programme ◽  
First Year ◽  
Training Experience ◽  
Counsellor Training ◽  
Student Dropout ◽  
Second Year ◽  
Neurological Research ◽  
First Year Of Life ◽  
And Control

In a seminal 1973 paper, Robert Clark described the very different “cultures” of the first and second year students in a four year clinical psychology PhD programme. The author applies Clark’s template to his own experiences as trainee or trainer in five different counsellor education programmes, one in the US and four in Australia. Each of the programmes, to varying degrees, demonstrates key features of the pattern identified by Clark, where the first year is “therapeutic” and other-oriented, the second is “professional” and self-focused. The author concludes that all the surveyed programmes exhibited some level of “second year crisis”, in which a significant number of students felt abandoned, dissatisfied, or rebellious. The author extends and refines Clark’s developmental analogy (first year = childhood; second year = adolescence) to reflect recent neurological research, in particular, the shift from a right hemisphere-dominant first year of life, prioritising affiliative needs, to a left hemisphere-dominant second year, prioritising autonomy and control. This shift is paralleled later by a more gradual move from a protective, supportive childhood to necessary, but sometimes conflictual, individuation in adolescence. The first two years of a counsellor training programme broadly echo this process, a process exacerbated by the second year internship/placement, in which students must “leave home” and adjust to unfamiliar, potentially less nurturing, authority figures. Finally, the author suggests introducing more rigorous “academic holding” into the first year, and greater attention to “therapeutic holding” of dissident students in the second, hopefully decreasing student dropout, and achieving a better balanced training experience.

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