Bromoxynil degradation in a Mississippi silt loam soil

BACKGROUND: The objectives of these laboratory experiments were: (1) to assess bromoxynil sorption, mineralization, bound residue formation and extractable residue persistence in a Dundee silt loam collected from 0–2 cm and 2–10 cm depths under continuous conventional tillage and no‐tillage; (2) to assess the effects of autoclaving on bromoxynil mineralization and bound residue formation; (3) to determine the partitioning of non‐extractable residues; and (4) to ascertain the effects of bromoxynil concentration on extractable and bound residues and metabolite formation. RESULTS: Bromoxynil K_d values ranged from 0.7 to 1.4 L kg^?1 and were positively correlated with soil organic carbon. Cumulative mineralization (38.5% ± 1.5), bound residue formation (46.5% ± 0.5) and persistence of extractable residues (T_1/2 < 1 day) in non‐autoclaved soils were independent of tillage and depth. Autoclaving decreased mineralization and bound residue formation 257‐fold and 6.0‐fold respectively. Bromoxynil persistence in soil was rate independent (T_1/2 < 1 day), and the majority of non‐extractable residues (87%) were associated with the humic acid fraction of soil organic matter. CONCLUSIONS: Irrespective of tillage or depth, bromoxynil half‐life in native soil is less than 1 day owing to rapid incorporation of the herbicide into non‐extractable residues. Bound residue formation is governed principally by biochemical metabolite formation and primarily associated with soil humic acids that are moderately bioavailable for mineralization. These data indicate that the risk of off‐site transport of bromoxynil residues is low owing to rapid incorporation into non‐extractable residues. Published 2009 by John Wiley & Sons, Ltd     

The influence of reduced cultivations and direct drilling on the long-term decline of a population of Avena fatua L. in spring barley

Changes in the numbers of Avena fatua seed, incorporated into soil, were monitored in four successive spring barley crops which were harvested early for silage to prevent seed shedding. In the first year there were four times as many seedlings after tine cultivation compared with ploughing, but this was reversed in the second year as re-ploughing brought up dormant seeds and gave more seedlings than tine cultivation. Only 11–14% of the sown seeds produced seedlings during the 4 years. When the seeds were first buried to 25 cm by ploughing, and the barley was direct drilled without cultivation, only 0.4% emerged as seedlings. Few viable seeds remained in the soil after 4 years whether the soil was cultivated annually or not but seed numbers decreased more rapidly with tine cultivation than with ploughing. A few of the deeply buried seeds persisted where the land was direct drilled without cultivation.     

Minimal soil disturbance combined with spring cropping can halt soil seedbank accumulation of Alopecurus myosuroides

The basic mechanism of soil inversion tillage for control of annual weeds is based on the vertical translocation of weed seeds from the soil surface to deeper soil layers. Buried weed seeds either remain dormant in the soil seedbank and are exposed to biological and chemical decay mechanisms, or they germinate but the seedlings cannot reach the soil surface (fatal germination). However, depending on the seed biology of the respective target species, frequent inversion tillage can lead to a build-up of the soil seedbank. For soil seedbank depletion based on available knowledge of the biology of Alopecurus myosuroides seeds, soil inversion tillage is suggested to be reduced to every third or fourth year with reduced or even no-tillage (direct seeding) in between (rotational inversion tillage systems). Including spring crops in the crop rotation could further help dampening the population growth and hence the seed return into the seedbank. This study investigated the effect of rotational inversion tillage in combination with reduced tillage or direct seeding on the soil seedbank and population development of A. myosuroides. In a long-term field trial, set up in 2012, these tillage strategies were compared with continuous inversion tillage in a 3-year crop rotation with two consecutive years of winter wheat (Triticum aestivum) followed by spring barley (Hordeum vulgare). The results showed a significant decline in the soil seedbank following the spring crop, irrespective of the tillage system. The continuous inversion tillage system and inversion tillage before spring cropping with reduced tillage (shallow tillage with a disc harrow) before winter wheat both led to accumulation of seeds in the soil seedbank. In contrast, inversion tillage before spring cropping with direct seeding of winter wheat depleted the soil seedbank significantly after only one crop rotation. Although only covering one intensively studied field site, these findings highlight the need for diversified cropping systems and indicate potential avenues for reducing soil tillage while controlling economically important weeds.     

Derived cleaved amplified polymorphic sequence, a simple method to detect a key point mutation conferring acetyl CoA carboxylase inhibitor herbicide resistance in grass weeds

Substitution of isoleucine by leucine at the equivalent of residue 1781 of acetyl CoA carboxylase (ACCase) in Alopecurus myosuroides (I1781L) has been shown to be a key point mutation conferring resistance to most aryloxypropionate and cyclohexanedione herbicides in Lolium spp., A. myosuroides, Avena fatua and Setaria viridis. This substitution results from changing an adenine residue to either thymine or cytosine at position 5341 in the ACCase coding sequence of A. myosuroides and at the homologous position in the other species. The I1781L mutation can be detected by allele‐specific amplification assays. These are, however, very dependent on the conservation of the nucleotide sequences flanking the causative single nucleotide polymorphism. Moreover, such assays cannot distinguish between homozygous and heterozygous individuals in a single polymerase chain reaction reaction. Here we present an alternative derived Cleaved Amplified Polymorphic Sequence (dCAPS) method to define I1781L status in the ACCase enzyme of four grass weeds. This dCAPS approach is simple, economical, highly transferable between species and can readily distinguish homozygous Leu/Leu 1781 and heterozygous Ile/Leu 1781 resistant individuals, providing the basis for accurate measures of the frequency of the dominant Leu allele in a given population.     

The survival of Alopecurus myosuroides Huds. seeds in soil

The survival of Alopecurus myosuroides seeds was studied in soil under arable cropping and short term grass leys in which seed return was prevented. At two winter wheat sites, where weed seeds were sown, the mean annual seed decline was 73–83% over a 2- or 3-year period. The rate of decline was similar with all the cultivation systems studied: ploughing, tine cultivation and direct drilling. Seeds buried initially by ploughing, and then not disturbed by cultivation, were slightly more persistent. At five arable sites with natural populations of A. myosuroides, seed numbers declined to an average of 3% of the original amount present after 3 years, and to 1% after 4 years. Initial populations of over 50 000 seeds m^?2 were recorded. Plant populations were not always proportional to the total seed content of the soil, especially on ploughed land. Seed decline in two grass fields was similar to that under arable cropping. A. myosuroides plants were recorded in a wheat crop following a 2-year grass ley. Weed plants did not persist in the vegetative state in grass used for conservation and grazing. At all sites, appreciable quantities of seeds were still present in the soil after 2–4 years. Although a relatively small proportion of seeds survived, the actual number of seeds surviving was substantial. For this reason, it was concluded that any eradication policy is unlikely to be effective in a cropping system dominated by winter cereals.     

土层深度对三种麦田禾本科杂草出苗及生长的影响

为明确小麦田禾本科杂草在不同土层深度的出苗及生长情况,选取雀麦Bromus japonicas、节节麦Aegilops tauschii和野燕麦Avena fatua三种小麦田常见禾本科杂草,采用盆栽法系统研究不同土层深度对杂草出苗及生长的影响。结果表明,小麦田禾本科杂草雀麦、节节麦和野燕麦出苗和生长与不同土层深度密切相关,在浅土层中均有较好的出苗率,且后期生长也正常。从出苗时间来看,雀麦和野燕麦集中出苗时间在播种后5～11 d,节节麦略晚于这2种杂草;从最适出苗土层深度来看,雀麦最适出苗土层深度为0.5～3.5 cm,出苗率在76.0%～87.0%之间,节节麦的最适出苗深度为0.5～8.0 cm,出苗率在66.7%～79.3%之间,而野燕麦的最适土层深度为0.5～18.0 cm,出苗率达84.2%～94.4%;从出苗后生长影响来看,0～20 cm土层对野燕麦后期生长没有显著影响,土层深度大于10.0 cm对节节麦生长有显著抑制作用,大于6.0 cm即对雀麦有显著影响。研究表明通过深翻土地可以对雀麦和节节麦达到一定的控制作用,但对野燕麦控制效果相对略差。     

Control of Avena fatua and Fagopyrum tataricum with tank mixtures of linuron or linuron + MCPA and sequential applications of linuron, and post-emergence A. fatua herbicides

Linuron (0.21 and 0.28 kg/ha) and linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture with field rates of barban, difenzoquat and flamprop-methyl reduced the phytotoxicity of these herbicides to Avena fatua. When linuron was applied immediately following or 6 days after the A. fatua herbicides no reduction in phytotoxicity to A. fatua occurred, suggesting that the antagonism may be occurring as a result of physical or chemical incompatability when the herbicides are mixed together. The possibility of obtaining broad-spectrum weed control with one trip over the field by applying linuron and one of these wild oat herbicides separately but at the same time using a double-boom, double-tank system deserves evaluation. When linuron was applied in a tank mixture (0.21 and 0.28 kg/ha), immediately after, or 6 days after diclofop-methyl (0.70 kg/ha), there was no reduction of A. fatua control, and wheat tolerance to the tank mixture was good. This tank mixture offers potential for control under field conditions of A. fatua and some broad-leaved weeds in one spray operation. Linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture severely reduced A. fatua control with diclofop-methyl. No loss of phytotoxicity to Fagopyrum tataricum occurred when the A. fatua herbicides tested were tank mixed with linuron or linuron + MCPA. Lutte contre Avena fatua et Fagopyrum tataricum avec des mélanges extemporanés de linuron ou de linuron + MCPA et des applications successives de linuron et d'herbicides de postlevée actifs contre A. fatua     

A review of the effects of crop agronomy on the management of Alopecurus myosuroides

This study reviews 52 field experiments, mostly from the UK, studying the effects of cultivation techniques, sowing date, crop density and cultivar choice on Alopecurus myosuroides infestations in cereal crops. Where possible, a statistical meta‐analysis has been used to calculate average responses to the various cultural practices and to estimate their variability. In 25 experiments, mouldboard ploughing prior to sowing winter cereals reduced A. myosuroides populations by an average of 69%, compared with non‐inversion tillage. Delaying drilling from September to the end of October decreased weed plant densities by approximately 50%. Sowing wheat in spring achieved an 88% reduction in A. myosuroides plant densities compared with autumn sowing. Increasing winter wheat crop density above 100 plants m^?2 had no effect on weed plant numbers, but reduced the number of heads m^?2 by 15% for every additional increase in 100 crop plants, up to the highest density tested (350 wheat plants m^?2). Choosing more competitive cultivars could decrease A. myosuroides heads m^?2 by 22%. With all cultural practices, outcomes were highly variable and effects inconsistent. Farmers are more likely to adopt cultural measures and so reduce their reliance on herbicides, if there were better predictions of likely outcomes at the individual field level.     

Designing a sampling scheme to reveal correlations between weeds and soil properties at multiple spatial scales

Weeds tend to aggregate in patches within fields, and there is evidence that this is partly owing to variation in soil properties. Because the processes driving soil heterogeneity operate at various scales, the strength of the relations between soil properties and weed density would also be expected to be scale‐dependent. Quantifying these effects of scale on weed patch dynamics is essential to guide the design of discrete sampling protocols for mapping weed distribution. We developed a general method that uses novel within‐field nested sampling and residual maximum‐likelihood (reml ) estimation to explore scale‐dependent relations between weeds and soil properties. We validated the method using a case study of Alopecurus myosuroides in winter wheat. Using reml , we partitioned the variance and covariance into scale‐specific components and estimated the correlations between the weed counts and soil properties at each scale. We used variograms to quantify the spatial structure in the data and to map variables by kriging. Our methodology successfully captured the effect of scale on a number of edaphic drivers of weed patchiness. The overall Pearson correlations between A. myosuroides and soil organic matter and clay content were weak and masked the stronger correlations at >50 m. Knowing how the variance was partitioned across the spatial scales, we optimised the sampling design to focus sampling effort at those scales that contributed most to the total variance. The methods have the potential to guide patch spraying of weeds by identifying areas of the field that are vulnerable to weed establishment.     

The influence of crop rotation and soil tillage on seed population dynamics of A vena sterilis ssp. ludoviciana

The dynamics of seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman in plots maintained under different crop rotations and tillage systems was studied over a 5-year period. The seed reserves buried in the soil were practically depleted during this period by using any of the three cropping systems evaluated. No significant differences were found between using a continuous barley rotation with annual application of herbicides and using a barley:fallow rotation with herbicides applied only as needed. The decline in seed populations was not affected by the tiliage system used during the fallow period (ploughing or no tillage). The tillage practices used in the various treatments, combined with the variable seed output from each treatment, resulted in different vertical distribution of the seeds in the soil profile. Shallow cultivation resulted in an accumulation of seeds in the upper soil layers; in contrast, a large proportion of the seeds were buried and maintained below 15 cm in the ploughed treatments. Although the seed distribution patterns produced by the various tillage systems had an effect on seedling recruitment, the largest changes in this parameter were associated with the different cropping sequences. Four times more seedlings were recruited in years under barley cropping than in those under fallow.     

An aspartate to glycine change in the carboxyl transferase domain of acetyl CoA carboxylase and non‐target‐site mechanism(s) confer resistance to ACCase inhibitor herbicides in a Lolium multiflorum population

BACKGROUND: The increasing use of ACCase‐inhibiting herbicides has resulted in evolved resistance in key grass weeds infesting cereal cropping systems worldwide. Here, a thorough and systematic approach is proposed to elucidate the basis of resistance to three ACCase herbicides in a Lolium multiflorum Lam. (Italian rye grass) population from the United Kingdom (UK24). RESULTS: Resistance to sethoxydim and pinoxaden was always associated with a dominant D2078G (Alopecurus myosuroides Huds. equivalent) target‐site mutation in UK24. Conversely, whole‐plant herbicide assays on predetermined ACCase genotypes showed very high levels of resistance to diclofop‐methyl for all three wild DD2078 and mutant DG2078 and GG2078 ACCase genotypes from the mixed resistant population UK24. This indicates the presence of other diclofop‐methyl‐specific resistance mechanism(s) yet to be determined in this population. The D2078G mutation could be detected using an unambiguous DNA‐based dCAPS procedure that proved very transferable to A. myosuroides, Avena fatua L., Setaria viridis (L.) Beauv. and Phalaris minor Retz. CONCLUSION: This study provides further understanding of the molecular basis of resistance to ACCase inhibitor herbicides in a Lolium population and a widely applicable PCR‐based method for monitoring the D2078G target‐site resistance mutation in five major grass weed species. Copyright © 2010 Society of Chemical Industry     

Herbicide Effects on Sugarcane Growth, Pythium Root Rot, and Pythium arrhenomanes

ABSTRACT Six herbicides were evaluated for their effects on Pythium root rot and growth of sugarcane in greenhouse experiments and on in vitro mycelial growth rate of Pythium arrhenomanes. Pendimethalin and atrazine were most inhibitory to mycelial growth, but neither reduced root rot severity. Asulam, atrazine, and metribuzin were not phytotoxic to sugarcane and did not affect root rot symptom severity in clay loam or silt loam field soils. Atrazine and metribuzin increased shoot number, and atrazine increased total shoot weight for treated plants in silt loam soil. Glyphosate, pendimethalin, and terbacil were phytotoxic to sugarcane. These herbicides increased root rot severity, but the extent to which growth reductions resulted from increased disease severity or from direct herbicide injury was not clear. Adverse effects on plant growth and root rot severity were greater in clay loam than in silt loam soil. The results suggest that sugarcane injury from some herbicides is compounded by increased severity of root rot.     

Application of bispyribac‐sodium provides effective weed control in direct‐planted rice on a sandy loam soil

An increasing water crisis, as well as the unavailability and high cost of labor, in Pakistan has forced rice‐growers to plant rice directly into the field. However, severe weed infestation causes disastrous effects on the productivity of this rice system. In this study, three herbicides (pendimethalin, penoxsulam and bispyribac‐sodium) were evaluated for weed control in direct‐planted rice on a sandy loam soil. Weedy check and weed‐free plots were established for comparison. Weed infestation decreased the rice yield by 75.2%. However, the application of herbicides suppressed the weed infestation, with a simultaneous increase in the rice yield. The postemergence application of bispyribac‐sodium was the most effective herbicide in reducing the total weed density and dry weight over the weedy check, followed by penoxsulam and pendimethalin, respectively. Bispyribac‐sodium increased the number of productive tillers, 1000‐grain weight, number of grains per panicle and grain yield over the control, as well as improved the water productivity and economic returns of direct‐planted rice. The weeds' proliferation increased the number of unproductive tillers and decreased the plant height. In conclusion, the postemergence application of bispyribac‐sodium can be used effectively to control weeds, increase water productivity and improve the economic returns and yield of direct‐planted rice on a sandy loam soil in Pakistan.     

Effects of Aglaia odorata granules on the seedling growth of major maize weeds and the influence of soil type on the granule residue's efficacy

This study was undertaken to explore the potential of Aglaia odorata Lour. granules in various soil types (sand, sandy loam and clay) at 0.25, 0.5 and 1 t ai ha^?1 to inhibit two major maize weeds, Digitaria adscendens and Trianthema portulacastrum L., in an experimental greenhouse. The results indicated that the emergence and seedling growth of both weeds were inhibited but varied with the soil type: the inhibitory effect of the A. odorata granules was stronger when applied in sand, followed by sandy loam and clay. The weed species responded differently to the A. odorata granule application. Generally, the inhibitory effect was greater for D. adscendens than for T. portulacastrum. Additionally, the potential of the A. odorata granules for weed control in maize field plots was evaluated. The three major weeds that were found in the experimental field were D. adscendens, T. portulacastrum and Amaranthus gracilis. The highest A. odorata granule dose (1 t ai ha^?1) had a significant inhibitory effect on the emergence and growth of all of the weed species and their emergence was reduced by 96.7%, 47.2% and 56.2%, respectively, compared with the control treatment (unweeded). The dry weight of the weeds was reduced in a similar manner to their emergence. In contrast, the emergence of maize was not affected by any of the A. odorata granule applications. Rather, at an application rate of 1 t ai ha^?1, the maize yield increased significantly and the effect was similar to that observed with an atrazine herbicide application under field conditions.     

The effect on yield of mixtures and sequences of herbicides for the control of Alopecurus myosuroides Huds. and broad-leaved weeds in winter cereals

Mixed infestations of Alopecurus m yosuroides Huds. and broad-leaved weeds in winter cereals were controlled with a commercial formulation of ioxynil + bromoxynil + mecoprop. used in mixtures or as sequences with isoproturon or clofop-isobutyl. As well as controlling A. myosuroides the mixtures, applied in the autumn, gave good control of Veronica persica Poir., Galium aparine L. Lilhospermum arvense L. and Viola arvensis Murr. weeds which were resistant to isoproturon used alone. A. myosuroides had the major influence on crop yield in three experiments. High infestations of A. myosuroides reduced the broad-leaved weeds so that crop yields were only slightly improved when all the weeds were controlled compared with the control of A. myosuroides alone. In the remaining experiment. V. persica was very competitive with wheat; additional control of A. myosuroides improved yields considerably. Ioxynil + bromoxynil + mecoprop gave better final control of broad-leaved weeds when applied in the spring rather than the autumn but the sequence of a spring application following isoproturon or clofop-isobutyl in the autumn did not improve yields compared with the mixtures applied in the autumn. In all experiments, the highest yields were obtained from controlling both A. myosuroides and broad-leaved weeds in the autumn, provided that good control of A. myosuroides was obtained.     

Performance of pyrazosulfuron-ethyl in non-puddled transplanted rainy season rice and its residual effect on growth of the succeeding crop in rice-wheat cropping pattern

Abstract

A study was carried out in sandy clay loam textured soil of Mymensingh, Bangladesh to evaluate weed control efficiency of pre-emergence herbicide pyrazosulfuron-ethyl either alone or in sequential application with post-emergence herbicide in transplanted rainy season rice under non-puddled strip-tilled (NPST) field condition and also to examine the residual effect of those herbicides on germination and growth of the subsequently grown wheat crop. Five treatment combinations of pyrazosulfuron-ethyl were tested against one weedy check and one weed-free check. The study revealed that NPST rice field was mostly infested by grass and sedge weeds and herbicide treatments offered a wide range of control (above 50% to 95%) on all types of weeds. Application of pyrazosulfuron-ethyl followed by (fb) orthosulfamuron fb butachlor plus propanil provided the most effective and economic weed control over two years of the study. Moreover, micro-plot bioassay study claimed germination and growth of subsequently grown wheat were not adversely affected by herbicides that were applied in rice. Therefore, application of pyrazosulfuron-ethyl followed by post-emergence herbicide could be effective and economic to control weeds in NPST rice under rice-wheat system, but proper rate and time of application should strictly be followed.     

Soybean Brown Stem Rot, Phytophthora sojae, and Heterodera glycines Affected by Soil Texture and Tillage Relations

ABSTRACT Investigations were conducted to determine whether the effects of tillage practices on the prevalence of brown stem rot of soybean (caused by Phialophora gregata), Heterodera glycines, and Phytophthora sojae were confounded by soil texture in samples collected in the fall of 1995 and 1996. Soil and soybean stem samples, along with tillage information, were collected from 1,462 randomly selected fields in Illinois, Iowa, Minnesota, Missouri, and Ohio in collaboration with the National Agricultural Statistics Service. The incidence of brown stem rot was determined from 20 soybean stem pieces collected from each field in a zigzag pattern. The detection frequency of P. sojae (expressed as percent leaf disks colonized) and population densities of H. glycines were determined from soil cores also collected in a zigzag pattern. The soil samples were grouped into various textural classes, and the effect of soil texture and tillage relations on the activities of each pathogen were determined. Both tillage and soil texture affected the incidence of brown stem rot; however, there was no interaction between tillage and soil texture. Conservation tillage had a greater (P < 0.05) incidence of brown stem rot in clay loam and silty clay loam than did conventional tillage. The detection frequency of P. sojae was not affected by tillage, but a tillage x texture interaction (P = 0.013) indicated that the effect of tillage depended on soil texture. There was a greater (P < 0.05) detection frequency of P. sojae in conservation tillage than in conventional tillage in silt loam and loam soils. However, in sandy loam, the detection frequency of P. sojae was greater (P = 0.0099) in conventional tillage than in conservation tillage. Population densities of H. glycines were significantly affected by both tillage and soil texture, but overall, there was no tillage x texture interaction. There was an inverse relationship between population densities of H. glycines and percent clay (r = -0.81, P = 0.01) in no-till fields, but little or no change in nematode densities was observed with increasing clay content in tilled fields. Population densities of H. glycines were less (P < 0.05) in no-till fields than in tilled fields in silty clay loam and clay soils. There was no difference in H. glycines densities between the tillage categories in soils sandier than silty clay loam or clay. The findings emphasize the need for cautious interpretation of the effects of tillage practices on diseases and pathogens in the absence of information on soil texture.     

Effect of seed age and cultivation on seedling emergence and seed decline of Avena fatua L. in winter barley

Avena fatua was sown in a cultivation experiment in the autumn of 3 successive years. For each population seedling emergence and viable seeds in the soil were recorded for 4 years in crops of winter barley in which new seed production was prevented. About half of the seeds sown were recovered after 1 year. In subsequent years viable seeds in the soil declined more rapidly with tine cultivation than with ploughing. After 4 years up to 5% of the original seeds were still viable. One population exhibited greater seed dormancy than the other two populations, due it is thought to higher summer rainfall and the greater availability of moisture during seed maturation. Most seedlings emerged in the autumn and spring, between 12 and 18 months after sowing. A total of 950 seedlings emerged from 12 000 seeds sown; 21% of these seedlings came from new seeds (< 1 year old), 57% from seeds 1–2 years old, 14% from seeds 2–3 years old and 8% from seeds 3–4 years old. Autumn seedlings arose fairly evenly from all age groups while spring seedlings mostly came from the 1–2-year-old seeds. With tine cultivation total seedlings over 4 years represented 9–7% and with ploughing 6–2% of the original seeds sown. A. fatua was more persistent than in previous experiments in spring barley, which suggests that control measures would have to be applied for longer in a succession of winter cereals than spring-sown crops to reduce A. fatua to low populations.     

UNTERSUCHUNGEN ZUR KONKURRENZWIRKUNG VON KULTURPFLANZEN UND UNKRÄUTERN AUFEINANDER

Summary. A 2-year comparison of the development of Avena fatua L. and Sinapis arvensis L., with spring barley and of Alopecurus myosuroides Huds, with winter wheat gave the following results:

• 1 Avena fatua emerged shortly before barley in both years. Development until tillering was somewhat slower than that of barley, but after tillering the growth of both species was about the same. The first seeds of A. fatua matured shortly before harvest.
• 2 Growth of Sinapis arvensis was slower than that of barley during the- early stages, but after tillering was more rapid. Growth ceased more than 10 days before harvest.
• 3 In 1962–63 Alopecurus myosuroides germinated mainly in spring, but in 1963–64 most germination occurred in autumn, so that early development was different in the two years. After tillering the development WAS much faster than that of wheat and at the flowering stage of A. myosuroides, the shoots were taller than those of wheat. Seed was ripened some time before harvest.
• 4 A comparison of the development of A. myosuroides and Avena fatua alone and in competition with cereals revealed no marked influence of competition on the pattern of development, but competition did cause some reduction in shoot length and a marked reduction in weight of the two weed species.

Compétition entre plantes cultivées et mauvaises herbes. I. Développement absolu el développement retalif des céréales et de quelques espèces de mauvaises herbes     

Reducing tillage intensity affects the cumulative emergence dynamics of annual grass weeds in winter cereals

Annual grass weeds such as Apera spica‐venti and Vulpia myuros are promoted in non‐inversion tillage systems and winter cereal‐based crop rotations. Unsatisfactory weed control in these conditions is often associated with a poor understanding of the emergence pattern of these weed species. The aim of this study was to investigate, understand and model the cumulative emergence patterns of A. spica‐venti, V. myuros and Poa annua in winter cereals grown in three primary tillage regimes: (i) mouldboard ploughing, (ii) pre‐sowing tine cultivation to 8–10 cm soil depth and (iii) direct drilling. Direct drilling delayed the cumulative emergence of A. spica‐venti and V. myuros (counted together) in contrast with ploughing, while the emergence pattern of P. annua was unaffected by the type of tillage system. The total density of emerged weed seedlings varied between the tillage systems and years with a higher total emergence seen under direct drilling, followed by pre‐sowing tine cultivation and ploughing. The emergence patterns of all species were differently influenced by the tillage systems, suggesting that under direct drilling, in which these species occur simultaneously, management interventions should first and foremost consider that A. spica‐venti and V. myuros emerge over a longer period to avoid control failures.