EFFECT OF MINIMUM SOIL TEMPERATURE ON DIFFERENTIAL DISTRIBUTION OF CYPERUS ROTUNDUS AND C. ESCULENTUS IN THE UNITED STATES*

Summary. The response of tubers to low temperatures was investigated to gain insight into a physiological basis for the differential distribution of Cyperus esculentus L. (yellow nutsedge) and C. rotundus L. (purple nutsedge) in the United States. Only C. esculentus tubers survived the winter of 1968–69 in the field at Urbana, Illinois. Less than 10% of C. rotundus tubers survived at 2°C for 12 weeks, whereas more than 95% of C. esculentus tubers survived this treatment. Exposures to -2°C for 4 h or longer killed 50% of C. rotundus tubers, whereas - 6·5°C was required to kill 50% of C esculentus tubers. C. rotundus distribution is restricted to regions where the soil seldom freezes, whereas C. esculentus is distributed in regions where the soil temperatures often get below freezing. Survival of C. esculentus tubers in soil which frequently freezes may account for its wide distribution. Death of C. rotundus tubers in soils which freeze apparently is the reason why the species is restricted to the southeastern and southwestern regions of the U.S.A. L'Influence de la température du sol sur la répartition différentielle de Cyperus rotundus et de Cyperus esculentus aux Etats-Unis     

Cyperus rotundus control using a mechanical digger and solar radiation

Cyperus rotundus (purple nutsedge) is considered one of the most noxious weeds affecting agricultural areas worldwide. With its fast growth rate, it competes with annual crops for water, minerals, light and space. It excretes allelopathic materials that impede crop development. Controlling this weed is difficult and is done mostly by manual weeding, cultivation and herbicides, with limited effectiveness. A method was developed for the control of C. rotundus. A machine penetrates the soil and rearranges it, so that the tubers are lifted to the upper soil layer, where they are left exposed to the hot summer climate, dehydrate and die. The method was tested in seven field experiments on various soil types. Two months after the experimental plots were irrigated, 70–100% weed control was observed. The machine's speed (at 1.2 or 1.8 km h^?1) and the number of treatments (one, or two treatments a month apart) did not influence the level of weed control. The method has a very high potential to replace manual weeding and application of herbicides. Further work will test whether the treatment has a long‐term effect or should be repeated every season.     

Local spread of the invasive Cyperus esculentus (Cyperaceae) inferred using molecular genetic markers

Over the last 20 years Cyperus esculentus (yellow nutsedge) has become invasive in south‐west France. Because the genetic variation of invasive species can affect the success of management strategies, amplified fragment length polymorphism markers were used to assess the amount and distribution of genetic diversity in this clonally reproducing weed. Population samples of C. esculentus were collected mainly in south‐west France, with 21 samples of C. eragrostis also included in this study. A total of 113 polymorphic loci were identified (50% of the bands scored) in C. esculentus. A low level of genetic diversity (0.140) was detected, of which 95% were partitioned among sites. The regional patterns of variation could have been caused by rapid range expansion of clones propagated by harvesting machinery. Implications of the high clonality detected in C. esculentus are discussed in the context of the development of weed management strategies: because reproduction of the weed in Haute Lande occurs by tubers only, vegetable production should be reduced in infested areas.     

Growth and reproduction of Cyperus esculentus L. and Cyperus rotundus L.

The growth of both species (as characterized by their total dry weight, inflorescence dry weight, root and rhizome dry weight and number of shoots per pot) was similar, but they differed in the manner in which the dry weight was partitioned to reproductive structures. Each species partitioned less than 2% of its dry weight into floral formation. However, yellow nutsedge (Cyperus esculentus L.) partitioned only 28% of its dry weight to tubers, whereas purple nutsedge (C. rotundus L.) partitioned 50% of its dry weight to fewer and larger tubers. The allocation of dry weight to reproductive structures was related to changes in day-length. Yellow nutsedge tuber formation increased as day-length decreased from 14.5 to 12.5 h, while floral formation did not begin until the day-length dropped below 14 h. Purple nutsedge formed inflorescences earlier and production continued throughout the remainder of the study, but tuber formation was curvilinear and accelerated as the day-length decreased.     

Effect of anaerobic soil disinfestation amendment type and C:N ratio on Cyperus esculentus tuber sprouting,growth and reproduction

Anaerobic soil disinfestation (ASD) is a cultural technique primarily targeted for control of soilborne plant pathogens, but can also impact weed propagules. A repeated pot study was conducted to evaluate ASD treatment impact on sprouting and growth of introduced Cyperus esculentus (yellow nutsedge) tubers using dry molasses‐based and wheat bran‐based amendment mixtures at four carbon‐to‐nitrogen (C:N) ratios (from 10:1 to 40:1) and compared with a non‐amended control. The mean percentage of sprouted tubers recovered after ASD treatment was lower for wheat bran‐based (42%) than dry molasses‐based (65%) amendments, and tuber production was 1.6‐fold higher in dry molasses‐based than wheat bran‐based treatments. The highest percentage of sprouted tubers (79%) and the highest mean production of large tubers (threefold higher than wheat bran‐based and 1.7‐fold higher than molasses‐based amendments) were observed for the non‐amended control. Tuber sprouting was significantly lower from all ASD treatments (regardless of amendment C:N ratio) compared with the non‐amended control at a 15 cm burial depth. New tuber production was lowest at C:N ratios of 10:1 and 20:1 and more than twofold higher in the non‐amended control. Wheat bran‐based amendments reduced above‐ground C. esculentus biomass compared with the non‐amended control and ASD treatments with molasses‐based amendments, and reduced below‐ground biomass compared with molasses‐based amendments. Above‐ground biomass was highest at amendment C:N ratio of 10:1, and below‐ground biomass was highest at amendment C:N ratio of 40:1 and the non‐amended control. ASD treatment with wheat bran‐based amendments at lower C:N ratios reduced tuber sprouting and reproduction compared with the non‐amended control, but not at rates high enough to use as a primary weed management tactic.     

Continuous non‐destructive monitoring of Cyperus rotundus development using a minirhizotron

A new method for non‐destructive monitoring of the subsurface development of Cyperus rotundus (purple nutsedge) is described. A minirhizotron (MR) system was adopted for use to observe vegetative growth of the weed in a net‐house and under field conditions. In particular, the key stages of tuber production and sprouting were monitored and quantified. The MR system allowed non‐destructive repeated measurements of the key stages in C. rotundus subsurface development, serving as a both quantitative and qualitative tool in the study of C. rotundus. A comparison between the MR method and a destructive method revealed that the former reduces experimental variance, thus providing a more accurate prediction of the sprouting process. The techniques presented in the current study offer advanced methodologies for continuous monitoring of C. rotundus development under the soil surface. The novelty of this method lies in its simplicity and efficiency, allowing continuous observation of specific organs of this noxious weed and potentially of other geophytes.     

Control of purple nutsedge (Cyperus rotundus) in cotton with benfuresate

The herbicide benfuresate applied preplanting to cotton (Gossypium hirsutum L.) fields infested with purple nutsedge (Cyperus rotundus L.) inhibited nutsedge growth for several weeks and was found selective for cotton. The best nutsedge control was achieved when the herbicide was mechanically incorporated following a preplant broadcast or band application which was activated by a sprinkler irrigation. The rate of benfuresate needed for effective and selective nutsedge control in cotton ranged from 0.80 to 1.60 kg/ha, the higher rates necessary in soils with higher clay and organic matter contents.     

Reconstructing the invasion of Cyperus esculentus in Central Europe

Cyperus esculentus (yellow nutsedge) is a serious weed in agriculture worldwide and observational data suggest that it has recently started to spread rapidly in Central Europe. We studied its spatiotemporal invasion pattern, rate of spread and habitat affiliation in Austria, Germany and Switzerland, using retrospective distribution data from various sources and a method that accounts for sampling bias. In total, we found 265 records of C. esculentus since 1900. Multiple accidental introductions, coupled with subsequent regional radial expansion, describe the spatiotemporal range expansion of C. esculentus in the study area. Cumulative number of records and of the number of invaded grid cells showed a continuous increase, but spread has become more pronounced recently (>2005). Invasion hotspots were located in the warmest regions of the study area, as well as in regions with an oceanic climate. On average, the rate of spread within these invasion hotspots ranged between 3.1 and 5.7 km per year. Cyperus esculentus was primarily found on arable land, while other habitats have been rarely invaded. The integration of different data sources improved the cover of distribution data and was useful for reconstructing the incipient and recent invasion phase of C. esculentus. The data suggest that control may be best achieved by preventing long‐range dispersal and containing or eradicating incipient infestations of C. esculentus.     

Metabolic fate of methazole in purple and yellow nutsedge

The mechanisms for the tolerance of purple nutsedge (Cyperus rotundus L.) and susceptibility of yellow nutsedge (Cyperus esculentus L.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] were studied. Both species absorbed and translocated[¹⁴C]methazole and metabolites from nutrient solution; however, greater amounts of ¹⁴C per unit weight were detected in yellow than in purple nutsedge. Although intact plants and excised leaves of both species rapidly metabolized methazole to DCPMU [1-(3,4-dichlorophenyl)-3-methylurea], detoxification of DCPMU to DCPU [1-(3,4-dichlorophenyl) urea] occurred more slowly in yellow than in purple nutsedge. Compared to yellow nutsedge, a greater percentage of the radioactivity in purple nutsedge was recovered as polar products. Polar products were converted to the free forms of the parent herbicide and to phytotoxic DCPMU by proteolytic enzyme digestion. Based on the findings of this study, at least three mechanisms (differential absorption, metabolism, and formation of polar products) account for the differential tolerance of these two species to methazole.     

Differences in growth and herbicide sensitivity among Cyperus esculentus clones found in Belgian maize fields

Cyperus esculentus is an invasive troublesome neophyte in many arable crops in Belgium. Applied weed control varies from field to field. One of the possible reasons for this variability might be a differential vegetative and reproductive behaviour among Belgian C. esculentus clones. In this study, growth characteristics and herbicide sensitivity of C. esculentus clones collected in Belgian maize (Zea mays) fields were evaluated. In a morphology Experiment, 25 clones were screened for growth characteristics and ability to set viable seeds under outdoor conditions. Dose – response experiments were conducted in the glasshouse to evaluate the effectiveness of two foliar‐applied herbicides (bentazon and glyphosate) and two pre‐sowing soil‐incorporated herbicides (S‐metolachlor and dimethenamid‐P) for controlling 14 C. esculentus clones. Response variables were aboveground dry biomass, tuber number, tuber dry biomass and individual tuber dry weight. Clones exhibited large differences in shoot number (up to 3.1‐fold), tuber dry biomass (up to 4.7‐fold), tuber number (up to 3.4‐fold), individual tuber dry weight (up to 4.8‐fold), inflorescence number and capacity to set viable seeds. Large interclonal differences in herbicide sensitivity (up to 8.3‐ and 4.0‐fold for aboveground dry biomass and tuber dry biomass, respectively) were observed. Contrary to foliar‐applied herbicides, soil‐incorporated herbicides were very effective and provided season‐long C. esculentus control at doses below the recommended maximum field dose. However, low doses stimulated tuber formation. Future C. esculentus management strategies should take into account differential growth characteristics and herbicide sensitivity of C. esculentus clones.     

Effect of glyphosate on the sprouting of Cyperus rotundus L. tubers

Post-emergence applications of glyphosate [N-(phosphonomethyl)glycine] have been shown not to eradicate purple nutsedge (Cyperus rotundus L.) in the field. It was not known if this was due to failure to control emerged plants or if dormant tubers produced new plants after application. Studies with individual plants were conducted in screenhouse facilities to determine the effects of glyphosate rate, time for translocation, area of foliage treated, and shade on the sprouting ability of tubers attached to treated plants. Rates of 1.5–2.0 kg/ha glyphosate inhibited tuber sprouting; 72 h were required for complete translocation at 1.0 kg/ha whereas 36 h were sufficient at 2.0 kg/ha. Treating less than all of the foliage reduced foliar control and increased tuber sprouting. Shading treated plants reduced control of the foliage but did not affect glyphosate translocation to the tubers. These studies showed that glyphosate kills C. rotundus foliage and the tubers attached to treated plants. Therefore, regrowth after glyphosate application under field conditions is due to dormant tubers which sprout after treatment.     

Bud inhibition of Cyperus rotundus L. tubers by inhibitor β or abscisic acid and the reversal of these effects by N-6-benzyl adenine*

The acidic ether fraction of methanol extracts from Cyperus rotundus L. (purple nutsedge) tubers contained inhibitory substances described hereafter as inhibitor β. Inhibitor β inhibited sprouting of excised C. rotundus buds and also the elongation of wheat coleoptiles. The inhibition of bud sprouting by inhibitor β was reversed by the application of N-6-benzyl adenine (BA). Applications of abscisic acid (ABA) also inhibited sprouting of the excised buds and this was similarly reversed by BA applications. Chromatographic evidence suggested that inhibitor β mainly consisted of phenolic materials and possibly ABA as a minor component. The role of BA in enhancing sprouting of C rotundus tubers is discussed. Inhibition des bourgeons de bulbes de Cyperus rotundus L. par I'inhibiteur β ou l'acide abscissique et réversion de ces effects par la N-6-benzyl adénine La fraction éther acide d'extraits, par le méthanol. de bulbes de Cyperus rotundus L. contient des substances inhibitrices decrites ci-après comme I'inhibiteur β. Cet inhibiteur β a inhibé la germination de bulbes isolés de C. rotundus ainsi que l'élongation de coléoptiles de blé. L'inhibition de la germination des bourgeons par I'inhibiteur βété renversée par l'application de la N-6-benzyl adénine (B.A.). Des applications d'acide abscissique (ABA) ont également inhibé la germination de bourgeons isolés et cet effet a été lui aussi renversé par des applications de B.A. Les chromatogrammes suggèrent que l'inhibiteur β est principalement constitué par des composés phénoliques et peut-être par I'ABA comme composant mineur. Le rôle de la B.A. dans l'inhibition de la germination des bulbes de C. rotundus est discuté. Knospenhemmung der Knollen von Cyperus rotundus L. durch Hemmstoff β oder Abscisinsäure und die Umkehrung dieser Effekte durch N-6-Benzylmlenin Die saure Fraktion aus methanolischen Extrakten von Cyperus rotundus L.-Knollen enthielten Hemmstoffe, die im folgenden als Hemmstoff β bezeichnet werden. Hemmstoff β hemmte das Sprossen isolierter C. rotundus-Knospen und die Streckung von Weizenkoleoptilen. Die Hemmung der Knospensprossung durch Hemmstoff β wurde durch An-wendung von N-6-Benzyladenin (BA) aufgehoben. Abscisinsäure (ABA) hemmte auch das Sprossen isolierter Knospen; durch BA wurde es auf ähnliche Weise aufgehoben. Der chromatographische Befund deutet darauf hin. Daß Hemmstoff β sich hauptsächlich aus phenolischen Verbindungen zusammensetzt und möglicherweise in gering-em Unfang ABA enthält. Die Rolle von BA auf die Förderung der Keimung von C. rotundus-Knollen wird diskutiert.     

GROWTH,TUBER FORMATION AND SPREAD OF CYPERUS ROTUNDUS L. FROM SINGLE TUBERS*

Summary. Single tubers of Cyperus rotundus L. were planted at intervals over the year. Plant growth was slow and sprouting of tubers was inhibited at temperatures below 20°C, but tubers overwintered at temperatures above freezing point. In the warm season, plant growth and tuber formation rate closely followed air temperature and tubers were forming within 1 month from planting. No inflorescence appeared during the cool season. In autumn-planted C. rotundus grown in containers, the ratio of aerial to subterranean weight decreased from 1·1 in December to 0·2–0·4 in summer. The weight of tubers in mid-summer was about 10 times more than that present in December. Tubers formed at ail times of year and at various locations on plants sprouted readily in laboratory tests (76–100% sprouting). C. rotundus planted in March at wide spacings was grown in field conditions free of other plant competition for 20 months. Within 2 months the plants had spread to 90 cm. At the end of the first and the second summer of growth, the mean area of one plant was 7·6 m² and 56·7 m², respectively, and patches had expanded then by 2·8 m and 5·4 m, respectively, from the initial shoot. After 20 months of growth all tubers were present within the 0–40 cm soil depth, 60–70% of them in the 0–20 cm layer. About 30% of the tubers were within 1 m and 60% within 2 m of the plant centre. Under the patch centre there were about 1000 tubers per m² with 0·3 kg dry weight; in the upper 20 cm more than 3500 tubers weighing 0·9 kg were present per m³ of soil. Croissance, formation de tubercules et propagation de Cyperus rotundus L. issu de tubercules uniques     

Tillage and herbicide treatments with inter‐row cultivation influence weed densities and yield of three industrial crops

Field experiments were conducted in northern Greece in 2003 and 2004 to evaluate effects of tillage regimes (moldboard plowing, chisel plowing, and rotary tilling), cropping sequences (continuous cotton, cotton‐sugar beet rotation, and continuous tobacco) and herbicide treatments with inter‐row hand hoeing on weed population densities. Total weed densities were not affected by tillage treatment except that of barnyardgrass (Echinochloa crus‐galli), which increased only in moldboard plowing treated plots during 2003. Redroot pigweed (Amaranthus retroflexus) and black nightshade (Solanum nigrum) densities were reduced in continuous cotton, while purple nutsedge (Cyperus rotundus), E. crus‐galli, S. nigrum, and johnsongrass (Sorghum halepense) densities were reduced in tobacco. A. retroflexus and S. nigrum were effectively controlled by all herbicide treatments with inter‐row hand hoeing, whereas E. crus‐galli was effectively reduced by herbicides applied to cotton and tobacco. S. halepense density reduction was a result of herbicide applied to tobacco with inter‐row hand hoeing. Yield of all crops was higher under moldboard plowing and herbicide treatments. Pre‐sowing and pre‐emergence herbicide treatments in cotton and pre‐transplant in tobacco integrated with inter‐row cultivation resulted in efficient control of annual weed species and good crop yields. These observations are of practical relevance to crop selection by farmers in order to maintain weed populations at economically acceptable densities through the integration of various planting dates, sustainable herbicide use and inter‐row cultivation; tools of great importance in integrated weed management systems.     

Effect of naptalam on growth of yellow nutsedge and subsequent control with glyphosate*

Naptalam applied to yellow nutsedge (Cyperus esculentus L., var leptostachvus Boeck.) plants through nutrient culture, as a foliar spray or to the soil surface significantly stimulated the transformation of rhizomes into new shoots when the plants were grown under a 20-h photoperiod. Applications of naptalam to plants grown under short-day conditions inhibited tuber production. Applications of glyphosate to yellow nutsedge foliage at 0·3 and 0·6 kg ha resulted in 57 and 68% dormant tubers respectively, compared to 27% in untreated plants. These lower rates did not significantly increase the number of nonviable tubers. The application of 1·1 and 2·2 kg ha resulted in 47 and 52% dormant tubers, respectively and approximately 40% nonviable tubers. When production of new shoots of yellow nutsedge was induced by soil treatment with napialam and followed later with glyphosate significantly greater control of the nutsedge was observed than from either herbieide alone. Effets du naptalame sur la crossance du experus aune et efficaeite ulterieure du glyphosate. Le naptalame appliquè sur des plantes de cypérus jaune (Cyperus esculentus L. var leptostachyus Boeck) a vee des éléments nutritifs, en pulvérisation fobaire ou à la surface du sol a significativement stimulé la transformation des rhizomes en nouvelles pousses forsque les plantes ont été soumises à une photopériode de 20 h. Les applications de naptalame aux plantes pousant dans des conditions de jours courts ont inhibe la production des tubercules. Des applications de glyphosate sur le feuillage du cypérus jaune à 0.3 et 0.6 kg ha ont donné respectivement 57 et 68% de tubercules dormants contre 27% chez les plantes non traitées. Ces doses plus faibles n'ont pas augmente significativement le nombre de tubercules nonviables. L'application de 1.1 et 2.2 kg ha a donné respectivement 47 et 52% de tubercules dormants, et approxativement 40% de tubercules non viables. Lorsque la production de nouvelles pousses de cypérus jaune a été induite par un traitement du sol au naptalame. suivi ulterieurement d'une application de glyphosate. l'efficacite observée sur le cypérus a été significativement meilleure qu'avee l'un ou l'autre de ces herdicides employé soul. Der Einfluss von Naptalam auf das Wachstum von Cyperus esculentus L. und nachfolgender Bekämpfung mit Glyphaxate Wird Naptalam in die Nähelösungskultur oder auf das Blatt von Cyperus esculentus var leptostachyus Boeek, sowj?e auf die Bodenoberfläche appliziert so stimulieri es die Bildung von neuen Trieben aus Rhizomen, wenn die Pflazen einer Photoperiode von 20 Std. ausgesetzt werden. Unter Kurztagshedingungen hemmt Napralam die Bildung von Knollen Wurde Naptalam auf die Blätter mít 0.3 und 0.6 kg ha appliziert so stieg die Zahl der dormanten Knollen von 27% bei unbehandelt auf 57% und 68% bei behandelt. Diese niedrigen Aufwandmengen steigerten die Zahl der keimfähigen Knollen nicht significant. Die Applikation von 1.1 und 2.2 kg ha resultiere in 47 und 52% dormanten und 40% nicht keimfähigen Knotlen. Wenn die Bildung von Trieben durch eine Behandlung mit Naptalam über dem Boden induziert wurde und diese nachfolgend mit Bekämpfungserfolg als wenn jades Herbizid allein angewandt wurde.     

Effect of intervals between application and tillage on glyphosate control of Cyperus rotundus L.*

Research conducted in El Salvador, Central America, demonstrated that an interval of 3 days between application of glyphosate and tillage was sufficient to cause 90% reduction in purple nutsedge (Cyperus rotundus L.) plants, while delays of 11–23 days generally gave slightly less reduction. à second application to the same plots 35 days following tillage resulted in more than 90% reduction with all intervals. Approximately 3 months after the initial treatment, tuber numbers had been reduced to half the original population. Germination of the remaining tubers was reduced by more than 50%. Glyphosate applied during the dry season caused an average of 79% reduction in plant numbers compared with 88% in the rainy season. However, in the dry season, the remaining plants had no competition from other weeds and after 5 months there was only à 40% reduction in nutsedge population. During the rainy season, 1, 2 and 3 kg/ha were equally effective, but 1 kg/ha was not sufficient in the dry season.     

Tuber production by purple nutgrass (Cyperus rotundus L.) in darkness

Observations were made on the development of new tubers from sprouts of isolated tubers of Cyperus rotundus grown in the dark. The metabolic events occurred primarily in the sprout itself, though the physiological state of the parent tuber affected the phenomenon. A seasonal variation in the behaviour of the sprouts was observed; maximum tuber formation was found in autumn and winter and minimum in spring and summer. The initiation of new tubers was independent of the sprout length and seemed rather to be dependent on its age. The physiological slate that enabled the sprouts to form tubers alternated with periods in which this condition was lost. Production de tubercules par le cyperus (Cyperus rotundus L.) à l'obscurité Des observations ont été faites sur le développement de nouveaux tubercules à partir de pousses de tubercules isolés de Cyperus rotundus croissant à robscurité. Les transformations métaboliques apparurent dans la pousse elle-même, bien que le phénomène fut affecté par l'état du tubercule parental. Une variation saisonniére fut observée dans le comportement des pousses: la formation maximale des tubercules fut constatée en automne et en hiver, la formation minimale au printemps et en été. L'initiation d e nouveaux tubercules fut indéependante de la longueur de la pousse et sembla plutøt dépendre de son âge. L'état physiologique, qui permet aux pousses de former des tubercules, alterna avec des péeriodes an cours desquelles cette faculté fut perdue. Knollenbildung bei Cyperus rotundus L. in Dunkelheit Es wurde die Entwicklung neuer Knollen aus den Sprossen von isolierten Knollen von Cyperus rotundus beobachtet, die bei Dunkelheit gewachsen waren. Die Stoffwechselprozesse verliefen hauptsächlich im Spross selbst, sie wurden aber vom physiologischen Zustand der Mutterknolle beeinflusst. Das Verhalten der Sprosse war von der Jahreszeit abhängig: die meisten Knollen wurden im Herbst und Winter, die wenigsten im Frühjahr und Sommer gebildet. Die Bildung neuer Knollen war von der Sprosslänge unabhängig und schien eher VOM Alter der Sprosse, abhängig zu sein. Der physiologische Zustand der Sprosse der sie zur Knollenbildung befähigte wechselte mit Perioden ab in denen keine Knollenbildung auftrat.     

Cyperus esculentus L. — A new weed in Israel

Cyperus esculentus L., a cosmopolitan noxious weed, has been recorded for the first time in an agricultural irrigated field in Israel. Hand-weeding, herbicides and soil disinfestation methods were only partially effective in controlling the weed. The distribution map of the weed is unknown, and it is unclear how the weed has been introduced into Israel. We estimate thatC. esculentus has a high risk potential to spread further and cause damage to Israeli agriculture, and therefore its spread should be restricted. http://www.phytoparasitica.org posting May 18, 2005.     

Reduction of growth and reproduction of Cyperus esculentus by specific crops

To assess the potential contribution of growing highly competitive crops to control Cyperus esculentus in the Netherlands, the influence of silage maize, hemp, winter barley and silage winter rye on emergence, growth and reproduction of this weed was studied in two field experiments. Growth and reproduction of C. esculentus (determined both as tuber production per plant and density of the weed in the subseuent crop maize) was reduced by each crop, compared to plots in which no crop was grown. In hemp, hardly any tuber production was observed. By growing a green manure crop after harvest of the winter barley the tuber production of the weed was reduced to about 40% of that in winter barley followed by fallow. Decreasing the light regime in a greenhouse experiment in the same order as was observed in the crops winter barley, maize and hemp, caused a similar reduction of tuber production to that found in the field. Therefore, it is suggested that competition for light is the main factor explaining the observed crop effects on the population dynamics of the weed. It is concluded that growing competitive crops as hemp in rotation may effectively complement chemical control of C. esculentus.     

刈割对油莎豆碳氮积累以及产量和品质的影响

为明确刈割对油莎豆（Cyperus esculentus L.）地上部碳氮积累、生物量、地下部块茎产量和品质的影响,寻求适宜留茬高度,以新疆沙区油莎豆为研究对象,比较6个不同留茬高度（LC10、LC20、LC30、LC40、LC50和未刈割）下油莎豆地上部碳氮积累及产量和品质的差异。结果表明：刈割后第1天,LC50有利于叶片碳氮含量的积累,碳、氮含量分别达到 22.79%和1.65%;刈割后第5天至20天,LC10和LC20叶片碳氮含量急剧下降;刈割后第5天和第10天,LC40的全碳和全氮含量高于其他处理,分别为39.78%、38.39%和1.48%、2.12%。LC40地上部干草质量和干豆质量最大,分别为4 310.39 kg·hm^-2和8 208.90 kg·hm^-2,且LC40块茎淀粉、粗蛋白、粗脂肪含量以及含油量显著高于其他处理,增幅分别为38.6%、28.8%、6.0%、22.44%,此外,该留茬高度下油莎豆块茎中不饱和脂肪酸油酸含量高达74.10%,明显高于其他处理。LC10 块茎中总糖与粗灰分含量最高,分别达到44.4%和2.3%,且块茎中棕榈酸、硬脂酸、棕榈油酸、亚麻酸和亚油酸含量相对其他处理较高,分别为14.00%、2.99%、0.28%、0.42%、11.21%。综上所述,留茬高度40 cm为适宜刈割高度,利于提高新疆沙区油莎豆的产量和品质。