THE EFFECT OF COMPETITION FROM CEREAL CROPS ON THE GERMINATION AND GROWTH OF AVENA FATUA L. IN A NATURALLY-INFESTED FIELD     

JOAN M. THURSTON 《Weed Research》1962,2(3):192-207

Summary. The effect of winter wheat, winter rye, winter barley, spring barley, and fallow cultivated as for a winter cereal, on germination and growth of wild oats ( A. fatua ) was investigated on a naturally-infested field. Treatments were continued for 2 years on the same plots and in the third year all plots were cropped with spring barley. Wild oats were not allowed to shed seeds.
A. fatua was controlled by a dense crop of an autumn-sown cereal. The crop genus was unimportant provided it grew well on the site; its effectiveness depended on its density when the wild oats germinated in spring. Winter wheat and winter rye were equally effective. Even in a light crop of barley, wild oats grew much less vigorously than on the fallow plots. Beyond a certain crop density dependent on soil fertility, further increase in crop did not decrease the size of wild oats. The heaviest crop did not completely suppress the wild oats.
The crop affected the wild oats mainly by decreasing growth of the seedlings, but under winter wheat and winter rye some wild oat seeds may have remained dormant, germinating in the spring barley in the third year, perhaps because the crops decreased the soil moisture content. Nitrogenous fertilizer increased the weight of both crops and wild oats. Barley was more severely affected by soil acidity than wild oats and on acid areas of barley plots the wild oats were larger than where the pH was higher. In wheat and rye which were scarcely affected by soil acidity the size of the wild oat plants was unaffected by soil pH.
L'effet du competition des céréales sur la germination et le développement d' Avena fatua dans un champ naturellement infesté .  相似文献   

A STUDY OF THE COMPETITION BETWEEN BARLEY AND OATS AS INFLUENCED BY BARLEY SEEDRATE, NITROGEN LEVEL AND BARBAN TREATMENT     

R. K. PFEIFFER  H. M. HOLMES 《Weed Research》1961,1(1):5-18

Summary. The object of the work described in this paper was to obtain information on the relationship between the effects of crop competition and barban treatment on oats growing in another cereal. The work was carried out on barley cross-drilled with cultivated oats. Variation in crop competition was obtained by using different barley seed-rates and nitrogen levels. Increasing the seedrate of barley without applying barban resulted in a reduction of the initial oat population. This reduction applied to weight of individual shoots, number of shoots and panicles per unit area and number of spikelets per panicle. The application of barban at selective rates gave an independent reduction of oats of the order of 80%. This value proved almost constant at each seedrate of barley. Crop competition and barban accordingly seem to art independently and their effects appear to be simply additive. The barley fresh weights per unit area increased substantially when oat competition was reduced by barban treatment. The highest increase occurred on the plots with the lowest barley seedrate in spite of the fact that these plots still appeared infested with oats at harvest time. Nitrogen application stimulated the growth of barley and oats to a similar degree and did not in consequence lead to a selective suppression of oats.
Etude de l'influence de la densité du Semis, du taux de fertilisation azotée et du traitement au barbane, sur la concurrence entre une Orge et une Avoine  相似文献   

THE CONTROL OF WEEDS IN SPRING CEREALS WITH MCPA, MCPB AND 2,4-DB     

S. A. EVANS 《Weed Research》1961,1(3):203-210

Summary. Eighteen experiments were carried out over a period of 4 years jointly by the National Agricultural Advisory Service and the Agricultural Research Council Unit of Experimental Agronomy to compare the effects of spraying spring cereals with MCPA, MCPB, 2,4-DB and mixtures of MCPA and MCPB, at two different times. The first applications was made before the cereal crop had reached the five-leaf stage and when it was judged that most of the weeds had germinated. The second application was after the crop had reached the five-leaf stage, which is the time normally recommended in Britain for the application of MCPA to spring wheat or spring barley. The earlier applications produced better crop yields and gave a better control of weeds except where conditions for spraying were unsatisfactory or where a considerable number of weeds germinated subsequently. Mild deformity of the ears of the crop occurred in some experiments following early applications of MCPA, otherwise there were no marked differences in the effect on the crop of the different herbicides at the doses used; the dose of MCPA was less than that of the other herbicides. In view of these results and the lower cost of MCPA, it is concluded that MCPA applied early is the most efficient of the treatments tested except where the risk of malformed ears occurring is not acceptable.
Le désherbage dans les céréales de printemps avec le MCPA, le MCPB, et le 2,4-DB  相似文献   

Field experiments to investigate long-term effects of repeated applications of MCPA, tri-allate, simazine and linuron: II. Crop performance and residues 1969–78     

J. D. FRYER  P. D. SMITH  R. J. HANCE 《Weed Research》1980,20(2):103-110

In four field experiments begun in 1963, each of four herbicides was applied to plots planted wilh the same crop each year. The annual treatments were: MCPA at 17 kg/ha to barley (Hordeum sativa Jess) and wheat (Triticum aestivum L.) at growth stage 15. tri-allate at 17 kg/ha pre-emergcnce to barley and wheat, simazine at l7kg/ha pre-emergence to maize (Zea mays L.) and linuron in two applications of 084 kg/ha pre- and post-emergence to carrots (Daucus carota L.). MCPA did not affect growth or yield of either barley or wheat. In general tri-allate also did not aftect the crops although wheat yield was depressed in 1978, wheat 1000 grain weight was reduced in 1972 and barley germination percentage was increased in 1973. Simazine did not influence the height, yield or appearance of maize. Linuron normally produced no effect on carrot yield, density and size. However, in 2 years when the post-emergence application was late, density but not yield was lower than in control plots. There was no accumulation of residues of any of these compounds in the soil. Rates of loss were similar to those predicted on ihe basis of laboratory experiments. In a fifth experiment these herbicides were applied twice per year (3 times in the case of linuron) at double the rales above on each occasion to bare plots. These applications ceased in 1968 (1969 for MCPA) but residues were monitored until 1972 except in the case of MCPA. Disappearance rates were similar to those in the cropped plots and residues were largely confined to the top 10 cm. The plots treated with MCPA had developed an enhanced ability lo degrade il prior to 1968. This persisted for 5 years after the final application.  相似文献   

Yield losses in weed-free wheat and barley due to post-emergence herbicides     

B. R. ELLIOTT  J. M. LUMB  T. G. REEVES†  T. E. TELFORD‡ 《Weed Research》1975,15(2):107-111

The tolerance of weed-free wheat and barley to a range of herbicides (bromoxynil, methabenzthiazuron, MCPA, bromoxynil + MCPA. linuron, prometryne, diuron, 2,4-D ester and 2,4-D amine) when applied at the crop three-leaf stage, was examined over the 5-year period 1968–72. All chemicals lowered grain yields to some extent, but the variation between chemicals was greater for wheat than for barley. In both crops, methabenzthiazuron was the safest chemical causing only small (<2·0%,) yield losses at rates up to 2·25 kg a.i./ha. At this rate of application yield losses of up to 36% were recorded for the substituted urea derivatives. Both crops had a low tolerance to 2,4-D ester and amine. Yield losses from bromoxynil, bromoxynil + MCPA and MCPA were similar, varying from 4 to 8% al 0·5 kg a.i./ha to 9–24% at 2·25 kg a.i./ha. Pertes de rendement dans le blé et l'orge provoquées, en l'absence de mauvaises herbes, par des herbicides de postlevée Pendant une période de 5 années (1968–1972) les auteurs ont examiné la résistance du béet de l'orge. Traités, en l'absence de mauvaises herbes, au stade 3 feuilles, avec une série d'herbicidcs (bromoxynil, méthabenzthiazuron, MCPA, bromoxynil-i-MCPA, linuron, prométrync. ditiron, 2,4-D ester et 2,4-D a mine). Tous ces produits ont diminué les rendements en grains dans des proportions variées, mais la variation entre produits a été plus grande pour le blé que pour l'orge. Pour les deux céréales, le méthabenzlhiazuron a été le produit le moins toxique, provotjuant seulement de faibles penes de rendement inférieurcs à 2,0%, à des doses allant jusquà 2,25 kg/m.a/ha. A cette dose d'application, des pertes de rendement allant jusquà 36% ont élé enregistrées avec des urées substituées. Les deux éréles ont manifesté uoe faible resistance au 2,4-D estr et amine. Les pertes de rendement provoquées par le bromoxynil, le bromoxynil + MCPA, et le MCPA ont été analogues, variant de 4 à 8% pour 0,5 kg/m.a./ha, jusqu’à 9 à 24% pour 2,5 kg/m.a./ha. Ertragsverluste durch Nachaufiatifherbizide in unkrautfreiem Weizen und Gerste In unkrautfreien Weizen- und Gerstebestánden wurde in fünfjáhrigen Versuthcn (1968–72) die Toleranz der beiden Arten gegenüber folgenden Herbiziden untersucht: Bromoxynil, Methabenzthiazuron, MCPA, Bromoxynil + MCPA. Linuron, Prometryn, Diuron, 2,4-D-Eister und 2,4-D-Amin- salz. Die Behandlung erfolgte jeweils im 3-Blattstadium. Alle Verbindungen erniedrigten zu einem gewissen Grad den kornertrag. Beim Weizen waren aber die Unterschiede zwischen den verschiedenen Herbiziden grösser als bei der Gerste. Methabenzthiazuron war bei Aufwandmengen bis zu 2.25 kg A.S./ha in beiden Getreidearten das sicherste Herbizid und verursachte nur geringe Ertragsdepressionen (<2%). Bei dieser Aufwandmenge wurden bei den Harn-stoffherbiziden bis zu 36% Ertragsverlust festgestellt. Gegen 2,4-D-Ester und 2,4-D-Aminsalz waren Weizen und Gerste wenig tolerant. Die Ertragsverluste durch Bromoxynil, Bromoxynil + MCPA und MCPA waren etwa gleich und betrugen 4–8% bei 0.5 kg A.S./ha bis 9–24% bei 2,25 kg A.S./ha.  相似文献   

A COMPARISON OF THE GROWTH AND COMPETITION BEHAVIOUR OF SEEDLINGS AND PLANTS FROM RHIZOMES OF AGROPYRON REPENS (L.) BEAUV. AND AGROSTIS GIGANTEA ROTH     

E. D. WILLIAMS 《Weed Research》1973,13(4):422-429

Summary. Seedlings and plants derived from single-node rhizome fragments of Agropyron repens and Agrostis gigantea were grown in au unheated glasshouse, separately or together with wheat ( cv. Kolibri), in sandy loam soil in well-spaced pots, adequately watered and moderately fertilized. Samples of crop and weeds were taken for growth analysis in mid- May, late June and early August (when the wheat was ripe).
On average, wheat decreased the weight of weed shoots by 84% and of rhizomes by 77%, but the weeds decreased the weight of wheat shoots by only 7% and of grain by 13%. Without wheat, seedlings of both weed species had, by late June, grown as much as plants from rhizomes, but with wheat, the weed seedlings were throughout most of the experiment more susceptible to competition than were plants from rhizomes. There was no simple relationship between the final dry weights of the weeds and the amount they decreased wheat yield: although Agropyron seedlings in competition with wheat were much lighter than Agrostis from rhizomes, they decreased grain yield of wheat as much, suggesting that they competed more intensely for a limiting factor, possibly nitrogen.
It is concluded that the faster initial growth rate of wheat seedlings relative to the weeds from rhizomes and a larger initial seed reserve relative to the weed seedlings enabled the wheat to dominate the weeds.
Comparaison de la croissance et comportement compétitif de plantules et de plantes issues de rhizomes d'Agropyron repens ( L.) Beauv. et d' Agrostis gigantea Roth  相似文献   

Yield responses of spring cereals to reduced herbicide doses     

J. SALONEN 《Weed Research》1992,32(6):493-499

Reduction of the dose of MCPA/mecoprop and MCPA/fluroxypyr mixtures to half or one-third of the recommended rates still provided good weed control efficacy in spring wheat (Triticum aestivum L.) and particularly in spring barley (Hordeum vulgare L). The average yield of treated plots was 8% higher in wheat and 1% higher in barley compared with untreated plots. However, yield reductions were observed in 32% of wheat plots and in 43% of barley plots treated with herbicides. The yield responses were poorly correlated with the weed density of mixed weed flora at the time of spraying. No reliable threshold density for chemical weed control was found. Réponses au rendement de céréales de printemps, à des doses d'herbicides réduites La réduction de la dose de MCPA/mecoprop et MCPA/fluroxypyr a la moitié ou au tiers des taux recommandés a encore assure une bonne efficacité herbicide chez le blé de printemps (Triticum aestivum L.) et specialement chez l'orge de printemps (Hordeum vulgare L.). Le rendement moyen des parcelles traitées était de 8% plus élevé chez le blé et de 1%élevé chez l'orge que dans les parcelles non traitees. Cependant, des reductions de rendement ont été observées dans 32% des parcelles de blé et dans 43% des parcelles d'orge traitées aux herbicides. Les reponses du rendement étaient faiblement liées a la densité en adventices d'une flore mixte au moment du traitement. Aucune densité seuil-sérieuse pour le desherbage n'a été trouvée. Ertragsbildung von Sommergetreide bei reduziertem Aufwand von Herbiziden Eine Reduzierung des Aufwands von MCPA-Mecoprop- und MCPA-Fluroxypyr-Mischungen auf die Halfte oder ein Drittel des empfohlenen Aufwands ergab in Sommerweizen (Triticum aestivum L.) und besonders in Sommergerste (Hordeum vulgare L.) noch eine gute Unkrautbekampfung. Im Mittel war der Ertrag der behandelten Parzellen beim Weizen um 8% und bei der Gerste um 1% höher als in den unbehandelten, aber in 32% der Herbizidparzellen mit Weizen und in 43% der mit Gerste wurden Ertragsminderungen beobachtet. Die Ertragsbildung stand kaum in Beziehung zur Unkrautdichte zur Zeit der Behandlung. Es wurde keine verläßliche Schadensschwelle gefunden.  相似文献   

FIELD EXPERIMENTS TO INVESTIGATE LONG-TERM EFFECTS OF REPEATED APPLICATIONS OF MCPA, TRI-ALLATE, SIMAZINE AND LINURON: REPORT AFTER 6 YEARS     

J. D. FRYER  K. KIRKLAND 《Weed Research》1970,10(2):133-158

Summary. In five long-term field experiments begun in 1963, each of four herbicides was applied to plots either planted with the same crop each year or uncropped. The following treatments were applied annually: MCPA at 24 oz/ac to barley at the 5-leaf stage, triallate at 24 oz/ac to barley pre-emergence, simazine at 24 oz/ac to maize pre-emergence, linuron at 12–24 oz/ac to carrots preand post-emergence. The main assessments reported in this paper are crop yield and persistence of herbicide residues. In the fifth experiment, these herbicides were applied twice each year at about double the above these to plots kept as far as possible free from all vegetation. MCPA did not affect the yield of barley and disappeared from the soil within 2–3 weeks of each application. In the uncropped plots, the time for the applied dose (3 lb/ac) to reach the limit of detection was reduced from 3 weeks in 1964 (after three previous applications) to 4 days in 1968 (after ten previous applications). Tri-allate did not affect the yield of barley. Soil residues could be detected for 5–6 months following each dose of 24 oz/ac. When applied at 48 oz/ac twice yearly, a residue persisted but with no progressive build-up during the 6-year period. Agreement between bioassay and CLC methods of determining residues varied from good to a factor of 4, with CLC usually, but not always, providing a higher figure. No residues of pre-allate could be detected in the barley straw or grain. Simazine did not influence the yield of maize during 1963–67. In 1968 there was a significant reduction in yield of foliage and stems but not in grain yield. Simazine applied to maize disappeared from the soil rapidly during the first 6 weeks; after this period 20–25% of the applied dose could be recovered. The remaining residues declined slowly and 1–2 oz/ac could be detected 23–50 weeks after application. No residues were found below the 0–2 in. soil level. When 48 oz/ac was applied twice annually a residue persisted varying from 8 to 27 oz/ac/6 in. There was no accumulation from year to year and no evidence that repeated treatment influenced breakdown rate. Most of the simazine remained in the 0–2 in. soil level. In three out of four determinations there was good agreement between CLC and bioassay results. Linuron reduced the yield and % dry matter content of carrot roots in 1965 and 1966 probably because of exceptional short-term phytotoxicity, otherwise there was no effect. Half the applied dose of 8–16 oz/ac disappeared from the soil within 8 weeks and residues were undetectable after 6 months. The residues in the uncropped plots did not fall below 11 oz/ac. Most remained in the 0–2 in. layer of soil but some herbicide was found in the 2–4 and possibly 4–6 in. layers. Progressive build-up of residues did not occur and repeated treatment did not influence breakdown rate. No linuron could be detected in carrot roots in 1965; in 1966, following an abnormally late application, 05 ppm was found. Chemical analyses of soil samples taken at regular intervals during 1964–67 showed that no major changes had been caused by the herbicide treatments in the levels of available potassium, nitrate nitrogen, ammonium nitrogen, available phosphorus or in pH. Information is presented on the variation in the deposit on the soil surface of applied herbicides immediately after spraying, also on subsequent distribution in the soil. It is concluded that this work provides an encouraging contribution to the evidence that these four herbicides, when used at the recommended rates, are unlikely to have any injurious effect on the capacity of soil to produce healthy crops. Six armies d'expériences au champ pour étudier les effets & long terme d'applieations répétiés de MCPA, tri-allate, simazine et linuron Résumé. Dans cinq expériences de longue durée effectuées en plein champ depuis 1963, chacun des quatre herbicides fut appliqué sur des parcelles, soit replantées chaque année avec la mème culture, soit non cultivées. Les traitements suivants furent appliqués chaque année: du MCPA à 1,680 kg/ha sur de I'orge au stade 5 feuilles; du tri-allate à 1,680 kg/ha en pré -levée sur de I'orge; de Ia simazine à 1,680 kg/ha en pre-levee sur du mais; du linuron à 0,840 et 1,680 kg/ha sur des carottes en pre-levee et en post-levée. Les principaux résultats mentionnés dans cette publication concernent les rendements et la persistance des résidus herbicides. Dans la cinquiéme expéerience, les herbicides ont été appliqués deux fois chaque année, à des doses approximativement doubles de celles indiquées ci-dessus, sur des parcelles maintenues autant que possible sans végétation. Le MCPA n'affecta pas le rendement de l'orge et disparut du sol dans les 2 à 3 semaines qui suivirent chaque application. Dans les parcelles non cultivées, le temps pour que la dose appliquée (3,3 kg/ha) décroisse jusqu à la limite de detection fut réduit de 3 semaines en 1964 (aprés trois traitements) à 4 jours en 1968 (aprées dix traitements). Le tri-allate n'afFecta pas le rendement de l'orge. Les résidus dans le sol purent étre détectés durant les 5 à 6 mois qui suivirent chaque traitement à la dose de 1,680 kg/ha. Quand ce produit fut appliqué 2 fois par an à 3,360 kg/ha, un résidu persista, mais sans qu'il en resulte une accumulation progressive, durant les 6 années de l'expérience. Entre les essais biologiques et les méethodes chimiques de détermination des résidus, la concordance fut tantôt bonne, tantôt correspondant à un coefficient 4, les méthodes chimiques fournissant généralement, mais pas toujours, des ehiffres plus élevés. Aucun résidu de tri-allate ne put être décelé dans la parcelle ou les grains de l'orge. La simazine n'influenca pas la production du mais durant la péeriode de 1963 à 1967. En 1968. il y cut une réduction significative de la production de tiges et de feuilles, mais non de la production de grain. La simazine appliquée sur le mais disparut du sol rapidement durant les six premiéres semaines; aprés cette période 20 à 25% de la dose appliquee pouvaient être retrouvês. Les résidus restants diminuérent lentement et 70 à 140 g/ha purent être de'celes 23 à 50 semaines apres l'application. II ne fut pas trouvé de résidus au-dessous de la couche située entre 0 et 5 cm à partir de la surface du sol. Aprfes les traitements à 3,360 kg/ha, appliqués deux fois par an, un résidu persistant, variant de 0,560 kg/ha à 1,890 kg/ha sur une profondeur de 15 centimétres. 11 n'eut pas d'accumulation d'une année à l'autre et pas d'indice de modification du taux de degradation resultant de la repetition des traitements. La plus grande partie de la simazine resta localisee entre 0 et 5 cm au-dessous de la surface du sol. Dans trois essais sur quatre, il y cut une bonne concordance entre les dosages chimiques et les dosages biologiques. Le linuron réduisit le rendement et le pourcentage de matére séche des racines de carottes en 1965 et 1966, probablement en raison d'une exceptionnelle phytotoxicitéà court terme. Les autres années, il n'y eut pas d'effet. La moitié de la dose appliqué e (dc 0,560 kg/ha 1,12 kg/ha) disparut du sol durant les 8 premieres semaines et il ne fut plus possible de detecter des résidus apres 6 mois. Les résidus dans les parcelles non cultivées ne descendirent pas en-dessous de 0,770 kg/ha. La plus grande partie restait entre 0 et 5 cm au-dessous de la surface du sol, maia des traces d'herbicide furent retrouvees dans la couche 5 à 10 cm et peut-être dans la couche 10 à 20 cm. II n'y et pas d'augnientation progressive des résidus et la répétition des traitements ne modifia pas le taux de dégradation. II ne fut pas décelé de linuron dans les racines de carottes en 1965; en 1966; à la suite d'une application anormalement tardive, il en fut trouvé 0,5 ppm. Des analyses chimiques d'échantillons de sols préieves à intervalles réguliers entre 1964 et 1967 montrirént que les traitements herbicides n'avaient pas provoqué de changements importants dans les taux de potassium utilisable, d'azote nitrique ou ammoniacal, de phosphore utilisable; le pH ne fut pas non plus affecté. Des informations sont présentées, eoncernant la variation du depot en surface des herbicides appliqués, immédiatement aprés le traitement, et aussi sur la distribution qui en résulta dans le sol. En conclusion, ce travail apporte une contribution encourageante à la preuve que ces quatre herbicides, quand ils sont utilisés aux doses recommandées, n'ont trés probablement pas d'effet nuisible sur la capacié du sol à produire des récoltes saines. Feldversuche zur Untersuchung der langfristigen Auswirkung wiederholter Applikationen von MCPA, Triallat, Simazin und Linuron. Bericht nach sechs Versuchsjahren Zusammenfassung. In fünf 1963 angelegten langfristigen Feldversuehen wurden vier Herbizide jeweils auf Flächen mit permanenter Monokultur und auf Brachflächen ausgebracht. Foigende Behandlungen erfolgten jährlich: 1,68 kg/ha MCPA zu Gerste im 5-Blattstadium, Vorauflaufbehandlung mit 1,68 kg/ha Triallat 2u Gerste, Vorauf-laufbehandlung mit 1,68 kg/ha Simazin zu Mais, Vorund Nachaufiaufbehandlung mit 0–84 bis 1,68 kg/ha Linuron zu Mohren. Die in dieser Arbeit berichteten Aus-wertungen beziehen sich vorwiegend auf den Ertrag und die Persistenz der Herbizid- Rückstände. Im fünften Versuch wurden die Herbizide zweimal jährlich in ungefähr doppelter Aufwandmenge auf weitgehend vegetationslosen Fläehen angewandt. MCPA beeinflusste den Ertrag von Gerste nicht und verschwand aus dem Boden innerhalb von zwei bis drei Wochen nach jeder Behandlung. Auf den Brachflachen war die Zeit des Abbaus bis zur Nachweisgrenze der ausgebrachten Menge (3,36 kg/ha) von drei Wochen im Jahr 1964 (nach drei vorausgegangenen Applikationen) auf vier Tage im Jahr 1968 (nach zehn vorausgegangenen Applikationen) zurückgegangen. Triallat beeinflusste den Ertrag von Gerste nicht. Rückstände im Boden waren fünf bis sechs Monate lang nach jeder Applikation von 1,68 kg/ha festzustellen. Wurden 3,36 kg/ha zweimal jährlich ausgebracht, so war eine permanente Ruckstandsmenge, jedoch keine Akkumulation im Verlaufe der sechs Versuchsjahre festzustellen. Die Oberein-stimmung zwischen Biotest und GLG-Methode zur Riickstandsbestimmung variiertc von gut bis zu einem Faktor vier, wobei mit GLG gewohnlich, jedoch nicht iminer, ein höherer Wert ermittelt wurde. Keine Triallat-Ruckstande waren in Stroh und Korn von Gerste nachzuweisen. Simazin beeinflusste den Ertrag von Mais in der Versuchszeit von 1963 bis 1967 nicht. 1968 war eine signifikante Ertragsminderung bei Blatt und Stengel, nicht jedoch beim Korn, eingetreten. Simazin verschwand in den Maisparzellen innerhalb der ersten sechs Wochen rasch aus dem Boden; danach konnten noch 20 bis 25% der ursprunglich ausgebrachten Menge wiedergefunden werden. Die verbliebenen Rückstandsmengen verschwanden nur langsam und 0,07 bis 0,14 kg/ha konnten noch 23 bis 50 Wochen nach der Behandlung nachgewiesen werden. Keine Ruckstande waren unterhalb 5 cm Bodentiefe festzustellen. Wurden 3,36 kg/ha zweimal jährlich ausgebracht, so war eine permanente Ruckstandsmenge von 0,56 bis 1,89 kg/ha ca. 15 cm vorhanden. Es konnte jedoch keine Akkumulation und kein durch die wiederholte Behandlung bedingter beschleunigter Abbau beobachtet werden. Das Simazin blieb vorwiegend in den obersten 5 cm des Bodens. In drei von vier Analysen war die Üereinstimmung zwischen Biotest und GLG-Methode gut. Linuron beeinträchtigte 1965 und 1966 Ertrag und % Trockengewicht der Möhren-wurzeln vermutlich wegen einer aussergewohnlichen, kurzfristigen, phytotoxischcn Wirkung des Mittels. Sonst war keine Beeinflussung der Möhren zu beobachten. Die Hälfte der ausgebrachten Menge von 0,56 bis 1,12 kg/ha verschwand aus dem Boden innerhalb von acht Wochen und nach sechs Monaten waren keine Rückstande mehr festzustellen. Die Ruckstande auf Brachflachen fielen nicht unterhalb 0,77 kg/ha. Linuron verblieb weitgehend in den obersten 5 cm des Bodens, doch war eine gewisse Menge auch in 5 bis 10 cm und möglicherweise auch in 10 bis 15 cm Bodentiefe nachzuweisen. Akkumulation trat ebensowenig auf wie beschleunigter Abbau nach wieder-holter Anwendung. 1965 waren keine Linuron-Rückstände in Mohrenunrzeln nachzuweisen; 1966 wurde nach einer anomal spaten Applikation eine Ruckstandsmenge von 0,5 ppm gefunden. Die chemische Analyse von Bodenproben, die von 1964 bis 1967 in regelmassigen Abstanden gezogen wurden, ergab keine grosseren herbizidbedingten Veranderungen im pH sowie im Gehalt an veräugbarem Kalium, Nitratund Ammonium-Stickstoff sowie Phosphor. Es werden weiterhin Informationen gegeben über die Variation der Herbizidmengen auf der Bodenoberfläche unmittelbar nach der Behandlung und über die anschliessende Verteilung der Herbizide im Boden. Es wird gefolgert, dass diese Arbeit einen ermutigenden Beitrag zu der Tatsache darstellt, dass diese vier Herbizide in praxisüblichen Auiwandmengen kaum negative Auswirkungen auf die Bodenfruchtbarkeit haben.  相似文献   

Correspondence     

Abdurrahman Saghir 《国际虫害防治杂志》2013,59(1):106-107

Abstract

Twenty-seven different herbicides were tested at the AUB Agricultural Research and Education Center in the Beqa'a, Lebanon, to determine their effects on weeds in wheat, barley, maize, onion and sugar beet. Each herbicide was tested at three different rates as pre-emergence and post-emergence applications. Unweeded and hand-weeded check plots were included. Data on yield, quality and other agronomic characteristics of the crops tested were recorded.

Concentrations of 1,000 and 10,000 ppm of 2, 4–D caused a significant decrease in the height and grain yield of wheat and barley when sprayed at the 3-leaf stage. At the 5-leaf stage, injury to wheat and barley occurred only when sprayed at 10,000 ppm, whereas an increase in the grain yield was obtained at 1,000 ppm of 2, 4–D acid equivalent (1 kg a.i./ha).

Pre-emergence treatments of atrazine and simazine at 2.5 kg a.i./ha caused a significant increase in the forage and grain yields of maize as compared to unweeded check plots. Wheat, oats, vetch and sugar beet were injured when planted after triazine-treated maize, whereas onions and soyabeans were tolerant. Other promising herbicides tested on maize were C 3095 (N–3–trifluoromethylphenyl–N'–methyl–N'–methoxyurea) and BV– 201 (1–(3′, 4′–dichlorophenyl)–3–methylpyrrolidin–2–one) applied as a pre-emergence spray at 1 and 2 kg/ha respectively.

Pre-planting treatment of EPTC and pre-emergence treatment of pebulate at 2 kg/ha gave a slight increase in the yield of roots of sugar beet. BV–201 and BV–207 (1–(3–chloro–4–methylphenyl)–3–methylpyrrolidin–2–one) were phytotoxic to beet.

In onions, nitrofen, BV–201 and BV–207 at 1–2 kg/ha were promising as pre-emergence and post-emergence sprays. DNOC and dinoseb at 1.5 kg/ha and ioxynil at 0.5 kg/ha sprayed post-emergence increased the yield of onions significantly over the check. No significant effects of these herbicides were observed on the bulb index, moisture content and total soluble solids of onions.  相似文献   

TRIAZINE HERBICIDES ON MAIZE AND THEIR RESIDUAL EFFECTS ON FOLLOWING CROPS*     

A. R. SAGHIR  A. H. CHOUDHARY 《Weed Research》1967,7(4):272-280

Summary. Pre-emergence application of 2–5 kg/ha (a.i.) of atrazine or simazine was the most effective treatment for control of broad-leaved weeds in maize. Other triazines injured maize at all rates tested. Among the crops following maize treated with atrazine or simazine at 2–5 kg/ha, sugar beet was injured whereas wheat, oats, vetch, onions and soybeans were not. Post-emergence application of triazine herbicides was not effective and did not increase maize yields significantly over those of the unweeded plots. Wheat, oats, vetch and sugar beet were injured when following maize treated with post-emergence sprays; onions and soybeans showed no visible injury except from atrazine or simazine at 5 kg/ha or more, and from mixtures of atrazine+prometryne or atrazine+ametryne at 12–5 kg/ha. Les triazines herbicides sur le mais et leurs arrière-effets sur les cultures suivantes  相似文献   

Weed control in direct-seeded lowland rice under poor water control conditions     

I. OKEZIE AKOBUNDU 《Weed Research》1981,21(6):273-278

Several herbicides applied singly and in combination were evaluated for weed control and for their effects on crop yield in direct-seeded lowland rice under poor water management conditions characteristic of the conditions in which lowland rice is grown by most farmers in West Africa. Several herbicides including cyperquat at 3.0 kg/ha, a mixture of cyperquat and 2,4-D at 2.0 + 0.5 kg/ha, bentazon at 2.0 kg/ha and avirosan satisfactorily controlled sedges in the 3-year study. Crop yield was consistently high in plots where weeds were controlled with post-emergence application of MCPA + propanil at 1.0+1.7 kg/ha, propanil + thiobencarb 2.2+1.2 kg/ha, oxadiazon 1.5 kg/ha, bentazon 2.0, granular 2,4-D at 1.0 kg/ha, and a pre-emergence application of bifenox at 2.0 kg/ha. Crop yields in plots treated with these herbicides were generally better than with two hand-weedings.  相似文献   

Interaction between difenzoquat and other herbicides for wild oat and broadleaved weed control in barley     

P.A. O'SULLIVAN  W.H. VANDENBORN 《Weed Research》1978,18(5):257-263

The interaction between barban and difenzoquat was additive upon application at the two-or four-leaf stage of wild oat. Wild oat control with a mixture of barban and difenzoquat at 0.14 + 0.42kg/applied at the two-or four-leaf stage was as effective as the recommended field rate of barban alone (0.28 kg/ha) at the two-leaf or difenzoquat alone (0.84 kg/ha) at the four-leaf stage. Barley yield increases with the mixture were comparable to those obtained with the full rates of the herbicides used alone their correct leaf stages This mixture offers the farmer excellent wild oat control, an extended Leaf-stage latitude (two-to four-leaf), excellent barley yield increases and the possibility of reduced operating costs. The herbicidal activity of difenzoquat or a barban + difenzoquat mixture was reduced on addition of amine formulations but not ester formulations of herbicides for broadleaved weeds. MCPA ester and bromoxynil plus MCPA were the most compatible broadleaf herbicides when mixed with difenzoquat Difenzoquat or difenzoquat + barban significantly stimulated the activity of various herbicides on Tartary buckwheat. A mixture of burban + difenzoquat + bromoxynil-MCPA or MCPA ester provided effective wild oat and Tartary buckwheat control The latter mixtures enable a farmer to eliminate one spray operation. The interaction between difenzoquat and diclofop methyl [4-(2,4-dichlorophenoxy) phenoxy propionic acid methyl ester was additive. Wild oat control with the mixtures was good and barley yield was increased over that obtained with a recommended field rate of diclofop methyl. Interaction entre le difenzoquat et d'autres herbicides pour la lutte contre la folle acoine et les mauvaises herbes dicotylédones dans l'orge L'interaction entre le barbane et le difenzonzoquat a été additive en ce qui concerne l'application aux stades 2- et 4- feuilles de la folle-avoine. L'efficacité contre la folle avoine avec un mèlange de barbane et de difenzoquat à difenzoquat à 0.14 + 0.42 kg/ha appliqué aux stades 2 ou 4 feuilles a été aussi bonne que la dose recommandée au champ de barbane seul (0.28 kg/ha) au stade 2 feuilles ou que le difenzoquat seul (0.84 kg ha) au stade 4 feuitles. Les augmentations de rendement de l'orge avec le mélange ont été comparables employès seuls au stade correct de développement foltaire. Ce folle-avoine. une latitude de stades plus grande (2 á 4 feuilles). de substantielles augmentations de rendement pour l'orge et la possibilité de réduire le prix de revient de l'opération. L'activité herbicide du difenzoquai ou d'un mèlange barbane + difenzoquat a été réduite par l'addition de formulat ions amine mais pas avec les formulations ester des herbicides pour les mauvaises herbes dicotylédones L'ester de MCPA et le bromoxynile plus MCPA ont été les plus compatibles parmi les herbicides anti-dicotylédones lorsqu'ils ont été mélangés avec le difenzoquat. Le difenzoquat ou le mélange difenzoquat + barbane ont significativement stimulé l'activité de divers herbicides vis-à-vis du Fagopyrum tartaricum. Un mèlange de barbane + difenzoquat + bromoxynil-MCPA ou MCPA ester s'est montré efficace contre la folle-avoine et F tartaricum Ces derniers mélanges permettent au cultivateur de faire l'èconomie d'un traitement. L'interaction entre le difenzoquat et le diclofop mèthyle (ester méthylique de l'acide 4(2,4 dichtorophénoxy)phénoxy propionique) a été additive. L'efficacite contre la folle-avorne avec les mèlanges a été bonne et le rendement de l'orge a été meilleur que celui obtenu avec la dose recommandée de diclofop méthyle. Wechselwirkungen zwischen Difenzoquat und anderen Herbiziden zur Bekämpfung von Flughafer und dikotylen Unkräutern in Gerste Wenn Barban und difenzoquat im 2-oder 4-Blattstadium des Flughafers appliziert wurden, konnte etne additive Wirkung zwischen den beiden Herbiziden beobachtet werden. Die Flug-haferbekampfung war mit einer Mischung von Barban und Difenzoquat bei Aufwandmengen von 0.14 + 0.42 kg/ha und Anwendung im 2- Oder 4-Blattstadium genauso gut wie bei alleiniger Anwendung von Barban mit der empfohlenen Aufwandmenge von 0.28 kg/ha im 2-Blattstadium. oder von Difenzoquat mit O.84 kg/ha im 4-Blattadium. Die Mehrerträge an Gerste die mit der Mischung erzielt wurden. entsprachen den Mehrerträgen bei alleibuger Anwendung der Herbizide im empfohlenen Entwicklungsstadium Diese Mischung beitet dem Landwirt eine ausgezeichnete Bekämpfung des Flughafers bei erweitertem Anwndungsbereich (2- bis 4-Blattstadium). deutlich Mehrerträge bei Gerste und die Möglichkeit geringerer Anwendungskosten. Die Wirkung von Difenzoquat oder der Barban + Difenzoquat-Mischung war schlechter. wenn Amin-formulierungen von Herbiziden zur Bekämpfung dikotlyer Unkräuter zugesetzt wurden, jedoch nicht bei Zusatz von Ester-formulierungen. MCPA-Ester und Bromoxynil plus MCPA waren die geeignetsten Mischungspartner für Difenzoquat gegen dikotyle Arten. Difenzoquat oder Difenzoquat + Barban steigerten signifikant die Wirkung verschiedener Herbizide gegenüber Fagoyprum tataricum. Die Mischung von Barban +Difenzoquat + Bromoxynil-MCPA oder MCPA-Ester ergab eine gute Bekàmpfung des Flughafers und von F. tataricum. Mit diesen Mischungen kann eine Spritzung emgespart werden Für Difenzoquat und Diclofop-methyl [2-[4-(2′,4′-Dichlorphenoxy)-phenoxy]-propionsäuremethylester wurde eine additive Wirkung festgestellt. Die Flughaferbekämpfung mit diesen Mischungen war gut und der Gersteertrag war höher als bei Anwendung der empfohlenen Aufwandmenge von Diclofop-methyl.  相似文献   

Influence of intra-row cruciferous surrogate weed growth on crop yield in organic spring cereals     

Bo Melander  Margaret R. McCollough 《Weed Research》2020,60(6):464-474

In Northern Europe, inter-row hoeing has become a popular tactic for controlling weeds in organic cereals. Hoeing is highly effective and can be implemented from crop emergence until stem elongation to maintain a nearly weed-free inter-row zone. However, hoeing has a lesser effect on weeds growing in the intra-row zone, where crop–weed proximity results in heightened competition. In the hoed cereal system, it is investigated whether tall-growing, competitive, cruciferous weeds in the intra-row zone affect crop biomass, yield and thousand kernel weight (TKW). An additive experimental design is employed to enable the fitting of rectangular hyperbolas, describing and quantifying the effects of increasing intra-row surrogate weed density on crop growth parameters. Regressions were studied under the influence of crop (spring barley and spring wheat), row spacing (narrow [12.5 or 15.0 cm] and wide [25.0 cm]) and nitrogen rate (50 and 100 kg NH₄-N/ha). Cruciferous surrogate weeds were found to impact crop yield and quality severely. For example, ten intra-row plants/m² of surrogate weed Sinapis alba reduced grains yields by 7%–14% in spring barley and by 7%–32% in spring wheat with yield losses becoming markedly greater in wheat compared to barley as weed density increases. Compared to wheat, barley limited yield and quality losses and suppressed intra-row weed growth more. Row spacing did not have a consistent effect on crop or weed parameters; in one of six experiments, the 25 cm row spacing reduced yields and increased intra-row weed biomass in wheat. Nitrogen rate did not affect crop or weed parameters. Results warrant the implementation of additional tactics to control intra-row weeds and limit crop losses.  相似文献   

Interactions between barban and benzoylprop etbyl, flamprop metbyl or flamprop isopropyl applied at two growtb stages for wild oat control in cereals     

P. A. O'SULLIVAN  W. H. VANDEN BORN 《Weed Research》1979,19(4):255-259

Barban was combined with benzoylprop ethyl, flamprop methyl, or flamprop isopropyl, and the eflects of the combinations on wild oat control and crop yield were assessed, tn greenhouse experiments, the interaction in all three combinations was synergistic, following application at the 2- or 4-leaf stage of wild oats. Under field conditions, combinations of barban + benzoylprop ethyl applied at the 2- or 4-leaf stage of wild oats were as eflective for wild oat control and wheat yield response as barban at 028 kg/ha applied at the 2-leaf or benzoylprop ethyl at 14 kg/ha applied at the 4-leaf stage of wild oats. Mixtures of barban + flamprop methyl applied at the 2- or 4-leaf stage of wild oats provided excellent wild oat control and wheat yield increases. Mixtures of barban + flamprop isopropyl applied at the 2- or 4-leaf stage of wild oats provided comparable wild oat control and barley yield increases to barban (028 kg/ha) applied at the 2-leaf or flamprop isopropyl (14 kg/ha) applied at the 4-leaf stage of wild oats.  相似文献   

EFFECTS OF WEED CONTROL AND NITROGEN APPLICATION RATE ON THE YIELD AND NTTROGEN CONTENT OF KALE     

J. L. HAMMERTON 《Weed Research》1967,7(1):37-50

Summary. The experiments reported show that weed competition throughout growth reduced kale yields by up to 89%. Competition until the 4-leaf stage reduced yields by about 12%. Application of nitrogen had little effect on the actual loss of yield. The same yield could be obtained by controlling weeds from emergence and giving little nitrogen, or by delaying weed control until the 4-leaf stage and giving a higher level of nitrogen, but kale crops that had suffered weed competition until the 4-Ieaf stage appeared to be incapable of achieving the same yield as crops clean-weeded from emergence. Data on nitrogen percentage and content suggest that competition between weeds and kale was not solely for i
Effets du desherbage et du taux de fertilisation azoiée sur le rendement et la teneuren azote du chou fourrager  相似文献   

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     

P. A. O'SULLIVAN 《Weed Research》1981,21(5):211-217

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  相似文献   

The Effects of Cultural Measures on Cereal Pests and Their Role in Integrated Pest Management   总被引：1，自引：0，他引：1  

David M. Glen 《Integrated Pest Management Reviews》2000,5(1):25-40

The influences of cultural control measures on invertebrate pests and their natural enemies in cereals (wheat, barley and oats) are described and discussed, with emphasis on the major pests in north-west Europe. Possibilities for additive and synergistic combinations of cultural measures are identified, together with opportunities for integrating cultural measures with chemical and biological control where appropriate. Recent studies confirm the central role of cultural control measures in integrated pest management and integrated production of cereal crops. However, cultural measures often have opposing effects on different pests as well as diseases and weeds, so that appropriate measures must be selected on the basis of an assessment of the risks from key pests, diseases and weeds. Crop rotation is not an important means of controlling cereal pests, but its use is recommended for control of cereal diseases and weeds, as well as pests of crops grown in rotation with cereals. Diversification of crops and non-crop habitats in predominantly cereal growing areas is thought to increase numbers of certain parasitoids and polyphagous predators of cereal pests. The presence of weeds or an intercrop in a field together with cereals may reduce the severity of aphid and slug damage to cereals. Trap cropping has not yet been adequately tested in wheat, barley or oats. Cover crops reduce damage by wheat bulb fly in a following wheat crop, but increase the risk of slug damage. Resistance to a wide range of cereal aphid species has been identified in wheat and barley, but in Europe, more emphasis is placed on selecting cultivars with resistance to cereal diseases rather than pest resistance. Resistance in wheat to wheat bulb fly and wheat blossom midge is recorded, and resistance to slug damage has been reported in some laboratory studies. Early sowing of winter cereals results in more damage by certain dipterous pests and increased numbers of the aphid vectors of barley yellow dwarf virus (BYDV), but early sowing results in less damage by wheat bulb fly and slugs in autumn/winter and by late infestations of aphids in summer. Avoidance of ploughing results in reduced incidence of wheat bulb fly, yellow cereal fly and aphids, but increased numbers of slugs, wheat blossom midge and bibionid larvae. Avoidance of ploughing can result in greater numbers of certain polyphagous predators, particularly in the first weeks following crop establishment. The presence of straw residues results in increased slug populations, but reduced incidence of yellow cereal fly and wheat blossom midge. Preparation of fine, firm seedbeds discourages attack by slugs and wheat bulb fly on cereals. Drilling at slightly greater depth in rough cloddy seedbeds helps to protect wheat seeds from slug damage. Nitrogen fertiliser applied in spring can help cereal plants compensate for losses by wheat bulb fly or slugs. However, nitrogen applications tend to result in increased summer infestations of aphids.  相似文献   

The effects of combining modified sowing methods with herbicide mixtures on weed interference in wheat crops     

T.K. Das  N.T. Yaduraju 《国际虫害防治杂志》2013,59(4):310-319

In India, wheat is prone to being heavily infested with weeds, which cause considerable yield losses. Agronomic practices, including sowing method, influence weed interference in wheat growth. A herbicide mixture is usually more effective than a single herbicide for controlling a broad-spectrum of weeds. It may prevent weed species shift and delay resistance development in weeds. This study attempted to develop an integrated approach, combining a modified sowing method with applying a herbicide mixture for efficient weed management in wheat. We found that flat bed missing-row sowing resulted in significant reductions in: (i) the three-year mean population densities of grassy, broad-leaved and total weeds at 40 days after sowing (d.a.s), (ii) total weed population density and biomass (dry weight) at 60 d.a.s., compared to a mainly, furrow-irrigated raised bed system. Applying a tank-mix of fenoxaprop-p-ethyl at 0.08 kg/ha and isoproturon at 0.4 kg/ha applied 30 d.a.s. resulted in significant reductions in total weed population density and biomass, leading to a significant improvement in wheat growth and yield compared to either a weedy check or a regime of fenoxaprop-p-ethyl applied at 0.10 kg/ha. However, a combination of the flat bed missing-row sowing and tank-mix application of fenoxaprop-p-ethyl 0.08 kg/ha and isoproturon 0.4 kg/ha 30 d.a.s. resulted in higher wheat yield through better management of weeds compared with other sowing/ weed control combinations.  相似文献   

野燕麦田间发生密度对小麦、青稞产量损失估测及防除策略的研究   总被引：7，自引：0，他引：7  

涂鹤龄  同秀莲 《植物保护学报》1983,10(3):197-204

杂草对农作物有很大危害是众所周知的,确切知道不同情况下的草害程度对防治对策有现实的指导意义。目前各地都在进行这方面的试验,方法和准确性也异。本文介绍了野燕麦对小麦、青稞在青海省条件下的危害,其方法可供各地参考。同时对试验中所应用的数理统计是否合宜,也可供讨论。1.田间野燕麦发生密度对小麦、青稞产量损失之间有着极显著的回归关系。野燕麦穗数即花序数每增加1万穗/亩,小麦产量损失5.39斤、穗粒数减少0.15粒、千粒重降低0.102克,青稞产量损失3.5斤、穗粒数减少0.17粒、千粒重降低0.02克。2.小麦三叶期以前田间出苗的野燕麦危害最大,在野燕麦10万株/亩左右密度下,减产35.5%;小麦开始拔节以后出苗的野燕麦危害较小,造成减产8%以下。3.田间野燕麦密度越大,后期复盖阴闭越严重。野燕麦株数每亩16万株以上,复盖度90%以上,并导致小麦倒伏。4.据野燕麦危害损失,结合当前生产水平,对野燕麦发生的轻度危害田、中等危害田、严重危害田、控制田的划分指标和防除策略进行了探讨。  相似文献   

EFFECTS OF ANNUAL DRESSINGS OF NITROGEN FERTILIZER ON WILD OAT INFESTATIONS     

F. B. WATKINS 《Weed Research》1971,11(4):292-301

Nitrogen fertilizer in three forms, urea, sulphate of ammonia and calcium ammonium nitrate, was applied at three rates, 26, 52 and 104 kg N/ha, early (January) and late (May) during land preparation for three consecutive barley crops, to determine the effect of fertilization on wild oat populations. On the fertilized areas there was significantly greater germination of wild oats prior to sowing than on the unfertilized areas, with calcium ammonium nitrate and sulphate of ammonia tending to be more effective in stimulating germination than urea. Despite the destruction of these heavy populations of wild oat seedlings by cultivation prior to sowing, in-crop infestations of the weed were still heavy. Late-applied nitrogen by comparison with the early application tended to produce greater numbers of wild oat panicles in the crop, particularly at the lower fertilizer rates. The overall effect after three annual dressings of nitrogen was one of greatly increased wild oat seed reserves in the soil. These had increased five-fold in no-nitrogen plots, six-fold in early-fertilized plots and eight-fold in late-fertilized plots. It was concluded that annual dressings of nitrogen fertilizer on winter cereals in wild-oat-infested areas led to an increase in the population of the weed. Some suggestions are made as to why nitrogen fertilizer stimulated wild oats to germinate, and the overall results are discussed in the light of the agricultural situation of the Darling Downs.  相似文献