The incidence of weed species in 482 cereal and 224 vegetable field plots in southern and central Finland was investigated. The occurrence of the 16 most common weed species was related to soil properties. Chenopodium album L., Lamium spp. L. and Fallopio convolvulus (L.) Löve were more abundant in clay than in coarse mineral or organic soils. Elymus repens (L.) Gould, Erysimum cheiranthoides L., Lapsana communis L., Myosolis arvensis (L.) Hill and Poa annua L. thrived better in coarse than in clay soils. Polygonum lapalhifolium L. and Rumex spp. L. were more abundant in organic than in mineral soils, and Lamium spp. was not found at all in organic soils. Rumex spp., Poa annua and Polygonum lapalhifolium had higher densities at the lowest pH level, < 5.2. Lamium spp. and Myosolis spp. thrived at the highest pH levels. Poa annua and Spergula arvensis were most common in soils where the extractable calcium concentration was below 1000 mg l-1 soil.

Summary: Résumé: ZusammenfassungM The persistence and movement of chlorsulfuron and metsulfuron in Finnish sandy, clay and organic soils were studied with onion bioassays. Field plots grown with barley were sprayed with 4 and 12 g a.i. ha−1 Chlorsulfuron and metsulfuron persisted and leached to nearly the same extent. They persisted longer in the sandy soils than in the other soils, and leaching was also deeper in the sandy soils. The phytotoxicity of the 4 g a.i. ha−1 dose persisted in the 0–5 cm layer of all soils for 1 month on average. The residues tended to leach deeper than 5 cm and, in some cases, were recovered up to 1 year after application. The phytotoxicity of the dose of 12 g a.i. ha−1 persisted for at least 1 month and generally for 1 year. Residues of this dose were found in the 0–5, 5–15 and 15–25 cm layers, and in clay, mostly in the 0–15 cm layer. Significant growth stimulation in bioassays was common 1–2 years after application in the 5–15 and 15–25 cm layers of sandy soils. Chlorsulfuron and metsulfuron generally had only a very small effect on microbial dehydrogenase and nitrification activities. Persistance et effets microbiologiques du chlorsulfuron et du metsulfuron dans des sols finlandais La persistance et le mouvement du chlorsulfuron et du metsulfuron dans des sols sableux, argileux et humiferes de Finlande ont ete etudies l'aide d'essais biologiques utilisant l'oignon. Des parcelles semees en orge ont ete traitees a raison de 4 et 12 g m.a. ha. La persistance et le lessivage du chlorsulfuron et du metsulfuron etaient similaires. Us persistaient plus longtemps dans les sols sableux que dans les autres et le lessivage y etait plus important. La plupart du temps, la phytotoxicite de la dose 4 g m.a. ha−1 persistait pendant un mois dans la couche 0–5 cm. Les residus tendaient a etre lessives plus profondement que 5 cm et dans certains cas etaient detects 1 an apres l'application. La phytotoxicite de la dose 12 g m.a. ha−1 persistail pendant au moins un mois et generalement pendant an. Les residus de cette dose etaient retrouves dans les couches 0–5, 5–15 et 15–25 cm et dans le sol argileux principalement dans le couche 0–15 cm. Des stimulations de croissance significatives, detectees par des essais biologiques, etaient communement observees 1–2 ans apres Tapplication dans les couches 5–15 et 15–25 cm des sols sableux. Le chlorsulfuron, et le metsulfuron la plupart du temps, n'avaient qu'un tres faible effet sur les activites microbiennes deshydrogenase et de nitrification. Persistenz und mikrobiologische Wirkungen von Chlorsulfuron und Metsulfuron in finnischen Boden Die Persistenz und Einwaschung von Chlorsulfuron und Metsulfuron in finnischen Sand‐. Lehm‐ und organischen Boden wurden mit Zwiebel‐Biotests untersucht. In Gerstenbestanden hatten die beiden Herbizide nach Anwendung von 4 und 12 g A.S. ha−1 ungefahr gleiche Persistenz und Einwaschung, die in den Sandboden starker als in den anderen waren. Die Phytotoxizitat blieb in alien Boden bis 5 cm Tiefe nach Anwendung von 4 g A.S. h...

The weeds in this study consisted mainly of Chenopodium album, Stellaria media, Viola arvensis, Polygonum convolvulus, P. aviculare and P. lapathifolium. Increasing cereal seed rates reduced the numbers, individual weights and total yields of the most abundant species, Chenopodium album. The decreases in plant weight and total yield of the weeds were very steep when the cereal seed rate was raised from 25 to 200 kg/ha. Increases in the seeding rate reduced the total yields of weeds rather than their numbers. The effect of the cereal on weeds became apparent as soon as heading of the cereal was complete and was further enhanced by prolonged competition. Added nitrogen raised the weed yields at cereal seed rates of 25—100 kg/ha but reduced them at higher seed rates. Nitrogen also raised the yield and individual plant weight of C. album. Cereal seed rate did not affect the nitrogen, phosphorus, potassium, calcium and magnesium contents of the weeds grown among the crop. Due to larger total weed yields, however, the amounts of these nutrients in the weeds were higher in sparse than in dense cereal populations.

Plants oi Chenopodium album L. were grown at a range of different densities in each of three years. The stem diameter, the number of main branches and the si2e and number ofleaves decreased with increasing density as did weight and leaf area per plant. The dr>'-matter yield per unit area increased with density up to 576 plants/m^ in two of the three trial years. The proportion of the seed yield relative to the total yield was higher in the leas dense than in the dense stands, or was almost constant. Density did not affect the seed yield per unit area, but seed yield per plant fell as density increased. Maximum seed production was 41 900 per plant and the mean seed yield over the three years was 8300 seeds per plant. The percentages of nitrogen, phosphorus, potassium and calcium were highest when the plants were at an early stage of development. The proportions of these elements in the dry-matter yield decreased with increasing age of the plants. The density ofthe stand did not affect the percentages of elements but the total amounts per plot were greatest at the flowering stage and in the denser stands.Effet de la competition intraspidfique sur le dA/eloppemenl de Chenopodium album L.Resume. Des plantes de Chenopodium album L. ont ^td cultivees i diverses densitds de pcuplrmcnt pendant trois ann^es. Le diam^tre des tiges, Ie nombre de rameaux principaux, la taillcetle nombre des feuilles diminu^rent k mesure que la density augmentait, ainsi que le poids et la surface foliaire par plante. La production de mati^re stehe par unit^ de surface augmenta avec la density jusqu'i 576 plantes au m^, dans deux des trois ann^es d'cssais. Le rapport de la production de semences par rapport k la production tolale fut plus 6lcv6 dans les peuplements clairs que dans lea peuplements denses, ou fut k peu pres constant. La density de peuplement n'affecta pas la production de semences par unit^ de surface, mais la production de semences par plante diminua lorsque la density augmentait. La production maximale de semences par plante fut de 41 900 et la production moyenne pendant le.s trois ans fut dc 8300 semenres par plante. Les pourcentages d'azote, de phosphore, de potassium et de calcium furent plus ilevds lorsque les plantes Etaient k un stade precoce de d^veloppement. Les proportions de ces il^ments dans la maticre scche produite diminuerent avec l'age des plantes. La density de peuplement n'affecta pas le pourcentage des dl^ments mais les quantitis totales par parcelle furent plus ^lev^es au stade floraison et dans les densit^s Ies plus fortes.Der Einfluss intraspeziflscher Konkurrenz auf die Entwickturtg von Cheaopodium album i.