Some effects of paraquat on crop establishment in killed swards

Abstract

Summary: Résumé: Zusammenfassung The establishment of crops direct‐drilled after various times into swards treated with paraquat (1,1′‐dimethyl‐4,4′‐bipyridylium‐ 2/A) was examined. Best results with Brassica napus and B. oleracea were obtained with 1–1 kg/ha applied 7 days before drilling and 2–3 kg/ha applied 14 days before. Although delaying drilling from 7 to 14 days after application reduced the phytotoxicity, the higher dose was needed when drilling was delayed, to reduce competition from the sward regrowth. In the glasshouse, mulches of paraquat‐treated herbage affected seedling growth and development of Brassica napus, Hordeum vulgare and Lolium perenne; B. napus was the most susceptible. Quelques effets du paraquat sur des cultures implantées aprés destruction d'herbages L'implantation de cultures en semis direct, apres divers intervalles de temps, dans des herbages trait6s au paraquat (l,r‐diméthyl‐4‐4′‐bipyridylium‐2/4) a été examinée. Avec Brassica napus et B. oleracea, les meilleurs résultats ont été obtenus par des applications de 1,1 kg/ha et de 2,3 kg/ha, respectivement 7 jours avant et 14 jours avant le semis. Bien que le fait de porter de 7 à 14 jours le délai entre le traitement été le semis ait réduit la phytotoxicité, la dose la plus forte a été nécessaire lorsque le semis a été retardé, pour réduire la competition due à la repousse de la prairie. En serre, des paillis d'herbages traités au paraquat ont affecté la croissance et le développement de Brassica napus, Hordeum vulgare et Lolium perenne; B. napus s'est montré le plus sensible. Einige Effekte von Paraquat auf die Entwicklung von Kulturpflanzen in abgetöteten Pflanzendecken Es wurde die Entwicklung von Kulturen untersucht, die in unterschiedlichen Zeitabständen direkt in mit Paraquat (l,l'‐Dimethyl‐4,4′‐bipyridylium‐2/4) behandelte Pflanzendecken gesät wurden. Die besten Ergebnisse mit Brassica napus und B. oleracea wurden erzielt, wenn 1.1 kg/ha 7 Tage und 2 3 kg/ha 14 Tage vor der Saat gespritzt wurden.

The effects of paraquat and glyphosate residues in sprayed herbage on the development of seedlings of a normal and a paraquat‐tolerant variety of Lolium perenne

“…In these experiments both germination and growth were affected and grasses were more susceptible than dicotyledons. Covering seeds with a mulch of grass clippings that had been previously sprayed with paraquat has also been shown to reduce germination and seedling growth (Warboys 1974;Klingman and Murray, 1976). Thus it is well established, as confirmed by the experiment reported in this paper, that 'second-hand' paraquat can be toxic to grass seedlings.…”

“…When paraquat has been sprayed on to an old grass sward or stubble, residues of the herbicide are present in the dying herbage, in organic dehris or on the soil surface. These residues are potentially toxic to germinating seedlings (Warboys, 1974;Klingman and Murray, 1976). There is therefore a risk of herbicide damage to grasses that are direct-drilled after spraying with paraquat.…”

Effect of Thatch on Residual Activity of Nonselective Herbicides Used in Turfgrass Renovation1

“…Several investigators have reported that paraquat residues in surface plant litter can adversely affect seedling development in mineral soils (1,2,9,11,21,22). However, the impact of clipping debris containing herbicide residues on seedling development has only been briefly studied under greenhouse conditions (11).…”

“…. Several investigators have reported paraquat toxicity on mineral soil sites where herbicide residues were present in surface litter (1,2,9,11,21,22,24)._ Emerging seedlings absorbed paraquat fn;>m plant h~ter lay• ers at the soil surface, but covenng seed with soil or incorporation of soil into the surface litter ~e duced the extent of herbicide injury. Surface disturbance of organic soils or introduction of clay into them also reduced paraquat residual activity due to the transfer of weakly adsorbed paraquat in peat wils to incorporated clays which inactivated paraquat (8,23).…”