The increased use of herbicides and minimum cultivation techniques for the establishment of crops has aroused further interest in sowings under trash or mulch. As part of a series of experiments on the effect of different mulches on seed germination and establishment and in view of disappointing results in the field when sowing into a paraquat-treated sward, it was decided to examine the eifect of such herbage on germinating seeds under glasshouse conditions. Part of a permanent pasture was sprayed with paraquat at the rate of 2 lb a.i. per acre. Samples of herbage were subsequently collected after 2, 7 and 14 days and stored in a deep-freeze until needed. Fifty seeds, per 10-in. diameter pot, of barley (Rika), perennial ryegrass (S321) or rape (Essex Giant) were sown on the surface of sterilized soil which had been saturated with water and allowed to drain freely for 24 hr. The seeds were then covered to a depth of l^-in. with herbage. The pots were watered daily, using a fine droplet sprayer, and notes were made on seedling numbers and growth characteristics. The results are shown in Tables 1, 2 and 3.Both crops and mulch treatments showed significant differences in emergence (Table 1).For all crops the shorter the interval between spraying and harvesting the mulch the greater was the depression of seedhng emergence.The growth of barley under the 7-and 14-day mulches could be regarded as satisfactory. With the 2-day mulch, growth was uneven and the first leaf of approximately 15-20% of the seedlings was white-tipped with yellowing along the veins. The seedlings were generally weakened and secondary infections, such as powdery mildew, were thus encouraged.The rape seedlings showed distinct symptoms of a physiological disorder under all treatments. The cotyledons had a white central vein, white edging and sometimes chlorotic spots. On a number of plants one cotyledon appeared to be more affected than the other, possibly due to shielding of one by the other during emergence. Formation of the true leaves appeared to be delayed on affected plants, and these true leaves also showed chlorotic areas. These adverse effects to growth occurred on approximately 90%, 60% and 20% of the plants growing in the 2-, 7-and 14-day mulches, respectively.Ryegrass was the slowest crop to emerge and gave the poorest total emergence. However, Table 1. Effect of mulch on the emergence of barley, rape and perennial ryegrass (angular transformation of % emergence)

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.

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