The effects of pH on the action of some dormancy-relieving chemicals were investi gated on seeds of Chenopodium album, Avena fatua and Rumex crispus. Sodium azide (A), potassium nitrate + ethephon (NE), NE + A, NE + A + thiourea + hydrogen peroxide were tested in soil trays or in paper (in vitro) with buffer solutions in controlled environment. The response to NE was not affected by pH from 3 to 9. Sodium azide had the gre ate st effect on seed decline, but its effect was pH-dependent. This compound was extremely deleterious for Chenopodium album L. and Avena fatua L. seeds in acid soil (pH 4), while in basic soil it relieved dormancy of A . fatua. At pH 6. 2 the combin ation of NE + A was detrimental to C. album and A. fatua, perhaps because of an antagonism between the compounds. Mixing the five compounds toge ther reduced the influence of pH on the deleterious effect of azide. deleterious effect of this compound was less affected by temperature than its dormancy -relieving action. The solution extracted from both soils did not affect the treatments in vitro at different temperatures compared with buffers at similar pH. The influence of soil characteristics on the efficacy of dormancy-relieving or weed killing treatments in the field is discussed.
Avena fatua; Chenopodium album; dormancy; emergence; germination; Rumex crispus; viability