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Single and combined effects were studied of root length, burial depth, cutting and competition from a seasonal green manure crop on the growth and development of C. arvense from roots found in the upper soil layer. The experiment was performed under field conditions and partly repeated in a green house. The green manure consisted of a mixture of phacelia, common vetch, red clover and Italian ryegrass. Root fragments of 5 and 10 cm length were buried at 5 and 15 cm soil depth, simulating soil tillage. Use of green manure alone reduced growth of C. arvense more than any other single factor (81–99%), while root length and burial depth were more variable in their effect (0–96% reduction). Combined treatments involving both green manure, deep root burial (15 cm) and short root length (5 cm) reduced growth of C. arvense consistently by 95–100%. At the minimum regenerative capacity of C. arvense the number of leaves was 3–7 in plots with no green manure, at which time cutting had the greatest effect on regrowth the following year. The level for minimum regenerative capacity was not possible to decide for C. arvense growing in competition with green manure. Combined multiple treatments in spring, including use of green manure and mechanical operations in the upper soil layers, appear to be a potential means of reducing C. arvense infestations. [ABSTRACT FROM PUBLISHER]