The effect of intercropping winter peas and non-legumes on the weed suppressive ability in deep and short-term shallow ploughed soils

The interaction between winter pea sole or intercropping and ploughing depth was investigated in field experiments in Northern Germany with regard to weed infestation. A normal-leafed (cv. E.F.B. 33) and a semi-leafless winter pea (cv. James) were grown as sole crops and in intercrops with oilseed rape or triticale. The two ploughing depths were short-term shallow ploughing to a soil depth of 8-10 cm and deep ploughing to 25-27 cm. E.F.B. 33 showed a better weed suppressive ability than James. Moreover, winter pea-triticale intercrops were more effective in suppressing weeds than winter pea-oilseed rape intercrops. No beneficial effect of intercropping the semi-leafless cv. James and oilseed rape was found with regard to a reduction in weed infestation. The ploughing depth had mostly no significant effect on the weed infestation in winter pea sole or intercrops. In one of three years, intercropping E.F.B. 33 and triticale compensated for a higher weed infestation after shallow ploughing.