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 in the growing seasons 2008/09-2010/11 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. The normal leafed winter pea cv. E.F.B. 33 showed a better weed suppressive ability than James. Moreover, winter pea-triticale intercrops were more effective than winter pea-oilseed rape intercrops in suppressing weeds. 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. Intercropping E.F.B. 33 and triticale, however, compensated for a higher weed infestation after shallow ploughing in 2008/09