Submitted to: Pacific Northwest Sustainable Agriculture Newsletter
Publication Type: Other
Publication Acceptance Date: 11/15/1993
Publication Date: N/A
Interpretive Summary: Currently, weed control in potatoes is highly dependent on herbicide inputs. Cultivation controls weeds early in the season, but reduces potato yield and is difficult to implement on a timely basis on large farms. In a two year trial, rapeseed grown as a fall-planted green manure crop and incorporated in the spring has suppressed weeds in the following potato crop on sandy soils. Greenhouse tests have demonstrated that white mustard or rapeseed tissue added to soil can reduce emergence and/or growth of several important weed species. This technology could reduce early season herbicide applications or herbicide rates in potatoes. These Brassica green manure crops have also been shown to reduce nematodes in potatoes.
Technical Abstract: In 1992 and 1993, planting rapeseed in late August and incorporating the residue in the soil in the spring, reduced weed biomass in the following potato crop by 90% and 50%, respectively. A sudangrass green manure was not effective in reducing weed populations or weed growth. When weeds were controlled with herbicides, potatoes following a green manure crop of rapeseed yielded equal to or greater than potatoes following fallow or sudangrass. In greenhouse trials, white mustard or rapeseed tissue added to soil at 20 g fresh weight per 400 g dry sandy soil reduced emergence or growth of five weed species to various degrees.