Development of effective non-chemical methods for controlling black-grass (<i>Alopecurus myosuroides</i> Huds.)

Abstract

In a seven-year long-term field experiment at two locations in Northern Germany (marshland and loamy soil, respectively), field trials were carried out within a crop rotation of winter oil seed rape, 3 x winter wheat and spring crops (cereals) during the last years. The aim was to find out which method of soil cultivation (ploughing, chisel plough, reduced tillage with power harrow) achieved the highest efficacy in controlling black-grass under field conditions. Furthermore, different drilling dates of winter wheat, the cultivation of winter oilseed rape and of spring cereals were tested with regard to their level of black-grass control.
In winter wheat, different herbicides were applied with the aim of black-grass control: Pre-emergence herbicides (flufenacet), followed by Atlantis (mesosulfurone) in March/April. On several experimental plots only pre-emergence herbicides were used. The reason: a fully developed resistance of black-grass against Atlantis should be simulated in order to see, what happened, when Atlantis was no longer applicable. Still now this resistance was not fact on the locations. Winter oilseed rape and spring cereal plots were treated with herbicides uniformly because of existing herbicide resistances of black-grass against ACCase-Inhibitors. So there were no more possibilities of differentiation. Black-grass plants/ears in the plots on both locations were counted about 10 times per year dependant on the emergence of black-grass.
In summer 2012 and 2016, soil samples from three different soil depths were taken before black-grass seed dispersal. In a greenhouse, soil samples were put into dishes, stirred in order to stimulate the germination of black-grass seeds by light and kept humid. All emerging black-grass seedlings were counted and then removed. This was repeated until no more black-grass plants emerged.
Results: When the herbicide Atlantis was applied and showed high efficacy, no effect of different tillage systems on black-grass populations was visible. Without Atlantis application, the level of black-grass exploded within three years of winter wheat production in plots where chisel plough or reduced tillage systems were utilised. Ploughing kept the level of black-grass low and late drilling dates of winter wheat reduced the level of black-grass infestation. A low level of black-grass in winter oilseed rape was only observed as long as ACCase inhibiting herbicides (DIMs) achieved a high efficacy. Otherwise, the control of black-grass in winter rape was not sufficient. Three years of spring cereals cultivation reduced the level of black-grass infestation within the crop as well as seed densities in the soil. Important: ploughing and making of the seedbed should be done in autumn. In spring: glyphosate-application before sowing and sowing spring crops with as little soil motion as possible.