Effect of cover crops in smothering weeds and volunteer plants in alternative farming systems

- Cover crops had a positive effect on the smothering of weeds and volunteer plants.
- Cover crop biomass was negatively correlated with density and biomass of weeds.
- The farming system influenced on weed and volunteer plant biomass and density.
- Neither weed biomass nor density were influenced by soil humus content.

Alternative farming systems such as sustainable and organic farming are used to produce premium price food products and retain the viability and fertility of soil. Field experiments were conducted at Joniskelis Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry in 2006-2012. The research objective was to investigate the competitive ability of plants cultivated as cover crops: narrow-leafed lupine (Lupinus angustifolius L.) in mixture with an oil radish (Raphanus sativus var. Oleiferus Metzg.) (LUPRA); white mustard (Sinapis alba L.) (WM); white mustard in mixture with a common buckwheat (Fagopyrum exculentum Moench.) (WMBU) to smother weeds in organic and sustainable farming systems in soil with low (1.90-2.01%) (LH) and moderate (2.10-2.40%) (MH) humus content. Cover crops cultivated for green manure were investigated during the post-harvest period of winter wheat. This experiment showed that cover crops have a strong competitive ability to smother weeds and emerged volunteer plants. It also demonstrated that narrow-leafed lupine in combination with oil radish, cultivated in the organic farming system, was less effective at smothering weeds compared with white mustard cultivated as a sole crop or in combination with buckwheat. In a rotation without cover crop in soil with low and moderate humus content, the number and biomass of weeds was higher compared with the farming systems with cover crops. A correlation-regression analysis showed that the cover crops had a higher impact on the biomass of weeds and volunteer plants in soil with low humus content to compare with moderate humus content. The most effective inhibition of volunteer plant and weed biomass in soils with both humus contents was observed, when white mustard and a mixture of white mustard and buckwheat were used as cover crops. The practical implication of this research is suggestion, that cover crops could be successfully used as integrated weed control tool in farm fields.