Evaluation of cover crop mixtures for weed management and soil fertility improvement in organic agriculture

Cover crops are promoted as a tool to preserve agrobiodiversity, to enhance soil chemical and physical properties, and to help suppress weeds. This study was conducted at two sites in northern Greece with similar climates, but different soil types, over two growing seasons in 2014-15 and 2017-18. Two multi-species cover crop mixtures with seven and eight types of legumes and grasses, respectively, were monitored to determine their weedsuppressing and soil fertility enhancement attributes compared to a vetch/oat (Vicia sativa L./Avena sativa L.) mixture, and single-species crops of triticale (×Triticosecale Wittm.), rye (Secale cereale L.) and ryegrass (Lolium multiflorum L.). A cultivated fallow treatment served as a control. The leguminous cover crop seeds were inoculated with rhizobium prior to planting. An unmanned aerial vehicle (UAV) or drone with an infrared camera was used to monitor cover crop growth and canopy development. Weed population and density within experimental plots were measured and weed suppression of each cover crop system was estimated. All cover crops exhibited high weed suppression during the 2014-15 season, while in 2017-18, weed suppression was less effective. The multi-species cover crop systems were shown to be very adaptable to weather conditions and consistently produced high biomass at both sites and years. The vetch/oat mixture was found to increase soil total nitrogen (TN) and nitrate-nitrogen (NO3-N), producing a high legume biomass and contributing significantly greater TN than the other cover crops. This study suggests the multi-species mixtures have potential to produce a sufficient biomass to suppress weeds and contribute nitrogen for the following cash crop