Ecological intensification using Persian clover to support weed management in winter wheat under semiarid conditions

There is a need for non-chemical weed control due to evolution of herbicide resistance in weeds and environmental issues that arise due to prolonged use of herbicides. In three field experiments conducted during 2016–2018 in the Nahavand region of Iran, the effects of under-sown Persian clover on weed suppression and yield of winter wheat were evaluated. Persian clover was under-sown in wheat at four seed rates (12.5, 25.0, 37.5 and 50.0 kg ha−1, called InW-C1, InW-C2, InW-C3 and InW-C4, respectively). Pure wheat in weedy and weed-free conditions were included as control treatments (Wh-We and PW, respectively). Persian clover biomass increased from 59 to 184 g m−2 from the lowest to the highest seed rate and the weed biomass decreased from 272 g m−2 with no Persian clover (Wh.We) to 20 g m−2 (InW-C4) with the highest seed rate. As expected, grain yield was highest (4604 kg ha−1) for wheat grown in weed-free conditions (PW), while wheat yield was intermediate (mean 2764 kg ha−1) at the three highest Persian clover seed rates (InW-C1, InW-C2, InW-C3) and lowest (1932 kg ha−1) in the weed-infested control (Wh-We). We conclude that the ecological intensification with Persian clover under-sown in wheat can reduce weed biomass without further negatively affecting yield. However, it might represent a feasible tool to manage weeds and for agriculture to become less dependent on herbicides. This approach could become economically viable if other values added by Persian clover, such as feed for livestock, green manure, or lower pesticide costs, exceed the cost of the grain yield reduction compared to a weed free situation.