The effects of self-regenerating annual clovers on plant species composition and heifer performance in an irrigated pasture in western Oregon, USA

The addition of self-regenerating annual legumes into permanent pastures can benefit rapid forage growth in early spring, leading to increased pasture production and animal live weight gain (LWG). The objective of this 2-year grazing study was to evaluate the effects of balansa clover (Trifolium michelianum) and subterranean clover (Trifolium subterraneum) on pasture and animal production in an irrigated dairy system in western Oregon, USA. Study results showed that balansa clover has a high potential to increase legume content of establishing pastures in early spring. Legume content of pastures sown with annual legumes increased by 25.3% in early spring compared to pastures sown without annual legumes. However, no significant increase in legume content was observed past the initial year of establishment. The persistence of balansa clover and subterranean clover was low in 2021, at <1% of the botanical composition. The overall benefits of balansa clover in early spring in 2020 were offset by reduced perennial forbs, white clover (Trifolium repens) and chicory (Cichorium intybus), in paddocks that were sown with annual legumes. However, this did not negatively affect the LWGs of heifers. This study found no significant difference between pastures sown with and without annual clovers pastures on dry matter production and animal production. Balansa clover was competitive in the establishment year; however, further research into improving its persistence past establishment is warranted.