The use of red clover (Trifolium pratense) in soil fertility-building: A Review

Red clover cultivation made significant contributions to soil fertility prior to the introduction of mineral nitrogen fertilizers. Its modern usage lies primarily in forage production, but reintegration into arable systems can enhance sustainability and preserve environmental integrity. Here we review red clovers nitrogen (N) contribution to subsequent crops, its capacity to fix N, and how this N is transferred to subsequent crops. The senescence of the root system following cultivation also contributes to soil organic matter, providing a suite of ecosystem services which are also reviewed. Potential contributions to allelopathic weed control and how this may be utilized to improve weed control is also discussed. Red clover varieties are diverse and can be split into categories of early/late flowering, erect/prostrate and diploid/tetraploid. This use of this diversity to different ends and purposes in fertility-building and the role of plant breeding in optimizing use of genetic resources is reviewed. Management strategies are also diverse; red clover can be grown in monoculture or with companion grasses, it can be harvested for forage or green manured (which can include or omit herbicides) and the consequence of this for soil fertility is discussed. High protein forage production is also a key benefit of red clover cultivation and the economic incentive this may provide to farmers is also reviewed.