Alfalfa / Lucerne

Medicago sativa

1. Identification and origin

Lucerne or alfalfa (Medicago sativa L.), belonging to the Fabaceae family, is one of the oldest and most widely cultivated forage crops in the world. Its origin lies in the region of Western Asia and the Caucasus, having been spread to Europe and the rest of the world owing to its high nutritional value and ability to adapt to diverse environments. It is a perennial species of great importance in sustainable livestock and agricultural systems.

2. Economic importance

Alfalfa is regarded as the “queen of forages” owing to its high protein content, digestibility and nutritional value. It is used fresh, as hay, silage or dehydrated for feed. Beyond livestock use, it contributes to improving soil fertility through the biological fixation of nitrogen. The main producers include the United States, Argentina, China, Spain, France and Italy. In Portugal, it is grown mainly in the irrigated areas of the Alentejo and Ribatejo.

3. Botanical characterisation

A perennial herbaceous plant, 40–90 cm tall, with an erect, branched stem. The leaves are trifoliate, with obovate leaflets and a serrated margin in the upper third. The flowers are papilionaceous, generally violet, grouped in axillary inflorescences. The pods are spiralled, containing several small, reniform seeds. The root system is deep and taprooted, conferring high tolerance to drought.

4. Soil and climate requirements

It prefers temperate, dry climates with good light. It tolerates high temperatures and moderate frosts. It develops best in deep, well-drained soils of medium to light texture, with a pH between 6.5 and 8.0. It is sensitive to waterlogging and acidity. Alfalfa requires good fertility, especially in phosphorus and potassium, and benefits from inoculation with Rhizobium meliloti in soils where it is not present.

5. Main pests

• Alfalfa weevil (Hypera postica): perforations and damage to leaves and shoots.
• Aphids (Acyrthosiphon pisum, Aphis craccivora): sap-sucking and transmission of viruses.
• Caterpillars (Noctuidae): significant defoliation of young shoots.
• Mites (Tetranychus spp.): chlorosis and reduction of photosynthesis.
• Nematodes (Meloidogyne spp., Pratylenchus spp.): root galls and decline in production.

6. Main diseases

• Wilt caused by Fusarium (Fusarium oxysporum f. sp. medicaginis): vascular necrosis and death of plants.
• Anthracnose (Colletotrichum trifolii): dark lesions on stems and leaves.
• Powdery mildew (Erysiphe spp.): white coating under dry conditions.
• Root rots (Phytophthora spp., Pythium spp.): wilting and rotting in moist soils.
• Leaf spot (Pseudopeziza medicaginis): circular lesions and leaf drop.

7. General crop management

This includes choosing varieties adapted to the local climate, correcting soil acidity, sowing in well-drained soils, weed control in the early stages and monitoring of pests such as the alfalfa weevil and aphids. Crop rotation reduces the pressure of diseases and nematodes. Cuttings should be carried out at the start of flowering to maximise crop quality and persistence.

Bibliographic references

• EPPO Global Database. Medicago sativa – pests and diseases.
• CABI Invasive Species Compendium. Medicago sativa – datasheets.
• Barnes, R. F., et al. (2003). Forages: An Introduction to Grassland Agriculture. Iowa State Press.
• Hanson, A. A., Barnes, D. K., & Hill, R. R. (1988). Alfalfa and Alfalfa Improvement. ASA‑CSSA‑SSSA.
• Radović, J., Sokolović, D., & Marković, J. (2009). Alfalfa – most important perennial forage legume. In: Yadav, S. S., et al. (Eds.), Legumes in the Omic Era. Springer.