Alfalfa roots can dig more than 15 metres down to find water
A knee-high forage plant hides an astonishing root system. Alfalfa taproots usually reach two or three metres, can grow about six feet in a single year in loose soil, and sometimes plunge beyond 15 metres to tap groundwater, which is why this ancient fodder shrugs off drought.
Alfalfa, called lucerne in Britain, South Africa, Australia and New Zealand, is a perennial legume that grows up to a metre tall and typically lives four to eight years, sometimes over 20. It bears clusters of 5 to 20 small flowers, usually purple, and yellowish seeds. The English word alfalfa, recorded from 1791, came through Spanish from an Arabic term often glossed as fresh fodder. Lucerne entered English from French in 1652, borrowed in turn from the Occitan word for glowworm, probably after the bright yellow seeds of some strains.
Its travels span millennia. The plant likely originated in south-central Asia, and Pliny wrote that the Persians brought it to Greece around 490 BC, where it was known as Median grass. The 12th-century agronomist Ibn al-'Awwam described growing it in Spain, Spanish colonists carried it to the Americas in the 16th century to feed their horses, and seeds shipped from Chile to California in the 1850s launched a rapid expansion in the American West.
Farmers prize it because it feeds itself. Partnering with rhizobia bacteria such as Sinorhizobium meliloti, it forms root nodules that fix nitrogen, giving a protein-rich crop regardless of soil nitrogen and leaving the ground richer. It usually has the highest feeding value of common hay crops and goes mainly to high-producing dairy cows, as well as beef cattle, horses, sheep, goats and meat rabbits. Mown three or four times a year in most climates, it can be cut up to 12 times in Arizona and southern California, with yields around 8 tonnes per hectare in temperate areas.
It has quirks. Alfalfa is autotoxic, so new seed struggles in an old stand, and fields are rotated with corn or wheat before reseeding. It also shelters predatory insects that can protect neighbouring crops like cotton, provided it is mown in strips rather than all at once.
Source: Alfalfa
