Lucerne, otherwise known as Alfalfa Medicago Sativa, is a perennial legume grown in many countries around the world. It is a high yielding forage crop of high nutritional value which can be successfully grown in Scotland.
It must however be sown only on free draining land with no possibility of water logging. As an extremely drought tolerant crop producing high protein, high mineral feed with a dry matter content of approximately 30% and digestibility of 70D it is a highly attractive crop.
Lucerne grows to a height of one metre with a deep root system. These roots generally grow to a depth of two to three metres depending on the subsoil they encounter. Root depths have in the past been recorded up to fifteen metres to reach ground water. The deep roots also help to improve soil nitrogen and aids protection against soil erosion and of course drought.
The crowns store carbohydrate as an energy reserve which also helps protect from drought during dry conditions.
A well established ley can last for four or even six years. It should provide three cuts per annum with the possibility of a fourth cut in some parts of the country.
A high protein leguminous crop which can be grazed in situ but more usually preserved as hay or silage, producing crude protein levels of seventeen to twenty-two percent which are not at all uncommon.
Lucerne is relatively slow to establish, but after a few months it forms a crown at the top of the roots. These crowns have shoot buds which enable the plant to regrow many times after successive harvests.
It can be sown at any time between April and August on a well drained soil with a fine firm seed bed. With a pH requirement of 6.8 to 7.5 it does rely on good levels of phosphates and potash. Sowing rates of eight to fifteen kg per acre, twenty to thirty-five kg per hectare depend on soil type and sowing method.
Lucerne seed should be treated with an inoculant of rhizobium bacteria prior to sowing. This is a simple process of mixing the seed with a powder and water. Thereafter the mixture is allowed to quickly dry before drilling.
Lucerne is a tiny seed best drilled no more than one centimetre deep in rows ten centimetres wide. Alternatively, the seed can be broadcast successfully thus ensuring it is not buried too deep. It is essential it is rolled after sowing.
Any weed emergence must be rigorously controlled as lucerne is relatively uncompetitive. There appears to be less pests and diseases in Scotland which attack the crop which is fortuitous as there are few chemicals approved for use on lucerne. Slugs are a potential hazard which should be regularly checked for at establishment and slug pellets employed as required. Eel worm can be problematic, mostly on lighter soils therefore varietal resistance is best taken into account on selection. Crop rotation of five years is advised.
Harvest starts with first cut during April, but more likely May and thereafter the cutting frequency should be approximately forty days. Cuts should be taken on the setting of the flower buds. At this stage the crop is at its highest protein level and least fibrous, hence maximum nutritional value.
Lucerne has low soluble carbohydrate levels which could lead to fermentation problems so a silage additive is strongly recommended. Also, a good wilt is greatly desirable raising the soluble carbohydrate concentration in the remaining sap. Cut the crop to leave a stubble of eight to ten centimetres. The wilting period is of prime importance as excess drying can result in loss of leaf leaving stalks only. Equally insufficient wilting naturally leads to excessive effluent problems. It is best to allow the top of the swarth to dry out while the centre of the swarth is still moist.
At the end of its life it leaves a nitrogen rich soil of which a subsequent crop of wheat for example can require a great reduction in applied nitrogenous fertiliser. It has also been suggested that some nitrogenous benefit can be seen up to three years later.
Altogether, lucerne is a highly digestible, high protein, drought resistant forage with an excellent mineral content coupled with nitrogen fixation quantities and the ability to produce home grown protein. Varietal choice is of great importance especially in Scotland for winter hardiness. Priority must be given to a variety with good dormancy figures. That refers to cold tolerance. Typically for Scotland select a variety with a figure of one to three or four for dormancy.
To summarise, lucerne produces a fresh yield of thirty-five to forty tonnes per hectare per year and a dry matter yield of ten to fifteen tonnes per hectare per year. Dry matter of thirty percent depending on stage of harvest which can reach forty percent and on occasions with big bale preservation has been recorded as high as fifty percent. Also, crude protein of seventeen to twenty-two percent and digestibility of seventy D, ME nine to eleven mj/kg DM and rich in minerals and vitamins due to its deep tap root system.
A soil test is essential before considering sowing a crop of lucerne. pH must be 6.5 to 7. Trace elements are important particularly molybdenum and boron. Phosphate, potash and calcium must be at good levels, also sulphur which is important in protein production and magnesium which is required for chlorophyll synthesis. Finally, the sowing process is of prime importance. A minimum soil temperature of ten degrees centigrade and adequate available moisture. A fine firm tilth and seed broadcast or drilled not more than one centimetre depth. The establishment phase as previously referred to is very slow and should be well over seen. Lucerne is a forage crop highly worthy of consideration where required conditions are available.
