Because of the problem of bloat, the use of lucerne in the form of hay is a popular practice in South Africa. Unpredictable thunderstorms may hamper the process, however, especially in summer rainfall areas, as they reduce the quality of the hay. Short-term weather forecasts should be obtained and, if sunny weather is predicted for the following 4-5 days, the process can begin.
Lucerne hay is cut with a rotary mower or sickle bar mower, usually at the early flowering stage.
The cut material is left on the lands for 3-4 hours to wilt, after which it is raked into windrows to dry. This limits the processes of respiration and the growth of fungus. After 2-4 days the lucerne can be baled, and it must be removed from the lands as soon as possible after this.
By using a crimper, water loss is speeded up, and risks reduced. It also reduces leaf drop.
Water availability and temperature, as well as the dormancy of the cultivar, greatly influence the productivity and survival of lucerne, as does the choice of a cutting schedule suitable for the region.
The potential number of cuts under irrigation can vary from 2-12 per season, depending on dormancy. Cutting schedules are based on the growth stage, fixed cutting intervals, or development of regrowth on the crown.
These different criteria lead to differences in yield and quality but, when cutting is determined by the growth stage, the plant itself is used as the indicator and in general a more constant yield and quality is obtained within each cultivar and over several seasons and in different localities.
Producers often use a combination of factors in scheduling hay making.
The yield of stems increases linearly between the early vegetative and the late flowering stages, while leaf yields increase until the early flowering period.
The quantity of stems and leaves is equal at early flowering stage, but by late flowering 60% of the total yield consists of stems and only 40% of leaves.
It is generally known that the quality of lucerne hay drops as the plant matures.
This drop is largely due to the increasing stem:leaf ratio and to an increase in the fibre content of the stems.
Protection of the leaves during hay making is necessary, as leaves contain more nutrition than stems.
During the early flowering stage, the leaves contain a greater concentration of digestible nutrients, proteins, fats, potassium, fibre, total non-structural carbohydrates, P, Ca, Mg, Al, Fe, Sr, B, Cu, Zn and Mn, than the stems.
Stems have more sugars, fibre, K and Cl. The digestibility and protein concentration of stems drops more rapidly with maturation than that of the leaves.
The highest concentration of nutrients is usually obtained when lucerne is harvested at an immature stage, with the highest concentration per leaf area at 10% flowering.
In moist areas, the amount of digestible nutrients, protein and minerals, drops after early flowering because of leaf loss due to shade, age and diseases.
In drier areas, where leaf diseases are fewer, the maximum amount of nutrients is still available up till 50% flowering.
The use of desiccants to dry hay more quickly, is a promising new method. However, it will only become economical when hay is priced according to quality.
Losses due to overheating, mould and breakdown of carbohydrates in lucerne hay that has been baled too damp (more than 20% moisture content) can be reduced by reducing plant and microbial metabolism. NH or organic acids are used to gain control of these and to preserve the hay.
Unless these losses are controlled, they will begin at 22% moisture and by 35-45% moisture one can expect total loss.
Hay with 18% moisture can still be protected by adding small quantities of propionic acid.
The energy necessary for regrowth of lucerne after cutting is stored in the form of non-structural carbohydrates in the roots and crown or in the remaining leaves and stems.
There is generally a cyclic pattern in the storage and use of non-structural carbohydrate reserves in the roots.
These are used during the early stages of regrowth after winter rest or cutting, then build up again in roots and crowns when the plant is mature and in full bloom, but generally reach a maximum at early flowering stage.
Carbohydrates accumulate in autumn in those cultivars which undergo dormancy.
This is a reaction to the reduction in daylength and temperature. These stored non-structural carbohydrates are the main source of energy during winter.
Frequent harvesting of immature lucerne (vegetative or bud stage) or harvesting in the autumn, prevents sufficient vegetative regrowth to replace the reserves of non-structural carbohydrates and leads to their depletion in the roots.
This leads to a decline of the stand and loss of productivity. It is a good practice to allow the last growth of the autumn to develop to full flowering to restore reserves, and only cut again in the spring.
High levels of carbohydrate allow rapid recovery after harvesting or after winter.
Regrowth after the second and later cuts may have already begun when the lucerne begins flowering. If harvesting is then delayed, the growing points needed to produce the next harvest are cut off, and the regrowth retarded.
Yield, quality and persistence of the stand are important factors to be taken into account in the development of a profitable harvest-management program. Increasing appreciation of the value of high-quality lucerne in terms of potential savings in energy and protein supplementation, have resulted in reconsideration of harvest-strategies.
The choice of harvesting schedule begins with the decision as to what quality feed is required.
Producers who want only high quality lucerne will prefer a shorter stand and lower yield. The number of cuts, cutting date, stage of maturity, interval between cuts and cutting height are factors to be taken into account in a harvest schedule.
The relation between the stage of maturity and yield, quality and sustainability makes it clear why the growth stage is often used to decide when to cut.
Cutting at a specific growth stage also makes it possible to take into account the variation due to various environments and growth tempos.
Lucerne must be allowed to grow out to full flowering once a year.
If it is under irrigation, then the best time for this is from the middle of May to the middle of June.
Regrowth left on the plant through the winter protects the crown and the growing points against cold damage.
It is unlikely that there will be serious losses of leaf material from leaf spot, as the cooler conditions of winter will inhibit its spread.
The lucerne will probably be in full flower from the end of July till the middle of August, at which stage the harvesting process can be resumed. If there is a likelihood of the lucerne being damaged by frost, as on the Highveld, the resting period must either begin sooner or else the first growth cycle in the spring must be left to go to flowering. The critical factor is that lucerne must be allowed to flower at least once a year.
Dryland lucerne must be allowed to grow out at the end of the summer, from February to late March. When the leaves begin to drop as a result of lack of water, the lucerne should be cut to limit further loss. If it is necessary to cut the lucerne because of water shortage before it has fully flowered, then the spring growth should be allowed to grow out.
Damage to young growth should be kept to a minimum. The less often a tractor is driven over the land, the less damage it will cause.
It is ideal to use machinery that will cut and load the lucerne in fewer operations. The cut lucerne is then removed from the land and dried, baled, milled and/or stored.
Losses of quality and quantity
Poor quality hay may be the result of rain damage. The longer the hay remains on the land, the greater the loss of leaves.
If lucerne is ensiled straight off the land, leaf loss may be as low as 2-4%, while if it is made into hay, losses may run to 20-40%.
The critical level of moisture is determined by storage conditions, temperature and ventilation.
It is generally recommended that lucerne be dried to <15% moisture content before the hay is baled.
This process can be advanced by use of rollers, crimpers and cutters, and the drying time may be reduced by as much as 30%. Crimping of lucerne can shorten drying time by up to a day.
Shortening the time on the land has a considerable influence on leaf loss, and the hay quality is greatly enhanced by a short drying period.
Lucerne is traditionally used to make hay, but the weather conditions may sometimes be unsuitable.
Silage is an alternative means of retaining nutritional quality.
Ensiling lucerne has many advantages over making hay, when it comes to retaining quality.
Weather conditions have little influence on the process. It also allows the lucerne a longer regrowth period if the cut lucerne is immediately removed from the field.
Lucerne silage can be divided into three types: high moisture silage made immediately from the cut lucerne while it still has a moisture content of 70%; wilted silage, which has 60-70% moisture, and low moisture silage with a moisture content of 40-60%.
Lucerne silage has more protein, calcium and phosphorous than some other silages, but less total digestible nutrients.
Where it is used as a substitute for maize silage, the rations must be supplemented.
It must be remembered that full-grown lucerne has a lower energy and digestible protein content than young lucerne. It therefore have a lower netto energy thus a lower feed value.
The principles for making lucerne silage are the same as for maize silage, except that maize has a higher concentration of fermentable carbohydrate which makes it unnecessary to supplement carbohydrate.
Lucerne, which is a high-protein feed, requires extra carbohydrate for good fermentation.
Principles of preservation
After lucerne has been harvested, it continues to respire actively for a short while. In this process, the plant enzymes and aerobic bacteria use the available carbohydrates to form heat and carbon dioxide.
As a result, extra carbohydrate is necessary to allow the bacteria to form the lactic acid, acetic acid and proprionic acid that will preserve the silage.
This they do by lowering the pH to 4.2 or lower. The low pH inhibits the further growth of bacteria and the activity of enzymes. The process takes 2-3 weeks.
The most critical time in making silage is the first couple of hours after storage.
Lengthy exposure to air can result in the loss of available carbohydrates.
This will prevent sufficient lactic acid forming, and the resulting high pH encourages the breakdown of plant material.
Undesirable bacteria of the genus Clostridium grow under these high pH conditions, forming butyric acid, ammonia and various amino acids associated with poor silage quality.
Loss of nutrients
In order to prevent seepage from the silo and the production of poor quality silage, the lucerne must remain in the windrows until moisture content is about 65%.
If it is higher than 65%, chemical preservatives must be added. Milled maize, barley, wheat, oats or molasses can be used to provide carbohydrates for fermentation.
Minerals such as formic acid, proprionic acid and lactic acids can be used as alternatives to lower the pH.
Lucerne silage can be made by traditional methods, i.e. in silos, bunkers, plastic bags or by wrapping it in plastic.
Problems with removing air from the plastic bags has often led to low quality silage or total loss.
Lucerne is an outstanding legume for grazing because of its high yield, quality and wide adaptability to different climates and soil types.
It is a reliable and economical source of protein because it is independent of the N-concentration in the soil.
The protein is of outstanding quality with a good amino acid profile, especially for non-ruminant animals such as pigs, poultry, ostriches and horses.
Lucerne is an excellent source of Ca, Mg, P, carotene and vitamin D.
Lucerne grazing is mainly used in the following regions in South Africa: South Western Cape, Northern and Eastern Cape, eastern Free State, North West Province and Mpumalanga.
It is rarely cultivated in the sour, high-potential areas of KwaZulu- Natal because of the high incidence of leaf diseases and the low pH of the soil.
Lucerne requires a rotational grazing system to ensure good stands at 2-3 years old.
It should be grazed as rapidly as possible for 7-10 days when in the late vegetative stage.
This should be followed by a rest period of 40-50 days before animals are again allowed on it.
Grazing differs from mechanical harvesting in that the photosynthetic material is removed gradually over a period of time, and also removal is not as complete.
Various factors influence the persistence of lucerne under grazing, i.e. the length of the grazing and resting periods, their timing with regard to growth, developmental stage and weather, as well as the grazing pressure. The time interval between grazing periods is the most critical factor.
If the rest period is too short there will be a loss of lucerne plants, and if it is too long, there will be a drop in quality linked to increasing stem:leaf ratio.
The deciding factor is the adaptability of the cultivar.
The more dormant the cultivar, the more the crown is protected, and the more the lucerne is resistant to damage-related crown- and root-diseases.
The lifespan of the sward is determined by the rate of death of the plants, and this is the result mainly of root diseases.
There are cultivars with broad crowns that are grazing tolerant, but these are often from such a low-dormancy group that they have a very low yield under SA conditions.
Most of these cultivars are also not resistant to the heavy grazing that is often experienced with sheep.
SA Standard, a landrace which has developed under South African conditions, has a unique adaptation in that the crown has developed into a cigar-shaped diffuse organ which can form side branches from as deep as 15 cm below ground level.
This characteristic makes this possibly one of the most grazing-resistant semi-dormant cultivars available.
SA Standard has a dormancy of 6, compared to most other grazing cultivars which have a dormancy of 2 or 3.
Even non-dormant cultivars can be grazed with success. In Argentina millions of hectares of CUF 101 are successfully grazed. The secret is in the resting period.
It is not the general practice in South Africa to plant lucerne together with a grass component.
Apart from the fact that chemical weed control is impossible, the following are the main reasons for this:
- Where lucerne is chiefly grown for hay, mixtures affect application of fertiliser, harvesting methods and quality.
- Where it is grown for grazing, mixtures make management difficult in terms of frequency of grazing, fertilisation, and the eventual effect on the botanical composition of the pasture.
Because more vigorous and long-lived lucerne cultivars have been developed, as well as improved management practices, it is seldom the case today that the grass component predominates over the lucerne after a couple of seasons.
The ideal legume:grass ratio of 30:70 in a mixture is determined by many factors, of which choice of species, planting date, sowing density, stand density, planting method (rows vs. broadcast), soil fertility, timing and height of grazing, are probably the most important.
From a plant-physiological point of view the tendency of the lucerne and the grass to compete for light, water, and nutritional elements, are further factors deter-mining the success of a mixture.
The cultivation and management of mixtures is therefore complex, more so as research results in SA are also limited. The advantages of establishing mixtures cannot be denied:
- Yield is higher with lucerne mixtures than with pure lucerne
- Nitrogen fixed by Rhizobium is available for the grass component (especially under grazing), and little or no N supplementation is needed during the season.
- The quality of feed intake is more balanced, as the lucerne component provides the protein and the grass component the roughage requirements of the ruminant.
- There is less danger of bloat because of the higher roughage-fibre intake from the grass component.
Regions characterised by warm sunny summers with little or no summer rain are ideal for production of lucerne seed.
Such a climate encourages the flowering of lucerne and provides favourable conditions for bee pollination and ripening of the seed, which must occur under dry conditions to prevent it becoming discoloured.
Successful lucerne seed production is influenced by the following factors, among others:
- Efficient pollination
- Thorough insect control
- Correct irrigation during the flowering periods
With the exception of weather conditions, the producer has a reasonable degree of control over factors influencing seed production.
In South Africa most lucerne seed is produced in the lower Orange River, Little Karoo and Calvinia districts.
Producers of certified seed must register with the Directorate Plant and Quality Control (Dept Agric) according to the Plant Improvement Act.
Information about this matter will be provided by the company with which you sign a contract.
Choice of soil and preparation for seed production
Well-drained soil with few soluble salts and the potential for roots to grow to 1.5 m or more, is ideal for production of lucerne seed under irrigation.
Deep clay soil, clayey loam or sandy clay soil with a high water retention capacity is preferable to sandy soil.
Soil with hard stony layers or shallow clay layers near the surface should be avoided.
Uniform soil texture will reduce the differences in development between plants.
Problems with weeds and the cost of combating them can be reduced by well-planned rotation systems and cultivation.
Land infested with perennial grass weeds such as Bermuda grass/kweek (Cynodon dactylon), Johnson grass (Sorghum sp.), etc., should be avoided, or else the weeds brought under control before sowing time.
In most lucerne seed producing areas, lucerne is sown in the autumn. This gives the maximum seed yield in the first year of production.
Everywhere in the world lucerne planted for seed is sown in rows, as this gives the highest seed production. The low seed production in dense stands can be partially attributed to low production of nectar, lack of attraction for pollinators and increased abortion of flowers.
Other advantages for row sowing are:
- Plants grow more erect and are therefore more accessible to pollinators, there is more light, and soil and air temperatures are higher early in the season.
- Flowering time is about 10 days earlier.
- There is less lodging of plants and the lower humidity reduces the incidence of leaf diseases and the amount of waterdamaged seed compared to broadcast stands.
- There is less loss of flowers and seeds.
- It facilitates spraying against insects and weeds.
- There is greater flexibility in the management of irrigation.
- Less seed is needed to sow the same area.
The following spacing is recommended for single rows:
- Sandy soil 20-150 cm
- Loamy soil 75-100 cm
- Heavy loam to clay 60-90 cm
It is recommended that the wider spacings should rather be used.
Most producers use 1-1.5 kg seed per ha with the aim of getting 3-7 plants per 300 mm in a row. A sowing density of 300 g/ha has, however, been used with great success.
Fertilisation will mainly depend on the fertility of the soil and the soil analysis. Small quantities of nitrogen and phosphate (15-20 kg/ha) can be applied at or before planting time to encourage growth and development of the young plants, which are not yet at a stage where they can fix sufficient N for themselves.
This is recommended only for lucerne intended for seed production, with a limited lifespan, not for hay or grazing. Most hair roots occur in the upper 15-30 cm of soil, and these are responsible for 85% of the nutrient uptake of the plant. Foliar feeding has a relatively small influence on seed production.
The land must be surrounded by an isolation area which:
- If it is intended to produce basic seed, must be at least 200 m wide where the area intended for production is 2 ha or less, and at least 100 m wide where the area intended is more than 2 ha, and
- If it is intended to produce certified seed, must be at least 100 m wide where the area intended for production is 2 ha or less, and at least 50 m wide where the intended area is more than 2 ha
Such an isolation area must be free of any plants of any lucerne cultivar or any species of Medicago which flowers at the same time as the plants on the piece of land concerned, unless:
- In the case of planned production of basic seed, these plants have been established from breeders seed of the same cultivar, and
- In the case of planned production of certified seed, these plants have been established from basic seed of the same cultivar.
Management of Established Stands
Whether lucerne intended for seed production should be irrigated is determined by soil texture and depth, rainfall, evaporation, temperature, length of growing period and cultivation practices.The highest production is obtained when irrigation practices prevent stress and encourage slow but sustained growth throughout the growing period without excessive stimulation of vegetative growth.
There must be sufficient water through the spring and summer to prevent stress while the flowers are being pollinated and the seed is ripening.
The seed producer must know the water-holding capacity of his soil and its fertility potential.
Heavy soil with a good water-holding capacity will give a good seed yield with a single irrigation just before flowering, while lighter soil will need a second irrigation during flowering.
The flowering stage is critical and it is here that moisture can determine the harvest.
Factors such as pollination, abortion of flowers and seed weight are directly linked to correct irrigation management.
Lucerne plants draw their water from a soil depth of 1.2 m, but the best results in seed production are obtained when water absorption up to 0.5 m is well controlled.
Overhead irrigation can be used successfully in seed production, especially on sandy soil where specific volumes of water must be given.
Seed producers must irrigate lucerne till before flowering, and again after pollination is complete. If used during flowering time, overhead irrigation can so reduce pollination that losses of up to 15% may result.
After seed has set there is need to guard against too high a moisture content in the air, which may result in seed damage. Once seed is nearly ripe, irrigation should be completely stopped.
Because there may be more than one cycle of flowering and seed formation, it is best to use soil that can provide sufficient water for an entire growing season.
Weeds reduce the stand and the yield, complicate harvesting, increase cost of cleaning and may contaminate successive crops.
It is simpler to control weeds when lucerne is still at the seedling stage.
The presence of weeds may result in downgrading and consequent financial loss. The most important weeds to note are dodder (Cuscuta), tongblaar (Plantago), wild oats (Avena), ryegrass (Lolium), hondebos (Chenopodium), misbredie (Amaranthus), kiesieblaar (Malva), predikantsluis (Bromus) and stinkblaar (Datura).
The most common insects found on lucerne are the lucerne caterpillar, the American bollworm, sand mite, earth flea and various types of aphids.
Good pollination comes before a good harvest.
Honey bees are the only insects in South Africa which can successfully pollinate the lucerne flower with its trigger mechanism.
Only about 2% of pollination is the accidental result of other insects.
The timing of placement of the hives in the lands is very important because early placement may result in the bees searching for other sources of food. Too late, and many flowers will wither before they can be visited.
After the lucerne is cut in the spring, the regrowth will begin flowering within 30-40 days, depending on cultivar.