When to Start Sowing Lucerne
Sowing lucerne (Medicago sativa), also known as alfalfa, is best undertaken when soil temperatures consistently reach approximately 10-12°C. This typically occurs in spring, from April onwards in many parts of the UK, extending into early summer. Avoid sowing too early, as cold, wet conditions can severely hamper germination and lead to seedling loss. Late summer sowing is also possible, but only if there is sufficient time for the plants to establish before the first hard frosts arrive, usually by mid-August at the latest. This timing ensures good root development before winter dormancy.
- Spring is the primary sowing window.
- Soil temperature above 10°C is crucial.
- Avoid late summer sowing if frost risk is high.
- Ensure adequate time for establishment before winter.
Choosing the right moment is paramount. Lucerne requires a decent growing season to establish a strong root system, which is key to its resilience and productivity in subsequent years. Sowing too late in the season means the young plants won't have developed the necessary vigour to survive the colder months, potentially leading to a failed crop. Likewise, sowing into soil that is still too cold and damp can result in poor germination rates, increased susceptibility to disease, and weak, spindly plants.
Spring Sowing Advantages
Spring sowing offers the longest possible growing period for the young lucerne plants. This extended period allows them to develop a robust taproot, which is essential for drought tolerance and longevity. The increasing daylight hours and warming temperatures in spring create ideal conditions for rapid germination and early growth, helping the crop get off to a strong start. This typically results in a more productive and persistent stand of lucerne.
Late Summer Sowing Considerations
While spring is generally preferred, a carefully timed late summer sowing can be an option in some regions. This is usually only advisable if you are certain the crop will have at least 6-8 weeks of good growing weather before the onset of autumn frosts. The goal is to allow the plants to establish a root system, even if top growth is limited. This approach can be useful for filling gaps in a rotation, but carries a higher risk of failure than spring sowing due to unpredictable weather patterns.
Preparing the Ground for Lucerne
Lucerne thrives in well-drained, fertile soil with a near-neutral pH (ideally between 6.5 and 7.5). Poor drainage is the most common cause of lucerne failure, so preparing the seedbed meticulously is essential. This involves deep cultivation to break up any compaction, as lucerne develops a deep taproot. The soil should be brought to a fine, crumb-like tilth, similar to what you would prepare for sowing vegetable seeds, but without being overly powdery, which can dry out too quickly.
Soil Testing and pH Adjustment
Before sowing, it is highly recommended to test your soil's pH. If the pH is too low (acidic), lime should be applied in the autumn or early spring, several weeks before sowing, to allow it to react with the soil. Incorporating well-rotted manure or compost can improve soil structure and fertility, but avoid applying fresh organic matter directly before sowing, as it can hinder germination. If growing lucerne for forage, consider the benefits of inoculating the seed with the correct rhizobia bacteria strain specific to lucerne, especially if it has not been grown on the site for several years. This ensures efficient nitrogen fixation.
Creating the Ideal Seedbed
A firm seedbed is critical for good seed-to-soil contact, which is vital for germination. After initial cultivation, the soil should be rolled or compacted. The final stages of preparation should involve light raking to create a fine surface tilth. The aim is a surface that is firm underneath but has a shallow layer of loose soil on top, protecting the delicate emerging seedlings from drying out. This meticulous preparation sets the foundation for the plant's deep root penetration and overall health, much like preparing a bed for sowing bulbs requires a fine, weed-free finish.
Weed Control
Lucerne is a slow starter and can be outcompeted by weeds. Effective weed control is therefore a significant part of seedbed preparation. Where possible, use stale seedbed techniques: cultivate the land, allow weeds to germinate, and then lightly cultivate again before sowing the lucerne. This process can be repeated a couple of times. For larger areas or where weed pressure is high, pre-emergence herbicides may be considered, but always follow manufacturer instructions and ensure they are suitable for lucerne crops.
How to Sow Lucerne Seed
Sowing lucerne seed is typically done using a seed drill for even distribution and correct depth, but can also be achieved by broadcasting. The recommended sowing rate is generally between 10-20 kg per hectare (approximately 4-8 kg per acre), depending on seed size and intended use. For smaller areas, this translates to about 1-2 grams per square metre. It is crucial to sow the seeds at a consistent depth of 1-2 cm. Planting them too deep will make it difficult for the seedlings to emerge, while sowing too shallow can lead to them drying out.
For the most even spread when broadcasting by hand, divide your seed into two equal halves and sow in perpendicular directions across the area.
Using a Seed Drill
A seed drill offers the most precise method for sowing lucerne. It ensures seeds are placed at the correct depth and evenly spaced, which is vital for optimal establishment and yield. Set the drill according to the manufacturer's recommendations for the specific seed type and desired rate. After drilling, a light pass with a roller or a drag harrow can firm the soil over the seeds, improving seed-to-soil contact and aiding germination.
Broadcasting Seed
If a seed drill is not available, lucerne seed can be broadcast by hand or with a broadcast spreader. It is essential to ensure an even spread to avoid clumping and bare patches. After broadcasting, the seed should be lightly covered with a rake or chain harrow, followed by a roller to firm the soil. This method is generally less accurate than drilling and may require a slightly higher seed rate to compensate for uneven distribution.
Depth and Spacing
The depth at which lucerne seed is sown is critical. A depth of 1-2 cm is ideal. Too deep, and the energy reserves of the seed may be depleted before reaching the surface. Too shallow, and the seed is vulnerable to drying out, bird predation, or being washed away by heavy rain. Achieving consistent depth across the sowing area is key to a uniform stand, much like ensuring all vegetable seeds are at their optimal planting depth for consistent germination.
Aftercare and Establishment
Once sown, lucerne requires careful management during its establishment phase, which can take up to two years to reach full potential. The first year is critical for developing a strong root system. Regular mowing is often recommended, but the timing and height are important. Mowing too frequently or too low in the first year can weaken the young plants and hinder root development. If the lucerne is grown for forage, the first cut is typically delayed until the plants are well-established, often around flowering stage.
Lucerne's longevity and resilience are directly proportional to the care taken during its initial establishment phase.
First Year Mowing/Cutting
For forage production, the first cut in the first year should ideally be delayed until the plants are at the early flowering stage. This allows for maximum root development. Subsequent cuts should be timed to leave at least 5-7 cm of stubble to help the plant regrow and protect the crown. If the lucerne is being grown as green manure or for seed production, mowing may be different or omitted entirely, depending on the specific objective. For general purposes, aim to cut before significant weed seed set occurs.
Grazing Management
If grazing is intended, lucerne is best grazed by sheep or cattle. Rotationally grazing is highly recommended to prevent overgrazing and allow the plants to recover. Ensure that grazing is not too close to the ground, leaving a residual height of at least 7-10 cm. Animals should be introduced gradually, especially if they are not accustomed to lucerne, as it can cause bloat if consumed in excessive quantities without proper management. Providing a fibre source like hay can help mitigate this risk.
Ongoing Care
As lucerne establishes, its deep taproot makes it very drought tolerant. However, in prolonged dry spells, especially during the first year, supplemental watering might be beneficial if feasible. Continue to monitor for weeds and address them promptly, particularly in the early stages. Established lucerne stands can last for many years, providing consistent yields of high-quality forage or contributing significantly to soil health through its nitrogen-fixing capabilities and deep root structure, similar to how deep-rooted plants contribute to soil structure.
Alternative Approaches and Considerations
While direct sowing is the standard method for lucerne, understanding alternatives and related concepts can enhance success. For instance, if establishing a cover crop or improving soil, similar principles apply to sowing other types of seeds, such as vegetable seeds or even propagating from cuttings, although lucerne is almost exclusively grown from seed. The 'meaning sowing' in agricultural contexts refers to the careful and intentional act of placing seeds into the ground with the expectation of germination and growth, a process demanding precision for any crop.
Intercropping and Companion Planting
In some horticultural settings, understanding companion planting can be beneficial. While lucerne is not typically companion planted in small gardens like herbs or flowering plants, in larger agricultural systems, its nitrogen-fixing properties can benefit subsequent crops. However, direct sowing lucerne alongside other crops on a large scale is uncommon due to its specific growth requirements and competition. For home growers, focusing on sowing vegetable seeds or propagating plants like lemon seeds or apple seeds might involve different strategies, often requiring seed scarification or specific germination conditions.
Seed Quality and Types
The quality of lucerne seed is paramount. Always source certified seed from reputable suppliers to ensure high germination rates and varietal purity. Different cultivars exist, bred for specific climates, pest resistance, or yield potential. While the act of sowing lucerne seed is straightforward, the choice of cultivar can significantly impact long-term performance. This is akin to selecting the right variety of vegetable seeds for your local climate or choosing specific seeds for propagation like how to grow mango from seed, where variety choice is key.
Lucerne as Green Manure
Lucerne is an excellent green manure crop. Its deep root system breaks up compacted soil, improving drainage and aeration, while its nitrogen-fixing bacteria enrich the soil with essential nutrients. When ploughed back into the soil after a growing season, it adds substantial organic matter. This practice benefits the soil structure and fertility for future crops, much like incorporating compost or other organic matter. The process of sowing lucerne for this purpose follows the same principles as for forage, focusing on healthy establishment to maximise biomass production.