One of the most frequent questions we hear when growers buy alfalfa seed concerns timing: autumn or spring? The answer from the field is that both are done. In our region alfalfa is sown in both windows, and what decides the window is often not the crop itself but the field’s place in the rotation. In this article we look at where the two windows differ, at the autumn calendar, at the weed pressure of spring sowing, at the seedbed and the rate per decare, and at the years alfalfa stays in the field. The data sheets of the varieties are on their own pages, Mirna and Central.
The rotation decides the sowing date
Alfalfa is a perennial; once sown it occupies the field for several years. The question of when to sow therefore turns, in practice, into the question of when the field becomes free. Where barley or wheat comes first, the decision is taken together with the harvest and the clearing that follows it; if the field can be prepared in time after the cereal is off, autumn sowing comes into play. With sugar beet the picture is different: the beet is lifted in December, the field is not free in autumn and the alfalfa waits for spring.
The choice between the two windows is thus shaped by the state of the previous crop. If the rotation clears the field in autumn, autumn sowing follows; if it does not, spring sowing does. It would not be right to say that one of the two periods is absolutely better than the other; each has its own calendar and its own point that asks for attention.
The autumn window and how the crop enters winter
The autumn calendar is narrow. Our recommendation for the region is to complete sowing by the middle of September; 15 September is taken in practice as the last date. In fields sown at the end of August the crop can develop far enough to give one cut before winter, and it enters winter in that state. When the calendar slips into November the picture changes: alfalfa is a delicate plant during emergence and does not find the time to complete its development before the cold arrives. In a late-sown field the problem is not the amount of seed but the number of days left to the plant.
As for winter losses, we generally do not see them where a cold-hardy variety suited to the region has been chosen. Alfalfa varieties are developed with different climates in mind; a variety selected for coastal conditions can suffer from cold when it is sown in a continental climate. With varieties selected for continental conditions, winter ceases to be the main obstacle in front of autumn sowing. The basic difference between Mirna and Central is that one is a domestic and the other an imported variety; for the choice of sowing period we have no separate recommendation for the two.
Weed pressure and water in spring sowing
The clearest difficulty of spring sowing is weeds. Alfalfa is sensitive in the seedling stage; because the young plants have not yet covered the soil, weeds establish their pressure easily. Herbicide control is carried out in this period, and after the first cut the weeds fall back; as the alfalfa recovers, the field changes hands. What matters in spring sowing is the first few weeks after emergence.
Early summer drought, contrary to expectation, causes little trouble in most fields, because alfalfa is grown mainly under irrigation. That alfalfa is difficult on a field without water is widely accepted in practice; since irrigation is applied, the hot and dry days of the seedling stage are usually not a problem. Rainfed alfalfa is not common in our region, and most of our sales go to irrigated land.
Seedbed, sowing depth and the rate per decare
Alfalfa seed is small, and this makes the seedbed the most critical subject of the crop. The field should be well levelled and the surface should stay as even as a carpet; sowing depth is around 1-2 centimetres. Seed that goes deeper emerges with difficulty, because a small seed has limited energy to reach the surface; this is one of the main causes of poor emergence in alfalfa. We recommend rolling after sowing; the roller closes the air gaps between soil and seed and makes emergence even.
Our recommended rate is in the range of 2-3 kilograms per decare; where to stand within that range is decided by the region, by the seedbed preparation and by whether the seed is drilled or broadcast. There are regional habits that go above this, and where seedbed preparation is not at the desired level more seed is usually applied. A similar picture holds in cereals; we discussed in detail where the figures come from in our article on how much seed per decare.
The number of cuts taken in the first year varies between three and five depending on management and climate, and this appears to be similar for autumn and for spring sowing. It would therefore not be right to say that the sowing period alone governs the number of first-year cuts.
Alfalfa is a lasting investment in the field. Yield rises from the first year, reaches its highest point in the third and declines from there towards the fifth; the stand rarely stays longer than five years. Since the establishment cost is spread over those years, the calculation should not be made over a single season. What follows the alfalfa belongs to the same calculation: because its roots fix nitrogen in the soil, the next crop uses that nitrogen, and in fields where cereals or industrial crops follow alfalfa the yield increase is visible to the eye. The fixing is done by bacteria on the roots; when the seed is inoculated with them, more nitrogen is fixed, and growers whose conditions allow it can carry out the inoculation themselves. The alfalfa seed we currently sell is not supplied inoculated. When the rotation and the water situation of the field are shared with us, our agronomist assesses which period and which variety suit those conditions: +90 506 101 01 50. The data sheets of the varieties can be compared on the alfalfa seed varieties page.