Lupin Agronomy

When the correct variety has been chosen, the second important factor with Lupins, is getting the agronomy right. The agronomy of Lupins is very simple, and is generally very low on inputs.

For all three types of Lupin the agronomy is similar, although there are some differences in that White Lupins are often sown slightly earlier in late March, whilst Blue and Yellow Lupins are sown in early April. The other notable difference is in weed control. Semi-determinate Lupins are taller and more aggressive in their growth habit, which generally means that they are better at outgrowing any weed competition, whereas fully determinate varieties do not branch and are shorter.

Sowing rates & target populations

Sowing rates can vary tremendously from Lupin to Lupin, depending on species, variety, and growth habits. Fully determinate Lupins do not branch, so to cover the ground, the sowing rate must be set for a high plant population per square metre. Semi-determinate varieties vary between the different species in ground covering ability, so sowing rates are adjusted accordingly.

The table below shows the different sowing rates and population targets of different types:

Variety      Species Type  Growth Habit  Target Population plants/ m²Typical Sowing Rate kg/Ha (kg/acre)
DietaWhiteSemi-D40 plants185kg/Ha (75kg/acre)
VolosWhiteSemi-D40 plants185kg/Ha (75kg/acre)
PootallongYellowSemi-D50 plants100kg/Ha (40kg/acre)
IrisBlueSemi-D55 plants110kg/Ha (45kg/acre)
Haags BlaueBlueDeterminate65 plants150kg/Ha (60kg/acre)

Sowing Date

The ideal sowing date for White Lupins is from late March onwards, whilst Blue and Yellow Lupins are sown from early April onwards. Growers who are planning to harvest with a combine can allow this to slip by three or four weeks and still expect to combine in reasonable time, however beyond this, the combining date can be compromised. For growers who intend to silage the crop, sowing date is less critical and they can sow up to the 15th of May, although a change of variety may be necessary.

Sowing Depth

Sowing depth should be 1 - 2 inches (2.5 - 5.0 cm) and growers should aim for a fine, firm, moist seedbed, free from compaction. Although seed can be broadcast and harrowed in, it is preferable to use a seed drill where possible, and commercial experience suggests that all drill makes, types and ages are suitable. The drill should be calibrated to take account of seed size, seed dressing and the inoculant, which will all affect seed flow.

Inoculation of Seed

Lupins are a legume and will fix large amounts of atmospheric nitrogen, however the strain of rhizobium bacteria that allows Lupins to do this is not generally found in UK soils. As a result, we have a choice of either applying large quantities of nitrogen fertiliser, which is expensive, or applying the correct strain of rhizobium to the seed and allowing the plant to make it's own. For this reason, it is always preferable and necessary for UK growers to use an inoculant. The good news is that Soya UK can now offer growers pre-inoculated seed. Pre-inoculation is a technology exclusive to Soya UK Ltd and simplifies the drilling operation through avoiding the need for the grower to inoculate seed as it goes into the drill.

Nitrogen Policy

Although lupins are a nitrogen-fixing plant, the root nodules need about five weeks before making an active contribution and the seedling crop will use 25kg/Ha of nitrogen in this period. It is thus advisable for growers to ensure that there is around 25kg/Ha of nitrogen available to the crop at sowing. Excessive nitrogen levels in the seedbed can be a negative factor, since this can delay the formation of the nodules and lead to a temporary nitrogen shortage later on when the crop has used all residual nitrogen. This effect is most damaging if it coincides with the onset of flowering.

Phosphate, Potash, Sulphur & Magnesium

Lupins remove 40-60kg/Ha of Phosphate (P2O5), 40-60kg/Ha of Potash (K2O), and 20-40kg/Ha of Sulphur, depending on yield. It is normal practice to either put this in the seedbed, or replace it later in the rotation if the indices are high enough to allow a "fertiliser holiday".

Typical recommendations are as follows:

Soil IndexPhosphate (kg/ha)Potash (kg/ha)Sulphur (kg/ha)
0608030
1405020
220300
3000
4000

Deficiencies & micro-nutrients

The most commonly observed deficiencies in UK-grown Lupins are, Phosphorus, Potassium, Manganese, Sulphur, and Magnesium, with Iron deficiency in yellow and blue Lupins where grown on soil pH above 7.0.

Advances in Soil pH Adaptation

There is a myth among growers and even academics in the UK that we cannot grow Lupins on a soil pH above 7.0. Traditionally this was true, and for many Blue and Yellow varieties it is still advisable not to exceed a pH of 7.0. It is also true to say that the problems associated with growing Lupins on high pH soils, has more to do with the availability of free calcium in the soil which inhibits the Lupins ability to metabolise iron, and so the symptoms of high pH soils usually manifest as a chronic iron deficiency which cannot be cured. The good news for producers is that plant breeders have been breeding for high pH tolerance, and the new varieties of White Lupins such as Dieta and Volos come from such a programme. This is important, since one of the big opportunities for UK Lupins, is to produce the crop as a cash crop in our arable regions such as East Anglia where soil pH's are frequently between 7.0 and 7.5. Commercial experience in the UK has shown that a pH range for Blue & Yellow Lupins of 5.0 - 7.0 is advisable, whilst for the White Lupins marketed by Soya UK Ltd, a range of 5.0 - 7.8 is acceptable, making them suitable for most arable situations in the UK.

Weed Control

Weed control has been a difficult subject in the past, with many Lupin crops becoming weedy due to lack of advice, poor advice, or poor availability of suitable chemicals. The knowledge base on chemical use has expanded very rapidly in recent years with many chemicals being tried and assessed.

Pre-emergence weed control

The crop will normally require a pre-emergence herbicide applied directly after the drill or rolls. With recent advances in the availability of agrochemicals, it is now standard practice to use a pre-emergence chemical and then follow up with a post-em spray.

Grassweed Control

For the post-emergence control of grass weeds in Lupins, there is an EAMU for the use of Aramo.

Lupin Pests

Generally, UK-grown Lupins have not suffered from any significant pest problems to date. Pigeons can be a problem for a short period at establishment and growers should keep them off until the first true leaf has appeared and the crop is well established, after which the pigeon threat goes away. Rabbits and hares can also be a problem for a short period at establishment where their populations are high. Growers should fence them out if they are likely to be a serious problem, but they are not a major pest of Lupin. Slugs, like the rabbits and hares, are only a problem in specific scenarios where the pest pressure is very high. In practice it is very unusual for growers to need to apply slug pellets. There are no significant invertebrate pests (bugs, beetles, flies, grubs, etc), so for now, UK growers can effectively regard Lupins as a fairly pest-free crop.

Lupin Diseases

Generally, Lupins have not suffered from any significant diseases in the UK to date. During the 2003 season, anthracnose gave some trouble, however, the introduction of new testing arrangements, better understanding of the disease, vigilance during seed production and the use of seed dressings has ensured that the problem remains well under control. It is the very significant threat from this disease in a wet climate like the UK, which makes the farm-saving of Lupin seed so risky. In other countries there are diseases other than anthracnose, which are significant. Phomopsis, cucumber mosaic virus, fusarium, and rusts all affect crops in other countries, but have not yet been seen to any level in the UK. There is always the possibility of them becoming a factor as the crop is more widely grown, however it is widely thought that the anti-anthracnose measures already in place, will significantly reduce the threat from these other diseases. Happily, for now, UK growers can effectively regard Lupins as a disease-free crop.

Harvesting

One of the great attractions of Lupins, and a big reason why they are such an important new crop, is the fact that they lend themselves to just about any farming system in any part of the country. They have flexibility in that they can be harvested at three different stages and they can be harvested and handled using existing machinery, even with older and less modern equipment.

  • 15-18 weeks
    Crop can be wholecropped (usually in early August)
  • 18-20 weeks
    Crop can be combine harvested and crimped at around 30% (usually in mid-August)
  • 20-22 weeks
    Crop can be combine harvested dry (usually in late August or early September)

Any of these methods work well and give a high protein feedstuff which can be fed directly to stock. Harvesting is very easy whether you mow the crop for forage, or cut it with a combine. Combining is normally very quick and simple with the pods well off the ground.