Lupin essentials – growing a successful lupin crop

Page last updated: Tuesday, 15 May 2018 - 1:53pm

Sowing rate

The recommended plant density for narrow-leafed lupin crops is 40-45 plants per square metre. Trials have shown, however, that optimum plant densities change depending on location and season. There is usually little or no yield penalty if plant densities are higher than the recommended range up to 70 plants/m2 but yield losses can be substantial if plant populations decline below 40 plants/m2. Plant density does not only affect yield. Research has shown that keeping lupin crop density high:

  • Substantially suppresses weed growth and reduces the effects of competition on the crop.
  • Reduces brownleaf spot and cucumber mosaic virus
  • Allows the crop to compensate for poor establishment due to sandblasting non wetting soils and root diseases.
  • It is usually easier to harvest dense crops.
Table 1 Sowing rate (kg/ha) required to achieve 45 plants/m2 - assuming 90% establishment rate
Germination rate (%) Lupin seed weight 140g/1000 seeds Lupin seed weight 160g/1000 seeds Lupin seed weight 180g/1000 seeds
70 100 114 129
80 88 100 113
90 78 89 100

Row spacing

Wider rows (50cm and greater) are more likely to yield better than narrow rows (18-25cm) in the warm dry environments of the medium and low rainfall northern wheatbelt. Significantly there is no yield penalty going wider.

Narrower rows are most likely to yield better in cooler longer season environments such as the Lakes district and areas further south. In situations where terminal drought is not severe and yield potential is very high, crops in 50cm rows tend to yield less than those in 25cm rows.

Seeding depth

Sow seeds 3-5cm below the soil surface.

Sowing very deep, below 5cm, will reduce the occurrence of pleiochaeta root rot. Shallow sowing (2-3cm) will reduce rhizoctonia hypocotyl rot disease. Because the ideal seed depths to avoid these two diseases are incompatible, a compromise is needed, hence the recommendation of 3-5cm. Seed should never be sown deeper than 7cm as establishment is very uneven and weak.

Inoculation

Lupins and other legumes have the ability to fix their own nitrogen. Rhizobium are required for nodulation and nitrogen fixation by lupins. All lupins sown in a paddock for the first time should be inoculated with rhizobium. On acid soils (pH below 6.5) once a well nodulated lupin crop has been grown in the paddock, a lupin crop will not need to be inoculated for the next five years.

If more than five years has passed, seed should be inoculated. On neutral and alkaline soils (pH above 6.5), the rhizobium do not survive in the soil for long, and seed must be inoculated every time a lupin crop is grown. Lupins should be inoculated with Group G inoculant. Serradella inoculant (Group S) is also compatible with lupins and can be used as a substitute if necessary.

Fertiliser

Use soil test or paddock history to determine fertiliser rates. Drill phosphate at seeding. Banding of phosphate below the seed can increase yields on some soils, particularly those with high phosphorous retention. If needed apply potassium within four weeks of sowing. On potentially manganese-deficient soils (mainly light sands), manganese can be applied as manganese super deep banded under the seed; alternatively it can be applied as a spray when first pods are 2.5cm.