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Build up nitrogen with biserrula in Western Australia

Biserrula is proving a beneficial pasture legume for cereal crop rotations in Western Australia. This persistent annual legume can be used to rest and rehabilitate heavily cropped country, and to manage weeds. Used in pasture phases, it can leave plenty of nitrogen available for future crops, and eventually provides good grazing for sheep.

Trials in WA’s Chapman Valley found biserrula seed persists well after four years of cereal crops, and can tolerate low pH soils. Other rotations being trialled are allowing pasture phases in alternate years, every third year and every fourth year between cereal crops.

Biserrula and available N

The WA trials showed a 5t/ha DM (tops and roots) biserrula crop will leave about 100 kg/ha organic N available for the next cereal crop. You need well nodulated roots to produce this much N.

Yields and protein levels in wheat and barley crops were just as good as where urea had been applied annually – for three years following the pasture rotation.

Golden rules for biserrula

To get the best out of this legume in cropping systems:

  • innoculate seed with the appropriate rhizobium strain
  • avoid sowing into waterlogged, saline, deep, infertile sands or frost prone paddocks
  • sow at the break of the season, or consider summer sowing
  • sow at a maximum depth of 1 cm
  • control weeds prior to establishment
  • avoid ‘SU’ (sulfonylureas) herbicides (Lontrel, Logran) in the year before the legume crop
  • only use Bromoxynil for weed control in-crop
  • watch for aphids in first year
  • rotationally graze heavily in summer, watch stock for photosensitisation
  • in WA, crop the paddock the second year after establishment.

More

from extensionAUS Crop Nutrition:

Get the best nitrogen benefit from legume rotations

Adding N with Legumes

What is the value of fixed N?

How to manage nitrogen in no-till residues

from other sources:

GRDC Updates – Biserrula

Pasture establishment – biserrula

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