Companion legume options for sub-tropical grasses in southern Western Australia

Page last updated: Friday, 6 October 2017 - 3:53pm

Please note: This content may be out of date and is currently under review.

To be productive a perennial grass pasture requires a companion legume to improve the feed quality over the winter growing season and provide the nitrogen input to drive productivity. In the south west agricultural area the growth pattern of annual legumes complements the sub-tropical grasses, which are dormant or grow slowly over winter. On the other hand, perennial legumes only have a limited role in these environments.

On the sandy soils where the perennial grasses are predominantly grown in the Northern Agricultural Region (NAR) the main annual legume options are yellow and French serradella and blue lupins. On the same soils across the South Coast (SC) the sub-tropical grass kikuyu is mostly grown with subterranean clover, with the exception of deep sands where it is best partnered with yellow or French serradella.

The use of sub-tropical perennial grasses in both the NAR and SC continues to increase, especially on sandy soils which are marginal or unsuitable for cropping. However, many perennial grass pastures have a low or highly variable legume content which limits both pasture and livestock productivity. Annual legumes are generally best suited as companion species for the sub-tropical grasses, as their growth pattern is complementary, whereas perennial legumes are unlikely to be persistent and will compete with the sub-tropical grasses for soil moisture following out-of-season rainfall.

Annual legume options

The annual legume options for sub-tropical perennial grasses are the same as those for annual pasture systems on the same soils. However it is worth considering an earlier flowering variety due to strong grass competition for moisture in spring resulting in a shorter season in some years. On the sandy soils where the perennial grasses are predominantly grown the main annual legume options are subterranean clover, yellow and French serradella and for some situations in the NAR blue lupins (Table 1).

Table 1 The suitability of companion annual legumes for perennial grasses on the main soil groups in both the NAR and SC of Western Australia. Note acronym: millimetres (mm)

Companion annual legume options

Yellow and French serradella

Blue lupins

Subterranean clover

Balansa clover

Minimum annual rainfall (mm)

325

~450*

350

350

Soil pHCaCl2

4.0-7

4.0-7

4.3-7.5

4.7-7.2

Pale deep sands

√√

X

X

Yellow deep sands

√√

√√√

X

Shallow sandy duplex soils

X

√√√

X

Deep sandy duplex soils

√√√

√√√

√√

X

Gravelly duplex soils

√√√

√√

√√√

X

Ironstone gravelly soils

X

√√

X

Winter waterlogged soils

X

X

√√**

√√

(Key: X- unsuitable; √ – marginally suitable; √√ – suitable; √√√ – highly suitable)

* Susceptible to frosts, so growth limited by frosts rather than rainfall per se

** Subspecies yanninicum has a high waterlogging tolerance (providing rainfall >425mm) 

close up of pasture
Subterranean clover and serradella growing with kikuyu on the south coast

Pages

Contact information

Geoff Moore
+61 (0)8 9368 3293
Paul Sanford
+61 (0)8 9892 8475