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).
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)