What are sub-tropical perennial grasses, and why grow them in southern WA?
They're summer-growing perennial grasses, such as Rhodes grass, panic, setaria and kikuyu, that grow whenever it's warm and moist. In southern WA they turn summer rain into feed, give year-round ground cover on sandy soils and use water that annual pastures leave behind. WA growers have sown more than 200,000 ha, mainly on the south coast and in the northern agricultural region.
When should I sow sub-tropical grasses in WA?
Sow in late winter to spring, once the soil temperature at 9 am stays above 15°C for several days and there's a good chance of follow-up rain. In the northern agricultural region that's usually August to early September, and on the south coast early September to early October. Spray a knockdown at least two weeks before seeding.
Why is it so hard to establish perennial grass from seed?
Sub-tropical grass seed is tiny, so the usual mistakes are sowing too deep, sowing into cold soil, and letting weeds or insects compete. Sow 5–10 mm deep into a firm, moist seedbed once soils are above 15°C, after a double knockdown with an insecticide. By the following autumn, 8–10 plants per square metre is a successful stand; they'll thicken up from there.
Which summer-growing grass suits my soil?
Match the grass to the soil. Panic and Rhodes grass handle deep, pale sands and are the mainstays in the northern agricultural region; Rhodes grass also tolerates salinity but not prolonged waterlogging. Setaria suits duplex soils and wetter sites on the south coast, and kikuyu does best in higher-rainfall or coastal country. Most growers sow a mix of two or three species to cover soil variation.
Is kikuyu a good pasture grass in WA?
In the right place, yes. Kikuyu is a vigorous, spreading summer grass suited to the higher-rainfall South West and south coast, where it's the most widely sown sub-tropical grass. It handles heavy grazing and binds sandy soil, but it can become invasive, is high in oxalate, so it's not ideal for horses, and occasionally poisons cattle after a dry spell. Oversow ryegrass or clover in autumn for winter feed.
My perennial grass pasture goes brown in winter. Is that normal?
Yes, if it's a sub-tropical grass. These grasses grow in warm weather and slow down or go dormant, often browning off, once soils cool in late autumn, and frost speeds this up. They regrow as temperatures rise in spring. To fill the winter gap, let an annual legume grow through them; hard-seeded serradella and rose clover suit the sandy soils these grasses usually grow on.
What summer-growing grass will handle salty ground?
Rhodes grass is the most salt-tolerant of the common sub-tropical pasture grasses, coping with soil salinity above 10 dS/m, and it spreads by runners to cover scalded, bare ground. It suits sandy to loamy soils from about 400 mm of rainfall. It doesn't like waterlogging, so where salty ground also stays wet in winter, puccinellia is the better choice.
Are tropical grasses safe for horses?
Some carry a risk. Setaria, kikuyu, couch and panic grasses contain oxalate, which locks up calcium and can cause 'big head' in horses grazing them for long periods; setaria is the worst. Rhodes grass is regarded as low in oxalate and suits horse paddocks. If horses graze higher-oxalate pasture, feed a balanced calcium and mineral supplement and talk to your vet or nutritionist.
How can I stop sandy paddocks blowing away over summer?
Perennial ground cover is the long-term fix. Summer-growing grasses such as Rhodes grass, panic and kikuyu keep live roots and leaf on the surface year-round, which is why they're widely sown on WA's erosion-prone sandplain. In the short term, keep at least 50% ground cover by controlling grazing, and sow cereal rye on bare patches in autumn to stabilise the sand.
What can I grow for quick summer hay for horses?
Teff grass is a good option: it's a fine-stemmed, leafy summer annual that horses find very palatable, and it can be ready to cut about 6–8 weeks after sowing with good moisture. Sow very shallow into warm soil, above about 15°C, from late spring at 3–6 kg/ha. In WA's dry summers it needs irrigation or plenty of stored soil moisture.
