Purple pigeon grass
Purple pigeon grass is a perennial summer-growing tussock grass
Purple pigeon grass (Setaria incrassata cv. Inverell) is a perennial summer-growing tussock grass for areas with an annual rainfall of more than 500 mm. It is tolerant of drought and cool conditions, but is sensitive to frost.
A valuable characteristic is its ability to germinate and establish more reliably than most other tropical grasses on medium- and heavy-cracking clay soils of the Darling Downs, the brigalow lands, and the Maranoa, where establishment of other tropical grasses has been poor.
Purple pigeon grass is suitable for permanent or ley pastures in a crop-pasture rotation. It will seed throughout the growing season, and can establish freely from fallen seed.
When to sow
Purple pigeon grass may be planted from October to late February. If planting in early spring be aware that even though evaporation is lower, weed competition at this time can be detrimental to young pasture seedlings. Mid-summer planting (January to February), when there is a higher probability of receiving consecutive rain days, has the best chance of success. It is also the most likely period to receive good follow-up rain after planting.
Winter legumes can be sown with the grass in March-April, or oversown when the established grass growth has slowed between May and June.
Best results are obtained from a prepared seedbed that has been fallowed for moisture and nitrogen accumulation and for weed control. The surface 50 mm should be fine and firm.
The odds of establishing a pasture improve if the sub-soil moisture is good at sowing. Depending on soil depth, aim for a minimum of 40 cm of wet soil under the seedbed. Rougher seedbeds with less soil disturbance need a higher seeding rate and give less reliable results.
Sow 1-3 kg/ha. Check the germination percentage before planting as freshly harvested purple pigeon grass seed has high levels of dormant seed.
Dormancy (hard seed) gradually breaks down if seed is stored for 6-12 months. If the initial establishment has been poor due to adverse seasonal conditions, dormancy can assist by having a viable seed reserve available in the soil that can provide germination/establishment opportunities when seasonal conditions improve.
Pelleting is not required. The seed is free flowing and will flow through conventional grain planting machinery or precision planters.
Legumes for purple pigeon grass pasture
Purple pigeon grass will combine well with lucerne and medics and this helps to improve the grazing quality of mature grass in autumn and spring.
Lucerne (1-2 kg/ha) can be sown as a mixture with the grass. Medics (2-4 kg/ha) can be sown under previous winter cereal crops or oversown later after the pasture has established.
Sowing method and sowing depth
Seed may be broadcast onto the dry seedbed surface, or drilled into a dry or moist seedbed with precision planters. The small seed should be within the first 10-25 mm of the soil surface.
Seed soil contact may be improved on non-crusting soils by rollers or presswheels that will firm the soil around the seed. Be careful if harrowing after sowing that the small pasture seed is not being buried by more than 25 mm of soil.
If purple pigeon is sown with winter cereal (a practice favoured by some), use fresh seed with a high dormancy (at least 50%).
A good fallow before planting will release enough nitrogen to accelerate grass establishment. Purple pigeon grass is adapted to clay and clay-loam soils whose basic fertility is moderate to high.
As it is usually uneconomic to apply nitrogen fertiliser to large areas of dryland pasture, a vigorous legume component is the best way to supply nitrogen to the grass. Renovation of mature pasture that is showing signs of decline will release nitrogen to rejuvenate the stand for a short time.
Good cultural practices in the season before sowing will help reduce the weed seed population. There are fewer options for control of weeds in a pasture based on grasses and legumes, and so the weed seed reserves should be reduced before planting pasture.
Purple pigeon grass is a strong aggressive grass that competes well with other species and with weeds during establishment. Although it is generally impractical to use herbicides for broadleaf weed control, a number are registered for this purpose. Care should be taken in their selection to avoid killing useful pasture legumes. For further information on herbicide selection consult your company agronomist.
Do not graze new pasture until follow-up rainfall allows seedlings to develop a strong root system and set some seed, then graze only lightly.
In established pasture, short periods of grazing are preferable to continuous stocking. Purple pigeon grass flowers throughout its growing season, with a rapid drop in feed quality as it matures. It often requires high stocking rates to prevent purple pigeon grass from becoming tall and rank.
Purple pigeon grass is readily eaten before going to seed. However, it is less palatable than some other grasses and can become tall and rank in a mixed grass sward.
While spelling the pasture in late summer helps to maintain its 'condition', this will decrease winter medic production. If the goal is to favour annual winter legumes, summer grasses need to be grazed heavily in late summer and autumn. Both practices should be used in different seasons to maintain both the winter legume seed reserves and to maintain the 'condition' of the grass.
Purple pigeon grass has about half the oxalate level of the other setaria grasses (Nandi, Kazungula, Narok and Solander). Oxalate can cause 'big head' in horses when these grasses form the major part of the diet over a long period.
Purple pigeon grass seed is ready for harvest when the seed in the head can be stripped easily, has a gritty feel and changes colour from dark to light green. It can be harvested by direct heading or by swathing and using a header with a pick-up front. Yields are high, and since the seed is fairly large and smooth, harvesting and cleaning are much easier than with awned seeds