Bambatsi

Bambatsi (Panicum coloratum var. makarikariense)is a perennial summer-growing grass that is well adapted to medium- to heavy-cracking clay soils of the Darling Downs, Western Downs and the Maranoa, where the average yearly rainfall is greater than 600 mm. Bambatsi can tolerate waterlogging, drought, frost and saline soil. It performs well on melon-hole (gilgai) soils in brigalow lands, but is unsuited to the sandy and loamy soil of lower fertility soils.

Bambatsi is the common variety name of all commercial seed of what was once called Makarikari grass. Cross-pollination has eliminated differences between the old varieties Pollock, Burnett and Bambatsi.

Sowing

When to sow

Sow either in the early spring or in mid to late summer. If sowing in early spring be aware that even though evaporation is lower, the rate of germination and development of seedlings is slow, and weed competition at this time can be devastating to successful establishment. Sowing in mid-summer (January to February) when there is a greater 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.

Seedbed

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 likelihood of establishing a quality pasture improves if the sub-soil moisture is good at sowing. Depending on soil depth aim for a minimum of 40 cm of wet soil in the seedbed profile. Rougher seedbeds with less soil disturbance need a higher seeding rate but give less reliable results and the imvestment is often wasted. The ash left after a scrub burn can make a good seedbed.

Sowing rate

Commercial Bambatsi seed usually has a germination of 50% or more. Sow 1-2 kg/ha of a good quality seed.

Bambatsi seed is free flowing and can be sown through conventional grain planting machinery and precision planters.

Legumes for Bambatsi pasture

Sowing an adapted legume with the grass will add nitrogen to the pasture system and will help improve both the quality of grazing and the fertility of the soil. Desmanthus, Caatinga stylo (on friable clay soils) and/or lucerne can be mixed with the grass seed, and medics can be oversown after the pasture has established. The sowing rate for each of the legumes will depend on the mixture chosen. Each (sown individually) or the mixtures can be sown at 2-3 kg/ha.

Sowing method and sowing depth

Seed may be broadcast onto the top of the seedbed or drilled into the seedbed with precision planters. The small seed should be placed preferably within the first 5-10 mm of the soil surface or drilled no deeper than 20 mm.

Seed and 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 buried by more than 10 mm of soil.

Establishment

Sowing dry ensures that pasture seed is in the best position to take advantage of the next rainfall event. Rain will start the germination process. The seed must maintain close contact with wet soil for about three days in the summer or longer in the spring to develop a root and establish a seedling. Sub-soil moisture will sustain the seedling until follow-up rainfall occurs. This rain will also promote the development of secondary roots that form the crown of an established grass.

Pasture seed in the bottom of shallow tine furrows or small depressions (microsites or surface pitting) in more roughly prepared seedbeds will establish seedlings because the depressions accumulate water and stay wetter for longer after rain - providing there is water in the sub-soil below the depressions.

Fertiliser

Before sowing

The fallow before planting should be of sufficient time to release enough nitrogen to allow the grass to establish. Phosphorus deficiency is unlikely to be a problem at establishment on many clay soils, but apply superphosphate to the seed bed if soil analysis or past history indicates a low level. Superphosphate also provides sulfur that may be deficient on some clay soils.

Annual maintenance

A vigorous legume component should be established to provide nitrogen for the grass. In an established dryland pasture it is often uneconomic to apply nitrogen fertiliser, although its strategic use should not be overlooked. Renovation of mature pasture that is showing signs of decline will release nitrogen to rejuvenate the stand for a short time. This should be accompanied by sowing (or re-sowing) legumes.

Legumes require sulfur and phosphorus to maintain production and to persist. Topdress in early spring or early autumn with superphosphate per year if soil phosphorus is low. If only sulfur is deficient, apply gypsum (0.5 t/ha) or elemental sulfur (60 kg/ha) every two to three years.

Weeds

Bambatsi seedlings are relatively slow to develop. Weed competition can retard their growth and affect establishment of the pasture. Good cultural practices in the season before sowing (pre-cropping or fallow), will help reduce the weed seed population in the pasture seed bed.

After establishment most broadleaved weeds should be suppressed by a dense, vigorous pasture growth. Although it is generally impractical to use herbicides for broadleaved 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.

Weed control in young pasture is difficult. Slashing or light grazing may reduce weed competition. Grazing can help control palatable weeds.

Grazing management

Successful pasture establishment can depend on the grazing management applied in the first year. Do not graze until follow-up rainfall allows seedlings to develop a strong root system and set some seed, then graze lightly. Ensure that the first year stand sets seed.

Bambatsi can be more palatable than some other grasses, particularly when foliage is young or regrowing.

Toxicity-photosensitisation

Young sheep and goats have occassionally suffered from photosensitisation when grazing wilted Bambatsi pasture during dry periods, or grazing regrowth after rain. Young cattle and horses may also be affected, but rarely more mature stock.

Stock are more likely to be affected when they have suffered stress (e.g. transportation, shearing). Early symptoms of toxicity are head shaking and facial irritation. The problem can be minimised by removing young stock from the pasture immediately as symptoms are observed.

  • Allow hungry young animals to eat roughage before they start grazing Bambatsi.
  • If wilted pasture has to be fed to young stock, monitor them closely to detect early signs of poisoning.
  • Do not graze young or stressed stock on fresh Bambatsi shoots for at least three weeks after rain.

Seed production

Seed is readily harvested with conventional grain harvesters. Seed crops can be direct headed or swathed and dried for a few days after being raked into a windrow and then picked up by the harvester. Swathing gives higher yields of good quality seed than direct heading provided the weather remains fine. Header settings for direct heading are similar to those for wheat but with the air draft cut back severly.

As with most grasses, seed falls from the head as it ripens. A seed crop is ready for harvest when most of the seed heads have shed seed from the top ¼-½ of the head. The mature seed is olive green to dark grey and will easily rub out of the seed heads.

Direct headed, freshly harvested grass seed is moist and must be dried or mould will grow as the seed mass generates heat. Heat must be removed by turning the seed or applying a forced air draft to prevent loss of seed viability.

In the turning process, seed is spread evenly (50-100 mm deep) over a shed floor or on tarpaulins, and turned regularly two or three times a day until dry. Drying time is normally about seven days but will depend on the depth of seed and ambient humidity.

Seed harvested after swathing will have a lower moisture content, and will require less drying.

Yields of clean seed are variable, generally 20-50 kg/ha from commercial paddocks. Yields of 200 kg/ha have been achieved with irrigation, nitrogen fertiliser and swathing.

Further information

  • Infopest - search for chemical products registered to control weeds, pests or diseases in crops and animals. Infopest ensures the right chemical for the right job and supports responsible chemical use. Infopest products offer a comprehensive guide to all agricultural and veterinary chemicals and their permitted uses, plus Material Safety Data Sheets (MSDS).

Publications

  • Henry DR et al (1995). Photosensitisation, Pasture Plants of Southern Inland Queensland, DPI Information Series Q195016, 27-29.
  • Dowling RM and McKenzie RA (1993). Photosensitisation, Poisonous Plants a field guide, DPI Information Series Q192035, 33.