Bahia Grass - Best Turf for Water Efficiency

In the rush to use new turf species and new varieties sometimes this old stalwart is overlooked.

Bahia grass - Paspalum notatum is one of the very best grasses for water efficiency in the monsoonal tropics.  In areas with an extended dry period, it will stay green for the longest, and quickly rebound after extended dry weather - even as long as 7 or 8 months - to continue to thrive.

In the NT, it is best to avoid using the more readily available variety - Pensacola - as it is not as tough as others, tends to be more clumping, often appearing to have bare areas betwen plants and most importantly, it produces abundant seed heads year round so you are always needing to mow.

The older areas of Darwin often have a locally adapted ecotype, of unknown origin.  It produces seeds, but is usually sown by runners [ the other varieties can be too].  It was the predominant lawn in Darwin from the 1950s to about the 1980s, but less used today.  This line is ok as a turf species, and is very tough, and water efficient, but does tend to have a lot of spicules on the leaves - silica spurs that can irritate skin, especially where kids are rolling around on the lawn.  Argentine has less of these spicules, and so does Pensacola.  Its disadvantage is planting by runners, a time consumimg job.

The preferred seed sown line is Argentine.  We originally organised testing of this variety in the early 1970s in the Top End, importing seed from the USA, and first seeds were sown at Berrimah Farm.  It is still there, looking great. 

From the original evaluation, Argentine was selected and used in a lot of the early development around Palmerston in grassed waterways, and in park and landscape development after Cyclone Tracy in the reconstruction of Darwin.  Seed sowing is relatively low cost and a lawn can be developed in 10 -12 weeks.  No Australian production of seed has occurred and all Bahia grass seed is imported from the USA [ so is all couch, zoysia seed etc too].

The advantages of the Argentine variety of Bahia grass include:

• almost no seed head production, except a small amount around January in the north of Australia
• excellent spread and forming a dense surface cover
• very tough, reasonably resistant to wear
• low water needs
• excellent drought resistance and quick recovery when water is applied
• easily mown at around 30 - 45mm high, although it does grow moderately quickly in warm, wet weather - weekly mowing needed in the wet season for domestic lawns; maybe every three weeks in the dry season
• very little thatch development
• mostly free of pests and diseases

All of the Bahia grass types tend to become invaded by the awful weed grass "red seedy grass" or "Mackey's pest", which is botanically Chrysopogon acicularis.  This spreads by very insidious runners and produces huge numbers of seed heads.  There are herbicide solutions available for the control of this weed in Bahia grass, but products are not easily available for domestic use because of commercial packaging sizes - we can do this work if needed.  Efforts to eradicate it will pay big dividends.  Often seed is carried on legs, clothes, equipment and similar items so a biosecurity approach is needed to keep it out in the first place.

For a large lawn or open space area and especially where there is a need to be prudent with water use in the dry season.......Argentine Bahia grass is a good option.  It is also widely used as a water efficient turf in Florida [which is where the photo was taken].  Do not over water, as this induces ingress by other water loving species, including broad leaved carpet grass in our environment.

Carpet grass control - Monument does work - maybe

Monument herbicide has been used - probably for the first time in the NT - as a control option for sedges, carpet grass and annual grasses - on the main oval of a private school, and it has been very successful, so far.

Conditions for spraying were excellent, about 48 hours after mowing, with good soil moisture, and about 48 hours between spraying and first rain. The Monument was followed up by a DSMA spray in about 12 days. After three weeks carpet grass control was over 85%, although some was suppressed rather than killed outright. What remained was a few plants in formerly large patches, suitable for spot spraying or sprayed with a overall spray of further DSMA in a few weeks. Almost all sedges, annual grasses and many other perennial grasses including Chrysopogon acidulatus have been mostly eliminated. A follow up is often used, but may not be needed.

Because of the regular emergence of Mullumbimby couch, almost all year round, periodic use of DSMA will be needed to continue to reduce infestations to a lowered level, and so this will also continue to provide a good option to further reduce the carpet grass "spots" remaining, and any remnant grasses. Hopefully this will be able to be discontinued by the early dry season.

So........Monument may be a good option. Trials locally [ see photo - 8DAT showing the damage to narrow leaf carpet grass, the yellowish patch] have been impressive as a single pass option for weedy grasses in couch, as well as sedges. Locally, it is true that sedges tend to emerge most months of the year on irrigated areas, although peaking in the wet season. Get those wet season weeds, and big improvements can be made to reduce sedge levels, as there is much less emergence after April.

While not a perfect solution, using Monument has made a fantastic improvement to carpet grass in couch on this oval!

UPDATE - 24 February 2012

Carpet grass is Axonopus compressus or broad leaved carpet grass; narrow leaf carpet grass is Axonopus affinis just to ensure readers understand the issue.

Many curators / superintendents in north Australia still use glyphosate as a solution; metsulfuron may also be useful, especially on couch which is very tolerant of higher rates. It is a REAL issue in the wet tropical regions and especially broad leaved carpet grass thrives in wet soil / higher rain conditions, so better controlled irrigation management at a lower but adequate level can be part of the holistic management needed to get it under contol.