Zoysia Seed To Develop a New Sports Oval - Part 2 - Seedlings at Four Weeks from Sowing and Weed Management

While early seedling growth was very good, the dreaded weeds then started to appear!

While herbicides for use on seeded zoysia have been a bit tricky in being able to choose one that had minimum collateral damage to the small zoysia seedling yet was efficacious in removing weedy plants, we decided to use quinclorac [trade name Drive], which will deal with some weedy annual grasses and many broadleaved and leguminous weeds, selectively, without damaging the zoysia seedlings.

Timing is still important...............very important.  It is important to apply Drive in the period of 14 - 28 days after emergence, and in our situation we had major emergence about 8 - 9 days after sowing and we sprayed 25 days after sowing, about 16-17 days after emergence.

Results have been good, with strong control of leguminous and broadleaved weeds, and some weedy seedling grasses.  More work will be needed over the next four weeks to deal with some of the weeds remaining which includes some broadleaved weeds as well as sedges and grasses.

About 4 weeks after sowing we also applied additional fertiliser [ Yara Hydrocomplex ] at a rate equivalent to about 30kg/ha of N.  Included was another approx 10 kg/ha P and 35kg/ha of K and more trace elements and sulfur.

With other species, more fertiliser is used eg couch, but trials have shown there is little additional growth benefit by applying more at this stage to seed sown zoysia, either Zenith or Compadre.  We expect to apply more fertiliser in about another four weeks.

Seedlings are growing well, weeds are mostly dying and the oval is developing steadily.  Yes, there is some uneven seedling distribution, but we did have a very high intensity rainfall event soon after sowing which resulted in washouts, which would have been much worse without the hydroseeding and use of mulch.

Over the past four weeks an early morning irrigation was applied almost every day, along with two very short daytime irrigation periods to boost dampness near the soil surface.  Some might have thought this irrelevant, as there has been quite a reasonable amount of rain - almost daily [ a few days break here and there] but it is essential to keep the surface damp in this initial period, especially as we often had hot sunny days.  Irrigation is now being reduced to three or four times a week, even though we are still receiving an occasional amount of  effective rain. Irrigation will be likely further reduced in coming days, if rain continues.

The next major exercise will be to start light mowing to enhance lateral growth of zoysia and help control any remnant weeds, and to continue with several other herbicide options for ongoing weed management.

weeds dying amid zoysia seedlings after selective herbicide application

close up of zoysia seedlings

overview of oval development at 29 days from sowing- some unevenness, but most areas with high seedling density

close up of dying weeds among zoysia seedlings  - note leaf twisting and colouration

overview of weeds dying at one corner with plenty of zoysia seedlings developing

All photos taken 29 days from sowing.

New and Old Herbicides - Tropical Turf

At last...............two new herbicides are available for use in tropical turf areas, especially zoysia turf. They may need to be purchased directly from national suppliers, as unlikely to be stocked in the NT.

The first is Drive - quinclorac is the active ingredient. Been around for a while, starting life as a crop herbicide with the name Facet. Active as both pre and post emergent, so will knock off emerged weeds and add a follow on pre-emerge control. Great for many annual grasses, and a few perennials too. Relatively few trials in the tropics of Australia, but some coming soon. Expect will be useful to control Bahia grass in both couch and zoysia, annual grasses and some hard to manage grass weeds. Will NOT control carpet grass.....period! Currently it is expensive, and in my opinion, very overpriced for an old product. BUT.......for some needs it is a great product and very effective. Has a lot of potential for widespread use in both zoysia and couch areas.

Next is Monument - a sulfonyl urea - and also reasonably pricey, but with the advantage of controlling both sedges and annual grasses in one package, it may be a suitable option. Work locally so far, shows fair results for carpet grass, with medium term suppression and some kill only, but excellent results for sedges and annual grasses. Rates are low - medium, depending on required outcomes, with higher rates required for grasses. Seems promising for tropical Australia.

Old herbicides do not get the advertising $$ once they are out of patent, but they can be effective. The products DSMA and MSMA are still effective for grass weed management in couch ovals or sporting arenas. BUT they need repeated applications, and unfortunately in the tropics it is never cool enough or [ for an oval] dry enough to fully eliminate the grass weeds it seems. They are also relatively poor options for carpet grass control, as they just cannot do the job!

Others though such as diuron and some of the triazenes can be a useful tool, at suitable rates. Be careful though, as some turf species do not tolerate these products.

Asulox will control carpet grass, but rates for use in turf are still to be worked out. It is a sugarcane product and known to have some potential. High rates will kill turf........it will be a balancing act to get rates correct. Currently Asulox is not registered for turf use

Ronstar - oxadiazon - is a very useful but expensive product for weed management while establishing couch or zoysia. Can be effective in Bahia grass, where grass contol options are more limited. Another oldie, but still goodie! Pity prices are still toooooooo high!

A good source of information is www.pestgenie.com.au . A great Australian web site focussing on agrochemicals for the Australian rural scene.

Take care with all agrochemicals and watch out for rain. Remember that in many areas, a good ally is the Met Bureau web site and the local radar. Quickly spots any likely storm clouds. For the Darwin area the link is www.bom.gov.au/weather/nt and go to radar image. Similar links are available in many other areas.