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.

Caring For Your Zoysia Lawn in Hot Weather

The Australian Bureau of Meteorology has today announced the next three months across the East and North of Australia will be drier and warmer than normal.

That means a strong likelihood of your turf areas needing more irrigation than usual.  Your turf might be stressed.  How can you best handle the issues that arise?

Adequate potassium fertiliser is a wise option.  Potassium boosts stress response in plants as it helps develop better structural tissues, including cell walls, and aids plants in overcoming or being resistant to water stress, as well as the related heat stresses, even in those varieties with superior heat adaptation.

Use a fertiliser mix with adequate potassium, applied soon, or add up to 1-2 kg / 100 sq  m of potassium sulfate or even potassium nitrate as the fertiliser. You may need to look more widely for these but they are around. Slow release NPK mixes tend to use one or other of these products, but you want a potash content of around 10-15% in the mix.  Avoid muriate of potash which is potassium chloride, as it can add saltiness to your turf area.  Muriate of potash is readily available, and can be cheap, but it a short term gain that can add to long term problems.

And what about the perennial issue of mowing?

There is a tendency to mow the lawn shorter in warm weather……..as if you might be able to avoid an extra cut by doing that.

Reality is you are best to actually cut the lawn less frequently and slightly higher, when there is hot, dry, stressing weather!  Long leaf that is uncut means less water loss from the cut edges and better soil cover from the leaves that helps control soil temperature and lower water loss from both evaporation and transpiration.  When weather turns and some decent rain arrives, then you could mow at a lower height………but not too low unless you have a very strong need for a “golf green” appearance, and the mower is suitable.

Zoysia is well adapted to hot weather, and can easily adapt to mowing heights between 15 – 60mm.  It is suggested that heights of 35 – 45mm [possibly slightly more] are suitable when the weather is hot and dry.  Switch to a lower cut height [around 20-25mm] once more regular rain is imminent.  Always remember that you do not want to remove more than one third of the sward height at any one mowing.

It is better to manage your turf and even avoid too much mowing.  You can achieve a good quality zoysia turf with maybe 50% of the water demand [ currently up to 50% of the 6-8mm a day of evapo-transpiration in Darwin] applied on every second or third day] especially if the turf has good soil cover.  Would you prefer mowing weekly or every three or four weeks?  It can be done to manage water, fertiliser and mow frequency to achieve a good turf that is functional and looks good, and is mown at 4 week intervals [ but check for weeds too].

You want your turf to develop a deep strong root system that can access water from up to around 150mm [ or more] deep in the soil profile, and not the shallow 25mm deep roots promoted by short watering that only superficially wets the profile to 25 – 40mm.  

Infrequently mown zoysia as a median strip in Kuala Lumpur Malaysia

Longer, less frequent irrigation is definitely superior and aids developing a robust root system that can be functionally efficient in scavenging water.

Sowing Compadre Zoysia Seed - Starter Fertiliser

The starter fertiliser we suggest is Nitrophoska Blue , Yara Mila [ sometimes sold as Yara Hydrocomplex] , Crop King 55 or Crop King 88.  All are okay and have slightly different NPK blends, and different retailers sell them,  so you need to see what might be around in your area through Bunnings, Elders, Landmark etc.

Companies such as Lesco and Scotts which specialise in turf products and equipment, also have small prilled, turf starter fertiliser with some slow release nitrogen.  Quite good to use but can be more expensive and may be more difficult to source.

 

Commonly the NPK ratios are around 20: 12: 15, often with 5-10% sulfur as well, plus trace elements, for these starter fertilisers.

 

There are other brands as well, but many other brands are less well known and less available for smaller users.

 

Use what is available and attractively priced in your region.  These products are soluble fertiliser and can be mobile ie leach, and need additional fertiliser within about 4 weeks of application.

 

We recommend 2kg / 100 sq m at or before sowing, another 2kg/100 sq m at about 4-6 weeks [after emergence and when small seedlings are present] and then to switch to a slow release turf product at about 8-10 weeks, and then repeat every 12 weeks after that, until cooler months [say May or June].  From the next year in September / October restart the slow release fertiliser and repeat at 12 weeks intervals.  From midway in the next year, cease fertiliser application when cooler weather starts, then recommence with a 2 or 3 times per year schedule of slow release turf fertiliser from September /October,  omitting mid-summer and mid-winter periods. [more details on product in an earlier post] 

For zoysia use half of the recommended rate on the bag, so normally use about 2kg/100 sq m [ usual recommendation is 3-5kg/100 sq m, which is based around couch - do not need as much for zoysia.]

 

It is very important to spread fertiliser evenly.  Use a push type spreader or a small hand applicator for smaller areas.  Lightly water into the ground after application, aiming to avoid burning the small seedlings.  In hot weather, apply fertiliser late afternoon or early evening to avoid burning plants.

 

 

Which Fertiliser for Compadre Zoysia?

Choice of fertiliser is always a bit of a conundrum these days with so many types and blends available.

There is some benefit in using organic fertiliser for example pelletised chicken manure , or DPM - densified poultry manure.  It adds organic matter and some nutrients but the nutrient level is relatively low, and it can be more expensive if freight costs are an issue eg in rural and remote areas.  It can be short in some nutrients as well.  It can be useful if the turf is growing on light sandy loam soil or sand.

Conventional inorganic fertiliser is modestly priced, and there are blends that mostly meet criteria for use on turf, but all have generally rapid availability of nutrients and they can often leach quickly.  Because they are mostly readily available you get rapid lawn growth = more mowing, then the nutrients disappear and you need more, maybe in 4 weeks.  And more mowing still!!  Not the best choice at all.

Slow release turf fertilisers are ideal.  They release the nutrients, especially the nitrogen, over an extended period [often 10 -16 weeks, but longer release period products are also available].  The result is less mowing, a better appearance lawn and better availability of plant nutrients.  Many are available in small bags through garden stores and chain shops - 2-4kg sizes, but for best cost effectiveness, buy a 25kg bag and store it in a sealed plastic bin, in the bag.  It will stay usable for 2-3 years at a lower cost.

Domestic Compadre zoysia turf - Darwin area, 20 weeks after sowing seed

The blend is important, and a general use product has around 15- 25% nitrogen, 1-3% phosphorus and 10 -20% potassium, plus some sulfur [ 5-10%] , trace elements if possible, and most importantly a small amount of iron - 0.5 -1.0%.  The iron boosts the lawn colour to a lovely green, without much effect on growth.

The potassium level is important, particularly in wetter and /or warmer climates.  Potassium is mobile so can leach out in wetter periods but its role is to strengthen cell walls and provide better stress resistance, hence the need for decent potassium levels in hot weather.  Modest to low phosphorus is better, assuming the soil does have a reasonable base P level.  With more P you tend to promote legume growth [ essentially a weed in turf].

For zoysia, which is not a prolific growing lawn, the iron is especially important as mowing is less frequent and that delightful green colour is impressive for many weeks, without being cut off.

The other question is always how much.  We suggest halving any recommendation on a fertiliser bag if applying to zoysia, of any type.  Many products recommend 3 - 4kg/100 sq m for slow release fertiliser for eg couch lawns.  For zoysia - 1-2 kg/100 sq m is usually enough.  The exception may be on new lawns less than 1 year old, when you are building up a store in the soil when the recommended rate may be okay in peak growth periods.

And of course in cooler months - applying fertiliser is really not needed as the lawn is not growing very much anyway.  And not too much in wet summer conditions - it means more mowing!

If one of the common types of slow release turf fertiliser is used with a nominal 12 week release period, for zoysia of any type - twice a year is okay, once established.  Nominally apply in Autumn and Spring [or late wet season and late dry season].

The fertiliser question is always tricky and individual areas may require a slightly modified approach in areas where particular nutrients are in short supply or even may be in abundance.

But the above maxims apply in many areas, and are a suitable starting point.

Enjoy your zoysia turf.....and apply a bit of TLC!!