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.