Tuesday, November 18, 2014

Irrigating A New Area of Zoysia Sown by Seed

It is absolutely critical to adequately irrigate a newly sown area of zoysia seed.  Because the seed needs light to germinate, it is sown close to the surface.

The problem with that in warm weather is that the surface normally dries out quickly. You need to use a few tips and tricks to ensure that adequate moisture is available to keep the germination process ticking along, then there is the need for water to sustain the small seedlings, once the seed germinates.

Warmer weather tends to promote faster germination, with 7-10 days often enough to see seedlings in warm conditions, but up to 21 days if cooler.  Remember, a ground temperature of 18 - 20C is about the bottom of the range to even get reasonable germination.  If below this........wait a little longer.

In the sub tropics and tropics, it is possible to sow year round but growth will be slow in cooler months and waiting until the cooler weather is past is often the best idea, as growth really picks up once the days are longer, soil is warmer and night temperatures rise to around 18 -20C.

But the water regime and surface management are very important.

Adding a very light [ I stress light cover] of thin mulch such as sugar cane bagasse or a thin even cover of compost to the soil surface will both help hold moisture close to the surface as well as preventing rapid loss of moisture and acting as a protection barrier if there is heavy rain.  The latter is almost inevitable in the tropics........and you need to plan for it.

Generally it is necessary to also irrigate several times during daylight hours to keep the surface moist....not wringing wet, just moist.  You can use pop up sprinklers -run for a few minutes only.  Unfortunately the output from sprinklers covers quite a range so time cannot be given.  Remember a moist surface, not wringing wet.

Some systems allow many starts each day, but many only allow two or three.  Ideally you need a good irrigation early in the morning and 2 or 3 short bursts during the day, with a modest spray later in the early evening.  Many areas have evaporation rates of 7- 10mm each day if the weather is hot.  Most of that needs to be replaced each day while the area is in the early stages.

Better than using pop up sprinklers is to use small, low pressure, low volume sprinklers used in horticulture  and landscape applications.  These operate on 12mm or 19mm pvc lines and deliver 1-2mm per hour, depending on the pressure.  You also need a pressure reduction valve and inline filter to be most effective.  Several brands are available, with Challenger mk2 a recommended type supplied through Philmac resellers..  These sprinklers have the water distributed evenly across the wetted diameter of the sprinkler, and the droplet impact is low.  They come in a range of diameters [ up to about 12m].  Also, droplets are larger and less prone to wind influence.  Costs for each sprinkler is less than $5 approximately.

These can be operated for an hour or so several times during the day [ through a normal irrigation controller and solenoid valve] to add a modest amount to the surface, refreshing the dampness on the surface.  If operated for longer periods, they are suitable to fully irrigate the area, as they tend to be very efficient sprinklers as well.

Once the area is about 3-4 weeks old, irrigation can be reduced and adjusted to using several days per week [ rather than every day]  and also altering the duration of each irrigation to adequately wet the area, to help create a deep root system.  That bit of drying out between waterings helps promote roots searching for water deeper in the profile to develop a resilient turf area.

Once established, zoysia turf is quite water efficient and tends to be drought tolerant, requiring less water than many other turf grasses of high quality.

Overwatering promotes weeds, especially sedges eg nutgrass and Mullumbimby couch.  Best to be a bit light on with the water on established areas of zoysia!

From the left - dripline, pressure reduction valve, filter , connection to water supply
Enjoy your zoysia turf.  Remember......the payoff is less mowing!

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