Tuesday, October 22, 2013

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!!

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