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Technical Notes Issue 6 - Over seeding

Spring renovation for turf - April 2008

It has been a pretty cold start to 2008. At Easter in 2007 we were all in tee-shirts and going to the sea-side. This year, we built a snowman!

This is the time of the year I always think turfgrass looks at its worst. It is starting to try to grow but hasn’t got enough temperature, daylight or food to move strongly yet. It appears sad, yellow and in need of a bit of TLC.

However, the soil temperatures are increasing. In the South of the country, soil temperatures are getting to double figures. Further north, they are a couple of degrees behind but almost there.

Spring renovation and fertilisation is especially important if any disease crept in over the winter months and has left unsightly scars. Lawn sand is a good start to the grass growth season, as the little bit of nitrogen helps to slowly break the winter dormancy, without supplying too much fertility at a time when soil temperatures are still low.  

Remember that spring renovation and fertilisation needs the grass to be growing for good results so don’t start too soon as the weather can turn cold again leaving greens struggling to recover from the renovation work. Importantly for turf renovation, GreenCast provides a record of current soil temperatures, and the forecast for the coming five days. 

The renovation required then depends on the specific management plan for the greens, but will include some of the following aspects. Once the grass has started to grow well, verticutting can be used to remove old dead grass leaves that accumulate over the winter period.

Over seeding can be carried out using a stitch or dimple seeder. I tend to find that when oversowing in spring, applying fescue seed only works best, as the soil temperatures are not always high enough to give good germination of bentgrass seed (which seems to take better following autumn oversowing). 

Where turf is actively growing at the time of over seeding, consider the benefits that can be achieved with Primo MAXX applications before and after seeding. This can help to suppress the existing turf and allow new seedlings to establish. (View the news article Over seeding for success). 

Microcoring or hollowcoring and topdressing may be carried out as part of an over seeding programme (especially if disease scars need to be addressed).  Spring fertiliser and seed can be applied at the same time, and brushed into the tineholes. This fertiliser will then encourage growth.  

A soil test will indicate whether the rootzone requires any potassium and phosphorus. During spring (and especially where new seedlings are growing) both P and K are required for new root growth. Therefore, on a soil based rootzone, using a fertiliser such as 6:5:10 N:P:K at 35 g m-2 or 14:5:10 at 20 g m-2 will supply a little phosphorus required for rooting and so will help the new seedlings grow and establish. If soil tests indicate enough P and K available in the rootzone, a fertiliser containing 8:0:0 N:P:K could be used. If you wish to use liquid products, Greenmaster Liquid spring and summer contains 12:4:6 N:P:K and could be applied at 80 L ha-1.  

On sand based rootzones, a slow release fertiliser should be considered and a product like Sierraform GT 16:0:16 N:P:K could be used where no phosphorus is required or 18:6:18 N:P:K where phosphorus is required. However, if the sward density is good, it may be appropriate to wait until soil temperatures are consistently around 10ºC and begin a liquid fertiliser/Primo MAXX programme for the whole season.