Tuesday 20 March 2018

Docks can reduce silage yields 20%

Munster farmer

Kevin O'Sullivan, Teagasc Adviser

Docks are the major weed of intensively managed grassland.

There are many species of docks but the most common and most damaging species in Ireland are broad leaf dock and curly dock.

Docks tend to prosper in silage fields where soil fertility is high. Silage fields, with long growing seasons, allow the dock to produce large vigorous leaves which in turn builds up huge root reserves.

Silage fields also tend to have an open sward which favours dock establishment. Docks compete with grass for light, moisture and nutrients thus reducing grass yields.

Where a heavy infestation of docks occur silage yields could be reduced by up to 20%. Docks are unpalatable and animals will only eat them if nothing else is available.

One dock plant can produce 60,000 viable seeds in a year and the seeds can germinate in the ground from July onwards in favourable conditions.

Dock seeds can remain viable in the ground up to 70 years and will germinate anytime when conditions are suitable.

The open nature of silage swards after cutting also favours dock growth and applying slurry after cutting provides an ideal seedbed for dock seedlings.

Cattle slurry is also high in potassium and when combined with chemical fertilizer potash can lead to excess potash in the soil which will favour dock growth.

Regular soil sampling will allow potash levels to be controlled and prevent build up.

There are a variety of sprays for docks and the choice depends on season and the importance of clover.

Do not expect one spray to kill the docks forever because even if you get a good kill there are plenty of seeds in the ground ready to grow for years to come.

Late April/early May is a good time to spray docks as there are plenty leaves on the dock plant and silage won't be cut for at least 30 days.

At this time of year docks are growing vigorously and nutrients are being transported to new leaves and roots.

This vigorous growth helps to get a good response from sprays.

If docks go to seed, are diseased or under pest attack it is better to cut /top first and allow regrowth before spraying.

Do not spray in a drought period as the chemical will not be taken up in sufficient quantities.

Always follow the manufacturers recommended guidelines and use the highest water rates for best effects.

Depending on the product used one spray application in early May followed by another 10 to 12 days after cutting silage gives a very good control of docks.