Topics:
Pasture

Managing sub clover for success

The second story in our subterranean clover series focuses on the specific management requirements of this early season clover.
Monday, 5 December 2016

Key points

  • Manage to allow seed-set by shutting the area up in late spring.
  • Use cattle to control competing vegetation, particularly in early spring and autumn.
  • Reap the rewards in winter and early spring
  • It takes time to set the sub “system up” – so manage for the forage while building plant populations and the seed bank.
  • Once the system is established - an area should be managed for re-seeding every 8-10 years.

The importance of seed-set

Allowing seed to set is critical to managing subterranean (sub) clover. As it is an annual clover, seed-set enables plant populations to be built and it is these plants that will provide a bulk of high quality feed the following winter and early spring. Sub is the earliest legume, growing four to six weeks earlier than white clover.

In late spring and summer the self-fertile flowers become burrs and the plant “pegs” burying its seed in the ground (hence the name subterranean clover) and dies. At the late flowering stage, the plant needs to be shut-off from stock so seeds can be buried, ready to germinate the following autumn. Managed correctly, one seed can, over time, produce 500 seeds and populations can build up. 

Once established, the seedlings can be lightly grazed when they have passed the “pluck” test. This is when tugged gently, the roots will remain securely in the ground as the leaves are plucked off.

Control competing vegetation

Lincoln University’s Professor Derrick Moot says controlling resident vegetation is important to prevent it out-competing the new sub seedlings. 

“Cattle are the best control option if the herbage is rank, but a hard summer clean-up graze with sheep can also set up a block before introducing new seed.” 

Long vegetation is sub clover’s greatest enemy. In spring, competing vegetation will cause the sub to elongate and compete for light. The elongated plant will not “peg” as many burrs so fewer seeds will be buried leading to lower germination in autumn.

Cattle are a valuable tool in controlling resident vegetation in a growthy spring and in autumn. Removing tag in autumn will allow the seedlings to flourish and unlike sheep, cattle will usually only graze the top leaves off the seedling which won’t damage them. Sheep, however, will graze the highly palatable and energy-dense seedlings to the ground.

The advantage of hard seeds

Autumn rain determines yield the following spring, so dry autumns can limit the productive potential of sub clover. Hard seeds are part of sub clovers survival mechanism, in that not all seeds will germinate in one year – some will take four to five years to germinate. Hardseedness is determined by the cultivar and the environment.

“The strength of having hard seed is that it doesn’t all germinate in the one rainfall,” says Derrick.

Some varieties will have more hard seeds than others and so cultivars are given a hardseedness ranking - although there will be still be variations within each cultivar. For this reason, Derrick suggests sowing a mix of cultivars, this will provide a mix of hard and soft seed and early and later flowering dates.