Will clover be the nitrogen fertiliser of the future?

“With the pressures from water quality and nitrates mounting, more farmers are going to be growing clover in the future.”

This was a statement by Dan Clavin – Teagasc organic farming specialist adviser – at an organic farm walk last Wednesday (February 20), in Co. Kildare.

A mixed grass clover sward has the ability to fix between 150kg/ha and 200kg/ha of nitrogen (N); driving grass silage production.

It is a high-yielding crop; yielding between 12-15t of dry matter (DM) / ha.

It is mainly grown by organic farmers. However, it is not known why more conventional milk production systems are not using it.

Benefits

“It has a multitude of benefits,” Dan stated.

Studies show that “higher growth rates are experienced in red clover swards in the months of June, July and August, than in grass only swards where N is frequently applied”.

The N that is fixed by the clover is there on a residual basis – in the soil – for three years after harvesting, adding to the production of further crops thereafter.

Dan also explained that: “Research shows very clearly that cows have a much higher weight gain and milk production, feeding on red clover silage than normal grass silage; due to its greater feeding value.

“Cows find it very palatable and actually prefer it over grass silage,” said Dan.

It is also drought tolerant and “survived well during the recent drought conditions” when compared to grass only swards.

Management

One of the main reasons why it is not used more readily is because it “demands good management”.

“You need to be going in and cutting it three-to-four times/year and you are depending on a good wilt to try and get the high-nitrogen content down. This can be difficult in our unpredictable Irish weather.

“It takes a lot off the field, so it’s important to replace that phosphorus (P) and potassium (K) taken off; farmyard manure (FYM) is very important for this,” Dan highlighted.

In order for it to persist in the soil, pH needs to be greater than 6.5, with good levels of phosphate and potash and a generally good mineral soil.

When sowing a red clover grass sward, a 50:50 mix of a tetraploid perennial ryegrass and clover should be used.

Red clover should persist for three to four years in the sward; although, some “research shows that it can last for up to six years in the sward”.

Including an additional 1kg of white clover in the mix when sowing will ensure that, if the red clover does loose persistency, an underlying layer of white clover will remain and can take over after that.

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