Lucerne is back in fashion.
The crop’s ability to produce high-quality feed in drought-prone areas is making it a popular choice for dryland east coast farms. New Zealand’s champion of lucerne is Prof Derrick Moot, of Lincoln University, who leads the Dryland Pastures Research programme. He has encouraged farmers to graze their lucerne crops, rather than “cut and carry”, and has done away with management myths that had been causing difficulties.
Beef and Lamb New Zealand recently enlisted Prof Moot to speak on a teleconference call open to farmers. For those who could not dial in, BLNZ has summarised his advice.
Prof Moot said the main reason for growing lucerne was its deep tap root, which could access soil moisture at a much deeper level than traditional ryegrass roots.
Because it fixes nitrogen (N), lucerne is never N deficient and is able to use every millimetre of water very efficiently. Water use efficiency in plants depends on nitrogen availability.
“Pastures that are N deficient do not use water efficiently.”
Heading into spring, Prof Moot said farmers needed to consider the moisture available within their soil profile. This varies between soil types and winter rainfall. Like any plant, lucerne would struggle to be productive when there was no moisture available.
Farmers with soil moisture deficits should just manage the lucerne as they normally would in spring, but cannot expect the same post-grazing recovery.
Because lucerne’s growing points are at the top of the plant, it should be rotationally grazed. Prof Moot advised against set-stocking in spring, as stock would remove all the growing points. This would set the lucerne stand back by up to four weeks.
The exception is where farmers have a large area in lucerne, so a small area can be sacrificed for set-stocking ewes at lambing. The crop should be very lightly set-stocked for a short period.
“It cannot be nailed.”
In rotational grazing, stock can be run on to the crop when it is 10cm-15cm high, ideally at a stocking rate of 14 ewes and lambs per hectare, and moved to a new paddock every three to four days.
Prof Moot said farmers really need at least 20ha of lucerne before they could start a rotation that resulted in good livestock and forage growth rates – a 5ha paddock is really only a cut-and-carry proposition.
On a five-six paddock rotation, stock would return to the first paddock when the crop was 25cm-30cm tall, which meant it had retained its feed quality.
Prof Moot debunked the myth that lucerne needed to flower in spring before it could be grazed. Lucerne responds to day length – in spring and early summer, it can get very tall before it flowers and feed quality declines.
“If you wait until 10% of the stand is flowering, then the stem will be lignified.”
In spring, the plant draws on its root reserves to bring carbon and N to the surface.
In late summer and autumn, it must replenish these root reserves for the following season, so it needs to be spelled for six weeks while it is actively growing.
Often the crop will flower during this time.