Winning with sericea

The issues preventing more widespread acceptance of sericea among farmers have been solved - so get planting.

Sericea Lespedeza is adaptable to a wide range of soil types and climates. But when developing low-cost productive pastures, this legume used to be way down on the list. One of the problems that had held sericea back for so long was the poor seedling vigour of old seed. But things are changing.

Where sericea went wrong
In 1983, a leading South African seed company imported a small consignment of sericea seed from the US. Most went to farmers who had pre-booked it and the rest was sold. A much larger consignment was imported the following year. Most of the farmers who planted seed from the first consignment experienced good germination, but poor growth. Virtually all the plantings were overrun by weeds, so it took three years for lands to produce good yields.

This wasn’t a good advert for sericea. Seed sales dropped and it took about five years to deplete the large stockpile of imported seed. During this time, farmers reported unsatisfactory germination results and many wrote sericea off as a mistake. They concluded they’d been sold bad seed, but the supplier said that regular seed tests showed germination was up to standard.

Solving poor seeding vigour
It seemed this potential winner was destined for failure. Then Dr Cathy Immelman of the Roodeplaat Agricultural Research Council came to the rescue. She did numerous laboratory tests, which confirmed that the seed was indeed up to standard, germination-wise. But it was quite a different story with her outdoor plot and pot-planting tests. She found that although the seed germinated, the seedlings were very weak and failed to develop.

Fresh seed was flown to South Africa and planted next to the old seed in a hothouse that simulated Highveld summer temperatures. The results were stunning. The fresh seed produced vigorous seedlings, whereas the old seed couldn’t even produce one strong seedling.

Dr Immelman explained that in some plants, seedling vigour declined faster with age than germination percentage did. Sericea is obviously one of these plants. Sericea seed is normally de-hulled after reaping as it improves the germination percentage. But apparently seedling vigour declines after de-hulling.

Hendrik Botha and his sons Rikus and Francois, who farm in Matatiele, produce certified sericea seed in vacuum-sealed bags, which prolong the effective life of the seed. They’ve planted sericea pastures from seed that was stored for five years. The Bothas have planted more than 1 000ha to sericea, a South African record. Seed that hasn’t been vacuum-packed should be planted within a year of harvesting.

The other factor that hampered the acceptance of sericea was that it was mostly planted in autumn, which is the wrong time. Seedlings are slow to develop then, so when the first frost occurs the plants are still small and weak. And it’s very slow to get going the following spring when the land is usually overrun by weeds.

Weeds compete with other plants for moisture, nutrients and sunlight. They also secrete growth inhibitors into the soil, without affecting their own growth. Sericea is very sensitive to these inhibitors. Dr Immelman found that sericea germinates better in early summer than when planted in autumn, provided weeds are effectively controlled.

An effective weed-control programme

Pre-emergence: Work Eptam and Treflan into the soil one week before planting. This will control nut-grass and some broad-leaved weeds.Post-emergence: Spray 600mâ„“ of 2,4-D Amine when sericea is at the four-leaf stage. Repeat if necessary.  None of these herbicides are registered for use on sericea. If you use them, you do so at your own risk. Ask your chemical rep about dosage rates for your particular conditions.

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Tags: biological farming Sericea soil types weed-control programme

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