29 November 1996

Green grains could be culprit when it comes to low Hagberg

Quality cereals production was the topic at last weeks Society of Chemical Industries conference in London. Andrew Blake reports some interesting developments

GREEN grains which shrivel after drying may account for low Hagbergs in otherwise good wheat samples. But the problem can be partly overcome by storage, says Peter Kettlewell of Harper Adams Agricultural College.

Mr Kettlewell noted that the inner skin of immature grains contains lots of alpha-amylase, the cause of low Hagberg readings.

In the past this was not thought to be significant because pericarp alpha-amylase is different to the type induced by sprouting and it breaks down faster when heated, explained Mr Kettlewell.

But Swedish work in the 1970s, which suggested otherwise, encouraged Mr Kettlewell to have a fresh look. "We repeated the work by mixing freeze-dried green grain in various proportions with a fully ripe sample of known Hagberg."

The experiment showed quite small proportions of unripe grain can have a big impact. Only about 2% was needed to pull a 350 Hagberg sample down to 250 and 5% took it below 200.

The good news, said Mr Kettlewell, was that pericarp alpha-amylase breaks down with age. If you store it for several months you will get much less effect."

Just how long that storage period needs to be to avoid trouble is unknown. "We are planning an experiment to test it next harvest."

One message is that early lodged crops, even though they may avoid ear sprouting, are still prone to low Hagbergs. More light gets into the base of the crop to encourage secondary tillering, said Mr Kettlewell.

Growth regulators help avoid lodging. But rabbit damage and rain after drought can both encourage late tillering and green ears at harvest, he warned.

Green grains from secondary tillers contain high alpha-amylase levels that may have a bigger impact on Hagbergs than some growers realise.