CATCH CROPS may have lost favour in recent years, but they remain a valuable source of forage, particularly in drought-prone areas and where an extended grazing season is the aim.
But, to maximise the benefits, good crop establishment is a priority, says Martin Titley of Advanta Seeds.
“The first decision when planning catch crops is to ensure they are sown in the right fields. Winter-grazed stubble turnips need to be sown into lighter, free draining soils to ensure livestock remain as clean as possible and poaching is kept to a minimum,” he says.
Soil pH is also important and soils should be balanced to a pH of 6 to 6.5 to maximise chances of success.
Where crops are to be grazed in summer, it is essential to retain as much moisture as possible in the seed-bed to aid germination. “It is possible to slot seed or broadcast stubble turnips in silage aftermaths or in tightly grazed grass fields. But this can have mixed results, so ploughing may be a better option.”
However, David Long, of Barenbrug Seeds, says with producers more aware of the need to avoid poaching in the light of cross-compliance rules, this method of establishment may become more common. “Sowing stubble turnips into existing swards means poaching may be reduced.
“It is best to harrow fields a couple of times with a set of rigid-tined harrows. This breaks up the sward and removes thatch. It also means there is more soil around the seed and more soil moisture is retained.”
Brassicas are robust crops which will germinate and grow under most conditions, as long as they have contact with soil and moisture levels are good, adds Mr Long.
Where seed-beds are prepared by ploughing, moisture retention can be more problematic, so working seed-beds and sowing soon after ploughing is best. It may also help to roll after sowing to cut the chances of moisture loss, says Mr Titley.
Agronomy for stubble turnip crops is relatively simple, he suggests. “But when sowing a summer grazing crop in April or May it will probably be worthwhile sowing treated seed to limit flea beetle damage. This adds about 4/kg to seed costs, but it cuts out the need for post-emergence spraying.”
Crops also benefit from fertiliser at sowing, he says. “About 75kg/ha of nitrogen should be enough to give crops a boost for both spring and autumn grazed crops. Seed rate is also important, but it depends on how the crop is sown. Direct-sowing should be at about 4-5kg/ha, while broadcast crops should be sown at about 6-8kg/ha.”
When planning crops, Mr Titley advises leaving sufficient dry run-back areas to help stock stay clean and dry, particularly finishing lambs.
Looking to other catch crops, Mr Long suggests Italian ryegrass, particularly when undersown into cereal or maize crops. “This can be grazed in both autumn and spring, or cut for first cut silage and ploughed in again. It should be sown at about 20-25kg/ha.”
Other options include vetches or tares which can be sown in early autumn for grazing in winter or a spring silage crop. “These should be sown at about 100-125kg/ha.”