Hybrid rape comes out on
top in forage brassica trial
By Richard Allison
GROWING a hybrid forage rape can offer two successive crops of summer grazing in the same season, but time of drilling still remains crucial as with traditional root crops.
Dwarf leafy rape Winfred has been successfully grown in Devon for several years by organic producer Richard Quick. "The farm is fairly dry and suffers from grass shortages during most summers. Growing 30ha of a forage rape crop helps fill this grazing gap."
Stubble turnips have also been grown, but Winfred stays palatable longer and grows back to provide a second grazing crop two months later. "It seems to grow and grow, but a back fence is essential to maximise regrowth."
Applying slurry and chicken manure also boosts regrowth. This was found by accident last year when slurry had to be spread on half the field and yields were visibly higher, says Mr Quick.
"Grazing policy is based on splitting the 300 cows into two groups. One group grazes forage rape during the day and grass at night, while the other does the opposite. This ensures cows eat a mix of grass and forage rape."
In the first week of April, about 5ha (14 acres) of Winfred, from Oliver Seeds, was drilled to provide an early bite. "This is perhaps a bit early, but the low input cost means we can take a risk. The remaining 68 acres will be sown at the end of April to avoid drought later in the season."
If conditions become too dry at sowing, Mr Quick irrigates the crop for 4-5 days to ensure good establishment.
The importance of adequate moisture in the seed-bed was also found in a trial carried out in Sussex, says Kingshay senior technical specialist John Hocknell. "The crop sown in June, following first cut grass silage, only yielded about 1t/acre of dry matter due to a lack of moisture."
To avoid this, forage brassica crops should generally be sown by May. The later you leave it, the lower the yield potential, particularly in the south-east where this crop was grown, says Mr Hocknell.
In contrast, the earlier crop sown on May 14 at Kingshays Bridge Farm in Somerset achieved more than 5.4t/ha (2t/acre) dry matter within eight weeks of drilling. "This is twice the yield at the Sussex site."
The Kingshay trial also found that Winfred seemed to withstand stress better than other root crops, resulting in leaves staying greener for longer. Mr Quick believes it stays green and palatable twice as long as stubble turnips. "Stubble turnips are usually past their best after three weeks of grazing."
Despite growing the crop organically, weeds are not a major problem, says Mr Quick. "Stubble turnips or Winfred will eventually smother weeds. The only problem has been frit fly last year, but everyone in the valley seemed to suffer from this pest last year."
Seed rates are also a little higher at 6.8kg/ha (2.5kg/acre) than recommended to compensate for higher losses when using non-dressed seed. This is also justified with a low seed cost of about £5/kg. It is a cheap forage crop, he says.
Higher seed rates also avoid the problem experienced by Kingshay. It is tricky calibrating the drill at the standard sowing rate of 4kg/ha (1.5kg/acre), says Mr Hocknell. "Its like drilling clover seed."
The crop is also useful on non-organic farms. Last year, Brian Radford grew about 2ha (5 acres) of Winfred on his Somerset unit to supplement summer grazing for his 140-cow herd. "This meant less buffer feed was needed without compromising milk yields, so cutting costs and maintaining forage stocks.
"But we were caught out with cows entering the crop when above knee high." He believes they should have started grazing it earlier because it was above waist height during the latter half of grazing.
"A battery powered electric fencer is likely to struggle when the crop is this high. We have a strong mains powered fencer which copes with plants taller than the fencer without the hassle of cutting them away from the wire."
The crop also provided grazing for sheep during December as a result of the considerable regrowth during autumn. "We got all this with virtually no input costs, requiring only a couple of bags of nitrogen and two applications of spray for frit fly," adds Mr Radford. *
Forage brassica crops should be sown by May to maximise yield potential, says John Hocknell.
• Two crops/year.
• Simple and cheap.
• Sowing date crucial.